Terrain driving control algorithm for skid-steered in-wheel driving vehicles

Abstract

This thesis describes torque distribution control of six-wheeled skid-steered in-wheel motor vehicles with consideration of friction circle of each wheel to maximize terrain driving and maneuvering performance. To decide desired yaw rate according to drivers steering command, the maximum performance of yaw rate in accordance with vehicle speed and lateral tire force disturbance have been analyzed. In order to satisfy both desired net longitudinal force and desired yaw moment, which are decided in accordance with drivers intension, the torque distribution algorithm determines torque command to each wheel, in consideration of friction circles of all wheels, slip condition and motor torque limitation, based on control allocation method. Vehicle speed estimation algorithm for six-wheeled independent driving vehicles is designed to estimate accurate speed using six wheel speed, acceleration and yaw rate signals. The friction circle of each wheel is estimated using linear parametrized tire model with two threshold values, based on recursive least square method. The response of the six-wheeled and skid-steered vehicle with the proposed torque distribution algorithm and friction circle estimation algorithm has been evaluated via computer simulations using TruckSim and Matlab/Simulink co-simulation. The simulation studies show that the proposed friction circle estimation algorithm is sufficiently accurate even when a wheel is lifting under terrain-driving condition. Hill-climbing and terrain driving performance with the proposed torque distribution and friction circle estimation is enhanced in comparison with proportional torque distribution. Maneuvering performance will be verified via comparison with Ackerman steered vehicles in the near future.