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Detection and quantification of valve stiction by the method of unknown input estimation

Detection and quantification of valve stiction by the method of unknown input estimation,10.1016/j.jprocont.2009.10.004,Journal of Process Control,San

Detection and quantification of valve stiction by the method of unknown input estimation   (Citations: 2)
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Valve stiction is one of the most common causes of oscillations in industrial process control loops. Such oscillations can degrade the overall performance of the loop and eventually the final product quality. The detection and quantification of valve stiction in industrial process control loops is thus important. From previous studies in the literature, a sticky valve has been shown to have a distinct signature of the stiction phenomena in its valve positioner data. However, the position of the modulating control valves is seldom available. We consider the problem of estimating the valve position as an unknown input estimation problem. In this work, we propose a novel application of the unknown input estimator in order to estimate the valve position given the process model and the data of the process variable and controller output. Using the estimated valve position, we can detect and also quantify the amount of stiction. We demonstrate the efficacy of the method through simulation examples where a sticky valve is deliberately introduced in the closed loop using a two-parameter stiction model available in the literature. Application of the proposed methodology to a laboratory scale flow control loop is presented. An industrial case study is also presented in which the algorithm accurately detects and quantifies stiction in the level control loop of a power plant.
Journal: Journal of Process Control - J PROCESS CONTROL , vol. 20, no. 2, pp. 206-216, 2010
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    • ...Chitralekha et al.[12]consideredthe problem of estimating the valve position as an unknown input estimation problem.However, standard Kalman filter limits process dynamic and reducesflexibility of this method...
    • ...Typically, the controller will be P or PI. For a normal valve, the mv and op signal will be equal at all times [12]...
    • ...If we model this transformation of the op by adding an additive, nonlinear, external signal which enters the loop just after the controller output, we get an equivalent representation as shown in Fig.3 with the valve block replaced by an externalunknown input signal[12], [16]...

    Y. Arbabi Yazdiet al. Modelling and quantification of valve stiction by unknown input estima...

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