Journal Papers: C. R. Koch Mechanical Engineering University of Alberta

Author	Title	Year	Journal/Proceedings	Reftype	DOI/URL
Bussiere, M., Bessa, G.M., Koch, C.R. and Nobes, D.S.	Application of a Combinatorial Vortex Detection Algorithm on 2 Component 2 Dimensional Particle Image Velocimetry Data to Characterize the Wake of an Oscillating Wing [BibTeX]	2024	Fluids Vol. 9(3), pp. 53	article	DOI
BibTeX: @article{Bussiere2024, author = {Bussiere, Mathew and Bessa, Guilherme M. and Koch, Charles R. and Nobes, David S.}, title = {Application of a Combinatorial Vortex Detection Algorithm on 2 Component 2 Dimensional Particle Image Velocimetry Data to Characterize the Wake of an Oscillating Wing}, journal = {Fluids}, publisher = {MDPI AG}, year = {2024}, volume = {9}, number = {3}, pages = {53}, doi = {https://doi.org/10.3390/fluids9030053} }
Cassol, G.O., Koch, C.R. and Dubljevic, S.	The chemostat reactor: A stability analysis and model predictive control [BibTeX]	2024	Journal of Process Control Vol. 138, pp. 103223	article	DOI
BibTeX: @article{Cassol2024, author = {Cassol, Guilherme Ozorio and Koch, Charles Robert and Dubljevic, Stevan}, title = {The chemostat reactor: A stability analysis and model predictive control}, journal = {Journal of Process Control}, publisher = {Elsevier BV}, year = {2024}, volume = {138}, pages = {103223}, doi = {https://doi.org/10.1016/j.jprocont.2024.103223} }
Jiang, L., Kheyrollahi, J., Koch, C.R. and Shahbakhti, M.	Cooperative truck platooning trial on Canadian public highway under commercial operation in winter driving conditions [BibTeX]	2024	Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering	article	DOI
BibTeX: @article{Jiang2024, author = {Jiang, Luo and Kheyrollahi, Javad and Koch, Charles Robert and Shahbakhti, Mahdi}, title = {Cooperative truck platooning trial on Canadian public highway under commercial operation in winter driving conditions}, journal = {Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering}, publisher = {SAGE Publications}, year = {2024}, doi = {https://doi.org/10.1177/09544070241245477} }
Tofigh, M., Salehi, Z., Kharazmi, A., Smith, D.J., Hanifi, A.R., Koch, C.R. and Shahbakhti, M.	Transient modeling of a solid oxide fuel cell using an efficient deep learning HY-CNN-NARX paradigm [BibTeX]	2024	Journal of Power Sources Vol. 606, pp. 234555	article	DOI
BibTeX: @article{Tofigh2024, author = {Tofigh, Mohamadali and Salehi, Zeynab and Kharazmi, Ali and Smith, Daniel J. and Hanifi, Amir Reza and Koch, Charles Robert and Shahbakhti, Mahdi}, title = {Transient modeling of a solid oxide fuel cell using an efficient deep learning HY-CNN-NARX paradigm}, journal = {Journal of Power Sources}, publisher = {Elsevier BV}, year = {2024}, volume = {606}, pages = {234555}, doi = {https://doi.org/10.1016/j.jpowsour.2024.234555} }
Abediasl, H., Meresht, N.B., Alizadeh, H., Shahbakhti, M., Koch, C.R. and Hosseini, V.	Road transportation emissions and energy consumption in cold climate cities [BibTeX]	2023	Urban Climate Vol. 52, pp. 101697	article	DOI
BibTeX: @article{Abediasl2023, author = {Hamidreza Abediasl and Navid Balazadeh Meresht and Hossein Alizadeh and Mahdi Shahbakhti and Charles Robert Koch and Vahid Hosseini}, title = {Road transportation emissions and energy consumption in cold climate cities}, journal = {Urban Climate}, publisher = {Elsevier BV}, year = {2023}, volume = {52}, pages = {101697}, doi = {https://doi.org/10.1016/j.uclim.2023.101697} }
Abediasl, H., Ansari, A., Hosseini, V., Koch, C.R. and Shahbakhti, M.	Real-time vehicular fuel consumption estimation using machine learning and on-board diagnostics data [Abstract] [BibTeX]	2023	Journal of Automobile Engineering, Part D	article	DOI
Abstract: Instantaneous fuel consumption estimation of fleet vehicles provides essential tools for fleet operation optimization and intelligent fleet management. This study aims to develop practical and accurate models to estimate instantaneous fuel consumption based on on-board diagnostics (OBD) data. Fuel consumption data is measured by a high-precision fuel flow meter. Two machine learning algorithms of Random Forest (RF) and Artificial Neural Networks (ANN) are trained with real-world urban and highway driving data of four fleet vehicles with different types and powertrain systems. In addition, the cold-start period of the vehicle operation is included to cover the fuel consumption penalty in the warm-up period. The validation results show that the RF method is more accurate than the ANN method, and both of the machine learning models have a better accuracy compared to the existing fuel consumption calculation methods based on the engine control unit (ECU) parameters.
BibTeX: @article{JAUTO_HR_2023, author = {Hamidreza Abediasl and Amir Ansari and Vahid Hosseini and Charles Robert Koch and Mahdi Shahbakhti}, title = {Real-time vehicular fuel consumption estimation using machine learning and on-board diagnostics data}, journal = {Journal of Automobile Engineering, Part D}, year = {2023}, doi = {https://doi.org/10.1177/09544070231185609} }
Jiang, L., Kheyrollahi, J., Koch, C.R. and Shahbakhti, M.	Performance Analysis of Cooperative Truck Platooning under Commercial Operation during Canadian Winter Season [BibTeX]	2023	SAE International Journal of Connected and Automated Vehicles Vol. 7(2)	article	DOI
BibTeX: @article{Jiang2023, author = {Jiang, Luo and Kheyrollahi, Javad and Koch, Charles Robert and Shahbakhti, Mahdi}, title = {Performance Analysis of Cooperative Truck Platooning under Commercial Operation during Canadian Winter Season}, journal = {SAE International Journal of Connected and Automated Vehicles}, publisher = {SAE International}, year = {2023}, volume = {7}, number = {2}, doi = {https://doi.org/10.4271/12-07-02-0012} }
Norouzi, A., Shahpouri, S., Gordon, D., Shahbakhti, M. and Koch, C.R.	Safe deep reinforcement learning in diesel engine emission control [BibTeX]	2023	Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, pp. 095965182311534	article	DOI
BibTeX: @article{Norouzi2023, author = {Armin Norouzi and Saeid Shahpouri and David Gordon and Mahdi Shahbakhti and Charles Robert Koch}, title = {Safe deep reinforcement learning in diesel engine emission control}, journal = {Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering}, publisher = {SAGE Publications}, year = {2023}, pages = {095965182311534}, doi = {https://doi.org/10.1177/09596518231153445} }
Norouzi, A., Heidarifar, H., Borhan, H., Shahbakhti, M. and Koch, C.R.	Integrating Machine Learning and Model Predictive Control for automotive applications: A review and future directions [BibTeX]	2023	Engineering Applications of Artificial Intelligence Vol. 120, pp. 105878	article	DOI
BibTeX: @article{Norouzi2023a, author = {Armin Norouzi and Hamed Heidarifar and Hoseinali Borhan and Mahdi Shahbakhti and Charles Robert Koch}, title = {Integrating Machine Learning and Model Predictive Control for automotive applications: A review and future directions}, journal = {Engineering Applications of Artificial Intelligence}, publisher = {Elsevier BV}, year = {2023}, volume = {120}, pages = {105878}, doi = {https://doi.org/10.1016/j.engappai.2023.105878} }
Shahpouri, S., Gordon, D., Hayduk, C., Rezaei, R., Koch, C.R. and Shahbakhti, M.	Hybrid emission and combustion modeling of hydrogen fueled engines [Abstract] [BibTeX]	2023	International Journal of Hydrogen Energy	article	DOI URL
Abstract: Zero carbon fuels can be used to reduce CO2 emissions from internal combustion engines. Hydrogen is an important zero-carbon fuel that can be used as the primary fuel for spark ignition (SI) engines or in dual-fuel operation in compression ignition (CI) engines. The combustion properties of hydrogen often result in high combustion temperature which produces harmful nitrogen oxides (NOx) emissions. To reduce NOx and soot emissions from hydrogen fueled engines, an engine can be optimized using a hardware-in-the-loop (HIL) setup to reduce calibration efforts for the engine. In addition, optimal model based combustion control (MCC) can reduce engine-out emissions. Both of HIL and MCC techniques require fast and accurate NOx and soot emission models. The accuracy of a fast physics-based engine model with pre-mixed combustion is dependent on predicting the laminar flame speed (LFS). In this study, LFS is predicted using an artificial neural network (ANN) machine learning (ML) method. Then the LFS model and engine combustion model are validated for both an SI hydrogen engine and for a CI hydrogen-diesel engine. Next, black-box and gray-box soot and NOx emission models are developed for the hydrogen-diesel engine using ANN, support vector machine (SVM) and Gaussian process regression (GPR) methods with different feature-sets and compared with the a common one-dimensional physics-based NOx model. The developed gray-box emission models can predict NOx and soot emissions with an Rtest2 value of higher than 0.99 which makes them suitable for engine HIL setups where accuracy is very important. On the other hand, the black-box emission models can predict NOx and soot emissions with Rtest2 value higher than 0.95 with a run time thousands of times faster than the gray-box models. This makes the black-box models suitable for model-based real time hydrogen combustion control where limited computational power is available.
BibTeX: @article{SHAHPOURI2023, author = {Saeid Shahpouri and David Gordon and Christopher Hayduk and Reza Rezaei and Charles Robert Koch and Mahdi Shahbakhti}, title = {Hybrid emission and combustion modeling of hydrogen fueled engines}, journal = {International Journal of Hydrogen Energy}, year = {2023}, url = {https://www.sciencedirect.com/science/article/pii/S0360319923012156}, doi = {https://doi.org/10.1016/j.ijhydene.2023.03.153} }
Shahpouri, S., Norouzi, A., Hayduk, C., Fandakov, A., Rezaei, R., Koch, C.R. and Shahbakhti, M.	Laminar Flame Speed modeling for Low Carbon Fuels using methods of Machine Learning [Abstract] [BibTeX]	2023	Fuel Vol. 333, pp. 126187	article	DOI URL
Abstract: Artificial Neural Network (ANN) and Support Vector Machine (SVM) methods are designed to accurately predict Laminar Flame Speed (LFS) over the entire engine operating range for Ammonia (NH3), Hydrogen (H2), and Methanol (CH3OH). These are promising zero-carbon or low-carbon alternative fuels for the transportation sector but require combustion models to optimize and control the engine performance. These developed Machine Learning (ML) methods provide an LFS prediction that requires several orders of magnitude less computation time than the original thermo-kinetic combustion mechanisms but has similar accuracy. Then an SVM and an ANN LFS model for blends of the three fuels was developed by combining LFS datasets of different fuels. Results show that for single fuels, ANN shows better performance than SVM and can predict the LFS with a correlation coefficient Rtest2 higher than 0.999. For fuel blends, SVM has better performance with Rtest2 close to 0.999. These predictive ML LFS models can be integrated into 0D and 1D engine models and their low computation time makes them useful for engine development and for future model-based combustion control applications.
BibTeX: @article{SHAHPOURI2023126187, author = {Saeid Shahpouri and Armin Norouzi and Christopher Hayduk and Alexander Fandakov and Reza Rezaei and Charles Robert Koch and Mahdi Shahbakhti}, title = {Laminar Flame Speed modeling for Low Carbon Fuels using methods of Machine Learning}, journal = {Fuel}, year = {2023}, volume = {333}, pages = {126187}, url = {https://www.sciencedirect.com/science/article/pii/S0016236122030113}, doi = {https://doi.org/10.1016/j.fuel.2022.126187} }
Xie, J., Humaloja, J.-P., Koch, C.R. and Dubljevic, S.	Approximate moving horizon estimation for switching conservative linear infinite-dimensional systems [BibTeX]	2023	Automatica Vol. 158, pp. 111306	article	DOI
BibTeX: @article{Xie_Autom_23, author = {Junyao Xie and Jukka-Pekka Humaloja and Charles Robert Koch and Stevan Dubljevic}, title = {Approximate moving horizon estimation for switching conservative linear infinite-dimensional systems}, journal = {Automatica}, publisher = {Elsevier BV}, year = {2023}, volume = {158}, pages = {111306}, doi = {https://doi.org/10.1016/j.automatica.2023.111306} }
Aliramezani, M., Koch, C.R. and Shahbakhti, M.	Modeling, diagnostics, optimization, and control of internal combustion engines via modern machine learning techniques: A review and future directions [Abstract] [BibTeX]	2022	Progress in Energy and Combustion Science Vol. 88, pp. 100967	article	DOI URL
Abstract: A critical review of the existing Internal Combustion Engine (ICE) modeling, optimization, diagnosis, and control challenges and the promising state-of-the-art Machine Learning (ML) solutions for them is provided in this paper. Some of the major challenges include Real Driving Emission (RDE) modeling and control, combustion knock detection and control, combustion mode transition in multi-mode engines, combustion noise modeling and control, combustion instability and cyclic variability control, costly and time-consuming engine calibration, and fault diagnostics of some ICE components. In this paper, conventional ICE modeling approaches are discussed along with their limitations for realtime ICE optimization and control. Promising ML approaches to address ICE challenges are then classified into three main groups of unsupervised learning, supervised learning, and reinforcement learning. The working principles of each approach along with their advantages and disadvantages in addressing ICE challenges are discussed. ML-based grey-box approach is proposed as a solution that combines the benefits from physics-based and ML-based models to provide robust and high fidelity solutions for ICE modeling and control challenges. This review provides in-depth insight into the applications of ML for ICEs and provides recommendations for future directions to address ICE challenges.
