Nonlinear pressure control of self-supplied variable displacement axial piston pumps

The present paper deals with the pressure control of self-supplied variable displacement axial piston pumps subject to fast changing, unknown loads. First, the setup of the system and the mathematical model are described. As the pump is self-supplied, the mathematical model exhibits a switching right-hand side which makes the control design a challenging task. A nonlinear two degrees-of-freedom control strategy, comprising a feedforward and a feedback control, in combination with a load estimator is proposed for the pressure control. The proof of the stability of the overall closed-loop system is based on Lyapunov's theory. The performance of the control concept is verified by means of experiments. The results show that the proposed control concept has an excellent and robust behavior.