The elastic element enables the elastic connection between the frame (or car body) and the axle (or wheel) to withstand and transmit vertical loads and mitigate the impact caused by uneven road surface, emergency braking, acceleration and turning. The shock absorber is used to attenuate the vibration caused by the impact of the elastic system. The guiding mechanism is used to make the wheels (especially the steering wheels) move relative to the body according to a certain trajectory. At the same time, the above three have the function of transmitting power. If the leaf spring is used as an elastic element, it also has a guiding function, and no additional guiding mechanism is required.