具备差动助力转向功能的电动轮独立驱动汽车转矩协调控制机理研究

Motorized wheel drive technology is developing orientation of power train of future vehicle. And differential drvie assist steering technology is a novel technology based on the characteristic of independent wheel drive of these kind of electric vehicle with in-wheel motor drive. According to the driver's demand of property of power steering, the traction force difference will generate the steering assist force when the outer wheel has greater drive torque, and the inner one has less drive torque. However, with the responsibility of providing traction force for the car, the drive wheels not only have to meet the demand of differential drive assist steering system to improve steering portability, but also it must take account of the torque demand of vehicle stability control system. It can be concluded that torque coordination control is particularly critical. Based on the study on the mechanisum of power assist steering and road feel keeping of differential drive assist steering system, a novel hierarchical strategy of torque coordination control is estabilished on the basis of the theory of multi-objective programming. the top-level is composed of differential drive assist steering system and yaw moment stability control, the low-level is composed of optimal slip-ratio traction control and anti-windup compensation control. The top-level optimizes and distributes the torque demand for each drive wheel, the low-level corrects the torque demand according to road adhesion condition and in-wheel motor working situation. On the basis of the four-wheel independent drive electric vehicle developed by ourself and hardware-in-loop simulation platform, the mechanisum of power assist steering and torque coordination control are studied deeply in this project. The final purpose of this project is to verify the effect of this torque coordination control and the research achievement will provide theoretical foundation for applying differential drive assist steering technology to electric vehicle actuated by four in-wheel motor.

电动轮驱动技术是未来汽车传动技术的发展方向。差动助力转向技术是由各轮独立驱动特点催生的新技术。依据驾驶员对转向助力特性的需求，在汽车转弯时增加外侧减小内侧车轮驱动转矩，由左右驱动力差产生助力转向的作用。肩负驱动车辆行驶的驱动轮不仅要满足差动助力转向系统的转矩需求，还要兼顾汽车行驶稳定性控制的转矩指令，为此驱动轮转矩的协调控制尤为关键。本项目拟在研究差动助力转向系统助力和路感保持机理的基础上，建立以多目标规划为理论基础的分层转矩协调控制策略。上层由差动助力转向控制和横摆力偶矩稳定性控制系统组成，下层由四轮最佳滑转率控制和轮毂电机抗积分饱和补偿系统组成。上层优化分配各轮的目标转矩，下层根据路面附着和电机工作情况修正各轮转矩指令。通过自主研发的四轮独立驱动电动车和硬件在环仿真平台，研究转向助力和转矩协调控制机理，验证控制理论和方法。本项目研究成果将为电动轮汽车差动助力转向系统的应用提供理论基础。

电动轮独立驱动技术是电动汽车传动技术未来发展方向，也是引发汽车底盘集成化、电动化革命的基石。它解放了左右车轮的机械连接，使各个驱动车轮转矩解耦，独立可控。差动助力转向正是在这种独特优势的前提下被提出来。在驾驶员操纵汽车转向时，该技术按照一定规律分配左右转向驱动轮驱动转矩，从而产生转向助力和横摆力偶，辅助驾驶员操纵汽车机械转向系统完成转向行驶，实现随速可调助力大小的动力转向功能。.本项目是国内外首次将该技术应用于电动轮独立驱动汽车的尝试。主要利用仿真和实验验证的方式解决了如下关键科学问题：（1）差动助力转向理论体系构建。受到履带车辆的滑动转向方式以及电动轮实验车差动利于转向现象的启示，从转向动力学和整车侧向动力学两个方面构建了差动助力转向理论体系，解释了汽车转弯时差动驱动对于降低转弯阻力和降低转向手力的内在机理，从理论关系上证明了差动助力转向的可行性。（2）差动助力转向控制策略研究。首先利用抗积分饱和PID控制算法初步验证了其可行性，之后对于其间接性助力特征提出了针对性的转向盘转矩直接控制策略。其次，仿真分析了路面不平度、前轮定位参数变化、传感器信号噪声三方面对转向品质的影响，最终制定了以参考驾驶员转向手力为控制目标，采用鲁棒H∞回路成形控制算法控制左右驱动前轮转矩差实现转向手力的闭环控制策略，解决了助力不稳定、路感不佳的缺点。（3）差动助力转向转矩协调控制方法研究。对于各个底盘控制系统提出的多个控制目标，提出了涵盖差动助力转向控制子系统、直接横摆力偶矩稳定性控制子系统、牵引力控制子系统在内的上中下三层的转矩协调控制架构，协调控制各个驱动轮转矩，保证助力同时不失汽车稳定性。（4）差动助力转向系统的快速原型实车试验验证。完成了在改装的四轮轮毂电机驱动的试验车上进行基于dSPACE实时系统的原型实车试验。重点验证了差动助力转向控制策略，验证了其助力可行性和助力品质。.项目运行期间，发表SCI/EI论文共11篇，其中标注基金资助的相关论文7篇（SCI/EI：2/6），另有2篇SCI、2篇EI期刊稿件已投稿审阅中；申请相关国际发明专利1项；申请相关国内专利26项（发明/实用新型：16/10）；授权相关专利15项（发明/实用新型：5/10）；2013年相关研究成果获得吉林省自然科学学术成果奖三等奖1项；培养博士2人，硕士5人。后续拓展研究得到了吉林省自然科学基金的持续资助。