A Linearization Approach in Control of PWM-Driven Servo-Pneumatic Systems

In this paper, three linearization approaches are proposed for PWM-driven servo-pneumatic systems and improved performances are achieved by using simple linear controllers instead of complex and costly nonlinear ones. As the first approach in linearization, a simple pneumatic circuit with only one fast switching valve is designed. It is shown that in spite of internal nonlinearities, the proposed circuit leads to a quasi-linear input-output relation. As the second approach, the nonlinear dead bands due to the valve opening and closing delay times, are omitted via a simple PWM algorithm. Feedback linearization is realized as the third approach, by designing a Kalman filter to observe the velocity of the cylinder which is fed back in a minor loop. Experimental results indicate that highly improved tracking performances are achieved by the linearized system with simple P- controllers compared to the nonlinear controllers of previous works.