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Stiction Compensation
The Valve Stiction Compensation Tool was developed to compensate for valve stiction in a single-loop control system. Valve Stiction, the static friction present in a valve stem, causes problems in controlling systems, which may affect the product quality, production efficiency, and safety of a process. The Valve Stiction Compensation Tool offers a convenient way to resolve the valve stiction problem without interrupting the process or adding any extra costs.
The frequency response of the closed-loop system and the describing function for the process are used to study the stability and oscillation of a system in the presence of a single sticky valve. The describing function is used to explain the relationship between the response of the nonlinear system and its dynamics (in this case, the slip-jump and deadband factors for a sticky valve). The describing function consists of a complex number representing the frequency and magnitude of the oscillations due to the nonlinear component. As well, frequency analysis is used to determine the oscillations and stability of the control loop.
The algorithm used by programme can be stated in the following steps:
- Determine a range of controller tunings to search based on the original controller tuning;
- Calculate the frequency response and determine whether the closed-loop system is stable and has oscillations; and
- Generate a visual representation to guide the user in selecting an appropriate controller tuning.
Manual
The manual for using the toolbox can be found here.
System Requirements
This programme has the following prerequisites:
- Windows XP or newer.
- MATLAB® 2009a or newer. The programme has not been tested on older versions of MATLAB®.
Download
The required files can be downloaded from the Downloads section.
Developers
This software has been developed by the following people:
References
- M.A.A. Shoukat Choudhury, Sirish L. Shah, Nina F. Thornhill, and David S. Shook (2006). “Automatic detection and quantification of stiction in control valves” in Control Engineering Practice, Volume 14, pp. 1395-1412. doi: 10.1016/j.conengprac.2005.10.003
- Kwan Ho Lee, Zhengyun Ren, and Biao Huang (2008). “Novel closed-loop stiction detection and quantification method via system identification” in Proceedings of the ADCONIP Conference Jasper, Alberta, Canada, May 4th-7th, 2008. Download copy.
- Mahdi Alemohammad (2011). Detection and Compensation For Stiction In Multi-loop Control System, Master’s thesis, University of Alberta, Edmonton, Alberta, Canada. Download copy.