Hub motor is considered to be the main driving form of electric vehicles In the future due to its many advantages. Hub motor technology is also known as in-wheel motor technology. The characteristics of this technology are that the driving motor is designed to be installed inside the wheels of new energy vehicles, which greatly simplifies the transmission structure of vehicles using this technology. Hub motor drive mode is to install two or more motors inside the wheel, compared with internal combustion engine cars and single motor centralized drive electric vehicles have a great advantage.

Compared with the traditional central motor, wheel hub motor to the drive motor and controller are integrated within the wheel hub, eliminate gearbox, axle, differential of several major parts, thus achieve wider efficiency, less power components will change the structure of the chassis, on the vehicle design, lightweight, and auto parts industry will have far-reaching influence.

At the same time, the hub motor drive system can be flexibly arranged in the wheels of all kinds of electric vehicles, and directly drive the hub rotation. Compared with internal combustion engine, single motor and other traditional centralized drive mode, its technical advantages and characteristics in power configuration, transmission structure, control performance, energy utilization and other aspects are obvious, mainly manifested as:

(1) The power system is changed from hard control of mechanical transmission to soft control of electronic system, and the power control is changed from hard connection to soft connection. Through the electronic controller, the infinitely variable speed and the difference between hubs can be achieved from zero to greater speed. The traditional mechanical gear shift, clutch, transmission, drive shaft and mechanical differential devices are avoided, which makes the drive system and the vehicle structure simple and uniform, the available space increases, and the transmission efficiency is improved (theoretical value is 10%).

(2) the motor torque and rotational speed can be directly controlled by electronic devices, control more convenient and flexible, not rigid connection between driving wheels on both sides of the shaft, do not need mechanical differential, the vehicle can be adjusted by respectively when turning on both sides of the driving wheel speed greatly reduce vehicle turning radius, if further import four-wheel steering (4 ws) technology, Zero radius steering can even be achieved in extreme cases.

(3) The torque of each wheel is independent and controllable, the response is fast, the positive and negative rotation is flexible, and the instantaneous dynamic performance is superior, which significantly improves the driving ability to adapt to harsh road conditions.

(4) The freedom of vehicle layout and body shape design is greatly increased. Taking the automobile as an example, after separating the bearing function and transmission function of the chassis, the structure of the bridge is greatly simplified, and it is easier to realize the product diversification and serialization of different body shapes of the same chassis, shorten the development cycle of new cars and reduce the development cost.

(5) Easy to realize the wheel hub electrical braking, electromechanical composite braking and energy feedback in the braking process, with good regenerative braking performance, efficiency can reach more than 80%, but also to the efficient use of the vehicle energy optimization control and management, effective energy saving.

The increase of unsprung mass caused by hub motor has an impact on vehicle ride comfort, handling stability and safety. Due to the high power density and lightweight design requirements of the hub motor, the unsprung mass increase is limited. By readjusting the chassis suspension, the performance of the vehicle reduced by the increase of unsprung mass can be restored, especially for the vehicle equipped with independent suspension such as multi-link. However, the installation space of the external interface of the hub motor may be limited by the size of the chassis parts of the vehicle.