| In recent years,the sustained and rapid development of the electric vehicle has become one of the effective ways to promote China’s energy structure reform and solve long-term development problems such as energy security and environmental pollution.Distributed wheel drive electric vehicles have outstanding advantages such as short transmission chains,flexible handling,high efficiency and energy conservation,and easy implementation of vehicle active safety,which have become one of the future development directions for electric vehicles at home and abroad.As one of the key execution components of distributed hub drive electric vehicles,the driving performance of the wheel traction motor directly affects the overall performance of the electric vehicle.Currently,permanent magnet motors have the advantages of high efficiency and high power density,and have been widely used in the field of automotive drive motors.However,due to the inherent characteristics of permanent magnet motors,the air gap field of permanent magnet hub motors remains basically constant,which limits their application in electric vehicles that require wide speed regulation(with a speed range of no less than 5 times the base speed).It can be seen that how to effectively regulate and control the air gap field of permanent magnet wheel hub motors,improve the output torque of permanent magnet wheel hub motors,and expand the speed range of such motors has become an urgent problem in the current research field of distributed wheel drive electric vehicle drive motors.In response to the above issues,a partitioned stator hybrid excitation axial field permanent magnet hub motor(PS-HEAFPMHM)is studied in this thesis.It not only retains the high torque density and high efficiency of axial field permanent magnet motors,but also the introduction of electric excitation makes this type of motor have the advantages of convenient magnetic adjustment,low speed and high torque,especially suitable for applications requiring wide speed range,high power and output torque.It can adapt to the complex operating conditions of distributed hub drive electric vehicles.However,the introduction of electric excitation has increased the difficulty of controlling this type of motor,and how to coordinate the control relationship between armature current and excitation current has become the key to efficient driving control and rapid promotion and application of this type of hybrid excitation axial flux permanent magnet hub motor.Therefore,considering the driving performance requirements of distributed hub traction drive electric vehicles under complex operating conditions,this thesis proposes a hybrid excitation axial field permanent magnet hub motor drive control strategy based on variable operating conditions,and conducts efficient driving control research on this type of the PS-HEAFPMHM,providing a theoretical basis and technical reference for the application of this type of motor system in the field of distributed hub drive electric vehicles,Meanwhile,it will also enrich the research content of axial field permanent magnet motors and improve the overall research level of axial field permanent magnet motors.The main research content of this thesis is as follows:1)This thesis presents the background and significance of the research,elaborates on the research status of permanent magnet hub motors,and analyzes in detail the existing basic control strategies and coordinated control strategies of hybrid excitation axial field permanent magnet motors.In addition,the development status and key problems of model predictive control technology in the motor domain are summarized.2)The mapping relationship between different operating conditions of electric vehicles and hub motors is studied.On this basis,the topology and magnetic tuning principle of the PS-HEAFPMHM are analysed in detail,and the mathematical model is established under a synchronous rotating coordinate system.A multiple vector model predictive current control is proposed to address the impact of field coupling under independent control of armature and excitation.The semi physical simulation system platform based on d SPACE1007 was constructed to experimentally verify the effectiveness of the control strategy,laying the foundation for the research on control strategies in subsequent chapters.3)A multi current optimal control strategy for the PS-HEAFPMHM considering variable operating conditions is proposed.Based on the Lagrange multiplier method,the reference current constraint equations are constructd.Considering the control requirements of drive motors under different operating conditions,the multi-operating condition objective functions are designed.Based on the constructed experimental platform,the experimental research is conducted on the operational performance of different control strategies under different operating conditions to verify the effectiveness of the multi current optimal control strategy.4)A adaptive model predictive current control method for the PS-HEAFPMHM is proposed.The variation characteristics of motor parameters and their sensitivity to predictive control are analysed in detail.On this basis,according to Popov’s hyperstability theory,the three-inequalities stability criterion is introduced to design the adaptive law of each parameter,and corresponding experimental studies were conducted to verify the effectiveness of the control strategy.5)A parameter free model predictive control for the PS-HEAFPMHM is proposed.Based on the gradient of current variation,the prediction model of the PS-HEAFPMHM is constructed.On this basis,the recursive least squares method is introduced,and identification matrices and multi-resolution coefficients are designed for different operating conditions to achieve online optimization of identification target and frequency.Through experimental research on the operational performance of this control strategy under different operating conditions,the effectiveness of this strategy is verified. |
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