Research On Yaw Stability Control Of Electric Vehicle Driven By Four-wheel Hub Motor

Hub-motor electric vehicles have manytechnical advantages such as higher energy efficiency,more flexible active chassis control,and faster control response,and it has become the research direction of many automobile manufacturers and scientific research institutions.The drive form of in-wheel motor-driven electric vehicle is completely different from traditional internal combustion engine vehicle,and is not suitable for all traditional active safety systems.Therefore,it is required to develop the active safety systems purposefully.At present,in the active safety system research of four-wheel hub motors driven electric vehicles,most researchers have only conducted theoretical research,and few researchers have conducted experimental research.The yaw stability control system,as one of the most important active safety technologies for vehicles,is of great significance for improving its stability.In this study,a small electric test vehicle driven by four wheel hub motors of the research group is used as the research object to study its yaw stability control system.Mainly studied the vehicle motion state estimation algorithm,modified yaw moment decision algorithm,modified yaw moment distribution algorithm,and carried out simulation and actual vehicle test verification.Firstly,in order to accurately estimate the motion state of vehicle,based on the seven-degree-of-freedom vehicle dynamics model and the Dugoff nonlinear tire model,a nonlinear observer was proposed to jointly estimate the transverse and longitudinal speed and the yaw rate.Secondly,based on the two-degree-of-freedom reference vehicle model and the estimated vehicle motion state parameter values,a modified yaw moment decision device was designed using the sliding mode variable structure control algorithm.Then,considering the constraints of road adhesion and in-wheel motor torque,modified yaw moment distributors based on the equal distribution and load proportional distribution methods were designed.Last,a simulation model of the designed yaw stability control system was built in Simulink for simulation verification.Due to the Moto Hawk series software development platform-D2P(From Development to Production)rapid prototyping development platform provided by Woodward,the design of actual vehicle test was carried out.Then the control algorithm was imported into the D2 P rapid prototyping development platform,the software code was generated,and the software was flashed into the D2 P controller hardware,and the actual vehicle test under limited conditions was completed.The simulation results show that the vehicle state estimation algorithm proposed in this study has high accuracy and can be adapted to different operating conditions.The response speed of the designed yaw stability control strategy can be increased by 3%,the longitudinal speed can be raised by up to 3.75%,and the steering wheel angle was reduced by up to 31.93%,which significantly improves the yaw stability of the car.The actual vehicle test results reveal that the yaw stability control strategy designed in this study can increase the vehicle’s response speed by up to 2.12%,and the dynamic performance of the vehicle can be improved by up to 4.75%,which significantly improves the yaw stability performance of the vehicle.