Stiction compensation using PI-sliding mode control for pneumatic valve

Oscillations in process control loops greatly affects the performance of the controller and lead to a waste of energy, an increase of process variability, and a severe degradation of product quality. Such oscillations are either the result of badly tuned controller or produced by the undesirable presence of a nonlinear element. Stiction valve due to wear and tear or due to mishandling of the actuator is an example of malfunction control loop component that leads to such situation. Stiction problem is by far the most frequent anomaly in process and control. In this paper, we propose a new method to compensate for valve stiction, reduce the variability of the process, and increase the life cycle of the valve. Therefore, a new approach based on sliding mode control is applied to compensate for an unknown valve stiction degree. The performance of the new approach is presented through various simulation results which demonstrate the strength of the approach when compared to recent published methods.