Design And Research On Four-side-wheel-Motor-Driving System Of Electric Vehicle

Compared with the single motor centralized drive,the multi-motor-distributed-drive electric vehicle is promising in improving dynamic performance,handling stability and economy of the vehicle.In recent years,the multi-motor-distributed-drive electric vehicle has attracted widespread attentions in both vehicle industry and academia.Generally,the distributed control is realized based on the in-wheel motor or the side-wheel motor.In light of the technical bottlenecks that have not been well figured out,the side-wheel motor becomes the best solution for the real practice and the industrialization,as compared with the case of in-wheel motor.In this research,a refitting work from a mass-production electric vehicle with single middle-motor to a distributed-drive electric vehicle with four-wheel side-wheel motors is conducted with the assistance of cooperative enterprise.The modified vehicle is named as "New Fire No.3" of which the power matching,design of mechanical structure,and reconstruction of the high voltage electric system have been completed.A three-layer hierarchical control strategy is proposed for the distributed--four-wheel drive electric vehicle,including:1)Decision making layer for the desired yaw moment and the total driving force.In this layer,the total driving force is calculated via the driver operation on the opening proportion of the accelerator pedal.Moreover,taking the yaw rate and the side slip angle of center of mass as the parameters,the difference between the ideal value and the actual value can be obtained as the input of the fuzzy controller so as to determine the desired yaw moment.2)Objective function based distribution layer for the driving force.In this layer,an integrated objective function which considers both the handling stability and economy is pre-defined,by which the target output torque of the four wheels can be calculated under a certain constraint.3)Anti-slip control layer.In this layer,a fuzzy PI controller is developed.The proposed controller enables the wheel slip ratio to be controlled within a pre-set optimal value when a drive wheel slip occurs,thus carrying out the anti--slip function,as well as the improvement of the handling stability of the vehicle.A co-simulation platform is constructed by utilizing MATLAB/Simulink and CarSim,and the control strategy program is implemented via MATLAB/Simulink.In this connection,a vehicle model is created in CarSim based on the parameters of "New Fire No.3".In order to verify the effectiveness of the proposed control strategy,the stability-oriented objective allocation strategy,the economy-oriented objective allocation strategy and anti-slip control strategy are designed for the numerical simulations,respectively.A vehicle communication network is constructed by employing software and hardware of NI Company,and a rapid control prototype(RCP)test platform is built as well.Subsequently,the real vehicle test of the distributed drive control is carried out.Finally,the model accuracy of the distributed-four-wheel side-wheel-motor-drive electric vehicle is verified based on the comparison between the experimental results and the numerical simulation.