Collision Avoidance of Wheel-Legged Robots on Complex Topography Based on Vertical Artificial Potential Field Method

The ability to navigate complex topography poses a significant challenge to the computational power of controllers for wheel-legged robots, as it requires the planning of the robot's motion path based on terrain height information and considering the sophisticated dynamics of the wheel-leg mechanism. Therefore, we propose a virtual force control method based on the vertical artificial potential field (APF) to address this problem. The virtual attractive and repulsive forces of the robot's center of mass (CoM) are obtained through pre-determined poles in the robot's body. We distribute the generalized virtual force to each tire by quadratic programming (QP) and then map it to the actuation joints of the legs and wheels. Additionally, a residual observer for external torque is implemented to determine the ground contact state of the wheels. The proposed control architecture is evaluated through simulations in the Simulink environment under conditions of obstacle avoidance and slope climbing. The results of these simulations demonstrate the effectiveness as well as potential of the proposed method in this paper.