基于功能安全的分布式驱动电动汽车前轮失效补偿控制

分布式驱动电动汽车可以实现四轮转矩分配和差动转向，提升整车的动力学控制性能和经济性，但是四轮转矩独立可控的特点也对功能安全提出挑战。当前轮单侧电机出现执行器故障失效情况时，不仅会产生附加横摆力矩降低车辆安全性，差动转向功能的存在还会使车辆严重偏航。基于此，在设计分布式驱动-线控转向一体化底盘的基础上，基于功能安全提出一种分布式驱动电动汽车前轮失效补偿控制策略。首先建立分布式驱动失效动力学模型，分析前轮失效对车辆状态的影响机理，发现单一的驱动转矩截断控制无法满足车辆状态修正需求；其次设计一套备用的线控转向结构，通过变截距滑模控制算法提高切换状态下线控转向系统的转角跟踪性能，并用台架试验验证跟踪的准确性；然后设计自适应失效诊断观测器实时诊断驱动系统的电机故障，在将对应轮进行驱动转矩截断后，通过模型预测控制算法对车轮转矩重新分配实现纵向和侧向的状态跟踪；最后通过仿真和实车试验验证所提失效补偿控制策略的有效性和可用性。研究结果表明：分布式驱动电动汽车前轮单侧电机失效后，备用的线控转向系统能及时矫正前轮转角，所提出的失效补偿控制策略能够快速恢复车辆的稳定性和路径跟踪能力。

Compensation Control of Distributed Drive Electric Vehicles Based on Functional Safety

Distributed drive electric vehicles have four wheels with torque that can be controlled independently. It can achieve four-wheel torque distribution and differential steering control without a steering motor, which improves the vehicle dynamics control performance and driving economy. When the hub motor responsible for differential steering fails, it will not only generate additional yaw moment that affects the safety and stability of the vehicle but also cause the differential steering system to lose control, inducing a sudden change in the steering angle. This change forces the vehicle to deviate from the route significantly. In this study, a steering-by-wire compensation control approach for distributed drive electric vehicles with front-wheel failure was developed based on an integrated chassis design with a distributed drive and a steering-by-wire. First, the dynamic failure model of the distributed drive electric vehicle was established. The failure of the differential steering front wheel was used as an example, and the variations in the vehicle driving state were analyzed. The results show that the single-drive torque truncation control cannot satisfy the requirements of vehicle state correction. Second, a standby steer-by-wire structure was designed for the distributed drive chassis. The angle-tracking performance of the steer-by-wire system was improved using the control algorithm for variable intercept sliding mode, and the accuracy of the steer-by-wire system was verified through platform tests. An adaptive failure diagnosis observer was then designed to diagnose the motor faults of the drive system in real time. After cutting off the driving torque of the corresponding wheel, the torque was redistributed using the model predictive control algorithm to achieve longitudinal and lateral state tracking. Finally, the effectiveness and applicability of the proposed compensation control approach were verified through simulations and vehicle tests. The results show that after the front-wheel motor of the distributed drive electric vehicle fails, the standby steer-by-wire system can promptly correct the front wheel angle. The proposed steering-by-wire compensation control approach can rapidly restore the stability and tracking performance of the vehicle.