BibTeX: @article{ALIRAMEZANI2022100967, author = {Masoud Aliramezani and Charles Robert Koch and Mahdi Shahbakhti}, title = {Modeling, diagnostics, optimization, and control of internal combustion engines via modern machine learning techniques: A review and future directions}, journal = {Progress in Energy and Combustion Science}, year = {2022}, volume = {88}, pages = {100967}, url = {https://www.sciencedirect.com/science/article/pii/S0360128521000654}, doi = {https://doi.org/10.1016/j.pecs.2021.100967} }
Norouzi, A., Saeid Shahpouri, D.G., Winkler, A., Nuss, E., Abel, D., Andert, J., Shahbakhti, M. and Koch, C.R.	Deep learning based model predictive control for compression ignition engines [Abstract] [BibTeX]	2022	Control Engineering Practice Vol. 127, pp. 105299	article	DOI URL
Abstract: Machine learning (ML) and a nonlinear model predictive controller (NMPC) are used in this paper to minimize the emissions and fuel consumption of a compression ignition engine. In this work machine learning is applied in two methods. In the first application, ML is used to identify a model for implementation in model predictive control optimization problems. In the second application, ML is used as a replacement of the NMPC where the ML controller learns the optimal control action by imitating or mimicking the behavior of the model predictive controller. In this study, a deep recurrent neural network including long�short term memory (LSTM) layers are used to model the emissions and performance of an industrial 4.5 liter 4-cylinder Cummins diesel engine. This model is then used for model predictive controller implementation. Then, a deep learning scheme is deployed to clone the behavior of the developed controller. In the LSTM integration, a novel scheme is used by augmenting hidden and cell states of the network in an NMPC optimization problem. The developed LSTM-NMPC and the imitative NMPC are compared with the Cummins calibrated Engine Control Unit (ECU) model in an experimentally validated engine simulation platform. Results show a significant reduction in Nitrogen Oxides (NOx) emissions and a slight decrease in the injected fuel quantity while maintaining the same load. In addition, the imitative NMPC has a similar performance as the NMPC but with a two orders of magnitude reduction of the computation time.
BibTeX: @article{CEP_Norouzi_2022, author = {Armin Norouzi and Saeid Shahpouri, David Gordon and Alexander Winkler and Eugen Nuss and Dirk Abel and Jakob Andert and Mahdi Shahbakhti and Charles Robert Koch}, title = {Deep learning based model predictive control for compression ignition engines}, journal = {Control Engineering Practice}, year = {2022}, volume = {127}, pages = {105299}, url = {https://www.sciencedirect.com/science/article/pii/S0967066122001472}, doi = {https://doi.org/10.1016/j.conengprac.2022.105299} }
Chen, K., Nishida, R.T., Koch, C.R. and Olfert, J.S.	Development and testing of a universal aerosol conditioner [Abstract] [BibTeX]	2022	Aerosol Science and Technology Vol. 0(0), pp. 1-12	article	DOI URL
Abstract: A general purpose aerosol conditioning device called the Universal Aerosol Conditioner (UAC) has been designed and tested. The device may be used to condition an aerosol in multiple ways: dilute the entire aerosol (gas- and particle-phase), dilute only a gas-phase component of the aerosol without diluting the particle concentration, denude the aerosol by removing semi-volatile material from the particle phase, and humidify or dehumidify an aerosol. The UAC accomplishes these processes by bringing the aerosol into contact with sheath air and allowing enough time for gas-phase components of the aerosol to diffuse into the sheath flow. A model was developed to assess the theoretical performance of the UAC and was solved numerically. From the model it was determined that two parameters dictated the rate of diffusion between the two flows: the P�clet number and the ratio of sheath-to-aerosol flow rates. A prototype was designed and built and the theory of operation was experimentally validated by measuring the particle penetration efficiency and the gas dilution factor at various particle sizes and flow conditions. The results showed that at low aerosol and sheath flows, the prototype behaved closely to the theoretical model but diverged from the theory once the sheath flows were increased, presumably due to mixing between the two flows.Copyright � 2022 American Association for Aerosol Research
BibTeX: @article{Chen2022, author = {Chen, Kerry and Nishida, Robert T. and Koch, Charles Robert and Olfert, Jason S.}, title = {Development and testing of a universal aerosol conditioner}, journal = {Aerosol Science and Technology}, publisher = {Taylor & Francis}, year = {2022}, volume = {0}, number = {0}, pages = {1--12}, url = {https://doi.org/10.1080/02786826.2022.2030463}, doi = {https://doi.org/10.1080/02786826.2022.2030463} }
Gordon, D.C., Norouzi, A., Winkler, A., McNally, J., Nuss, E., Abel, D., Shahbakhti, M., Andert, J. and Koch, C.R.	End-to-End Deep Neural Network Based Nonlinear Model Predictive Control: Experimental Implementation on Diesel Engine Emission Control [BibTeX]	2022	Energies Vol. 15(24), pp. 9335	article	DOI
BibTeX: @article{Gordon2022, author = {David C. Gordon and Armin Norouzi and Alexander Winkler and Jakub McNally and Eugen Nuss and Dirk Abel and Mahdi Shahbakhti and Jakob Andert and Charles R. Koch}, title = {End-to-End Deep Neural Network Based Nonlinear Model Predictive Control: Experimental Implementation on Diesel Engine Emission Control}, journal = {Energies}, publisher = {MDPI AG}, year = {2022}, volume = {15}, number = {24}, pages = {9335}, doi = {https://doi.org/10.3390/en15249335} }
Wine, O., Vargas, A.O., Campbell, S.M., Hosseini, V., Koch, C.R. and Shahbakhti, M.	Cold Climate Impact on Air-Pollution-Related Health Outcomes: A Scoping Review [BibTeX]	2022	International Journal of Environmental Research and Public Health Vol. 19(3), pp. 1473	article	DOI
BibTeX: @article{Wine2022, author = {Osnat Wine and Alvaro Osornio Vargas and Sandra M. Campbell and Vahid Hosseini and Charles Robert Koch and Mahdi Shahbakhti}, title = {Cold Climate Impact on Air-Pollution-Related Health Outcomes: A Scoping Review}, journal = {International Journal of Environmental Research and Public Health}, publisher = {MDPI AG}, year = {2022}, volume = {19}, number = {3}, pages = {1473}, doi = {https://doi.org/10.3390/ijerph19031473} }
Xie, J., Humaloja, J.-P., Koch, C.R. and Dubljevic, S.	Constrained Receding Horizon Output Estimation of Linear Distributed Parameter Systems [BibTeX]	2022	IEEE Transactions on Automatic Control, pp. 1-8	article	DOI
BibTeX: @article{Xie2022, author = {Junyao Xie and Jukka-Pekka Humaloja and Charles Robert Koch and Stevan Dubljevic}, title = {Constrained Receding Horizon Output Estimation of Linear Distributed Parameter Systems}, journal = {IEEE Transactions on Automatic Control}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, year = {2022}, pages = {1--8}, doi = {https://doi.org/10.1109/tac.2022.3217111} }
Ebrahimi, K., Gordon, D., Canteenwalla, P. and Koch, C.R.	Evaluation of ASTM D6424 standard for knock analysis using unleaded fuel candidates on a six cylinder aircraft engine [BibTeX]	2021	International Journal of Engine Research Vol. 23(7), pp. 1159-1179	article	DOI URL
BibTeX: @article{Ebrahimi2021, author = {Khashayar Ebrahimi and David Gordon and Pervez Canteenwalla and Charles R Koch}, title = {Evaluation of ASTM D6424 standard for knock analysis using unleaded fuel candidates on a six cylinder aircraft engine}, journal = {International Journal of Engine Research}, publisher = {SAGE Publications}, year = {2021}, volume = {23}, number = {7}, pages = {1159--1179}, url = {/ ckoch/open_access/Ebrahimi2021.pdf}, doi = {https://doi.org/10.1177/14680874211008703} }
Norouzi, A., Heidarifar, H., Shahbakhti, M., Koch, C.R. and Borhan, H.	Model Predictive Control of Internal Combustion Engines: A Review and Future Directions [Abstract] [BibTeX]	2021	Energies Vol. 14(19)	article	DOI URL
Abstract: An internal combustion engine (ICE) is a highly nonlinear dynamic and complex engineering system whose operation is constrained by operational limits, including emissions, noise, peak in-cylinder pressure, combustion stability, and actuator constraints. To optimize today's ICEs, seven to ten control actuators and 10 -20 feedback sensors are often used, depending on the engine applications and target emission regulations. This requires extensive engine experimentation to calibrate the engine control module (ECM), which is both cumbersome and costly. Despite these efforts, optimal operation, particularly during engine transients and to meet real driving emission (RDE) targets for broad engine speed and load conditions, has still not been obtained. Methods of model predictive control (MPC) have shown promising results for real-time multi-objective optimal control of constrained multi-variable nonlinear systems, including ICEs. This paper reviews the application of MPC for ICEs and analyzes the recent developments in MPC that can be utilized in ECMs. ICE control and calibration can be enhanced by taking advantage of the recent developments in the field of Artificial Intelligence (AI) in applying Machine Learning (ML) to large-scale engine data. Recent developments in the field of ML-MPC are investigated, and promising methods for ICE control applications are identified in this paper.
BibTeX: @article{ENER_MPC_Norouzi2021, author = {Norouzi, Armin and Heidarifar, Hamed and Shahbakhti, Mahdi and Koch, Charles Robert and Borhan, Hoseinali}, title = {Model Predictive Control of Internal Combustion Engines: A Review and Future Directions}, journal = {Energies}, year = {2021}, volume = {14}, number = {19}, url = {/ ckoch/open_access/energies-14-06251.pdf}, doi = {https://doi.org/10.3390/en14196251} }
Gordon, D., Norouzi, A., Blomeyer, G., Bedei, J., Aliramezani, M., Andert, J. and Koch, C.R.	Support vector machine based emissions modeling using particle swarm optimization for homogeneous charge compression ignition engine [Abstract] [BibTeX]	2021	International Journal of Engine Research Vol. 0(0), pp. 14680874211055546	article	DOI URL
Abstract: The internal combustion engine faces increasing societal and governmental pressure to improve both efficiency and engine out emissions. Currently, research has moved from traditional combustion methods to new highly efficient combustion strategies such as Homogeneous Charge Compression Ignition (HCCI). However, predicting the exact value of engine out emissions using conventional physics-based or data-driven models is still a challenge for engine researchers due to the complexity the of combustion and emission formation. Research has focused on using Artificial Neural Networks (ANN) for this problem but ANN's require large training datasets for acceptable accuracy. This work addresses this problem by presenting the development of a simple model for predicting the steady-state emissions of a single cylinder HCCI engine which is created using an metaheuristic optimization based Support Vector Machine (SVM). The selection of input variables to the SVM model is explored using five different feature sets, considering up to seven engine inputs. The best results are achieved with a model combining linear and squared inputs as well as cross correlations and their squares totaling 26 features. In this case the model fit represented by R2 values were between 0.72 and 0.95. The best model fits were achieved for CO and CO2, while HC and NOx models have reduced model performance. Linear and non-linear SVM models were then compared to an ANN model. This comparison showed that SVM based models were more robust to changes in feature selection and better able to avoid local minimums compared to the ANN models leading to a more consistent model prediction when limited training data is available. The proposed machine learning based HCCI emission models and the feature selection approach provide insight into optimizing the model accuracy while minimizing the computational costs.
BibTeX: @article{GordenIJER2021, author = {David Gordon and Armin Norouzi and Gero Blomeyer and Julian Bedei and Masoud Aliramezani and Jakob Andert and Charles R Koch}, title = {Support vector machine based emissions modeling using particle swarm optimization for homogeneous charge compression ignition engine}, journal = {International Journal of Engine Research}, year = {2021}, volume = {0}, number = {0}, pages = {14680874211055546}, url = {https://doi.org/10.1177/14680874211055546}, doi = {https://doi.org/10.1177/14680874211055546} }
Norouzi, A., Koch, C.R. and Aliramezani, M.	A Correlation Based Model Order Reduction Approach for a Diesel Engine NOx and BMEP Dynamic Model Using Machine Learning [BibTeX]	2021	International Journal of Engine Research	article	DOI URL
BibTeX: @article{IJER_AN_2020, author = {Armin Norouzi and Charles Robert Koch and Masoud Aliramezani}, title = {A Correlation Based Model Order Reduction Approach for a Diesel Engine NOx and BMEP Dynamic Model Using Machine Learning}, journal = {International Journal of Engine Research}, year = {2021}, url = {/ ckoch/open_access/IJER_AN_2020.pdf}, doi = {https://doi.org/10.1177/1468087420936949} }
Shahpouri, S., Yengeje, A.N., Hayduk, C., Rezaei, R., Shahbakhti, M. and Koch, C.R.	Hybrid machine learning approaches and a systematic model selection process for predicting soot emissions in compression ignition engines [BibTeX]	2021	Energies Vol. 14(23)	article	DOI URL
BibTeX: @article{Saeid_Energies2021, author = {Saeid Shahpouri and Armin Norouzi Yengeje and Christopher Hayduk and Reza Rezaei and Mahdi Shahbakhti and Charles Robert Koch}, title = {Hybrid machine learning approaches and a systematic model selection process for predicting soot emissions in compression ignition engines}, journal = {Energies}, year = {2021}, volume = {14}, number = {23}, url = {https://www.mdpi.com/1996-1073/14/23/7865}, doi = {https://doi.org/10.3390/en14237865} }
Xie, J., Robert Koch, C. and Dubljevic, S.	Discrete-time model-based output regulation of fluid flow systems [Abstract] [BibTeX]	2021	European Journal of Control Vol. 57, pp. 1-13	article	DOI URL
Abstract: Model-based discrete-time output regulator design is proposed for fluid flow systems using a geometric approach. More specifically, a class of vortex shedding and falling thin film phenomena modelled by complex Ginzburg-Landau equation (CGLE) and Kuramoto-Sivashinsky equation (KSE) are considered. Differently from a traditional continuous-time controller design, a novel discrete-time modelling technique is proposed in a general infinite-dimensional state-space setting, which does not pertain any spatial approximation or model reduction, and preserves model intrinsic properties (such as stability, controllability and observability). Based on the time discretized plant model (CGLE and KSE systems) by the Cayley-Tustin method, discrete regulator regulation equations are established and facilitated for an output regulator design to achieve fluid flow control and manipulation. To address model instability, a spectrum analysis is utilized in stabilizing continuous-time CGLE and KSE systems, and a link between discrete- and continuous-time closed-loop system stabilizing gains is established. Finally, the proposed methodology is demonstrated through a set of simulation cases, by which the output tracking, disturbance rejection, and model stabilization are achieved for the considered CGLE and KSE systems.
