Multimodel PD-control of a pneumatic actuator under variable loads

Abstract

In this paper, a multimodel controller is designed and implemented to a variably loaded pneumatic actuator. A particular design of the pneumatic system with one PWM-driven switching valve is utilized which has a quasilinear input–output behavior under constant load conditions. Therefore, under a constant load, position control is properly accomplished by a linear PD-controller. In order to use the system in variable load applications such as robot actuators, a multimodel controller is designed based on the PD-controllers. For this purpose, a number of constant loads are considered and corresponding to each load, a linear model is identified and a PD-controller is tuned for the system. Then, a switching algorithm is applied which determines the best model and selects the corresponding controller in any load condition. Also, for the realization of the D-action in PD-controllers, a Kalman filter is designed to observe the velocity instead of direct differentiation of the output position. Experimental results indicate the high performances of the multimodel controller under variable load conditions.