Obstacle Avoidance Trajectory Planning and Model-predicted Trajectory Tracking of Wheel Loaders

To address the problem of poor trajectory planning and tracking during obstacle avoidance for wheel loaders, a trajectory-planning method considering the constraints of the turning radius and dynamic change in vehicle speed was proposed. A model-predictive trajectory-tracking system for the entire vehicle based on the dynamic model of the wheel loader was constructed. In this method, based on the optimal rapidly exploring random tree algorithm and considering the number of inflation circles in the automobile body based on collision risk, the global optimal obstacle avoidance path was generated for the automobile wheel loader. By considering the minimum stable steering radius of the vehicle as a constraint, the path for obstacle avoidance was smoothed using the continuous curvature steer algorithm, and the path-velocity decomposition algorithm was adopted to plan the obstacle avoidance trajectory of the vehicle under the condition of variable-speed driving. Based on the dynamic model of the wheel loader and considering the lateral deviation and relative yaw angle in the course of driving, the vehicle powertrain was regarded as the first-order inertia link, and the vehicle dynamics prediction model was established based on model-predictive control. The objective function was converted into a quadratic programming problem by considering the acceleration, articulation angle, and vehicle speed as constraints, and a model-predictive trajectory-tracking control system was established to satisfy the obstacle avoidance of wheel loaders in the working area. Based on the obstacle avoidance trajectory generated by the planning, the model predictive trajectory-tracking control system was used to perform obstacle avoidance simulation. The results demonstrate that the constructed system can control the autonomous wheel loader from the initial position to the target position, realize the obstacle avoidance process of the vehicle in the working area, and meet the constraints of the vehicle to ensure the safety and stability of the vehicle during trajectory tracking. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.