Torque Distribution Algorithm of Six-Wheeled Skid-Steered Vehicles for On-Road and Off-Road Maneuverability

This paper is concerned with the torque distribution problem including slip limitation and actuator fault tolerance to improve vehicle lateral stability and maneuverability of six-wheeled skid-steered vehicles. The torque distribution algorithm to distribute wheel torque to each wheel of a skid-steered vehicle consists of an upper level control layer, a lower level control layer and an estimation layer. The upper level control layer is designed to obtain longitudinal net force and desired yaw moment, while the lower level control layer determines distributed driving and braking torques to six wheels. The algorithm takes vehicle speed, slip ratio and tire load information from the estimation layer, as well as actuator fault information from each in-wheel motor controller unit. Wheel torque command to each wheel is determined to minimize allocation error for longitudinal net force and desired yaw moment, to keep wheel slip ratio below the limit value, and also to tolerate a failure of an in-wheel motor. The maneuvering performance of the six-wheeled and skid-steered vehicle with the proposed driving controller for both on-road and off-road conditions has been compared with a conventional vehicle via computer simulations.