Configuration Analysis And Structural Research Of In-wheel Motor

Electric vehicle becomes more and more popular because that it is the only kind ofvehicle which creates no pollution. As an important developing aspect of electric cars,the electric wheel especially which is driven directly by external rotor in-wheel motor,can extensively simplify the power transmission system, making power transmissionwith a high efficiency. The electric car’s power system lies in the wheels, providingmore inner space available for users. Meanwhile, the permanent magnet synchronousmotor can provide in-wheel motor with high power-density. Through the wire control tothe in-wheel motor, the wheels response quicker to the control, providing moreprobabilities to achieve independent control policy for the wheels. However, moving thepower system from the body to the wheels brings a problem to the placement in thewheel; further more, the wheel mass will increase, the mass ratio of the body to wheelwill decrease by the mounting of power system, thus decreasing the car smoothness,increasing dynamic load of wheels, decreasing road friendly and driving security,causing vertical negative effect problems to the car. Above are the key problems thatneed to be solved by in wheel motor driven cars today. Involving with the analysis onsuspension structure of in-wheel motor driven car, this study gives a deep research onin-wheel motor’s structure, in order to place the driven system, braking system,transmission system and connection system right in the wheel, make full use ofin-wheel space, design electric wheels that can drive the car speedily, stably, safely andlightly.The in-wheel motor driven car’s kinetic structure elicited by analyzing differentmounting modes of in-wheel motor proves that the suspension motor in the wheel is theoptimized kinetic structure, which can solve the exacerbating problem of verticalvibration. In this essay, we studies the affection to the smoothness caused by the massincrease of in-wheel motor, systematically analyze and compare the vehicle suspensionstructure and its kinetics differential equation by different mounting modes of theelectric wheel. Applying the in-wheel motor as the vibration absorber will be limited inthe spaces of the wheel in a damping action. In this situation, we put the verticalmovement as an restriction to optimize parameters of different suspension structures,work out the optimized suspension structure of electric wheel where the in-wheel motorand arrester are suspended to the axis. We conclud after comparison that electric car with optimized structure can not only solve the negtive unsprung affection of thein-wheel motor, but also obtain smoothness and safty better than the one without thatoptimized structure.In-wheel initiative damping system basing on optimized control algorithm canreduce the relative displacement between the motor and the wheel. Taking the spacelimit of the wheel, driving road differences, and the unfixed ratio of body’ssprung/unsprung mass into account, we found that the space required by in-wheel motorwould interact with the vertical relative displacement of the wheel in limited space.Meanwhile, this essay uses keeping the vehicle smoothness as basic condition, reducingthe vertical relative displacement between in-wheel motor and the wheel as the target,studies on the in-wheel initiative damping system, for reducing the space requirement ofthe in-wheel motor. By way of simulation, this study validates that in-wheel initiativedamping system can not only insure the smoothness, but also greatly reduce the relativedisplacement between the in-wheel motor and the wheel during shock absorption, whichmeans reducing the space requirement of the damping system. In addition, the initiativedamping system can reduce the space requirement; also can avoid the re-design matchof the damping system structure by way of adapting changes of the motor, wheel andbody mass through a controller.This study introduces a new high speed electric wheel. Based on the theory thattransforming in-wheel motor’s unsprung mass to vibration absorber will improve thesmoothness according to optimized kinetic structure, we use a sprung damper tosuspend the annular motor and the arrester in the wheel, and a crisscross slidertransmission system to achieve the transmission between the motor and wheel at aneven speed. In this way, we can resolve the problem of the suspension motor structure inthe wheel, meeting the demand of a high driving speed, improving the smoothness andstability at the same time. By comparing different motors according to the claim of theelectric vehicle to in-wheel motor, we fix on the external rotor permanent magnetsynchronous motor as the motor of electric wheels. Also, according to the calculationabout the motor performance matching the vehicle’s kinetic performance, we analyzethe key parameters of in-wheel motor through the method of field circuit combination.By the simulation analysis and test-bed validation, we conclude that the torque andspeed of the motor can meet the requirement of vehicle’s kinetics performance.The lightness design of electric wheel is researched from below three aspects.Firstly, shape the electromagnetism scenario of in-wheel motor with a9kg mass reduce which satisfies the vehicle kinetics performance by using the motor design and analyzesoftware; secondly, based on the Finite Element Analysis result about the structure ofmotor shell, brake disc and transmission system, redesign the motor shell andtransmission system with aluminum alloy material, reducing the mass by23kg alike;thirdly, by integrating disc spring hydraulic damping device with the sprung of thedamping system, oriented pole and hydraulic damper, improving smoothness andreducing wheel mass at one time.