Identification and control design for path tracking of hydraulic loader crane

The controlled operation of hydraulic machines with multiple degrees of freedom is challenging due to complex nonlinear dynamics of cylinder actuators, in addition to multibody dynamics like in the case of hydraulic manipulators. This paper addresses the system identification and control design for path tracking of a standard hydraulic loader crane. The kinematics of the crane is solved for operation in the vertical plane and generation of trajectories for the tool tip to be followed. A frequency response measurements and analysis have been done for dynamics modeling of both hydraulic cylinders actuating main boom and jib. The static dead-zone type input non-linearity has been identified and compensated through the inverse. A suitable control structure combining the proportional feedback regulator with model-based feed-forward control part has been derived and implemented. The experimental evaluation is shown for the Cartesian path tracking with a constant tangential velocity. The results demonstrate a way of application-related identification and control design for hydraulic manipulators with limited access into internal actuator and control structure.