BibTeX: @article{XIE20211, author = {Junyao Xie and Charles Robert Koch and Stevan Dubljevic}, title = {Discrete-time model-based output regulation of fluid flow systems}, journal = {European Journal of Control}, year = {2021}, volume = {57}, pages = {1-13}, url = {/ ckoch/open_access/XIE20211.pdf}, doi = {https://doi.org/10.1016/j.ejcon.2020.10.005} }
Gordon, D., Wouters, C., Wick, M., Xia, F., Lehrheuer, B., Andert, J., Koch, C.R. and Pischinger, S.	Development and experimental validation of a real-time capable field programmable gate array - based gas exchange model for negative valve overlap [BibTeX]	2020	International Journal of Engine Research Vol. 21(3), pp. 421-436	article	DOI URL
BibTeX: @article{GordenIJER2020, author = {David Gordon and Christian Wouters and Maximilian Wick and Feihong Xia and Bastian Lehrheuer and Jakob Andert and Charles R Koch and Stefan Pischinger}, title = {Development and experimental validation of a real-time capable field programmable gate array - based gas exchange model for negative valve overlap}, journal = {International Journal of Engine Research}, year = {2020}, volume = {21}, number = {3}, pages = {421-436}, url = {/ ckoch/open_access/Gorden2018.pdf}, doi = {https://doi.org/10.1177/1468087418788491} }
Xie, J., Koch, C.R. and Dubljevic, S.	Discrete output regulator design for linear distributed parameter systems [BibTeX]	2020	International Journal of Control Vol. 0, pp. 1-17	article	DOI URL
BibTeX: @article{IJC_Xie2020, author = {Junyao Xie and Charles Robert Koch and Stevan Dubljevic}, title = {Discrete output regulator design for linear distributed parameter systems}, journal = {International Journal of Control}, publisher = {Taylor & Francis}, year = {2020}, volume = {0}, pages = {1-17}, url = {/ ckoch/open_access/IJC_Xie2020.pdf}, doi = {https://doi.org/10.1080/00207179.2020.1807059} }
Gordon, D., Wouters, C., Kinoshita, S., Wick, M., Lehrheuer, B., Andert, J., Pischinger, S. and Koch, C.R.	Homogeneous charge compression ignition combustion stability improvement using a rapid ignition system [Abstract] [BibTeX]	2020	International Journal of Engine Research Vol. 21(10), pp. 1846-1856	article	DOI URL
Abstract: When compared to traditional engines, homogeneous charge compression ignition has the potential to significantly reduce NOx raw emissions, while maintaining a high fuel efficiency. Homogeneous charge compression ignition is characterized by compression-induced autoignition of a lean homogeneous air-fuel mixture. Since homogeneous charge compression ignition does not utilize direct ignition control, it is strongly dependent on the state of the cylinder charge and can suffer from high cyclic variability. With spark-assisted compression ignition, it has been demonstrated that misfires can be reduced, while preserving the high thermal efficiency of homogeneous charge compression ignition as a result of the more favorable physical mixture properties due to dilution. However, spark-assisted compression ignition reduces the NOx benefits of homogeneous charge compression ignition, as it increases the local combustion temperatures. To merge the advantages of the homogeneous charge compression ignition and the spark-assisted compression ignition combustion processes, a field-programmable gate array for detailed simulation of the physical gas exchange is combined with a rapid spark system. The low latency and computational speed of the field-programmable gate array allows the simulation process to be implemented in real time. When combined with the rapid reaction time of the high-frequency current-based rapid ignition system, a feedforward controller based on the cylinder pressure or heat release is realized. The developed model-based controller determines if a spark is required to assist the homogeneous charge compression ignition combustion process. The use of the field-programmable gate array and rapid ignition system allows for the calculation of combustion properties and controller output within 0.1 CA. This article presents the development and experimental validation of the developed controller on a single-cylinder research engine. The combustion stability has been significantly improved as reflected in an improved standard deviation of the indicated mean effective pressure and a reduction of the combustion phasing variations. Furthermore, compared to a traditional homogeneous charge compression ignition system, the hydrocarbon emissions can be reduced, while maintaining low NOx emissions.
BibTeX: @article{IJER_Rapid_Ign_DG_2020, author = {David Gordon and Christian Wouters and Shota Kinoshita and Maximilian Wick and Bastian Lehrheuer and Jakob Andert and Stefan Pischinger and Charles R Koch}, title = {Homogeneous charge compression ignition combustion stability improvement using a rapid ignition system}, journal = {International Journal of Engine Research}, year = {2020}, volume = {21}, number = {10}, pages = {1846-1856}, url = {/ ckoch/open_access/IJER_Rapid_Ign_DG_2020.pdf}, doi = {https://doi.org/10.1177/1468087420917769} }
Zhang, L., Xie, J., Koch, C.R. and Dubljevic, S.	Model Predictive Control of Jacket Tubular Reactor with Reversible Exothermic Reaction [BibTeX]	2020	Industrial & Engineering Chemistry Research Vol. 59(42), pp. 18921-18936	article	URL
BibTeX: @article{LZ_IECR2020, author = {Lu Zhang and Junyao Xie and Charles Robert Koch and Stevan Dubljevic}, title = {Model Predictive Control of Jacket Tubular Reactor with Reversible Exothermic Reaction}, journal = {Industrial & Engineering Chemistry Research}, publisher = {American Chemical Society}, year = {2020}, volume = {59}, number = {42}, pages = {18921--18936}, url = {/ ckoch/open_access/LZ_IECR2020.pdf} }
Aliramezani, M., Norouzi, A. and Koch, C.R.	A grey-box machine learning-based model of an electrochemical gas sensor [BibTeX]	2020	Sensors and Actuators B: Chemical Vol. 321, pp. 128414	article	DOI URL
BibTeX: @article{MA_SENAB2020, author = {Masoud Aliramezani and Armin Norouzi and Charles Robert Koch}, title = {A grey-box machine learning-based model of an electrochemical gas sensor}, journal = {Sensors and Actuators B: Chemical}, year = {2020}, volume = {321}, pages = {128414}, url = {/ ckoch/open_access/MA_SENAB2020.pdf}, doi = {https://doi.org/10.1016/j.snb.2020.128414} }
Gordon, D., Wouters, C., Wick, M., Lehrheuer, B., Andert, J., Koch, C.R. and Pischinger, S.	Development and experimental validation of a field programmable gate array--based in-cycle direct water injection control strategy for homogeneous charge compression ignition combustion stability [BibTeX]	2019	International Journal of of Engine Research Vol. 0(0), pp. 1-12	article	DOI URL
BibTeX: @article{Gorden2019, author = {David Gordon and Christian Wouters and Maximilian Wick and Bastian Lehrheuer and Jakob Andert and Charles R Koch and Stefan Pischinger}, title = {Development and experimental validation of a field programmable gate array--based in-cycle direct water injection control strategy for homogeneous charge compression ignition combustion stability}, journal = {International Journal of of Engine Research}, year = {2019}, volume = {0}, number = {0}, pages = {1-12}, url = {/ ckoch/open_access/Gorden2019.pdf}, doi = {https://doi.org/10.1177/1468087419841744} }
Aliramezani, M., Koch, C.R. and Patrick, R.	A Variable-Potential Amperometric Hydrocarbon Sensor [Abstract] [BibTeX]	2019	IEEE Sensors Journal Vol. 19(24), pp. 12003-12010	article	DOI URL
Abstract: Using the understanding of an inexpensive production NOx sensor, the operating parameters are changed to enable hydrocarbon measurement using the same sensor. A limiting-current-type amperometric hydrocarbon sensor for rich conditions (in the absence of O2) is developed in this work. To do this, an inexpensive three-chamber amperometric sensor with three separate electrochemical cells is parameterized to measure propane concentration. The sensor is tested using a controlled sensor test rig at different propane concentrations. The inputs to the sensor electrochemical cells have been modified to determine the best HC measurement parameters (HCMPs) for measuring propane at different concentrations. First, the transient performance and stability of the sensor are optimized by changing the sensor temperature, the reference cell potential, and the stabilizing cell potential at a high propane concentration (5000 ppm - balanced with nitrogen). Over the range tested, the sensor has the longest stable output duration at the temperature of 1009 K, the reference cell potential of 0.67 V and the stabilizing cell potential of 0.45 V. Using these sensor inputs for sensor temperature, reference cell potential and stabilizing cell potential, the sensor steady state behavior is studied to find the diffusion-rate-determined operating region. The sensor is shown to have a linear sensitivity to propane concentration from 0 to 3200 ppm. Finally, the sensor response time to different step changes from 0 up to 5000 ppm propane concentration are studied. It is shown that propane stepsize does not have a significant effect on the sensor response time. Consequently, using the working principles of an existing production amperometric NOx sensor and changing the sensor operating parameters, an amperometric hydrocarbon sensor that works in diffusion rate determining operating region is developed.
BibTeX: @article{IEEE_sens_MA_2019, author = {Masoud Aliramezani and Charles Robert Koch and Ron Patrick}, title = {A Variable-Potential Amperometric Hydrocarbon Sensor}, journal = {IEEE Sensors Journal}, year = {2019}, volume = {19}, number = {24}, pages = {12003-12010}, url = {/ ckoch/open_access/IEEE_sens_MA_2019.pdf}, doi = {https://doi.org/10.1109/JSEN.2019.2938920} }
Izadi, M., Koch, C.R. and Dubljevic, S.S.	Model Predictive Control of Ginzburg-Landau Equation [Abstract] [BibTeX]	2019	Active Flow and Combustion Control 2018, pp. 75-90	inproceedings
Abstract: This work explores the realization of model predictive control (MPC) design to an important problem of vortex shedding phenomena in fluid flow. The setting of vortex shedding phenomena is represented by a Ginzburg-Landau (GL) equation model and leads to the mathematical representation given by complex infinite dimensional parabolic PDEs. The underlying GL model is considered within the boundary control setting and the modal representation is considered to obtain discrete infinite dimensional system representation which is used in the model predictive control design. The model predictive control design accounts for optimal stabilization of the unstable GL equation model, and for the naturally present input constraints and/or state constraints. The feasibility of the optimization based model predictive controller is ensured through a large enough prediction horizon. The subsequent feasibility is ensured in a disturbance free model setting. The applicability of an easily realizable discrete controller design is demonstrated using simulation with known parameters from the literature.
BibTeX: @inproceedings{Izadi2019, author = {Izadi, Mojtaba and Koch, Charles R. and Dubljevic, Stevan S.}, title = {Model Predictive Control of Ginzburg-Landau Equation}, booktitle = {Active Flow and Combustion Control 2018}, publisher = {Springer International Publishing}, year = {2019}, pages = {75--90} }
Gibeau, B., Koch, C.R. and Ghaemi, S.	Active control of vortex shedding from a blunt trailing edge using oscillating piezoelectric flaps [BibTeX]	2019	Phys. Rev. Fluids Vol. 4, pp. 054704	article	DOI URL
BibTeX: @article{PRFL_2018, author = {Bradley Gibeau and Charles Robert Koch and Sina Ghaemi}, title = {Active control of vortex shedding from a blunt trailing edge using oscillating piezoelectric flaps}, journal = {Phys. Rev. Fluids}, publisher = {American Physical Society}, year = {2019}, volume = {4}, pages = {054704}, url = {/ ckoch/open_access/PRFL_2018.pdf}, doi = {https://doi.org/10.1103/PhysRevFluids.4.054704} }
Aliramezani, M., Koch, C.R., Secanell, M., Hayes, R.E. and Patrick, R.	An electrochemical model of an amperometric NOx sensor [Abstract] [BibTeX]	2019	Sensors and Actuators B: Chemical Vol. 290, pp. 302-311	article	DOI
Abstract: To help design future amperometric NOx sensors, a physics-based sensor model that includes diffusion and electrochemical submodels is developed. It is shown that NO is partly reduced in the O2 sensing chamber which affects NO concentration in the O2 sensing and in the NOx sensing chamber. Therefore, the electrochemical model is developed to simulate partial reduction of NOx on the O2 sensing electrode and reduction of NOx on the NOx sensing electrode. A transport model that simulates diffusion of the gas species through the sensor diffusion barriers and sensor chambers is coupled to the electrochemical submodels. A fully controlled sensor test-rig that provides controlled gas mixtures is employed to carry out experiments to estimate model parameters. Then, the sensor is installed on the exhaust system of a medium duty Diesel engine and then on a port injection spark ignition engine. Experiments at different engine operating conditions with different NOx concentrations from 0 to 2820 ppm have been performed to validate the model accuracy at different operating conditions. Through the validation process, the NOx sensing cell voltage is changed experimentally at different NOx concentrations to evaluate the model accuracy at different cell voltages. The model results closely match the experiments with the maximum 12% error for the NOx sensing pumping current.
