1.1 The purpose andsignificance of the design

With the rapiddevelopment of the electrification and intelligentization of the automotiveindustry, the world’s major automotive manufacturers have regard electricvehicles as the main development trend in the future. The electric drive systemis the core technology of the electric vehicle powertrain system. Electricdrive systems currently fall into three main categories: concentrated motordrives, wheel-side motor drives, and electric wheel drives. Concentrated motordrive is used to drive an engine in an internal-combustion engine to anelectric motor. A wheel-side motor drive means that a motor and a constantspeed ratio reducer are integrated into a frame, and power is output from theoutput shaft of the speed reducer. The section is transmitted to the wheelaxles to drive the wheels. The electric wheel drive, also known as the hubmotor drive, integrates the hub motor, transmission mechanism, brake and othercomponents in the rim, and the power is directly driven by the hub motorthrough the transmission mechanism. Is a separate drive unit. The first twodrive technologies have now been widely applied to mass-produced pure electricvehicles and hybrid vehicles, and electric wheel drive technology has not beenwidely applied to mass-produced pure electric cars because of high technicaland cost requirements. . However, because electric wheel drive still has manyadvantages compared to the former two technologies, electric wheel technologyis a very promising research direction.
Compared with other driving methods,electric wheels driven by electric wheels have many advantages:

(1) The transmissioncomponents such as clutch, transmission, transmission shaft and differentialare eliminated, the transmission system is simplified, the transmissionefficiency is improved, and the driving speed is reduced. Noise.

(2) Improve the passingperformance of off-road vehicles. The arrangement of the electric wheel drivesystem is flexible, which facilitates the realization of multi-axis multi-wheeldrive. Using the measures of all-wheel drive and drive wheel control alone canmaximize the use of the ground's ability to be attached. At the same time, thesimplified drive system can also increase the lift of the vehicle gap.

(3) Flexible cableconnection between the electric wheel and the power source occupies less space,and the layout of the vehicle is very flexible.

(4) It is easy to applythe wire-controlled four-wheel steering technology, effectively reducing thesteering radius and improving the steering performance. , Or even achieve zeroturning radius, increasing steerability.

(5) The electric wheeldrive system can control and distribute the drive torque of each drive wheel bycontrolling the output torque of the hub motor, which overcomes the longresponse time of the traditional internal combustion engine due to the drivesystem. The defect of low control accuracy avoids the increase of energyconsumption due to the use of brakes to achieve anti-skid drive control intraditional cars.

(6) The electric wheeldrive system can achieve rapid and efficient by adopting electromechanical compoundbraking or full electric braking system. The brake control, at the same timeachieve regenerative braking function, reduce energy consumption and increasethe driving range of electric vehicles.

(7) The simplification ofthe chassis structure of the electric wheel-driven electric vehicle greatlyincreases the degree of freedom of the overall layout of the vehicle and thedesign of the body shape. By separating the chassis load-bearing and bodyfunctions, it is possible to realize product diversification and serializationof the same chassis with different body shapes, thereby shortening the newtype. Car development cycle, reduce development costs. Therefore, the electricwheel technology is very research significance.