Sliding mode approach to PWM-controlled pneumatic systems

This paper presents a modeling and control design method for PWM-controlled pneumatic systems. Difficulties associated with servovalves typically used to continuously control pneumatic systems, in addition to a general lack,of analytic control design techniques available for MW controlled pneumatic systems, motivate the development, of a modeling and control design technique for PWM pneumatics. Specifically, the method presented here is to model a PWM-based pneumatic system using a state-space averaging approach. This provides the analytic machinery necessary to remove the discontinuities associated with switching and results in a model tractable to standard nonlinear control design techniques. Thereby, issues such as stability robustness and performance bandwidth may be addressed directly. The control of a single degree of freedom pneumatic positioning system illustrates this technique experimentally.