Cascade control of hydraulic actuators during contact tasks

Due to the complex interactions between hydraulic components, the contact task control of hydraulic manipulators is a challenging problem. In this paper, a controller is proposed which incorporates the nonlinear hydraulic effects and actuator-environment dynamics into the control procedure. The approach allows partitioning the hydraulics control from the actuator-environment interaction control so that, a different control algorithm could be applied to each part. The communication between the two parts is performed through an appropriate input-output arrangement. In this paper, a proportional control with feedforward compensation is applied to the hydraulic portion of the system and a bounce-less contact controller is applied to the actuator-environment interaction. Simulation and experimental results demonstrate that the proposed controller remains stable following contact with the environment.