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Detection and Control of Stiction in Control Loops

Author: ChenCai
Tutor: RenZhengYun
School: Donghua University
Course: Systems Engineering
Keywords: Control loop Sluggish Modeling Detect Control
CLC: TP273
Type: Master's thesis
Year: 2011
Downloads: 39
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Abstract

Nature of the control system in the process industry is non-linear, linear systems is relatively rare in the general study of the nonlinear process is approximated as a linear process. Valve is most commonly used in the control loop, the implementing agencies, their performance will affect the control effects of the control loop. According to statistics, about 30% of the circuit is in the oscillating state in the process in industrial processes, of which 1/3 is caused due to the regulating valve (actuator) hysteresis. So, Hysteresis is the most common valve problem in the process of industrial control process, it exists a serious impact on the implementation of the good performance of the control system. Hysteresis control to improve the accuracy of the control loop, stability is of great significance. And so far in the related field of research is still relatively small, in recent years, although some foreign scholars hysteresis modeling and testing a variety of theories and methods. However, to date, few studies hysteresis control problems. The basis of analysis of the hysteresis model established by foreign scholars to analyze the advantages and disadvantages of a variety of models, and propose a way to more accurately reflect the actual valve characteristic hysteresis model. At the same time foreign scholars on the regulating valve hysteresis detection methods, these theories and methods in terms of speed, accuracy, and simplicity there are one or more limitations, thus limiting the prospects for the application of these theories and methods. The the Hysteresis detection method based on system identification. The method is the use of closed-loop operation, the control loop controller output OP process variable PV data using the method of least squares identification, closed-loop identification control loop exists regulating valve hysteresis. Regulating valve hysteresis effects for the oscillation control loops in the process industry, focused on research and analysis Hagglund hysteresis compensation control method, proposed a new method of control. These new methods can be effectively reduced and the oscillation amplitude of the control loop. Simulation hysteresis model and control method created by Matlab software, and simulation results indicate the validity and accuracy of the hysteresis model and hysteretic control method. The research not only to detect and control the regulating valve hysteresis, but also to improve product quality, reduce energy consumption, to maintain process stability and reduce operating strength. Hysteresis control not only over-fill the blank in this field in China, and a wide field of applications, great application prospects, can greatly improve the economic efficiency of the process industry.

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