Design And Characteristic Research Of Permanent Magnet Synchronous Motor For Vehicle Electronic Power Steering

With the improvement of people's living standards,cars are becoming more and more popular.The problem of traffic safety has attracted more and more attention,and people put forward higher requirements for automobile safety.Electric power steering system can relieve fatigue during driving,but the torque of the power steering system directly acts on the steering wheel input rod,so the stability and accuracy of the output torque is particularly important.The power motor is the actuator of the electric power steering system,and its output characteristics directly affect the performance of the electric power steering system.Many scholars and technicians have studied the selection,design and optimization of the power motor.Permanent magnet synchronous motor is widely used as the power motor because of its high efficiency,small size and large output power.However,the permanent magnet synchronous motor has the disadvantages of high vibration,high noise and high output torque ripple.These are extremely detrimental to the electric power steering system.In order to solve these problems,an interior permanent magnet synchronous motor for the electric power steering system of cars is proposed in this paper.The broken-line permanent magnet and non-uniform rotor core structure can effectively reduce the cogging torque and the harmonic content of air gap magnetic field,and it can reduce noise and vibration.In this paper,the background,working principle,application and research status of the electric power steering system are introduced firstly,and characteristics of the common steering power motor are analyzed and compared.The research status of reducing cogging torque and output torque ripple is also introduced.Secondly,this paper introduces the structure type and operation principle of interior permanent magnet synchronous motor,and an important factor affecting torque ripple is obtained by theoretical deduction: the content of harmonic;It can be reduced by designing the air gap length reasonably.On the basis of this theory,an interior permanent magnet synchronous motor with broken-line permanent magnets is proposed in this paper,and mathematical model of the interior permanent magnet synchronous motor is established.Meanwhile,its rotor core,permanent magnet,stator punch,winding and other structures are preliminarily designed.Then,the finite element model is established by using the software ANSYS Maxwell.By comparing with the traditional interior permanent magnet synchronous motor,the magnetic field distribution and air gap magnetic density of the interior permanent magnet synchronous motor proposed in this paper are studied,and the cogging torque?the waveform of the back-EMF?inductance?other characteristics of the motor are also studied.Finally,the paper optimizes the four structural parameters of the interior permanent magnet synchronous motor with broken-line permanent magnets,and introduces the theory of the Taguchi method.It finds out the best parameter combination.In addition,the software is used to simulate the models before and after optimization,and the simulation results prove the effectiveness of the optimization method.