Modelling and control of an unmanned excavator vehicle

This paper investigates the modelling and control of a full-scale excavator vehicle. A detailed analytical model for an unmanned excavator vehicle is developed. The model takes into account the kinematics and dynamics of the mobile platform (vehicle) and the excavation arm (links and hydraulic system). The model describes the dynamic relationship between the operator input commands (fuelling and joystick commands to excavation arm and steering lever) and the trajectories and forces of the excavator vehicle. The dynamic model of the excavation arm system is validated against measured data. The validation of the model is conducted in collaboration with QinetiQ Limited (the new science and technology company formed from the major part of DERA, the British Government's defence research and development organization). A unified model is important for design of control strategies, since in order to move the bucket of a mobile excavator, movements of the entire vehicle are required. A key requirement for automating the excavation task is automated trajectory tracking, and a proportional-integral-derivative (PID) controller for trajectory tracking is developed and tested. It is noted that even though the results presented in this paper are focused on a particular excavator, the research is generic and can be adapted to any tracked ground vehicle with an on-board closed-chain manipulator.