Flatness based control of a two valve hydraulic joint actuator of a large manipulator

For the hydraulically driven joint of a large manipulator, a new control scheme is applied using the flatness of the hydraulic actuator with two valves. Position and pressure can be controlled independently by expanding the SISO system with one valve to a MIMO system with two valves. The model is described by piecewise defined nonlinear equations. It is shown that the system is flat. The flatness property allows a piecewise defined approach for the nonlinear tracking problem. For this, suitable trajectories for the displacement of the actuator and the pressure inside are chosen that can be tracked based on static state feedback linearization. The usefulness of the proposed concept is verified in simulation and by a laboratory test bench.