A Practical Modelling Approach for Stiction in Control Valves

Abstract

Pneumatic control valves are widely used in the process industry and it has surprisingly received little attention until recently. The presence of non-linearities in a control valve limits the control loop performance. Stiction is the commonly existing valve problem. It is essential for one to know the dynamics of stiction, so that the relationship directly linked to the physical situation can be understood. Both physical model and empirical data driven models have been developed in the past decade to investigate the valve stiction behaviour. But, there is a need to better understanding of stiction physics through theoretical analysis as well as empirical investigations. A new nonlinear control valve model is developed and its effectiveness in simulating valve stiction is demonstrated. This paper focuses on the development of a MATLAB/Simulink model for control valve with stiction. The reliable stiction model that captures the stiction behaviour provides an important tool in order to investigate by analysis and simulation, the properties of stiction that are relevant to control design.