A High Performance Pneumatic Force Actuator System Part 2 - Nonlinear Controller Design ∗

I this article we developed two nonlinear force controllers based on the sliding mode control theory. We used the detailed mathematical model of a pneumatic system developed in the first part of the paper. The first controller uses the complete model, and exhibit superior performance both in the numerical simulation and experiments, but requires very complex online computation for the control law. The reduced order controller neglects the valve dynamics and the time delay due to connecting tubes. The control law is greatly simplified, and the numerical simulations and experimental verification shows only slightly reduced performances in configurations with relatively short tubes, and at frequencies up to 25 Hz. At higher frequencies or when long connecting tubes are used, the performances are significantly lower than those provided by the full order Sliding Mode Controller.