The Research Of Drive System Failsafe In Four In-wheel Motor Drive Electric Vehicles

Electric vehicles use motor as power source, which can able to diversify drivestructure and arrangement. Because of its high transmission efficiency, shorttransmission chain and easy to implement integrated electronic control technology,electric vehicles become an important study direction. People pay more attentionand study on active safety technology, differential steering, driving reliability andsecurity of in-wheel motor drive type electric vehicle, using four separate hub motoras a power source, the probability of failure of the electric drive system increased.Electric drive system failure would impact torque of hub motor, driving dynamicsand driving safety performance of four-wheel direct-drive vehicles.The impact of failure in electric drive system of the wheel direct drive electricvehicle on the dynamic performance of the vehicle was studied, which includesvehicle dynamics and handling stability. In-wheel motor failure will cause the vehicleloss the power and would lead to over steer or under steer when the vehicle is turning.The wheel hub motor failure conditions and failure modes were classified, whichcan be divided into single-wheel motor failure, coaxial opposite side wheel hub motorfailure, different axis different wheel hub motor shaft failure, wheel hub motor failureand multi-wheel motor failure, where the latter two cases is a dangerous occasion,which need to stop the car, the first three conditions need to adopt appropriatealgorithm to ensure driving safety of the vehicle.The failure control system of electric drive system was also studied. The systemincludes a signal detection layer, logic layer and the torque distribution layer.Depending on the failure modes, fail-safe control strategy is proposed based on thepower of the electric drive system and a comprehensive coordination based on anintegrated and coordinated stability control strategy, respectively.In order to verify the validity of the control algorithm, seven degrees of freedomvehicle dynamics model was built based on MATlab software, which includes driversub-model, tire dynamics sub-model, vehicle dynamics sub-models, the failurecontrol algorithms model and so on.Several simulation conditions were proposed and the failure control algorithm was simulated based on seven DOF vehicle dynamic models. The simulation resultsshow that the control algorithm can improve vehicle dynamic quality when thevehicle accelerator pedal value exceeds the threshold value and the steering anglesignal is less than the threshold value, and when the accelerator pedal signal is lessthan the threshold value or steering wheel angle signal exceeds the threshold valuefailsafe control algorithm can improve vehicle handling and stability.