Comparison of Stiction Compensation Methods Applied to Control Valves

Control valves are common instruments in industrial settings. As with any device with mobile parts, they suffer from the effects of stiction. Normally, a valve in good state of preservation presents low stiction; however, over time, this nonlinearity tends to increase. The presence of stiction decreases the control loop efficiency and can even cause oscillations in the controlled variable. Despite being the best solution, sometimes removing the valve for maintenance is not possible. In this work, two stiction compensation techniques were enhanced (knocker and modified two-move method). Then, they were tested along with other known methods to compensate for stiction effects in the flow control loop of a pilot plant. In addition, a method for estimating the stiction parameters using the same kind of signal as used by most previous compensators (single step) is proposed.