Design of Hydraulic Force Control Systems with State Estimate Feedback

Abstract The control problem to keep a desired force acting on a machine part can often be solved by using a servo controlled oil hydraulic actuator unit. This paper describes the results of an analytical and experimental investigation of some new design principles of force control systems which are based on the application of an electro-hydraulic servovalve controlling the volume rate flow to a hydraulic motor. It is shown how the system performance can be improved compared to a conventional force feedback by using the following control principles: (1) A controller with output feedback and velocity feedforward, (2) A Luenberger observer and state estimate feedback, (3) A Luenberger observer, state estimate feedback, and unity output feedback, and (4) Velocity feedforward combined with (3).