Research On Strategy Of Multi-axle Electromechanical Compound Wheel Drive Vehicle

In the dynamics study of multi-axle electromechanical wheel drive vehicle, the number of actuators is significantly larger than that of controlled factors. The control allocation method is an effective way to solve the redundancy control of the actuators. The multi-axle electromechanical compound wheel drive vehicle could transmit power thorough the combination of multi-power sources. Also, the structure of its power transmission system is dynamic and it has a big difference with the traditional fuel vehicles in the driving system, which means the traditional multi-wheel drive technology might not be completely applied on the multi-axle electromechanical compound drive vehicle. The vehicle control system should realize the control allocation of the driving torque on the basis of the vehicles' feedback, which could solve the following problems. For the multi-wheel drive vehicle, the problem is the movement interference, which is caused by the drive structure, between the front, back and both sides drive wheels. The second is to improve the vehicles' passing ability and the driving motors fault-tolerant control through controlling the slip ratio of the wheels.The multi-axle electromechanical compound drive vehicle is a complex multi-degree of freedom nonlinear system. To provide a basis for the strategy of the inter-axle and inter-wheel torque distribution, we establish the 11-freedom-degree model with eight-wheel-drive system and the dynamics model according to the kinematics and dynamics simulation analysis and the dynamic model.Under the hybrid-driven mode, we analyze the inter-axle and inter-wheel drive strategy for multi-axle electromechanical compound drive vehicle. The optimal object is the interaxial distribution coefficient, which is defined as the maximum of the total torque of the mechanical path and electricity transmission path. In addition, the reference model is generated from the linear two-degree-freedom model, through which the optimal side slip angle and the yaw rate are computed. The motion controller calculates the error through the feedback of the actual vehicles. Particularly, we get the yaw moment by using the feed forward and feedback compound control method. Finally, the distributor would allocate the yaw moments to each actuator motor reasonably to realize the optimal inter-wheel torque distribution.Due to the complexity of the driving environment and the life of the motor etc., the vehicle may encounter the motor failure or motor controller failure, which might cause the inefficiency of the driving force. Therefore the motor fault detection based on the adhesion coefficient estimation is proposed. Furthermore, the sliding mode control method is adopted to design the controlling distributer. Thus the robustness of the system could be improved. Besides, for the situation of the J-turn during acceleration, single-lane change during acceleration and the acceleration along a straight line, the simulation on the fault-tolerant control of the electronic motor is implemented to verify the validity of each strategy under different driving cycles.To check the vehicle control results of different strategies—namely inter-axle and inter-wheel torque optimization distribution strategies, the hardware-in-loop simulation is developed, which is based on the SIMULINK simulation environment, realizing the control communication via CAN bus and vehicle controller. Based on this simulation, the results of inter-axle and inter-wheel torque distribution strategies under different driving cycles could be verified.