| As one of the key technologies of the next generation of pure electric drive system，in-wheel motor driven electric vehicles have gained great importance in the industry due to itsobvious technical advantages in vehicle’s overall arrangement, chassis active control andhandling convenience. Currently, the research and development of in-wheel motor drivenelectric vehicles are still in their infancy, research interests are mainly focused on the designof motor itself with integrated development of control system, drive-by-wire/brake-by-wire,speed differential control, etc. The electric wheel driven by in-wheel motor integrates themotor, wheel hub, reducing gearbox and brake as a whole, which increases the unsprung mass,meanwhile, tyre runout under the excitation of uneven road, non-uniform load, bearing wearand installation error will cause the motor air gap non-uniform, which will worsen thevibration excitation induced by the in-wheel motor, cause the vibration of stator and rotor aswell as adjacent parts, and bring adverse effects on vehicle’s ride and ride comfort. How toreduce or even eliminate these adverse effects has become one of the key problems to besolved in the development of in-wheel motor driven electric vehicles.Focusing on the existing problems in current in-wheel driven vehicles, this articleproposes a novel topology scheme with autonomous intellectual property rights for electricwheel with embedded mount system. This scheme elastically isolates the in-wheel motor as awhole from the unsprung mass by setting elastic elements, converts the motor to a parallelmass of the sprung mass. Meanwhile, to utilize the elastic elements to absorb the vibrationenergy passed to the motor from the ground to minimize the effect on the motor air gap due toroad excitation in order to improve the vehicle’s dynamic characteristics. Around this novelstructure scheme, this article mainly carried out research in the following aspects:(1) Based on the vibration model of the novel in-wheel vehicle established according tothe topology scheme, to derive the frequency response function of vehicles’ ride performanceindicator such as body acceleration, wheel’s relative dynamic load and relative displacementbetween stator and rotor with respect to road roughness’s velocity input, and then perform thefrequency response analysis for the novel in-wheel structure as well as current electric-wheelstructure in frequency domain, to prove the superiority of the novel structure in verticaldynamic characteristics by principle; to perform the sensitivity analysis of vehicles’ rideperformance indicator with respect to some important structural parameters such as motormass, bearing stiffness, mount element stiffness and damping in order to realize the systemparameters’ effect on vibration response, which make great significance in vibration damping vibration damping for in-wheel motor driven cars as well as building foundation forsubsequent system parameters optimization;(2) According to the result of sensitivity analysis of vehicles’ ride performance indicatorwith respect to mount elements’ parameters, combined with the actual wheel structural size todesign and make prototype for mount elements, and then to gain the nonlinear stiffness modelfor every mount element based on static compression test, and utilizes the nonlinear stiffnessmodel to make comparative analysis for the vibration response under road excitation of thenovel and current electric wheel system, to verify the structural design result and dampingeffect of the mount elements, building foundation for the subsequent research on nonlineardynamics of in-wheel driven system.(3) From the constitutive structure of this study’s in-wheel motor prototype, Maxwell’sstress tensor is used to derive the analytical expression of the motor’s electromagneticmoment, the electromagnetic force wave is to be analyzed under uniform/non-uniform air gapcondition, and then research into the effect on in-wheel motor’s electromagnetic force by airgap unevenness, at the same time, the dynamic characteristics of the novel in-wheel motordriven vehicle under uniform/non-uniform air gap will be analyzed in the following aspect:nonlinear vibration response characteristics of vehicle under simultaneous acting of roadexcitation and electromagnetic excitation;(4) Building the physical model of in-wheel motor system, and then general Lagrangeequation is used to build the system’s electromechanical coupling dynamics model with thehelp of energy principle, the vibration response of motor in-wheel motor system is analyzedunder the electromagnetic excitation. The research work in this chapter can providetheoretical basis of the design and vibration control of in-wheel motor driven system.(5) To perform the lightweight design of the in-wheel motor driven system with outerrotor and inner stator. Direct reduction of unsprung mass is used to improve the ride and ridecomfort. Lightweight design mainly include two aspects:○1under the premise of ensuringvehicles’ dynamic performance, lightweight design of in-wheel motor is performed bycombining Finite Element Method (FEM), Response Surface Method (RSM) and ParticleSwarm Optimization (PSO) algorithm, to minimize the mass of in-wheel motor, and thenmake comparative analysis of in-wheel motor’s magnetic field distribution and torquecharacteristics before and after optimization to verify the result of optimization;②according to the result of optimization in step○1, to modify the size of stator bracket andperform topology optimization under stress constraint by using variable density method, and then verify the result of optimization by performing stress analysis to the structure afteroptimization.(6) Completing the development of the novel electric wheel prototype system, functionaltest will be performed to the pre-prototype, and then preliminary feasibility verification of theability of this novel electric wheel structure of in-wheel motor drive system with embeddedmount to solve the non-uniform air gap problem due to road excitation will be performed. |
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