BibTeX: @article{SAB_MA_2019, author = {Masoud Aliramezani and Charles Robert Koch and Marc Secanell and Robert E. Hayes and Ron Patrick}, title = {An electrochemical model of an amperometric NOx sensor}, journal = {Sensors and Actuators B: Chemical}, year = {2019}, volume = {290}, pages = {302-311}, doi = {https://doi.org/10.1016/j.snb.2019.03.135} }
Wick, M., Bedei, J., Andert, J., Gordon, D., Koch, C.R., Wouters, C., Lehrheuer, B. and Nuss, E.	In-cycle control for stabilization of homogeneous charge compression ignition combustion using direct water injection [BibTeX]	2019	Applied Energy Vol. 240, pp. 0306-2619	article	DOI
BibTeX: @article{Wick2018, author = {Maximilian Wick and Julian Bedei and Jakob Andert and David Gordon and Charles R Koch and Christian Wouters and Bastian Lehrheuer and Eugen Nuss}, title = {In-cycle control for stabilization of homogeneous charge compression ignition combustion using direct water injection}, journal = {Applied Energy}, year = {2019}, volume = {240}, pages = {0306-2619}, doi = {https://doi.org/10.1016/j.apenergy.2019.01.086} }
Aliramezani, M., Koch, C.R. and Patrick, R.	Phenomenological model of a solid electrolyte NOx and O2 sensor using temperature perturbation for on-board diagnostics [Abstract] [BibTeX]	2018	Solid State Ionics Vol. 321, pp. 62 - 68	article	DOI URL
Abstract: Abstract Amperometric NOx\ sensors are increasingly used in automotive industry to meet the stringent emission measurement regulations. These sensors measure O2 and NOx concentration using two different sensing cells. In this work, a physics-based model was developed and then employed to predict the sensor output for oxygen as a function of sensor temperature and oxygen concentration. A temperature perturbation method was also developed based on the model to calibrate the sensor output with respect to oxygen concentration. The model accurately matched the experimental results for steady state and transient conditions. A two step sensor diagnostics procedure based on the sensor temperature perturbation method was then proposed. The first diagnostics step evaluates the sensor output to check if it is within the acceptable range. The second diagnosis step checks the plausibility of the sensor output based on the physics based model and temperature perturbation. A self-calibration procedure was also implemented inside the diagnostics procedure using temperature perturbation at engine-off. This self-recalibration only requires an external relative humidity measurement.
BibTeX: @article{Aliramezani201862, author = {Masoud Aliramezani and Charles Robert Koch and Ron Patrick}, title = {Phenomenological model of a solid electrolyte NOx and O2 sensor using temperature perturbation for on-board diagnostics}, journal = {Solid State Ionics}, year = {2018}, volume = {321}, pages = {62 - 68}, url = {/ ckoch/open_access/Aliramezani201862.pdf}, doi = {https://doi.org/10.1016/j.ssi.2018.04.004} }
Gibeau, B., Koch, C.R. and Ghaemi, S.	Secondary instabilities in the wake of an elongated two-dimensional body with a blunt trailing edge [BibTeX]	2018	Journal of Fluid Mechanics Vol. 846, pp. 578-604	article	DOI URL
BibTeX: @article{gibeau_koch_ghaemi_2018, author = {Gibeau, B and Koch, C. R. and Ghaemi, S.}, title = {Secondary instabilities in the wake of an elongated two-dimensional body with a blunt trailing edge}, journal = {Journal of Fluid Mechanics}, publisher = {Cambridge University Press}, year = {2018}, volume = {846}, pages = {578-604}, url = {/ ckoch/open_access/gibeau_koch_ghaemi_2018.pdf}, doi = {https://doi.org/10.1017/jfm.2018.285} }
Nazaripoor, H., Koch, C.R. and Sadrzadeh, M.	Ordered high aspect ratio nanopillar formation based on electrical and thermal reflowing of prepatterned thin films [BibTeX]	2018	Journal of Colloid and Interface Science Vol. 530, pp. 312-320	article	DOI URL
BibTeX: @article{Hadi_2018_JCIS, author = {Nazaripoor, Hadi and Koch, Charles R. and Sadrzadeh, Mohtada}, title = {Ordered high aspect ratio nanopillar formation based on electrical and thermal reflowing of prepatterned thin films}, journal = {Journal of Colloid and Interface Science}, publisher = {The Royal Society of Chemistry}, year = {2018}, volume = {530}, pages = {312-320}, url = {/ ckoch/open_access/Hadi_2018_JCIS.pdf}, doi = {https://doi.org/10.1016/j.jcis.2018.06.080} }
Nazaripoor, H., Flynn, M.R., Koch, C.R. and Sadrzadeh, M.	Thermally induced interfacial instabilities and pattern formation in confined liquid nanofilms [BibTeX]	2018	Physcical Review E Vol. 98, pp. 043106	article	URL
BibTeX: @article{Hadi_2018_PYRE, author = {Nazaripoor, Hadi and Flynn, M. R. and Koch, Charles R. and Sadrzadeh, Mohtada}, title = {Thermally induced interfacial instabilities and pattern formation in confined liquid nanofilms}, journal = {Physcical Review E}, year = {2018}, volume = {98}, pages = {043106}, url = {/ ckoch/open_access/Hadi_2018_PYRE.pdf} }
Aliramezani, M., Koch, C.R., Hayes, R. and Patrick, R.	Amperometric solid electrolyte NOx sensors - The effect of temperature and diffusion mechanisms [Abstract] [BibTeX]	2017	Solid State Ionics Vol. 313, pp. 7 - 13	article	DOI
Abstract: Abstract The diffusion mechanism of a zirconia-based amperometric NOx\ sensor was examined by studying the effect of sensor temperature on sensor output. The structure and the exact dimensions of a production automotive NOx\ sensor were first measured using x-ray tomography. A simplified heat transfer model was employed and validated to estimate the sensor temperature based on sensor heater power. The sensor temperature was then changed by changing the sensor heater power to evaluate different diffusion mechanisms. Normal multi-component diffusion mechanism, Knudsen diffusion mechanism and a combination of both mechanisms (Normal and Knudsen diffusion) were evaluated at different sensor temperatures. The normal multi-component diffusion mechanism was experimentally found to be the dominant diffusion mechanism that affects the diffusive flow through the sensor diffusion barriers. A sensor model was developed based on this dominant diffusion mechanism to predict NOx\ concentration. Finally, the sensor model output for NOx\ was validated with the experiments at different Diesel engine operating conditions with different species concentrations.
BibTeX: @article{Aliramezani_SSI_2017, author = {Masoud Aliramezani and Charles Robert Koch and Robert Hayes and Ronald Patrick}, title = {Amperometric solid electrolyte NOx sensors - The effect of temperature and diffusion mechanisms}, journal = {Solid State Ionics}, year = {2017}, volume = {313}, pages = {7 - 13}, doi = {https://doi.org/10.1016/j.ssi.2017.10.024} }
Graves, B.M., Koch, C.R. and Olfert, J.S.	Morphology and volatility of particulate matter emitted from a gasoline direct injection engine fuelled on gasoline and ethanol blends [Abstract] [BibTeX]	2017	Journal of Aerosol Science Vol. 105, pp. 166 - 178	article	DOI URL
Abstract: Abstract The particulate matter emitted from a turbocharged, four cylinder, wall-guided, gasoline direct injection (GDI) engine fuelled with gasoline and ethanol blends was investigated, and characterized by size distribution, mass-mobility exponent, effective density, and volatility using tandem measurements from differential mobility analysers (DMA) and a centrifugal particle mass analyser (CPMA). Three engine loads were tested at 2250 RPM\ (4%, 13%, and 26% of maximum load) in addition to an idle condition while the engine was fuelled using gasoline mixed with ethanol fractions of 0% (E0), 10% (E10), and 50% (E50) by volume. An increase in engine load increased particle number concentration, although idle produced approximately as many particles as at 13% load. In the majority of cases, an increase in ethanol fraction decreased number concentration. The fraction of the number of particles comprised of only volatile material to total number of particles (number volatile fraction) both overall and as a function of particle mobility-equivalent diameter was under 10 percent at all engine conditions and fuels (measured after a three-way catalytic converter). The size-segregated ratio of the mass of internally mixed volatile material to total particle mass was similarly low. Volatility measurements were conducted using a thermodenuder set to 300C. Mass-mobility exponent was seen to range between 2.28 and 2.60. Effective density increased with load, and in general mass-mobility exponent increased as well. Effective density decreased with an increase in ethanol fraction and a slight decrease in mass-mobility exponent was also observed for all conditions except idle. No significant changes in effective density, particle size, or number concentration were observed in GDI\ soot after denuding particle samples.
BibTeX: @article{Graves_JAS_2017, author = {Brian Mackenzie Graves and Charles Robert Koch and Jason Scott Olfert}, title = {Morphology and volatility of particulate matter emitted from a gasoline direct injection engine fuelled on gasoline and ethanol blends}, journal = {Journal of Aerosol Science}, year = {2017}, volume = {105}, pages = {166 - 178}, url = {/ ckoch/open_access/Graves_JAS_2017.pdf}, doi = {https://doi.org/10.1016/j.jaerosci.2016.10.013} }
Nazaripoor, H., Koch, C.R. and Sadrzadeh	Enhanced electrically induced micro-patterning of confined thin liquid films: Thermocapillary role and its limitations [BibTeX]	2017	Industrial & Engineering Chemistry Research Vol. 56(38), pp. 10678-10688	article	DOI URL
BibTeX: @article{Hadi_lndCR_2017, author = {Nazaripoor, Hadi and Koch, Charles R. and Sadrzadeh}, title = {Enhanced electrically induced micro-patterning of confined thin liquid films: Thermocapillary role and its limitations}, journal = {Industrial & Engineering Chemistry Research}, year = {2017}, volume = {56}, number = {38}, pages = {10678-10688}, url = {/ ckoch/open_access/Hadi_lndCR_2017.pdf}, doi = {https://doi.org/10.1021/acs.iecr.7b02814} }
Sabbagh, R., Lipsett, M.G., Koch, C.R. and Nobes, D.S.	An experimental investigation on hydrocyclone underflow pumping [BibTeX]	2017	Powder Technology Vol. 305, pp. 99-108	article	DOI URL
BibTeX: @article{Sabbagh_PowT_2016, author = {R. Sabbagh and M. G. Lipsett and C. R. Koch and D. S. Nobes}, title = {An experimental investigation on hydrocyclone underflow pumping}, journal = {Powder Technology}, publisher = {Elsevier B.V.}, year = {2017}, volume = {305}, pages = {99--108}, url = {/ ckoch/open_access/Sabbagh_PowT_2016.pdf}, doi = {https://doi.org/10.1016/j.powtec.2016.09.045} }
Sabbagh, R., Koch, C.R., Lipsett, M.G. and Nobes, D.S.	Hydrocyclone equivalent settling area factor at higher concentrations and developing a performance chart [Abstract] [BibTeX]	2017	Seperation and Purification Technology. Vol. 182, pp. 171-184	article	DOI
Abstract: The equivalent settling area factor allows for comparison amongst different centrifuge separators. For hydrocyclones, the so far developed factor does not consider the effect of concentration of solid particles c in the feed stream, because particle interactions at high concentrations cause hindered settling and reduce hydrocyclone performance. The focus of this paper is a modification of this factor to allow prediction of the influence of higher particle concentration in the feed stream. In particular, the equivalent areafactor is modified at high particle concentration by applying different forms of hindered settling concentration functions and using data obtained from experiment or from existing empirical correlations. This results in a set of modified models that are evaluated using statistical techniques. Through statistical analysis, the function f(c)=c^(0.0488) * exp(-0445c) is selected to modify the equivalent settling area for hydrocyclones. A performance chart is developed for hydrocyclones by undertaking the modified equivalent area model that can be used in hydrocyclone design applications. The developed performance chart is validated and is shown to be capable of predicting the hydrocyclone performance over a wide range of hydrocyclone flow rates and separation cut sizes. This chart is compared with a performance chart available in the literature and the chart in the literature is shown to over-predict the hydrocyclone performance.
BibTeX: @article{Sabbagh_SPT_2015, author = {R. Sabbagh and C. R. Koch and M. G. Lipsett and D. S. Nobes}, title = {Hydrocyclone equivalent settling area factor at higher concentrations and developing a performance chart}, journal = {Seperation and Purification Technology.}, year = {2017}, volume = {182}, pages = {171-184}, doi = {https://doi.org/10.1016/j.seppur.2017.02.054} }
Shahidi, S., Koch, C.R., Bhattacharjee, S. and Sadrzadeh, M.	Dielectric behavior of oil-water emulsions during phase separation probed by electrochemical impedance spectroscopy [Abstract] [BibTeX]	2017	Sensors and Actuators B. Chemical Vol. 243, pp. 460-464	article	DOI URL
Abstract: Electrical impedance spectroscopy (EIS) is applied to studying the stability and phase behavior of oil-water emulsions. The method involves EIS on 500-micron-thick samples of emulsions in a parallel-plate capacitor test cell. The frequency response data is fitted to an equivalent circuit model to estimate the electrical impedance of the samples. The technique is used for investigating the capacitance and resistance of emulsions during phase separation. A theoretical explanation based on the capacitance of the emulsion layer is provided to understand the reason behind the variation in the dielectric constant of the samples during phase separation. It is observed that creaming and sedimentation can be captured as a permittivity decay, so permittivity measurements can be utilized to sense phase separation. The technique is shown to be more effective for oil-in-water emulsions rather than water-in-oil ones.
BibTeX: @article{Shahidi_SNB_2017, author = {Shahidi, S. and Koch, Charles R. and Bhattacharjee, Subir and Mohtada Sadrzadeh}, title = {Dielectric behavior of oil-water emulsions during phase separation probed by electrochemical impedance spectroscopy}, journal = {Sensors and Actuators B. Chemical}, year = {2017}, volume = {243}, pages = {460-464}, url = {/ ckoch/open_access/Shahidi_SNB_2017.pdf}, doi = {https://doi.org/10.1016/j.snb.2016.11.072} }
Nazaripoor, H., Koch, C.R., Sadrzadeh, M. and Bhattacharjee, S.	Compact micro/nano electrohydrodynamic patterning: using a thin conductive film and a patterned template [Abstract] [BibTeX]	2016	Soft Matter Vol. 12(4), pp. 1074-1084	article	DOI URL
Abstract: The influence of electrostatic heterogeneity on the electric-field-induced destabilization of thin ionic liquid (IL) films is investigated to control spatial ordering and to reduce the lateral dimension of structures forming on the films. Commonly used perfect dielectric (PD) films are replaced with ionic conductive films to reduce the lateral length scales to a sub-micron level in the EHD pattering process. The 3-D spatiotemporal evolution of a thin IL film interface under homogenous and heterogeneous electric fields is numerically simulated. Finite differences in the spatial directions using an adaptive time step ODE solver are used to solve the 2-D nonlinear thin film equation. The validity of our simulation technique is determined from close agreement between the simulation results of a PD film and the experimental results in the literature. Replacing the flat electrode with the patterned one is found to result in more compact and well-ordered structures particularly when an electrode with square block protrusions is used. This is attributed to better control of the characteristic spatial lengths by applying a heterogeneous electric field by patterned electrodes. The structure size in PD films is reduced by a factor of 4 when they are replaced with IL films, which results in nano-sized features with well-ordered patterns over the domain.
