Design and Experimental Validation of an Output Feedback Controller for a Pneumatic System with Distributed Parameters

This paper considers the model-based control of a pneumatic system, where a tank is connected to a valve via a long tube. Due to the significant distance between the control input and the pressure in the tank to be controlled, a distributed-parameter model is used for the tube, involving quasilinear hyperbolic partial differential equations. In contrast, the tank is modelled by ordinary differential equations. Experimental data verifies the validity of the corresponding quasilinear system model. Based on a less accurate, linear PDE-ODE system model, derived there upon, both, a back-stepping controller and a backstepping observer are designed. The resulting output feedback controller is augmented by a flatness-based feedforward controller. Experimental results for tube lengths of approximately five and twenty meters show that this controller allows to track fast pressure changes in the tank almost perfectly.