Research On Electronic Differential Of Electric Vehicle Based On Double Hub Motor

With the decrease of fossil energy such as oil,the problem of air pollution and exhaust emissions from fuel cars is becoming more and more serious,and more and more attention has been paid to electric cars.Because of its simple mechanical structure and easy to realize complex driving mode,hub motor driven electric vehicle has become the general direction of development in the automotive field at home and abroad.However,there are many problems in the electronic differential system of electric vehicles driven by hub motors,such as unbalanced differential speed,poor steering stability and high cost of the vehicle.Aiming at these problems and shortcomings,and according to the dynamic analysis and model establishment of the double-hub motor electric vehicle,this thesis put forward the electronic differential calculation method of direct yaw torque control based on terminal sliding mode with the double-hub motor electric vehicle being taken as the research object.The method solved the problem of poor stability in the limit working condition of traditional torque control.At the same time,an improved Ackerman steering model based on slip rate and yaw rate is proposed,and a slip ratio feedback module is introduced for the speed control electronic differential algorithm.Under the premise of low cost,the electronic differential algorithm can have Good steering characteristics for the purpose.Firstly,this thesis took the double-hub motor electric vehicle as the research object,and completed the establishment of the complete vehicle dynamics model of the double-hub motor electric vehicle.By establishing a two-degree of freedom reference model,the ideal centroid deflection angle and ideal yaw angle velocity were obtained,which could be used to guide the calculation of electronic differential velocity.And the use of Simulink to build a vehicle simulation model of seven degrees of freedom,CarSim and Simulink to establish a joint simulation of the vehicle model,respectively was applied as the speed control electronic differential algorithm and torque control electronic differential algorithm simulation research foundation.Secondly,the electronic differential algorithm of torque control was studied.Aiming at the problem of poor stability under the limit working condition of torque control,a direct yaw torque control based on terminal sliding mode was proposed.Based on the established 2-dof reference model and the co-simulation model of CarSim and Simulink,the direct yaw moment control based on fuzzy control and the direct yaw moment control based on terminal sliding mode control were designed.The advantages and disadvantages of the two kinds of torque control and the traditional vertical load control were compared through the joint simulation of the double shift line working condition and the limited working condition.At the same time,the electronic differential velocity method was studied based on velocity control.Aiming at the situation that the traditional Ackerman steering model could not adapt to the medium speed and high speed,the improved Ackerman steering model based on slip rate and yaw velocity was put forward.Based on the two-dof reference model and the seven-dof vehicle model proposed,the simulation analysis of the whole speed control electronic differential algorithm was completed by Simulink.Finally,based on the speed control electronic differential algorithm,the design and construction of the electric vehicle experimental platform were completed,including the vehicle body design,acceleration pedal,front bridge selection,rear drive wheel support,steering sensor and front and rear bridge connection design,as well as the selection of the main controller.The feasibility of the proposed electronic differential velocity control method was verified by a real vehicle test.According to the analysis of the experimental results and the existing problems of the experimental platform,the future research trend was determined.