Force/position tracking for electrohydraulic systems of a robotic excavator

Presents the sliding mode axis control of the electrohydraulic servo systems of a robotic excavator. The dynamic systems are described by a comprehensive model that accounts for nonlinearities and friction effects of asymmetric hydraulic cylinders. A sliding mode controller is developed for the electrohydraulic actuator of each working axis to provide stable force tracking. With a proper choice of the reference force, the control law can also allow tracking of a desired piston displacement trajectory. Numerical simulation demonstrates the validity of the proposed technique. Experimental results show good performance and strong robustness in both force and position following.