Abstract:In order to promote the overall performance of four wheel drive (4WD) vehicles, its torque distribution was analyzed and a new control strategy was put forward. The 7DOF dynamic model of vehicle was built based on Matlab/Simulink software, including transmission system model, tire model, and submodules, like slip ratio calculation module and tire sideslip angle calculation module. The effects of interaxial torque distribution ratio and intertire torque distribution under the conditions of different roads, speeds and angles on sideslip angle and yaw rate of vehicle were analyzed. The results showed that when the car was steering, the slips of both interaxial torque and intertire torque would have some impacts on the sideslip angle and yaw rate, and the influence of intertire distribution was considerably evident. When the front axle gained more torque, the over steering trend could be improved to a certain extent. When the outside tire gained more torque, the steering ability of vehicle was promoted. When the inside tire gained more torque, the over steering trend could be effectively restrained. Taking the linear 2DOF half vehicle model as the reference object, the torque distribution control system was designed based on the seeker optimization algorithm (SOA) and PID control system. Besides, simulation was carried out with road friction coefficient of 07 and 03, initial speed of 20m/s and front wheel angle of 01rad. The result showed that the proposed control strategy can implement the driver’s steering intention successfully under different road conditions to improve the driving stability of the vehicle. Based on the NI PXI equipment, hardware in the loop (HIL) experiment platform for torque distribution was established. And according to JASO-C-707 and ISO3888-2 vehicle lanechange performance test criteria, the front wheel angle signal was taken as the input of HIL experiment for validating the proposed control system. The result demonstrated that, compared with the ones without control, the peak value of yaw rate and sideslip angle were reduced by 0067rad/s and 0033rad, respectively. Besides, the delayed response was also changed for the better. The experiment result verified the effectiveness of the proposed control system.
