(1) Increase the unsprung mass and the moment of inertia of the hub, which will affect the handling of the vehicle
For ordinary civilian vehicles, some relatively light materials such as aluminum alloys are often used to make suspension components to reduce the unsprung mass and improve the response speed of the suspension. However, the in-wheel motor just increases the unsprung mass to a large extent, and also increases the moment of inertia of the wheel hub, which is detrimental to the handling performance of the vehicle. However, considering that most electric models are limited to transportation rather than the pursuit of dynamic performance, this is not the biggest flaw.
(2) The electric braking performance is limited, and it takes a lot of electric energy to maintain the operation of the braking system
At present, many traditional power commercial vehicles have been equipped with auxiliary deceleration devices that use the principle of eddy current braking (that is, resistance braking), such as the electric retarder used in many trucks. Due to the relationship between energy sources, electric braking is also the first choice for electric vehicles. However, for vehicles driven by in-wheel motors, due to the small electric braking capacity of the in-wheel motor system, it cannot meet the requirements of the braking performance of the whole vehicle, and additional mechanical mechanisms are required. However, for ordinary electric passenger cars, without a vacuum pump driven by a traditional internal combustion engine, an electric vacuum pump is required to provide braking assistance, but it also means greater energy consumption, even if regenerative braking can recover some energy, If the efficiency of the braking system is to be ensured, the energy consumed by the braking system is also one of the important factors affecting the cruising range of electric vehicles.
In addition, the working environment of the in-wheel motor is harsh, facing the influence of water, dust and other aspects, and it also has high requirements in terms of sealing. At the same time, it is also necessary to consider the heat dissipation problem separately for the in-wheel motor in design.