Adaptive control for position control of a pneumatic actuator under variable loads

Under a constant loading condition, use of a controller with constant coefficients can be acceptable for servo pneumatic systems. However in variable loads with widespread changes, more advanced control methods should be considered to achieve desirable performance. In this paper, an adaptive controller is designed and implemented to a variably loaded servo pneumatic system with PWM driven switching valve. In the under examination servo pneumatic system, PWM driven fast switching valve is used instead of expensive servo or proportional valves. Real time identification of system parameters is performed using input-output data and controller parameters are adjusted instantaneously. “Self-tuning regulators” algorithm, in which controller parameters obtain from solving a design problem, is applied to design the proposed adaptive controller. The designed controller is applied to the servo pneumatic system via an interface board and its performance is compared with PD and multi model controller. Unlike the proposed method in multi model control method, a number of constant loads should be considered and corresponding to each load a fixed controller is designed. Experimental results demonstrate the high performance of the adaptive controller under variable loads.