Research On Yaw Stability Control Of Distributed Drive Electric Vehicles

Energy conservation,security and environmental protection are three important themes of the vehicle development.In recent years,due to the energy crisis and worsening pollution,the new energy vehicles especially electric vehicles have received wide attention from the society.In addition to the advantages of energy conservation and environmental protection,security is also the main theme of electric vehicles.In the field of active safety of conventional vehicles,the function of yaw control was added to the stability control system,which was based on anti-lock braking system and traction control system.Several sensors are used to monitor the driving status of vehicle and the expected travel path is confined based on these messages.When it finds that the vehicle has the trend to beyond the expected travel trajectory,the yaw stability control system will go into operation.But at present this technology is mainly researched based on the conventional vehicle,the research aimed at electric vehicles is imperfect.In fact,the motors in the distributed drive electric vehicles are independent and controlled,which is more convenient for the stability control.In hence,the yaw stability control system based on the distributed drive electric vehicles is studied in this paper.Firstly,this paper selected four in-wheel motor to drive each wheel,and for the dynamics simulation of the distributed driving electric vehicle,the seven degrees of freedom vehicle model was built,which includes vehicle body model,tire model,driver model and so on.At the same time,the desired two degrees of freedom was built as the reference model.In order to control the stability of vehicles,two kinds of upper controller were designed based on fuzzy theory.They were used to calculate the required yaw moment through the comparison between the real state and desired state.In addition,in order to optimize the distribution of moment,two kinds of strategy were put forward.Those are distribution in one in-wheel motor and two in-wheel motors.In order to test and verify the performance of these stability control system,the simulation model was built in the platform of Simulink and was simulated under four conditions.The results indicate that these stability control system can improve the performance of the stability in a way.Through the comparison,the braking strategy is better than the driving strategy for one in-wheel motor control strategy.When the distribution coefficient of braking moment is larger than the driving moment for two in-wheel motor control strategies,the performance of stability control is much better.At the same time,it needs much smaller tire force compared with braking strategy for one-wheel motor control strategy.