Research On Dynamic Torque Allocation And Model Predictive Direct Torque Control Of Dual Permanent Magnet Motor Under Distributed Drive

Distributed drive electric vehicles have become one of the mainstream development directions for electric vehicles due to the characteristics of short transmission chains,high efficiency,simple and reliable structure,and flexible handling.However,the variable situations in driving conditions,operating modes,and structural parameters of the distributed drive vehicles put forward higher requirements of the precise torque distribution,coordinated control,and torque quality and speed range for the drive motors.In recent years,flux-intensifying interior permanent magnet motors with high efficiency,high torque density,and wide speed range have received widespread attention from experts and scholars in the field of distributed drive electric vehicle drive motor systems at home and abroad.The enhanced magnetic field operating and negative saliency(L_d>L_q)characteristics of the motor can meet the requirements of high torque,wide speed regulation,fast response,and efficient operation under the complex operating conditions with frequent acceleration and deceleration,climbing,high-speed cruising,etc.in the full speed range.However,in distributed drive applications,the switching between the multiple operating modes often leads to instability and parameter mutations of the control system.In addition,the existing torque distribution control under distributed drive regards the driving motor as a mass point which neglects its own drive characteristics.It only considers the overall vehicle economy through the relationship among motor speed,torque,and efficiency.They always pay more attention to the control of the vehicle yaw stability,and cannot fundamentally solve the coordination of the motor speed and torque,which makes it more difficult to efficiently and accurately meet the complex and variable driving and riding conditions of multi motor collaborative control.In view of the existing problems of the distributed electric vehicle drive system,this paper studies the distributed electric vehicle drive motor system based on the two FI-IPM motors.And then,based on flux partition concept,the model predictive direct torque control strategy of flux-intensifying interior permanent magnet motor in flux full-speed domain is proposed.On this basis,considering the torque and speed distribution requirements of the dual FI-IPM motors,a dynamic torque distribution strategy based on the optimal comprehensive energy efficiency is proposed.The main contents of this paper are as follows:(1)This paper provides a detailed introduction to the research background and significance of distributed drive electric vehicles,summarizes the current research status of distributed multi motor torque allocation and model predictive direct torque control at home and abroad,analyzes the problem of neglecting the characteristics of drive motors by multi motor torque allocation strategies,and the advantages of model predictive direct torque control.On this basis,the research content and chapters of the paper were clarified.(2)The basic structure and main parameters of the FI-IPM motor were elaborated,a mathematical model of the FI-IPM motor was constructed,and the impact of negative saliency characteristics of the FI-IPM motor on motor control was analyzed.The application of traditional current segmented control strategy in the FI-IPM motor was studied,and corresponding experimental research was conducted.The problems in this type of control algorithm were discussed.(3)Propose a full speed domain model predictive direct torque control strategy for FI-IPM motors based on flux partitioning,which solves the problem of current discontinuity caused by characteristic parameter changes caused by switching between multiple operating models of FI-IPM motors under traditional control strategies.Based on the mapping relationship between the speed operating region and the flux state of the FI-IPM motor,combined with the flux partitioning,a predictive flux and torque model is constructed.On this basis,the difference between the given and observed magnetic flux is used as the judgment condition for the operation of the increasing and weakening magnetic regions,achieving smooth and continuous switching current between different operating domains of the FI-IPM motor under full speed domain conditions.(4)Taking a dual motor four-wheel drive electric vehicle based on dual FI-IPM motors as the research object,this paper analyzes the loss characteristics of the FI-IPM drive motor system,constructs a loss distribution model for the front and rear dual FI-IPM motors,derives a dynamic torque allocation strategy for the dual motors based on comprehensive energy efficiency optimization,and improves the collaborative control efficiency of the distributed dual motor drive system.(5)A dual motor drive system experimental platform was constructed to conduct experimental research on the full speed domain model predictive direct torque control of FI-IPM motors based on flux partitioning control and the dynamic torque allocation strategy of dual motors based on comprehensive energy efficiency optimization,respectively,to verify the effectiveness and correctness of the proposed control strategy.