基于人群搜索算法的四驱汽车扭矩分配控制策略

Control Strategy and Experiment of Torque Distribution for 4WD Vehicle Based on SOA

为了提高四驱汽车的整车性能,对四驱汽车扭矩分配特性进行了相关分析,并提出了一种新的扭矩分配控制策略。基于Matlab/Simulink构建了整车7自由度动力学模型;研究了不同路面、不同车速和不同转向工况下轴间扭矩分配和轮间扭矩分配对汽车质心侧偏角及横摆角速度的影响规律。以线性二自由度半车模型作为参考对象,基于人群搜索算法(Seeker optimization algorithm,SOA)和PID控制系统设计了扭矩分配控制系统,并进行了仿真分析。基于NI PXI设备构建了扭矩分配硬件在环试验平台,进行了试验验证。结果显示:该控制策略能较好地跟随驾驶员的转向意图,车辆行驶稳定性得到提升,试验结果也验证了控制系统的有效性。

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 7-DOF dynamic model of vehicle was built based on Matlab/Simulink software, including transmission system model, tire model, and sub-modules, like slip ratio calculation module and tire sideslip angle calculation module. The effects of inter-axial torque distribution ratio and inter-tire 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 inter-axial torque and inter-tire torque would have some impacts on the sideslip angle and yaw rate, and the influence of inter-tire 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 2-DOF 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 0.7 and 0.3, initial speed of 20 m/s and front wheel angle of 0. 1 rad. 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 lane-change 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 0. 067 rad/s and 0. 033 rad, respectively. Besides, the delayed response was also changed for the better. The experiment result verified the effectiveness of the proposed control system.