Research On Dual Motor Cascade Drive Control System For Electric Vehicles

As an important way to solve the energy crisis and environmental pollution,electric vehicles and their drive systems have always been the focus of research.With the continuous improvement of the performance demand of electric vehicles,it is difficult to adopt a single-motor drive control system to simultaneously meet the needs of large torque at low speed and high-power at high speed.While modular cascade motor system can effectively solve this problem.As an important part of the modular cascade motor system,the dual-motor cascade drive control system has a broader application prospect in the fields of complex operating conditions,high reliability,and wide speed range.Through the cooperation of two different parameter motors,a high efficient system which is more suitable for electric vehicles can be matched.On the basis of cascade dual motor,this paper studies the matching method,optimal torque distribution and maximum efficiency control strategy of dual motor cascade system.At the same time,the development of the whole drive control system,including hardware design,software debugging,is studied in order to improve the system performance.In order to study the optimal matching problem of dual motor,this paper completes the overall architecture design of the system on the basis of combing the interaction and mutual restriction among the various parts of the system and establishes the mathematical model of the whole vehicle based on the energy macroscopic expression method.At the same time,the characteristics and application scenarios of motor matching in different modes,such as torque and rotational speed coupling mode,series parallel topology and so on,are studied.Finally,a quantitative analysis method based on the fast efficiency estimation of permanent magnet motor and the willians model for different basic speed motor matching is proposed,which provides the basis for the subsequent selection of drive motor.In order to achieve the optimal control of the system,the system torque allocation strategy is studied on the basis of the analysis of the control architecture of the dual motor cascade drive control system.The optimal control strategy of the dual motor efficiency is put forward with the goal of the optimal system efficiency.Considering the worsening of the cooling conditions after the cascading of the two motors,this paper takes temperature into account the factors affecting the motor efficiency and then the efficiency map of the motor at different temperatures is corrected.In order to improve the motor running status and system reliability,this paper studies the dual-motor fuzzy control strategy,which optimizes the motor operating point distribution and solves the problem of frequent start and stop of the motor.According to the control requirements of the dual motor cascade drive system,the overall design scheme of the vehicle controller is analyzed.This paper design the hardware including the minimum system,the power supply conversion circuit and so on.The controller software is developed by using the idea of layering and modularization.Based on DSpace,the hardware in loop method is used to build the control platform of hardware-in-loop simulation.The torque control strategy is tested and the performance of the control strategy is verified.