BibTeX: @article{c5sm02258d, author = {Nazaripoor, Hadi and Koch, Charles R. and Sadrzadeh, Mohtada and Bhattacharjee, Subir}, title = {Compact micro/nano electrohydrodynamic patterning: using a thin conductive film and a patterned template}, journal = {Soft Matter}, publisher = {The Royal Society of Chemistry}, year = {2016}, volume = {12}, number = {4}, pages = {1074-1084}, url = {/ ckoch/open_access/c5sm02258d.pdf}, doi = {https://doi.org/10.1039/c5sm02258d} }
Khaligh, S.P., Fahimi, F. and Koch, C.R.	A System Identification Strategy for Nonlinear Model of Small-Scale Unmanned Helicopters [Abstract] [BibTeX]	2016	Journal of the American Helicopter Society Vol. 61, pp. 1-13	article
Abstract: A system identification strategy to identify the parameters of a small-scale unmanned helicopter's nonlinear physics-based model suitable for nonlinear control design applications is described. A time-domain technique, which allows for the identification of a nonlinear model of the helicopter without linearizing the model, is used. A combination of ground and flight-test data is used to parameterize the model. The ground test data are used to identify the physical parameters of the main and tail rotors such as the lift and drag coefficients using an aerodynamic force measurement test bed. The unknown parameters of the rotor dynamics and empennage drag are identified using flight-test data and applying a nonlinear leastsquares method. A 10-degree-of-freedom nonlinear physics-based model including rotor and stabilizer bar dynamics is developed and validated using flight-test data. The results indicate that the overall response of the identified nonlinear model of the helicopter matches the real flight data.
BibTeX: @article{KhalighJAHS2016, author = {Sepehr P Khaligh and Farbod Fahimi and Charles Robert Koch}, title = {A System Identification Strategy for Nonlinear Model of Small-Scale Unmanned Helicopters}, journal = {Journal of the American Helicopter Society}, publisher = {AHS International}, year = {2016}, volume = {61}, pages = {1-13} }
Nazaripoor, H., Koch, C.R., Sadrzadeh, M. and Bhattacharjee, S.	Thermo-Electrohydrodynamic Patterning in Nanofilms [Abstract] [BibTeX]	2016	Langmuir Vol. 32(23), pp. 5776-5786	article	DOI
Abstract: To improve the electrically assisted patterning process and create smaller sized features with the higher active surface area, the combined thermocapillary-electrohydrodynamic (TC-EHD) instability of liquid nanofilms is considered. First, the 3-D thin film equation is re-derived for nonisothermal films and then the influential factors on the dynamics and stability of thin liquid film are found using linear stability (LS) analysis. Non-linear studies are also conducted to investigate the long-time evolution of the interface using an in-house developed Fortran code employing high order finite difference and adaptive time step solver for the spatial and time derivatives. The number density of pillars (columnar raised structure) formed in 1mm2 area is significantly increased compared to the EHD base-case and nano-sized pillars are created due to the thermocapillary effects. Relative interface area increases of up to 18% due to this pattern miniaturization are realized. It is also found that increase in the thermal conductivity ratio of layers changes the mechanism of pattern formation resulting in nonuniform and randomly distributed micro pillars being generated.
BibTeX: @article{Nazaripoor2016lang, author = {Nazaripoor, Hadi and Koch, Charles R. and Sadrzadeh, Mohtada and Bhattacharjee, Subir}, title = {Thermo-Electrohydrodynamic Patterning in Nanofilms}, journal = {Langmuir}, year = {2016}, volume = {32}, number = {23}, pages = {5776-5786}, doi = {https://doi.org/10.1021/acs.langmuir.6b01810} }
Sabbagh, R., Lipsett, M.G., Koch, C.R. and Nobes, D.S.	Predicting Equivalent Settling Area Factor in Hydrocyclones; A Method for Determining Tangential Velocity Profile [BibTeX]	2016	Separation and Purification Technology Vol. 163, pp. 341-351	article	DOI URL
BibTeX: @article{Sabbagh_SEPPUR-2016, author = {R. Sabbagh and M. G. Lipsett and C. R. Koch and D. S. Nobes}, title = {Predicting Equivalent Settling Area Factor in Hydrocyclones; A Method for Determining Tangential Velocity Profile}, journal = {Separation and Purification Technology}, publisher = {Elsevier B.V.}, year = {2016}, volume = {163}, pages = {341--351}, url = {/ ckoch/open_access/Sabbagh_SEPPUR-2016.pdf}, doi = {https://doi.org/10.1016/j.seppur.2016.03.009} }
Babazadeh, H., Nobes, D.S. and Koch, C.R.	Active and passive flow control on a precessing jet [Abstract] [BibTeX]	2015	Experiments in Fluids Vol. 56(1)	article	DOI URL
Abstract: A precessing jet nozzle with water as the working fluid is investigated under passive and active flow control. Passive control is applied by modifying the geometry of the precessing jet either by adding a center body near the chamber exit or varying the chamber length. Active control of the flow is achieved using twelve micro-jets around the nozzle inlet. The flow behavior under control is studied using pressure measurement at the chamber exit plane to monitor jet precession. The pressure data was analyzed using a phase plane representation which determines the motion of the jets high velocity region in the chamber exit plane. The standard deviation of the phase of the triggered pressure data is used for stability analysis. This analysis results in a phase diagram in terms of Reynolds number and actuation frequency. Active control can be utilized over a range of actuation Strouhal numbers to control precession direction and stability which can be further enhanced with passive control mechanisms. However, the flow follows the actuation with lowest variation when the active actuation matches with the natural Strouhal number (0.002 < St < 0.006) of the nozzle-jet flow.
BibTeX: @article{babazadeh_ctrl_2015, author = {Babazadeh, Hamed and Nobes, David S. and Koch, Charles Robert}, title = {Active and passive flow control on a precessing jet}, journal = {Experiments in Fluids}, publisher = {Springer Berlin Heidelberg}, year = {2015}, volume = {56}, number = {1}, url = {/ ckoch/open_access/babazadeh_ctrl_2015.pdf}, doi = {https://doi.org/10.1007/s00348-014-1873-7} }
Nazaripoor, H., Sadrzadeh, M., Koch, C.R. and Bhattacharjee, S.	Electrohydrodynamic patterning of ultra-thin ionic liquid films [Abstract] [BibTeX]	2015	Soft Matter Vol. 11, pp. 2193-2202	article	DOI URL
Abstract: In the electrohydrodynamic (EHD) patterning process, electrostatic destabilization of the air-polymer interface results in the micro and nano-size patterns in the form of raised formations called pillars. The polymer film in this process is typically assumed to behave like a perfect dielectric (PD) or leaky dielectric (LD). In this study, an electrostatic model is developed for the patterning of an ionic liquid (IL) polymer film. The IL model has a finite diffuse electric layer which overcomes the shortcoming of assuming infinitesimally large and small electric diffuse layer inherent in the PD and LD models respectively. The process of pattern formation is then numerically simulated by solving the weakly nonlinear thin film equation using finite difference with pseudo staggered discretization and an adaptive time step. Initially, the pillar formation process in IL films is observed to be the same as PD films. Pillars initially form at random locations and their cross section increases with time as the contact line expands on the top electrode. After the initial growth, for the same applied voltage and initial films thickness, the number of pillars on IL films is found to be significantly higher than in PD films. The total number of pillars formed in 1 [small mu ]m2 area of the domain in IL film is almost 5 times more than similar PD film for the conditions simulated. In addition, the pillar structure size in IL films is observed to be more sensitive to initial film thickness compared to PD films.
BibTeX: @article{C4SM02477J, author = {Nazaripoor, Hadi and Sadrzadeh, Mohtada and Koch, Charles R. and Bhattacharjee, Subir}, title = {Electrohydrodynamic patterning of ultra-thin ionic liquid films}, journal = {Soft Matter}, publisher = {The Royal Society of Chemistry}, year = {2015}, volume = {11}, pages = {2193-2202}, url = {/ ckoch/open_access/C4SM02477J.pdf}, doi = {https://doi.org/10.1039/C4SM02477J} }
Khaligh, S.P., Fahimi, F. and Koch, C.R.	A Fast Inverse Kinematic Solution for the Nonlinear Actuating Mechanisms of a Small-Scale Helicopter [Abstract] [BibTeX]	2015	Multibody System Dynamics Vol. 35, pp. 257-275	article	DOI URL
Abstract: An inverse kinematic solution for the main rotor actuating mechanism of a small-scale helicopter that includes a 4-point swashplate system and a Bell-Hiller mixer and the tail rotor actuating mechanism are derived using an approach that is suitable for real-time control applications. A closed-form solution is obtained for the inverse kinematics of the swashplate mechanism and for the forward and inverse kinematics of the tail rotor. Then, a computationally efficient solution is obtained for the inverse kinematics of the Bell-Hiller mixer by converting the nonlinear kinematic equations into a generalized eigenvalue problem. The nonlinear kinematic model is compared to a linear approximation and is validated using experiments.
BibTeX: @article{JMBD2015, author = {Sepehr P Khaligh and Farbod Fahimi and Charles Robert Koch}, title = {A Fast Inverse Kinematic Solution for the Nonlinear Actuating Mechanisms of a Small-Scale Helicopter}, journal = {Multibody System Dynamics}, publisher = {Springer Netherlands}, year = {2015}, volume = {35}, pages = {257-275}, note = {Journal of Multibody System Dynamics}, url = {/ ckoch/open_access/JMBD2015.pdf}, doi = {DOI 10.1007/s11044-015-9452-0} }
Sabbagh, R., Lipsett, M.G., Koch, C.R. and Nobes, D.S.	Hydrocyclone Performance and Energy Consumption Prediction: A Comparison with Other Centrifugal Separators [Abstract] [BibTeX]	2015	Separation Science and Technology Vol. 50(6), pp. 788-801	article	DOI URL
Abstract: Centrifugal separators have many applications in the separation industry. Comprehensive information based on performance and energy consumption for a detailed comparison between different types of centrifugal separators is essential to allow design optimization and is the focus of this work. A framework for comparing performance with an updated performance chart for four types of centrifugal separators and a comparison with a continuous gravity settling tank is described. A model and chart for performance and energy consumption, which makes it possible to compare different separators, is a key result of this work which extends current available handbooks and guidelines.
BibTeX: @article{Sabbagh_SST_2015, author = {R. Sabbagh and M. G. Lipsett and C. R. Koch and D. S. Nobes}, title = {Hydrocyclone Performance and Energy Consumption Prediction: A Comparison with Other Centrifugal Separators}, journal = {Separation Science and Technology}, publisher = {Taylor & Francis}, year = {2015}, volume = {50}, number = {6}, pages = {788-801}, url = {/ ckoch/open_access/Sabbagh_SST_2015.pdf}, doi = {https://doi.org/10.1080/01496395.2014.978463} }
Bidarvatan, M., Shahbakhti, M., Jazayeri, S. and Koch, C.	Cycle-to-cycle modeling and sliding mode control of blended-fuel HCCI engine [Abstract] [BibTeX]	2014	Control Engineering Practice Vol. 24(0), pp. 79 - 91	article	DOI URL
Abstract: Fast and robust control of combustion phasing is an important challenge for real-time model-based control of Homogenous Charge Compression Ignition (HCCI). In this paper a new discrete Control Oriented Model (COM) for predicting HCCI\ combustion phasing on a cycle-to-cycle basis is outlined and validated against experimental data from a single cylinder Ricardo engine. The COM\ has sufficient accuracy for real-time HCCI\ control and can be implemented in real-time. A Discrete Sliding Mode Controller (DSMC) coupled with a Kalman filter is designed to control combustion phasing by adjusting the ratio of two Primary Reference Fuels (PRFs). The results indicate the DSMC\ maintains the stability of the engine operation in a wide range of loads and speeds. The DSMC\ is compared with an empirical Proportional Integral (PI) controller. The results show the SMC\ outperforms a PI\ controller particularly in rejecting disturbances while maintaining HCCI\ combustion phasing in its desired range.
BibTeX: @article{Bidarvatan201479, author = {M. Bidarvatan and M. Shahbakhti and S.A. Jazayeri and C.R. Koch}, title = {Cycle-to-cycle modeling and sliding mode control of blended-fuel HCCI engine}, journal = {Control Engineering Practice}, year = {2014}, volume = {24}, number = {0}, pages = {79 - 91}, url = {/ ckoch/open_access/Bidarvatan201479.pdf}, doi = {https://doi.org/10.1016/j.conengprac.2013.11.008} }
Nazaripoor, H., Koch, C.R. and Bhattacharjee, S.	Electrical Perturbations of Ultrathin Bilayers: Role of Ionic Conductive Layer [Abstract] [BibTeX]	2014	Langmuir Vol. 30(49), pp. 14734-14744	article	DOI URL
Abstract: The effect of electrostatic force on the dynamics, morphological evolution, and drainage time of ultrathin liquid bilayers (<100 nm) are investigated for perfect dielectric-perfect dielectric (PD-PD) and ionic liquid-perfect dielectric (IL-PD) bilayers. The weakly nonlinear "thin film" equation is solved numerically to obtain spatiotemporal evolution of the liquid-liquid interface responses to transverse electric field. In order to predict the electrostatic component of conjoining/disjoining pressure acting on the interface for IL-PD bilayers, an analytical model is developed using the nonlinear Poisson-Boltzmann equation. It is found that IL-PD bilayers with electric permittivity ratio of layers (lower to top), epsilon_r, greater than one remain stable under an applied electric field. An extensive numerical study is carried out to generate a map based on epsilon_r and the initial mean thickness of the lower layer. This map is used to predict the formation of various structures on PD-PD bilayer interface and provides a baseline for unstable IL-PD bilayers. The use of an ionic liquid (IL) layer is found to reduce the size of the structures, but results in polydispersed and disordered pillars spread over the domain. The numerical predictions follow similar trend of experimental observation of Lau and Russel. (Lau, C. Y.; Russel, W. B. Fundamental Limitations on Ordered Electrohydrodynamic Patterning; Macromolecules 2011, 44, 7746-7751).
