2020-01-0993 Published 14 Apr 20 20Direct Yaw Moment Control of Electric Vehicle with 4 In-Wheel Motors to Improve Handling and Stability Yongqiang Zhao College of Automotive Engineering Jilin University Jinlong Cui, Zehui Zhou, Yang Fang, Deping Wang, Tianqiang Zhang, Aibin Wu, Qichun Sun, and Yang Zhao China FAW Group Corporation Citation: Zhao, Y., Cui, J., Zhou, Z., Fang, Y. et al., “Direct Yaw Moment Control of Electric Vehicle with 4 In-Wheel Motors to Improve Handling and Stability,” SAE Technical Paper 2020-01-0993, 2020, doi:10.4271/2020-01-0993. Abstract More and more OEMs are interested in in-wheel-motor drive vehicles. One of the in-wheel-motor drive vehicle key technologies is multi-motor torque distribution. A direct yaw moment control strategy for torque distribution was introduced in this paper to improve 4 in-wheel-motor electric vehicle’s handling and stability. The control method consists of three components: feedback control based on target yaw rate, feedforward control based on current lateral acceleration and deceleration control based on under/oversteer situation. Feedback control is used to make vehicle’s real yaw rate following the driver’s target yaw rate and improve vehicle yaw rate response and stability. The target yaw rate is calculated by 2DOF vehicle model and limited by lateral acceleration and vehicle current steering condition. The feedforward control is used to increase the vehicle yaw rate gain and reduce the vehicle understeer characteristic when accelerating in a curve. The deceleration control can reduce the driving torque of each motor to slow down the vehicle when in critical steering condition. The proposed control strategy was verified by an in-wheel-motor drive electric vehicle test and the experiment result showed that it can reduce vehicle understeer characteristic in steady steering condition, improve vehicle yaw rate response in transient steering condition and enhance vehicle steering stability in critical steering condition. Introduction In-wheel-motor drive electric vehicle has great advantages in flexible structure design, high drive efficiency, light vehicle weight, enhancing vehicle handling and stability and so on [ 1, 2, 3 ]. Recently, more and more OEMs are inter - ested in in-wheel-motor drive configuration and the major research filed is about in-wheel motor drive system, integrated chassis structure design and control strategy design. One of the key control techniques is direct yaw moment control, which was realized by multi-motor torque distribution and can generate an expected yaw moment to improve vehicle handling and stability. The most popular control method for direct yaw moment control was target yaw rate following control [ 4, 5]. Usually the target yaw rate was obtained from 2DOF vehicle model. In order to avoid excessive target yaw rate which may cause vehicle instability, the calculated target yaw rate should be  restricted by road adhesion condition. Many research institutes realized target yaw rate restriction by road adhesion coefficient or side slip angle information. However, the sensors price for measuring vehicle road adhesion coefficient or side slip angle was high and the reli - ability was poor. Some research institutes tried to estimate vehicle side slip angle [ 6] or road adhesion coefficient, but the research work was very difficult and the estimation accuracy need to be verified through large test. This paper introduced a novel and realizable yaw moment control method, which adopted the target yaw rate following control and limited the target yaw rate by lateral acceleration infor - mation and vehicle steering state. So, neither road adhesion coefficient nor vehicle side slip angle was needed. Meanwhile, three kinds of control mode are used together to meet the requirement of different steering conditions like steady steering condition, transient steering condition and critical steering condition. This paper is organized as follo