4WID轮毂电机式电动汽车横摆稳定性滑模控制研究

Study on sliding mode control for the yaw stability of 4WID wheel motor electric vehicle

针对目前所研究的四轮独立驱动(4WID)轮毂电机式电动实验车各轮驱动电机转矩独立控制且调节迅速的特点,对其横向失稳状态的稳定性控制进行了理论研究。采用分层方法,上层基于滑模控制理论,分别设计了以车身横摆角速度和质心侧偏角为控制变量并考虑其误差变化率的高阶滑模控制器,采用消除两控制变量耦合影响的协调控制策略产生维持汽车稳定所需的附加横摆力矩。根据所需附加横摆力矩的大小,在下层分配设定一个阈值判断模块,通过判定在效率车轮"差值驱动"或"差值驱动+差动制动同步协调"的四轮驱动/制动力协同分配这两种模式之间切换选择来产生附加横摆力矩的方法对汽车失稳状态进行主动干预,最后在所建立的包含"魔术公式"轮胎模型及集成电机控制模型的九自由度非线性4WID轮毂式电动汽车模型进行了典型试验工况下的仿真验证。结果显示,3个评价操稳性的重要参数在系统控制下得到很好地改善,横摆角速度的变化幅值能控制在0.291 rad/s以内,基本跟随转向输入的变化,且很好地跟踪二自由度理想汽车模型下的期望横摆角速度;同时质心侧偏角变化幅值则控制在0.077 rad以内,并接近所期望的质心侧偏角幅值0.025 rad;侧向加速度最大幅值也由无控制的8.224 m/s2变化到了6.545 m/s2,且跟随转向输入而变化。表明采用的控制方法能有效地提高汽车行驶工况下的操纵稳定性和主动安全性。

Because the drive motor torque in four-wheel independent drive （4WID） wheel motor e- lectric vehicle researched at present was independently controlled and quickly adjusted, a theoretical research was conducted on stability control of the vehicle lateral instability state. With layered meth- od and the upper layer based on the sliding mode ccontrol theory, higher-order synovial controllers were designed when the body yaw rate and the sideslip angle were respectively used as controlled variable and the error rate of the two variables were also considered. The coordinated control strategy was used to eliminate the coupling effects of the two controlled variables and to produce the desired additional yaw moment to maintain vehicle stability. A threshold determination module was set in the lower distribution control layer according to the desired additional yaw moment generated through de- termining and choosing the efficiency wheel combined with ＂differential drive＂ or ＂differential drive and differential brake＂ four-wheel drive/brake force distribution so that vehicle instability was inter- vened actively, and finally simulation verification was conducted on a nine degrees of freedom 4WID wheel motor electric vehicle with ＂magic formula＂ tire model and motor control models in the typical operating conditions. The results showed that three important parameters used to evaluate operating stability were improved a lot under the system; the variety range of the yaw rate was within 0. 291 rad/s, almost following the change of steering input and tracking the desired vehicle yaw rate of two degrees of freedom ideal vehicle well; meanwhile, the variety range of side slip angle was within a- bout 0. 077 rad, closing to the desired range of side slip angle 0. 025 rad, and the side acceleration changed from the uncontrolled 8. 224 m/s2 to 6. 545 in/s2, following the change of steering input. These showed that the control method could improve handing stability and active safety of vehicle in driving conditions.