Research On Driving Control Strategy For Distributed Driving Electric Vehicle

Compared with the centralized drive electric vehicle,the drive wheel torque of the distributed drive electric vehicle has some additional advantages,such as more efficient drive system,more convenient vehicle layout,quicker dynamic response,and more easily realizing the stability control and comfort control of the vehicle.Similar to the mechanical differential,the distributed drive electric vehicle needs to use electronic differential system to achieve smooth steering.The direct yaw moment control system(DYC)of the centralized drive vehicle needs to use ABS asymmetric braking to achieve,but the DYC of the distributed drive electric vehicle can be achieved by independent control of wheel driving and braking force.Therefore,how to exert technical advantages of the distributed drive electric vehicle,the realization of electronic differential and vehicle stability control have become the research hotspots of the drive control for the distributed drive electric vehicle.In this paper,the distributed drive electric vehicle of the front wheel independent drive is the research object,in order to improve the driving performance under the stable driving condition,the lateral stability and the longitudinal stability under extreme driving conditions,this paper studies the control technology(vehicle control strategy and motor control strategy)of driving system for the distributed drive electric vehicle.Firstly,this paper builds the vehicle control strategy based on the double-layer structure and the space vector control strategy of the permanent magnet synchronous motor(PMSM),establishes the co-simulation platform of distributed drive electric vehicle for the verification of vehicle control strategy based Carsim/Simulink,and the driving system simulation model and control system code model of PMSM for verification of space vector control strategy.Then,based on the hardware platform,the validity of the space vector control strategy of PMSM is verified by the model based design(MBD)method.The effectiveness of the vehicle control strategy is verified based on the simulation analysis of different driving conditions.The main contents of the thesis include:(1)This paper presents a double-layer vehicle control strategy for the upper layer as the driving force distribution layer and the lower layer as the slip rate control layer.In the driving force distribution layer,according to the performance requirements of different driving conditions,the equal power allocation control strategy is proposed to improve the driving performance of the stable steering condition.The direct yaw moment control strategy based on fuzzy control is proposed to improve the stability of the limited driving condition.The similar drive wheel slip rate control strategy is proposed to improve the stability of straight driving.A slip rate control strategy based on logic threshold is proposed for the slip rate control layer.(2)This paper analyzes the basic principle of space vector control strategy of PMSM,the basic principle of coordinate system transformation and space vector pulse width modulation(SVPWM)algorithm,and introduces the realization steps of space vector control of PMSM based on MBD and Simulink Embedded Coder Toolbox.(3)This paper presents the co-simulation platform amework of the distributed drive electric vehicle based on Carsim/Simulink,and establishes the vehicle model based on Carsim and each module model of proposed vehicle control strategies.This paper establishes the single closed loop space vector drive system model of PMSM.Combined with the laboratory hardware platform,and based on “V” development process,the simulation model of double closed loop space vector driving system and the code model of control system are established for PMSM.(4)This paper designs the GUI interface of the PMSM control system based on RTDX.Based on the experimental hardware platform and RTW code automatic generation technology,the experimental study of the driving control of PMSM is given,and the experimental results are analyzed to verify the effectiveness of the space vector control strategy.(5)The accuracy of the co-simulation platform of the distributed drive electric vehicle based on Carsim/Simulink is verified by comparing with the driving performance between the centralized drive electric vehicle and distributed drive electric vehicle with the equal torque distribution strategy.Aiming at the vehicle control strategy,the driving performance of the vehicle under steady steering condition is simulated,and the effectiveness of the equal power allocation control strategy is verified.The driving performance of the vehicle under the limited steering condition is simulated,and the effectiveness of the control strategy of DYC based on the fuzzy control plus equal power allocation strategy is verified.The driving performance of the vehicle under the limited straight driving condition is simulated,and the effectiveness of the control strategy of similar drive wheel slip rate is verified.