Why wheel hub assembly is the future?

Why is it that Tesla, stripped of its outer shell and with only the chassis remaining, is still a work of art, and has room for two large luggage compartments, front and back? The popular interpretation goes like this: "Tesla integration capabilities, they use the wheel side motor. ".

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That seems like a reasonable answer. But there is a serious error in this answer. Is the Tesla Electric drive system located between the rear axle wheels a wheel-side motor? On this misunderstanding today we will talk about what is the wheel motor, hub motor, centralized motor.

Hub Motor

The hub motor technology is also called the motor technology inside the wheel, because the hub motor has the characteristic of independent driving of single wheel, it can be easily realized in front drive, rear drive or four-wheel drive Full-time four-wheel drive in a hub-motor-driven vehicle is very easy to achieve. At the same time, hub motors can realize differential steering similar to tracked vehicles by varying the rotation speed of the left and right wheels or even reversing, greatly reducing the turning radius of the vehicles, and can almost realize in-situ steering under special circumstances This skill is very valuable for special vehicles, so this technology is used in special vehicles such as mining vehicles, engineering vehicles and so on.

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Structure of Michelin Hub Motor

And the application of hub motor can greatly simplify the structure of the vehicle, the traditional clutch, gearbox, drive shaft will no longer exist. It also means saving more space. More importantly, hub motors can be used in parallel with conventional power, which makes sense for hybrid vehicle as well.

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However, none of the mass produced passenger cars on the market use this technology, said so many advantages of mass production cars do not need to be a few meaning! The reason is that some of its disadvantages will make it in the use of passenger cars have a little acclimatization, hub motor to be installed in the rim, which makes the vehicle spring under the quality of the first problem is not conducive to control; Second, the Eddy current brake is not high capacity, in heavy vehicles need to cooperate with the mechanical braking system work together. For Electric Vehicles, to achieve a higher braking effect requires higher energy consumption, to a certain extent, affecting the range; Third, if the power output of a small gap in the high-speed driving of the direction of the vehicle control will also cause magnified many times the impact of out of control. And it is difficult to achieve lubrication, will make the planet gear reducer gear wear faster service life shorter, not easy to heat dissipation, poor process noise will be greater. High current is needed for starting, headwind or climbing, which can damage the battery and permanent magnet easily. The peak area of the motor efficiency is small, and the efficiency decreases quickly when the load current exceeds a certain value.

To sum up, the combination of hub motors and mass-produced passenger cars is still a bittersweet story for now.

Wheel Motor

The wheel motor is a motor which is mounted on the side of the wheel to drive the wheel separately. The wheel motor is a motor which is embedded in the wheel hub and the stator is fixed on the wheel The rotor is attached to the axle rather than transferring power to the wheels through the propeller shaft.

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The rim motor usually means that each driving wheel is driven by a separate motor, but the motor is not integrated into the wheel, but is connected to the wheel via the output shaft of the drive motor (this is the difference from the hub motor) .

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However, the motor installed on the body of the electric vehicle has a great impact on the overall layout of the vehicle, especially in the case of rear axle drive. Because of the great deformation movement between the body and the wheels, the universal drive of the transmission shaft is also limited. And I can't help but worry that if I had a car like this, I'd probably sleep with the wheels stolen along with the motor.

Centralized Motor

At present we are familiar with new energy vehicles such as Tesla, Baic new energy, BYD Company pure electric series products, Jianghuai IEV series and other mainstream pure electric products are using concentrated motor this form. However, with the development of electric vehicles and hybrid vehicles, more and more vehicles may not only carry a centralized motor, at this time, it may appear that the power output of a centralized motor is only transmitted to the front wheels Another centralized motor "pushes" on the rear wheels (for example, Tesla's various D series) .

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So the question is, how do you make sense of it more intuitively? If someone asks you what the difference is, say something like: "The single motor is positioned in the middle and is responsible for the arrangement of both wheels is called a centralized motor, and the Tesla X is not a wheel motor. ".

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Summarize the advantages of | rim motor / hub motor drive over centralized motor drive:

The electronic differential speed control technology is used to realize the different speed movement of inner and outer wheels when turning, which is suitable for special vehicles.

The elimination of mechanical differential device is beneficial to the reduction of power system mass, the improvement of transmission efficiency and the reduction of transmission noise.

3 simplify the structure of the vehicle, the traditional clutch, gearbox, drive shaft will no longer exist. It also means saving more space.

The performance index of electric vehicle motor is reduced, and the redundancy reliability is high.

And the downside is obvious

In order to meet the motion coordination of each wheel, the Synchronous Coordination Control of Multiple Motors is required.

The decentralized arrangement of the motor presents many technical problems, such as structure arrangement, heat management, electromagnetic compatibility and vibration control.

3 increasing the mass under the spring and the moment of inertia of the wheel hub has some influence on the control of the vehicle.

4. Fear of losing