BibTeX: @article{Hadi_langmuir_2014, author = {Nazaripoor, Hadi and Koch, Charles R. and Bhattacharjee, Subir}, title = {Electrical Perturbations of Ultrathin Bilayers: Role of Ionic Conductive Layer}, journal = {Langmuir}, year = {2014}, volume = {30}, number = {49}, pages = {14734-14744}, note = {PMID: 25419880}, url = {/ ckoch/open_access/Hadi_langmuir_2014.pdf}, doi = {https://doi.org/10.1021/la503839x} }
Khaligh, S.P., Martinez, A., Fahimi, F. and Koch, C.R.	A HIL Testbed for Initial Controller Gain Tuning of a Small Unmanned Helicopter [Abstract] [BibTeX]	2014	Journal of Intelligent and Robotic Systems Vol. 73(1-4), pp. 289-308	article	DOI URL
Abstract: A Hardware-In-The-Loop (HIL) testbed design for small unmanned helicopters which provides a safe and low-cost platform to implement control algorithms and tune the control gains in a controlled environment is described. Specifically, it allows for testing the robustness of the controller to external disturbances by emulating the hover condition. A 6-DOF nonlinear mathematical model of the helicopter has been validated in real flight tests. This model is implemented in real-time to estimate the states of the helicopter which are then used to determine the actual control signals on the testbed. Experiments of the longitudinal, lateral and heading control tests are performed. To minimize the structural stress on the fuselage in case of controller failure or a subsystem malfunction, a damping system with a negligible parasitic effect on the dynamics of the helicopter around hover is incorporated. The HIL testbed is capable of testing the helicopter in hover, as well as on any smooth trajectories such as cruise flight, figure-8, etc. Experimentally tuning the controller on the HIL testbed is described and results in a controller which is robust to the external disturbances, and achieves an accuracy of approx 2.5 cm in the position control on the longitudinal and lateral trajectory tracking, and approx 5 deg accuracy around the yaw axis on the heading trajectory tracking.
BibTeX: @article{JINT2014, author = {Sepehr P Khaligh and Alejandro Martinez and Farbod Fahimi and Charles Robert Koch}, title = {A HIL Testbed for Initial Controller Gain Tuning of a Small Unmanned Helicopter}, journal = {Journal of Intelligent and Robotic Systems}, publisher = {Springer Netherlands}, year = {2014}, volume = {73}, number = {1-4}, pages = {289-308}, url = {/ ckoch/open_access/JINT2014.pdf}, doi = {https://doi.org/10.1007/s10846-013-9973-9} }
Setayeshgar, A., Lipsett, M.G., Koch, C.R. and Nobes, D.S.	Particle motion in a macroscale multiwavelength acoustic field [Abstract] [BibTeX]	2014	J. of Fluids Eng. Vol. 137(1), pp. 011302	article	DOI URL
Abstract: Particle motion due to ultrasonic acoustic radiation in a macroscale, multiwavelength acoustic chamber is investigated and compared with available theories. Primary acoustic radiation force theory has been extensively developed to predict single particle motion in a microscale, single-node acoustic chamber/channel. There is a need to investigate the applicability of this theory to macroscale, multiwavelength acoustic channels utilizing the acoustic radiation force for separating polydispersed particles. A particle-tracking velocimetry (PTV) approach for measuring individual particle motion is developed specifically to track particles as they densify at an acoustic pressure node. Particle motion is tracked over the lifetime of their motion to a node. Good agreement between the experimental and theoretical results is observed in the early stages of particle motion, where particles can be considered individually. Only in the densified region of the acoustic pressure node is there some mismatch with theory. The acoustic energy density of the acoustic chamber, a parameter intrinsically associated with the system by the theory, is also determined experimentally for different conditions and shown to be constant for all investigated system settings. The investigation demonstrates the capability of available theory in predicting the motion of polydispersed particles in macroscale, multiwavelength acoustic chambers.
BibTeX: @article{Setayesgar_asme_jfe_2014, author = {A. Setayeshgar and M. G. Lipsett and C. R. Koch and D. S. Nobes}, title = {Particle motion in a macroscale multiwavelength acoustic field}, journal = {J. of Fluids Eng.}, year = {2014}, volume = {137(1)}, pages = {011302}, note = {ASME Journal of Fluid Engineering}, url = {/ ckoch/open_access/Setayesgar_asme_jfe_2014.pdf}, doi = {https://doi.org/10.1115/1.4027777} }
Firoozabadi, M.D., Shahbakhti, M., Koch, C. and Jazayeri, S.	Thermodynamic control-oriented modeling of cycle-to-cycle exhaust gas temperature in an HCCI engine [Abstract] [BibTeX]	2013	Applied Energy Vol. 110(0), pp. 236 - 243	article	DOI URL
Abstract: Model-based control of Homogenous Charge Compression Ignition (HCCI) engine exhaust temperature is a viable solution to optimize efficiency of both engine and the exhaust aftertreatment system. Low exhaust temperature in HCCI\ engines can limit the abatement of hydrocarbon (HC) and carbon monoxide (CO) emissions in an exhaust aftertreatment system. A physical empirical model is described for control of exhaust temperature in HCCI\ engines. This model captures cycle-to-cycle dynamics affecting exhaust temperature and is based on thermodynamic relations and semi-empirical correlations. It incorporates intake and exhaust gas flow dynamics, residual gas mixing, and fuel burn rate and is validated with experimental data from a single cylinder engine at over 300 steady state and transient conditions. The validation results indicate a good agreement between predicted and measured exhaust gas temperature.
BibTeX: @article{Firoozabadi2013, author = {M. Dehghani Firoozabadi and M. Shahbakhti and C.R. Koch and S.A. Jazayeri}, title = {Thermodynamic control-oriented modeling of cycle-to-cycle exhaust gas temperature in an HCCI engine}, journal = {Applied Energy}, year = {2013}, volume = {110}, number = {0}, pages = {236 - 243}, url = {/ ckoch/open_access/Firoozabadi2013.pdf}, doi = {https://doi.org/10.1016/j.apenergy.2013.04.055} }
Ghazimirsaied, A. and Koch, C.R.	Controlling cyclic combustion timing variations using a symbol-statistics predictive approach in an HCCI engine [Abstract] [BibTeX]	2012	Applied Energy Vol. 92(0), pp. 133 - 146	article	DOI URL
Abstract: Cyclic variation of a Homogeneous Charge Compression Ignition (HCCI) engine near misfire is analyzed using chaotic theory methods and feedback control is used to stabilize high cyclic variations. Variation of consecutive cycles of sigma Pmax (the crank angle of maximum cylinder pressure over an engine cycle) for a Primary Reference Fuel engine is analyzed near misfire operation for five test points with similar conditions but different octane numbers. The return map of the time series of Pmax at each combustion cycle reveals the deterministic and random portions of the dynamics near misfire for this HCCI engine. A symbol-statistic approach is used to predict sigma Pmax one cycle-ahead. Predicted Sigma Pmax has similar dynamical behavior to the experimental measurements. Based on this cycle ahead prediction, and using fuel octane as the input, feedback control is used to stabilize the instability of sigma Pmax variations at this engine condition near misfire.
BibTeX: @article{Ghazi_a_ener_2011, author = {A. Ghazimirsaied and C. R. Koch}, title = {Controlling cyclic combustion timing variations using a symbol-statistics predictive approach in an HCCI engine}, journal = {Applied Energy}, year = {2012}, volume = {92}, number = {0}, pages = {133 - 146}, url = {/ ckoch/open_access/Ghazi_a_ener_2011.pdf}, doi = {https://doi.org/10.1016/j.apenergy.2011.09.018} }
Tsai, J., Koch, C.R. and Saif, M.	Cycle Adaptive Feedforward Approach Controllers for an Electromagnetic Valve Actuator [Abstract] [BibTeX]	2012	IEEE Transactions on Control Systems Technology Vol. 20(3), pp. 738-746	article	DOI URL
Abstract: An electromagnetic valvetrain for an internal combustion engine can improve the engine thermal efficiency but requires soft landing control to avoid excessive wear and acoustic noise. To simplify the soft landing problem, the valve control algorithm is partitioned into approach and landing controllers. The landing control is responsible for the last part of the 8 mm valve travel while the approach control is responsible for the rest. This paper focuses on the approach control. The goal of the approach control is to achieve an end state that sets constant initial conditions for the landing control. In addition to an identified system model, information based on previous valve events is utilized to take advantage of the repetitive nature of the valve opening/closing. Nonlinear iterative learning, terminal iterative learning, and Nelder Mead direct search algorithms are three cyclic adaptive feedforward approach controllers that are tested in simulation for automotive electromagnetic valves. These results are compared but the emphasis of this paper is on the Nelder Mead approach which works well both in simulation and experiment for disturbances that are slow compared to the valve travel time.
BibTeX: @article{Tsai_2012, author = {Jimmy Tsai and Charles Robert Koch and Mehrdad Saif}, title = {Cycle Adaptive Feedforward Approach Controllers for an Electromagnetic Valve Actuator}, journal = {IEEE Transactions on Control Systems Technology}, year = {2012}, volume = {20}, number = {3}, pages = {738-746}, url = {/ ckoch/open_access/Tsai_2012.pdf}, doi = {https://doi.org/10.1109/TCST.2011.2126575} }
Visakhamoorthy, S., Wen, J.Z., Sivoththaman, S. and Koch, C.R.	Numerical study of a butanol/heptane fuelled Homogeneous Charge Compression Ignition (HCCI) engine utilizing negative valve overlap [Abstract] [BibTeX]	2012	Applied Energy Vol. 94(0), pp. 166 - 173	article	DOI URL
Abstract: The calibration and comparison to experimental data of a parallel computing multi-zone combustion model for simulating operational characteristics of an n-butanol/n-heptane fuelled Homogeneous Charge Compression Ignition (HCCI) engine utilizing the negative valve overlap (NVO) technology is described. The model is calibrated using one experimentally characterized operating point and by taking into account the major features of NVO. The model simulations at other four operating points closely match the cylinder pressure trace and heat release rates of the experiments. The unburned hydrocarbon emission is predicted to a reasonable level while NOx (nitric oxide NO and nitrogen dioxide NO2) formation is under-predicted. The difficulty in mapping the NOx emission is attributed to the fact that the combustion model operates within the closed cycle period of engines and therefore does not capture the complexity of the charge stratification within the NVO equipped engine. Nevertheless, the trend of increasing NOx levels with the increasing fraction of butanol in the fuel mixture is captured and the model is able to predict the pressure, heat release rates, and combustion phasing for the three fuel blends tested.
BibTeX: @article{Wen_a_ener_2012, author = {Sona Visakhamoorthy and John Z. Wen and Siva Sivoththaman and Charles Robert Koch}, title = {Numerical study of a butanol/heptane fuelled Homogeneous Charge Compression Ignition (HCCI) engine utilizing negative valve overlap}, journal = {Applied Energy}, year = {2012}, volume = {94}, number = {0}, pages = {166 - 173}, url = {/ ckoch/open_access/Wen_a_ener_2012.pdf}, doi = {https://doi.org/10.1016/j.apenergy.2012.01.047} }
Atta, A., Crawford, D.G., Koch, C.R. and Bhattacharjee, S.	Influence of Electrostatic and Chemical Heterogeneity on the Electric-Field-Induced Destabilization of Thin Liquid Films [Abstract] [BibTeX]	2011	Langmuir Vol. 27(20), pp. 12472-12485	article	DOI URL
Abstract: A numerical model for thin liquid film (<100 nm) drainage in presence of an external electric field is developed. Long-wave theory is applied to approximate and simplify the governing equations. A spatiotemporal film morphology evolution equation thus obtained is then solved using a combination of finite difference to resolve the spatial dimensions and an adaptive time step ODE solver for the temporal propagation. The effect of fluid properties, namely viscosity and surface tension, on the film drainage time is observed for homogeneous electric field, which leads to random dewetting spots. Electrically heterogeneous fields, achieved by modeling electrodes with various periodic patterns, are explored to identify its effect on the drainage time and behavior. Finally, chemical heterogeneity of the substrate is coupled with the periodic electric heterogeneity to understand the implication of combined heterogeneity. It is observed that introduction of any heterogeneity results in faster drainage of the film when compared with the homogeneous field. In all cases, the thin film is drained leaving submicron scale structures at the interface. Well-controlled surface patterns are found on the application of periodic heterogeneity. This study effectively demonstrates the immense potential of electrically induced thin film drainage as a means for faster de-emulsification and for the creation of ordered submicron scale surface patterns on soft materials.
BibTeX: @article{Atta2011, author = {Atta, Arnab and Crawford, David G. and Koch, Charles R. and Bhattacharjee, Subir}, title = {Influence of Electrostatic and Chemical Heterogeneity on the Electric-Field-Induced Destabilization of Thin Liquid Films}, journal = {Langmuir}, year = {2011}, volume = {27}, number = {20}, pages = {12472-12485}, url = {/ ckoch/open_access/Atta2011.pdf}, doi = {https://doi.org/10.1021/la202759j} }
Babazadeh, H., Koch, C.R. and Nobes, D.S.	Investigation of micro-jet active control of a precessing Jet using PIV [Abstract] [BibTeX]	2011	Experiments in Fluids Vol. 51, pp. 1709-1719	article	DOI URL
Abstract: A circular jet entering an open-ended concentric circular chamber can rotate or precess about the jet axis for certain flow conditions and chamber configurations. Active flow control of a precessing jet provides the ability to influence the flow field inside the chamber and the resulting flow after the chamber exit. Twelve micro-jets surrounding the jet at the chamber inlet are used as actuation. At the chamber exit, four pressure probes and three-component velocity measurement using stereo particle image velocimetry (stereo-PIV) is used to monitor the flow. A phase plane method using signals from the pressure sensors is developed to monitor the location of the jet high-velocity region in real-time. Phase-locked stereo-PIV, triggered by the micro-jet actuation signal, is used to investigate the flow field and validate the pressure phase plane results. The effectiveness of the micro-jet actuation and the validation of the pressure phase plane measurements demonstrate actuation and the sensing needed for future closed-loop control of the precessing jet.
