Dynamic model and adaptive tracking controller for 4-Powered Caster Vehicle

A new approach for adaptive torque distribution of 4-Powered Caster Vehicle (4-PCV) is presented on complex terrain without any additional sensor. The objective is that torques applied to wheels are dynamically redistributed based on the real time conditions of the whole wheel-ground interactions in order to track the desired trajectory. A novel approach based on the redundant actuated wheels is proposed to identify the status of the vehicle and the wheel slip ratio by only observing the velocity feedback from motors encoders. A dynamic model considering the wheel-ground interaction is described. Based on the slip ratio of the wheel joints and the null space of the operational space, control strategies are employed to redistribute the torques applied to the wheel joints so that each wheel can be self-adapted to meet a complex wheel-ground condition to eliminate slippage with high rate. Simulation results show the effectiveness of the proposed estimation approach and the performance of the torque distribution schemes.