Model predictive trajectory tracking control for hydraulic excavator on digging operation

In order to increase work efficiency, alleviating burden of operators is important. An autonomous hydraulic excavator is expected to improve it. In this paper, an automatic control of a digging operation for the hydraulic excavator is studied. We propose a method for the trajectory tracking control using model predictive control (MPC) which incorporates servo mechanism. MPC can optimize motion and avoids rapid change of velocity using constraints. However, it is difficult to cope with unknown reaction forces caused by contacting with underground objects. Servo mechanism suppresses the disturbance by the integration of the tracking error. However, the error may be accumulated in the integration. Hence, the trajectory tracking may result in rapid response when the objects are removed. By combining MPC and servo mechanism, we can expect that servo mechanism works against the disturbance and the tracking performance is improved. We show effectiveness of the proposed method through simulations under the presence of the disturbance.