Research On Key Technologies Of Modular In-wheel Motor

In-wheel motors have the advantages of compact structure,fast dynamic response,high driving efficiency,and good vehicle handling,and are suitable for driving of pure electric vehicles.In the context of electrification,light weight and intelligence of new energy vehicles,wheel in-wheel motors are favored by enterprises and scientific researchers.Electric vehicles have strict requirements on the reliability of in-wheel motors.In order to achieve fault-tolerant operation of in-wheel motors,an effective way is to modularize the motor structure.This paper studies the multiphysics of multi-unit modular in-wheel motors for electric vehicles.The work done includes:Firstly,the basic working principle of the modular in-wheel motor is analyzed,and the electromagnetic design of the modular in-wheel motor is complete.This paper analyzes the magnetomotive force of several kinds of fractional slot concentrated windings.To select the appropriate slot/pole combination of the unit motor,the characteristics of the unit motor using different windings is compared with the finite element simulation.The magnetic circuit method is used to calculate the air gap magnetic field and the back EMF of the motor when it is not loaded,and the electromagnetic torque when the motor is loaded.The accuracy of the analytical calculation is verified by finite element simulation.Secondly,the fault-tolerant strategy of modular in-wheel motors is studied.This paper analyzes the electromagnetic characteristics of the open-circuit fault of the in-wheel motor,and derives the fault-tolerant current of the remaining two phase windings of the open-circuit fault module when adopting the magnetomotive force compensation strategy.Regarding the torque distribution of each module during open circuit fault tolerance,three principles are proposed: the principle of average torque distribution,of equal current,and of minimum copper consumption,and the effects of different principles on fault tolerance performance is compared.This paper analyze the electromagnetic characteristics of in-wheel motors during short-circuit faults,and derives the fault-tolerant currents of the remaining two phase windings of the short-circuit fault module when using magnetomotive force compensation and electromagnetic power compensation strategies.two principles for electromagnetic power compensation fault tolerance are proposed: the principle of average torque distribution,and of minimum copper consumption.The impact of different short-circuit fault tolerance strategies on fault tolerance performance is compared.Thirdly,the electromagnetic vibration characteristics of the modular in-wheel motor are studied.The stator system is modeled and modal analysis is done to obtain the natural frequency and corresponding vibration mode of the stator system.According to the Maxwell tensor equation,the air gap magnetic field is used to calculate the air gap electromagnetic force of the modular in-wheel motor during normal operation,open circuit and short circuit faults,and fault tolerance.Using the electromagnetic field-structure field unidirectional coupling method,the electromagnetic vibration characteristics of the modular in-wheel motor under different working conditions are simulated and analyzed.Finally,This paper analyzes the temperature rise characteristics of the modular in-wheel motor.The temperature field model of the modular in-wheel motor is established.The modeling process involves the winding equivalent,air gap equivalent,and the calculation of surface heat transfer coefficient.The temperature rise characteristics of the in-wheel motor in normal operation,open circuit and short circuit faults and fault tolerance are simulated and analyzed.