By Mohieddine Jelali, Biao Huang
The presence of non-linearities, corresponding to stiction and deadband, areas limits at the functionality of keep an eye on valves. certainly, within the method industries, stiction is the commonest valve challenge, and over the past decade a number of various options for overcoming it were proposed.
Detection and analysis of Stiction up to the mark Loops represents a finished presentation of those tools, together with their ideas, assumptions, strengths and disadvantages. directions and dealing approaches are supplied for the implementation of every process and MATLAB®-based software program may be downloaded from www.ualberta.ca/~bhuang/stiction-book allowing readers to use the how to their very own facts. tools for the predicament of stiction results are proposed in the normal context of:
• oscillation detection on top of things loops;
• stiction detection and analysis; and
• stiction quantification and prognosis of a number of faults.
The cutting-edge algorithms offered during this publication are validated and in comparison in business case stories of numerous foundation – chemical substances, construction, mining, pulp and paper, mineral and steel processing. Industry-based engineers will locate the publication to be worthy counsel in expanding the functionality in their regulate loops whereas educational researchers and graduate scholars attracted to regulate functionality and fault detection will find a wealth of static-friction-related examine and helpful algorithms.
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Extra info for Detection and Diagnosis of Stiction in Control Loops: State of the Art and Advanced Methods
The disadvantage of a physics-based model is that it requires a knowledge of quantities such as the mass of the moving parts and the friction forces that makes it infeasible for industrial studies or span of the valve input signal. In industrial practice, stiction and other related problems are identified in terms of the percentage of the valve travel or span of the valve input signal. The relationship between the magnitudes of the parameters of a physical model and stiction expressed as a percentage of the span of the input signal is also not known explicitly.
4 is not complete by itself since the shapes depend on controller parameters and process dynamics. To summarise, the effect of stiction can be distinguished from other oscillation root causes by the following observations: • In general, non-linearity-induced oscillations, which are observed both on OP and PV, contain harmonics. • In the case of poor performance or external disturbance, both OP and PV follow sinusoidal waves; the induced oscillations have low harmonic content. • In the case of stiction, OP usually follows a triangular wave for self-regulating processes (Fig.
The flow-rate measurements proved coincident with that estimated by the stiction model. The valve-stiction model developed here is based on the balance among the elastic force, the air pressure, and the frictional force, and it can describe the behaviour of pneumatic control valves with only two parameters S and J. For example, an ideal situation exists when S = J = 0 and no slip jump when J = 0. 1 Similarities • Both models use the same parameters, S and J. • Both models can produce the stiction behaviour of a control valve both when the valve sticks during the change in travel direction and when the valve sticks while travelling in the same direction.