BibTeX: @article{babazadeh_piv_2011, author = {H. Babazadeh and C. R. Koch and D. S. Nobes}, title = {Investigation of micro-jet active control of a precessing Jet using PIV}, journal = {Experiments in Fluids}, publisher = {Springer Berlin / Heidelberg}, year = {2011}, volume = {51}, pages = {1709-1719}, url = {/ ckoch/open_access/babazadeh_piv_2011.pdf}, doi = {https://doi.org/10.1007/s00348-011-1193-0} }
M.Shahbakhti and Koch, C.R.	Physics Based Control Oriented Model for HCCI Combustion Timing [Abstract] [BibTeX]	2010	Journal of Dynamic Systems, Measurement, and Control Vol. 132(2), pp. 021010	article	DOI URL
Abstract: Incorporating Homogeneous Charge Compression Ignition (HCCI) into combustion engines for better fuel economy and lower emission requires understanding the dynamics influencing the combustion timing in HCCI engines. A control oriented model to dynamically predict cycle-to-cycle combustion timing of an HCCI engine is developed. The model is designed to work with parameters that are easy to measure and to have low computation time with sufficient accuracy for control applications. The model is a full cycle model and consists of a residual gas model, a modified knock integral model, fuel burn rate model, and thermodynamic models. In addition, semi-empirical correlations are used to predict the gas exchange process generated work and completeness of combustion. The developed model incorporates the thermal coupling dynamics caused by the residual gases from one cycle to the next cycle. The model is parameterized by over 5700 simulations from a detailed thermo-kinetic model and experimental data obtained from a single-cylinder engine. Cross validation of the model with both steady-state and transient HCCI experiments for four different Primary Reference Fuel (PRF) blends is detailed. With seven model inputs, the combustion timing of over 150 different HCCI points is predicted to within an average error of less than 1.5 degrees of crank angle. A narrow window of combustion timing is found to provide stable and efficient HCCI operation.
BibTeX: @article{ASMEJ2008, author = {M.Shahbakhti and C. R. Koch}, title = {Physics Based Control Oriented Model for HCCI Combustion Timing}, journal = {Journal of Dynamic Systems, Measurement, and Control}, publisher = {ASME}, year = {2010}, volume = {132}, number = {2}, pages = {021010}, url = {/ ckoch/open_access/ASMEJ2008.pdf}, doi = {https://doi.org/10.1115/1.4000036} }
Ghazimirsaied, A., Shahbakhti, M. and Koch, C.R.	HCCI Engine Combustion Phasing Prediction Using a Symbolic-Statistics Approach [Abstract] [BibTeX]	2010	Journal of Engineering for Gas Turbines and Power Vol. 132(8), pp. 082805	article	DOI URL
Abstract: Temporal dynamics of cyclic variation in a homogeneous charge compression ignition (HCCI) engine near misfire is analyzed using chaotic theory methods. The analysis of variation in consecutive cycles of CA50 (crank angle of 50% mass fraction fuel burnt) for an n-heptane fueled engine is performed for a test point near the misfire condition. The return map of the time series of CA50 cycle values reveals the deterministic and random portions of dynamics near misfire occurring in an HCCI engine. A symbol-statistic approach is also used to find the occurrence of possible probabilities of the data points under the same operating conditions. These techniques are then used to predict CA50 one cycle ahead. Simulated data points in phase space have similar dynamical structure to the experimental measurements.
BibTeX: @article{ghazimirsaied:082805, author = {A. Ghazimirsaied and M. Shahbakhti and C. R. Koch}, title = {HCCI Engine Combustion Phasing Prediction Using a Symbolic-Statistics Approach}, journal = {Journal of Engineering for Gas Turbines and Power}, publisher = {ASME}, year = {2010}, volume = {132}, number = {8}, pages = {082805}, url = {/ ckoch/open_access/ghazimirsaied082805.pdf}, doi = {https://doi.org/10.1115/1.4000297} }
Schoerling, D., Kleeck, C.V., Fahimi, F., Koch, C.R., Ams, A. and Loeber, P.	Experimental Test of a Robust Formation Controller for Marine Unmanned Surface Vessels [Abstract] [BibTeX]	2010	Autonomous Robots, Springer Vol. 28(2), pp. 213-230	article	DOI URL
Abstract: Experiments with two formation controllers for marine unmanned surface vessels are reported. The formation controllers are designed using the nonlinear robust model-based sliding mode approach. The marine vehicles can operate in arbitrary formation configurations by using two leader-follower control schemes. For the design of these controller schemes 3 degrees of freedom (DOFs) of surge, sway, and yaw are assumed in the planar motion of the marine surface vessels. Each vessel only has two actuators; therefore, the vessels are underactuated and the lack of a kinematic constraint puts them into the holonomic system category. In this work, the position of a control point on the vessel is controlled, and the orientation dynamics is not directly controlled. Therefore, there is a potential for an oscillatory yaw motion to occur. It is shown that the orientation dynamics, as the internal dynamics of this underactuated system, is stable, i.e., the follower vehicle does not oscillate about its control point during the formation maneuvers. The proposed formation controller relies only on the state information obtained from the immediate neighbors of the vessel and the vessel itself. The effectiveness and robustness of formation control laws in the presence of parameter uncertainty and environmental disturbances are demonstrated by using both simulations and field experiments. The experiments were performed in a natural environment on a lake using a small test boat, and show robust performance to parameter uncertainty and disturbance. This paper reports the first experimental verification of the above mentioned approach, whose unique features are the use of a control point, the zero-dynamic stability analysis, the use of leader-follower method and a nonlinear robust control approach.
BibTeX: @article{Schoeling2009, author = {D. Schoerling and C. Van Kleeck and F. Fahimi and C. R. Koch and A. Ams and P. Loeber}, title = {Experimental Test of a Robust Formation Controller for Marine Unmanned Surface Vessels}, journal = {Autonomous Robots, Springer}, year = {2010}, volume = {28}, number = {2}, pages = {213--230}, url = {/ ckoch/open_access/Schoeling2009.pdf}, doi = {doi.org/10.1007/s10514-009-9163-6} }
Shahbahkti, M., Ghazimirsaied, A. and Koch, C.R.	Experimental Study of Exhaust Temperature Variation in an HCCI Engine [Abstract] [BibTeX]	2010	Journal of Automobile Engineering - Part D Vol. 224, pp. 1177-1197	article	URL
Abstract: Homogeneous Charge Compression Ignition (HCCI) engines have low Nitric Oxides NOx and Particulate Matter (PM) engine-out emissions but have higher unburned Hydrocarbon (HC) and Carbon Monoxide (CO) emission compared to conventional spark/diesel engines. Only for sufficiently high exhaust gas temperatures an exhaust aftertreatment can be used, thus low exhaust gas temperature in certain operating conditions can limit the operating range in HCCI engines. The influence of engine conditions on the exhaust gas temperature in a single cylinder experimental engine is investigated at 340 steady-state operating points. The variation of the exhaust gas temperature is also studied under transient conditions and during a mode switch between Spark Ignition (SI) and HCCI combustion. For the conditions tested, a significant number of data has an exhaust gas temperature below 300C which is below the light-off temperature of typical catalytic converters in the market. Three different categories of engine variables are recognized and classified by how the exhaust temperature is affected by changing that variable. The first category is defined primary variables (e.g. intake pressure and fuel octane number) for which location of ignition timing is the dominant factor to influence exhaust temperature. The other groups include compounding variables like engine speed and opposing variables like intake temperature, coolant temperature and equivalence ratio. In addition experimental results show that exhaust temperature in HCCI is not strongly dependant on engine load, unlike SI engines where engine load is a main factor for determining exhaust temperature.
BibTeX: @article{Shahbahkti2009, author = {M. Shahbahkti and A. Ghazimirsaied and C. R. Koch}, title = {Experimental Study of Exhaust Temperature Variation in an HCCI Engine}, journal = {Journal of Automobile Engineering - Part D}, year = {2010}, volume = {224}, pages = {1177-1197}, url = {/ ckoch/open_access/Shahbahkti2009.pdf} }
Tzanetakis, T., Singh, P., Chen, J., Thomson, M.J. and Koch, C.R.	Knock Limit Prediction via Multi-Zone Modeling of a Primary Reference Fuel HCCI Engine [Abstract] [BibTeX]	2010	International Journal of Vehicle Design Vol. 54, pp. 47-72	article	DOI URL
Abstract: A multi-zone modeling methodology has been developed in order to predict the combustion behaviour of a single cylinder HCCI engine. A simple blow-by model was incorporated to more accurately capture engine performance at the low constant operating speed of 700 rpm. The multi-zone model was calibrated by matching predicted and experimental pressure trace data at a single engine operating point. Robustness was demonstrated by reproducing the experimental pressure trace at another point without further adjustment of any modeling parameters. The relative CO and unburned hydrocarbon emissions predicted at both operating points showed good agreement with experimental observations. The model was used to predict the high load or knock boundary of the engine with two different criteria: one based on maximum pressure rise rate and the other on the pressure equalization rate within the charge. Both methods demonstrate an adequate ability to predict the onset of knock during HCCI.
BibTeX: @article{Tzanetakis2010, author = {T. Tzanetakis and P Singh and J. Chen and M. J. Thomson and C. R. Koch}, title = {Knock Limit Prediction via Multi-Zone Modeling of a Primary Reference Fuel HCCI Engine}, journal = {International Journal of Vehicle Design}, year = {2010}, volume = {54}, pages = {47--72}, url = {/ ckoch/open_access/Tzanetakis2010.pdf}, doi = {https://doi.org/10.1504/IJVD.2010.034870} }
Shahbakhti, M. and Koch, C.R.	Dynamic Modeling of HCCI Combustion Timing in Transient Fueling Operation [Abstract] [BibTeX]	2009	SAE Int. J. Engines Vol. 2(1), pp. 1098-1113	article
Abstract: A physics-based control-oriented model is developed to dynamically predict cycle-to-cycle combustion timing in transient fueling conditions for Homogeneous Charge Compression Ignition (HCCI) engines. The model simulates the engine cycle from the intake stroke to the exhaust stroke and includes the thermal coupling dynamics caused by the residual gases from one cycle to the next cycle. A residual gas model, a modified knock integral model, a fuel burn rate model, and thermodynamic models for the gas state in combustion and exhaust strokes are incorporated to simulate the engine cycle. The gas exchange process, generated work and completeness of combustion are predicted using semi-empirical correlations. The resulting model is parameterized for the combustion of Primary Reference Fuel (PRF) blends using 5703 simulations from a detailed thermo-kinetic model. Semi-empirical correlations in the model are parameterized using the experimental data obtained from a single-cylinder engine. The dynamics of fuel transport from intake port into the cylinder is described using the wall wetting fuel dynamic model. Step Air Fuel Ratio (AFR) excursions are used to excite the HCCI engine to determine
BibTeX: @article{Shahbakhti2009sae_trans, author = {M. Shahbakhti and C. R. Koch}, title = {Dynamic Modeling of HCCI Combustion Timing in Transient Fueling Operation}, journal = {SAE Int. J. Engines}, year = {2009}, volume = {2}, number = {1}, pages = {1098-1113} }
Chladny, R.R. and Koch, C.R.	Flatness-Based Tracking of an Electromechanical Variable Valve Timing Actuator with Disturbance Observer Feed-Forward Compensation [Abstract] [BibTeX]	2008	IEEE Transactions on Control Systems Technology Vol. 16, pp. 652-663	article	DOI URL
Abstract: A comprehensive control strategy for an automotive solenoid variable valve timing actuator is presented that addresses the issues of feedback sensors, soft seating or landing control, disturbance rejection and feedforward design. In particular, the motion control of the engine exhaust valve actuator subject to large cycle-to-cycle gas force variations is successfully demonstrated in simulation and on an experimental testbench. Also provided is a method of characterization and online cycle-to-cycle identification of combustion gas force disturbances. The identified gas forces are used in energy-based feedforward and flatness-based landing algorithms. Simulated and experimental results indicate the proposed control methodology is capable of compensating for the combustion gas force disturbances experienced by exhaust valve solenoid actuators.
BibTeX: @article{Chladny2008b, author = {R. R. Chladny and C. R. Koch}, title = {Flatness-Based Tracking of an Electromechanical Variable Valve Timing Actuator with Disturbance Observer Feed-Forward Compensation}, journal = {IEEE Transactions on Control Systems Technology}, year = {2008}, volume = {16}, pages = {652-663}, url = {/ ckoch/open_access/Chladny2008b.pdf}, doi = {https://doi.org/10.1109/TCST.2007.912121} }
Crawford, D.G., Koch, C.R. and Bhattacharjee, S.	Characteristic Times for Pressure and Electrostatic Force Driven Thin Film Drainage [Abstract] [BibTeX]	2008	Journal of Computational and Theoretical Nanoscience Vol. 5(10), pp. 2060-2066	article	DOI URL
Abstract: The drainage of thin liquid films confined between two electrodes was studied employing the long wave approximation of the pertinent hydrodynamic equations. A general mathematical formulation was used for the case of electric field driven drainage of the film by solving the Laplace equation in conjunction with the approximate flow equations. The drainage of small periodic segments of the film was then studied employing the model under conditions that emulate purely pressure based drainage, as well as drainage in presence of an applied electric field. The final film morphologies and the drainage times in presence of electric fields were found to be considerably different from those observed for pressure based drainage.
