Friction compensation in control valves: Nonlinear control and usual approaches

This work presents different approaches to reduce the control valve friction effect on a process. One is to use the sliding mode control in different conditions and then to compare this controller to widely used algorithms and devices that reduce the control loop variability. The experiments were performed in the Flow Pilot Plant of Polytechnic School of the University of São Paulo with a pneumatic control valve with high friction in a flow control loop. The sliding mode controller yielded promising results, which can represent new horizons with respect to friction compensation in control valves.