A high performance pneumatic force actuator system: Part II - Nonlinear controller design

In this article we present two nonlinear force controllers based on the sli ding mode control theory. For this purpose we use the detailed mathematical model of the pneumatic system developed in the first part of the paper. Th e first controller is based on the complete model, and exhibits superior pe rformance both in the numerical simulation and experiments, but requires co mplex online computations for the control law. The second controller neglec ts the valve dynamics and the time delay due to connecting tubes. The perfo rmance of this controller exhibits slight degradation for configurations wi th relatively short tubes, and at frequencies up to 20 Hz. At higher freque ncies or when long connecting tubes are used , however, the performance exh ibits significant degradation compared to the one provided by the full orde r controller.