Closed loop pneumatic position control using discrete time model regulation

Nonlinear valve characteristics and the compressibility of air make pneumatic position control a quite difficult task. A model regulation scheme called discrete time model regulation (DMR) and originally proposed for sensitivity reduction in systems with significant amounts of plant model uncertainty is applied to a pneumatic system here to make its input-output relationship follow that of its nominal model, simplifying the remaining feedback position controller design significantly. First, the DMR method is introduced and its limitations are evaluated analytically. Its effectiveness in dealing with large changes in pneumatic system parameters is demonstrated using simulation results. It is finally shown that plant dynamics improvements comparable to those achieved using differential pressure feedback can be obtained by using DMR with the benefits of not having to use a pressure sensor.