BibTeX: @article{Crawford2008, author = {D. G. Crawford and C. R. Koch and S. Bhattacharjee}, title = {Characteristic Times for Pressure and Electrostatic Force Driven Thin Film Drainage}, journal = {Journal of Computational and Theoretical Nanoscience}, year = {2008}, volume = {5}, number = {10}, pages = {2060-2066}, url = {/ ckoch/open_access/Crawford2008.pdf}, doi = {https://doi.org/10.1166/jctn.2008.1014} }
Shahbakhti, M. and Koch, C.R.	Characterizing the Cyclic Variability of Ignition Timing in an HCCI Engine Fueled with n-Heptane/iso-Octane Blend Fuels [Abstract] [BibTeX]	2008	International Journal of Engine Research, Vol 9 Vol. 9, pp. 361 - 397	article
Abstract: The cyclic variations of homogeneous charge compression ignition (HCCI) ignition timing is studied for a range of charge properties by varying the equivalence ratio, intake temperature, intake pressure, exhaust gas recirculation (EGR) rate, engine speed, and coolant temperature. Characterization of cyclic variations of ignition timing in HCCI at over 430 operating points on two single-cylinder engines for five different blends of primary reference fuel (PRF), (iso-octane and n-heptane) is performed. Three distinct patterns of cyclic variation for the start of combustion (SOC), combustion peak pressure (Pmax), and indicated mean effective pressure (i.m.e.p.) are observed. These patterns are normal cyclic variations, periodic cyclic variations, and cyclic variations with weak/misfired ignitions. Results also show that the position of SOC plays an important role in cyclic variations of HCCI combustion with less variation observed when SOC occurs immediately after top dead centre (TDC). Higher levels of cyclic variations are observed in the main (second) stage of HCCI combustion compared with that of the first stage for the PRF fuels studied. The sensitivity of SOC to different charge properties varies. Cyclic variation of SOC increases with an increase in the EGR rate, but it decreases with an increase in equivalence ratio, intake temperature, and coolant temperature.
BibTeX: @article{IJER2008, author = {M. Shahbakhti and C. R. Koch}, title = {Characterizing the Cyclic Variability of Ignition Timing in an HCCI Engine Fueled with n-Heptane/iso-Octane Blend Fuels}, journal = {International Journal of Engine Research, Vol 9}, year = {2008}, volume = {9}, pages = {361 - 397} }
Supeene, G., Koch, C.R. and Bhattacharjee, S.	Deformation of a Droplet in an Electric Field: Nonlinear Transient Response in Perfect and Leaky Dielectric Media [Abstract] [BibTeX]	2008	Journal of Colloid and Interface Science Vol. 318, pp. 463 - 476	article	URL
Abstract: Deformation of a fluid drop, suspended in a second immisciblefluid, under the influence of an imposed electric field is a widely studied phenomenon. In this paper, the system is analyzed numerically to assess its dynamic behavior. The response of the system to a step change in the electric field is simulated for both perfect and leaky dielectric systems, exploring the influence of the fluid, interfacial, and electrical properties on the system dynamics. For the leaky dielectric case, the dynamic build up of the free charge at the interface including the effects of convection along the interface due to electrohydrodynamic circulation is investigated. The departure of the system from linear perturbation theory is explained using these dynamic simulations. The present simulations are compared with analytic solutions, as well as available experimental results, indicating that the predictions from the model are reliable even at considerably large deformations.
BibTeX: @article{SupeeneJCIS2007, author = {G. Supeene and C. R. Koch and S. Bhattacharjee}, title = {Deformation of a Droplet in an Electric Field: Nonlinear Transient Response in Perfect and Leaky Dielectric Media}, journal = {Journal of Colloid and Interface Science}, year = {2008}, volume = {318}, pages = {463 - 476}, note = {JICS}, url = {/ ckoch/open_access/SupeeneJCIS2007.pdf} }
Chung, S.K., Koch, C.R. and Lynch, A.F.	Flatness-based feedback control of an automotive solenoid valve control [Abstract] [BibTeX]	2007	IEEE Transactions on Control System Technology Vol. 2, pp. 394 - 401	article	DOI URL
Abstract: This paper considers the control of solenoid valve actuators used for gas exchange in internal combustion engines. Although solenoid valves offer performance benefits over traditional camshaft-based valve systems, maintaining low impact velocity is a critical performance requirement. Flatness provides a convenient framework for meeting a number of performance specifications on the valve's end motion. The proposed control design incorporates voltage constraints, nonlinear magnetic effects, and various motion planning requirements. A flat output acts as a design parameter and is parameterized with a spline basis. A nonlinear feasibility problem is solved to obtain optimal spline coefficients such that performance requirements are met. The resulting flat output provides an open-loop control which is augmented with feedback so that a linear stable tracking error system results. The proposed control scheme is demonstrated in simulation and on an experimental testbed. The performance of a Proportional-Integral controller is compared experimentally to the flatness-based method.
BibTeX: @article{chung_2007_CST_sub, author = {S. K. Chung and C. R. Koch and A. F. Lynch}, title = {Flatness-based feedback control of an automotive solenoid valve control}, journal = {IEEE Transactions on Control System Technology}, year = {2007}, volume = {2}, pages = {394 - 401}, url = {/ ckoch/open_access/chung_2007_CST_sub.pdf}, doi = {https://doi.org/10.1109/TCST.2006.886440} }
Kirchen, P.N., Shahbahkti, M. and Koch, C.R.	A Skeletal Kinetic Mechanism for PRF Combustion in HCCI Engines. [Abstract] [BibTeX]	2007	Combustion Science and Technology Vol. 179, pp. 1059-1083	article	URL
Abstract: A single zone thermodynamic model, coupled to a kinetic mechanism, is developed and is capable of predicting the ignition timing of Primary Reference Fuels (PRFs) in a Homogeneous Charge Compression Ignition (HCCI) engine. A new combination of kinetic mechanisms is used, which includes 120 reactions and 58 species for both ignition and high temperature reactions. The model is validated using a step by step methodology. The validation compares ignition delays predicted by the model with published measurements from a rapid compression machine, shock tube as well as the cylinder pressure histories taken from two different experimental HCCI engines for various operating conditions. The model is able to qualitatively predict the effect of different parameters such as gas temperature, gas pressure, equivalence ratio and octane number on the HCCI ignition delay.
BibTeX: @article{Kirchen, author = {P. N. Kirchen and M. Shahbahkti and C. R. Koch}, title = {A Skeletal Kinetic Mechanism for PRF Combustion in HCCI Engines.}, journal = {Combustion Science and Technology}, year = {2007}, volume = {179}, pages = {1059-1083}, url = {/ ckoch/open_access/Kirchen.pdf} }
Olfert, J.S., Checkel, M.D. and Koch, C.R.	Acoustic method for measuring the sound speed of gases over small path lengths [Abstract] [BibTeX]	2007	Rev. of Scientific Instruments Vol. 78, pp. 1-8	article	URL
Abstract: Acoustic "phase shift" methods have been used in the past to accurately measure the sound speed of gases. In this work, a phase shift method for measuring the sound speed of gases over small path lengths is presented. We have called this method the discrete acoustic wave and phase detection (DAWPD) method. Experimental results show that the DAWPD method gives accurate (+-3.2 m/ s) and predictable measurements that closely match theory. The sources of uncertainty in the DAWPD method are examined and it is found that ultrasonic reflections and changes in the frequency ratio of the transducers (the ratio of driving frequency to resonant frequency) can be major sources of error. Experimentally, it is shown how these sources of uncertainty can be minimized.
BibTeX: @article{Olfert2007, author = {J. S. Olfert and M. D. Checkel and C. R. Koch}, title = {Acoustic method for measuring the sound speed of gases over small path lengths}, journal = {Rev. of Scientific Instruments}, year = {2007}, volume = {78}, pages = {1-8}, url = {/ ckoch/open_access/Olfert2007.pdf} }
Swan, K., Shahbakhti, M. and Koch, C.R.	Predicting Start of Combustion Using a Modified Knock Integral Method for an HCCI Engine [Abstract] [BibTeX]	2007	SAE Int. J. EnginesSAE Int. J. Engines, pp. 611-620	article
Abstract: Homogeneous Charge Compression Ignition (HCCI) is a promising combustion concept for internal combustion engines to reduce emissions and fuel consumption. Unlike spark ignition and diesel engines in which ignition is controlled by spark and spray injection timing respectively, HCCI combustion auto-ignites given the correct mixture conditions which makes HCCI ignition difficult to control. It is thus critical to understand the characteristics of HCCI ignition timing in order to find suitable strategies for ignition control. This paper presents a modified model of ignition timing which is based on the Knock-Integral Method. Since this model doesn't require instantaneous in-cylinder parameters, it is suitable for control application on HCCI combustion. The model is tested using both simulation results of a Thermo-Kinetic Model and experimental data. With seven model parameters, the ignition timing of over 250 HCCI points at different conditions for four different Primary Reference Fuels (PRF) is predicted to within an average error of less than 1.5 degrees of crank angle. This model is computationally efficient and could be implemented in the engine control unit of an HCCI engine to calculate the required inputs that are needed to get the desired ignition timing.
BibTeX: @article{Swant2006, author = {K. Swan and M. Shahbakhti and C. R Koch}, title = {Predicting Start of Combustion Using a Modified Knock Integral Method for an HCCI Engine}, booktitle = {SAE Int. J. Engines}, journal = {SAE Int. J. Engines}, publisher = {Society of Automotve Engineers}, year = {2007}, pages = {611-620} }
Atkins, M.J. and Koch, C.R.	The Effect of Fuel Octane and Diluent on HCCI Combustion [Abstract] [BibTeX]	2005	Proc. IMechE, Part D Vol. 219, pp. 665 - 675	article
Abstract: This paper presents some experimental operating and combustion properties of Homogeneous Charge Compression Ignition (HCCI) combustion. HCCI operating range, start of combustion, burn duration, indicated mean effective pressure, indicated specific emissions and indicated specific fuel consumption are evaluated as charge dilution and octane number are varied. Primary reference fuels with octane numbers of 20, 40 and 60 are used in this study. The auto-ignition properties of the air/fuel mixture are varied by changing the fuel octane number, the percent EGR and air/fuel ratio, while holding the intake temperature, engine speed and compression ratio constant. Results show that both the start of combustion and burn duration are sensitive to mixture dilution (excess air or EGR). However, only the start of combustion is affected by the fuel octane number. The fuel octane number is not an effective method of controlling the start of combustion or the burn duration, but can be used to increase the load range of the HCCI engine. Both the NOx emissions and indicated specific fuel consumption increases as the octane number is increased due to lower dilution and higher peak temperatures. Correct amounts of dilution are critical to control HCCI combustion. Separating dilution into EGR and excess air, it is found that a given amount of EGR is more effective at controlling the start of combustion and the burn duration, than the same amount of excess air.
BibTeX: @article{Atkins2005, author = {M. J. Atkins and C. R. Koch}, title = {The Effect of Fuel Octane and Diluent on HCCI Combustion}, journal = {Proc. IMechE, Part D}, year = {2005}, volume = {219}, pages = {665 - 675} }
Chladny, R.R., Koch, C.R. and Lynch, A.F.	Modeling of Automotive Gas-Exchange Solenoid Valve Actuators [Abstract] [BibTeX]	2005	IEEE Transactions on Magnetics Vol. Volume 41, Issue 3, pp. 1155-1162	article	DOI URL
Abstract: A promising method for enhancing automotive engine efficiency uses solenoids to directly control the gas exchange valves of an internal combustion engine. A FEA (Finite Element Analysis) model is developed to describe transient and static operation of the valve. The FEA model is validated by experimental testing on an actual automotive prototype valve. We show that a nonlinear lumped parameter model which uses FEA results also closely matches experimental data. The lumped parameter model is amenable to optimization of design and can be readily used for closed-loop simulation. A simplified lumped parameter model is presented to facilitate controller design. Finally, a dynamic open-loop simulation is compared with experimental results.
BibTeX: @article{Chladny_TMAG_2005, author = {R. R. Chladny and C. R. Koch and A. F. Lynch}, title = {Modeling of Automotive Gas-Exchange Solenoid Valve Actuators}, journal = {IEEE Transactions on Magnetics}, year = {2005}, volume = {Volume 41, Issue 3}, pages = {1155-1162}, url = {/ ckoch/open_access/Chladny_TMAG_2005.pdf}, doi = {https://doi.org/10.1109/TMAG.2004.841701} }
Supeene, G., Koch, C.R. and Bhattacharjee, S.	Deformation of a Droplet in an Electrical Field: Transient Response in Dielectric Media [Abstract] [BibTeX]	2004	Journal of Computational and Theoretical Nanoscience Vol. Volume 1, Number 4, pp. 429-437	article	URL
Abstract: Deformation of droplets in an externally imposed electrical field is a widely studied phenomenon, and is an important component of microfluidic operations involving electrical actuation of droplets. The ability to control deformation of a droplet provides the ability to manipulate these droplets in a controlled manner on a microfluidic chip. In this study, we explore a general mathematical formulation for the deformation of droplets under an imposed electrical field. The coupled fluid mechanical and electrostatic governing equations are solved numerically using finite element analysis, and the solution is presented for two perfect dielectrics carrying no free charge. The numerical solutions are first compared with an asymptotic analytic result to assess the accuracy of the numerical code. Following this, the dynamics of the deformation are presented to characterize the typical response of a droplet subjected to a step change in the electric field. The results provide a basis for modeling the dynamic response and formulating control strategies for droplet manipulation, and may provide considerable insight into microfluidic operations based on electrowetting.
BibTeX: @article{Supeene2004, author = {G. Supeene and C. R. Koch and S. Bhattacharjee}, title = {Deformation of a Droplet in an Electrical Field: Transient Response in Dielectric Media}, journal = {Journal of Computational and Theoretical Nanoscience}, year = {2004}, volume = {Volume 1, Number 4}, pages = {429-437}, url = {/ ckoch/open_access/Supeene2004.pdf} }
Lynch, A.F., Koch, C.R. and Chladny, R.R.	Nonlinear Observer Design for Sensorless Electromagnetic Actuators [BibTeX]	2003	Dynamics of Continuous Discrete and Impulsive Systems-Series B- Applications & Algorithms. Vol. Suppl S	article
BibTeX: @article{Lynch2003a, author = {A. F. Lynch and C. R. Koch and R. R. Chladny}, title = {Nonlinear Observer Design for Sensorless Electromagnetic Actuators}, journal = {Dynamics of Continuous Discrete and Impulsive Systems-Series B- Applications & Algorithms.}, year = {2003}, volume = {Suppl S} }