The vehicle suspension system is suspended from the original non - independent to the independent suspension, and then derived from the independent suspension of Mcpherson, double fork, and so on. Here we introduce the most advanced design in the independent suspension: multi link suspension.

The so-called multi link suspension, as the name implies, is a suspension mechanism connected to wheels by means of various link configurations. The number of connecting rods is more than 3, which is called multi link. At present, the number of connecting rods is 5 links. So its structure is much more complicated than that of double fork and Mcpherson. We know that the double fork suspension is positioning the wheels through two upper and lower A type control arms. Because the A type control arm can only float in the upper and lower direction, the design and configuration of the control arm length can achieve the purpose of dynamic control of the wheel obliquity, and improve the control performance of the turning of the car. But for steering wheels and follower wheels, it is obviously limited to control the camber to improve the performance of the curve. In the four wheel positioning parameters, besides the obliquity, and the front angle is also an important parameter that affects the control of the bend, how can we control the angle of the front beam dynamically like the control of the obliquity? This can be done with double fork arms, but the performance is very limited. Although the double arm suspension is designed to have a great design freedom, it is usually to load a soft rubber bushing at the front end connecting the A type control arm to the body if you want to use a double arm to control the front beam.

When the front and back bushings are different when the vehicle turns, the wheel will change a certain angle of front beam to the direction of the bend. If this design is used in the rear wheel, the rear wheel can turn under the action of the lateral force, although the angle of the steering is very small, the performance is still higher. Through the design of the stiffness of the rubber bushing to a certain variable angle angle and the servo steering function, the primary task of the rubber bushing is to connect the suspension and isolation vibration, so the stiffness can not be too low. This causes the limitation of the variable front beam and the servo steering, and it can gain a very small angle. < segment > multi link suspension completely solves this problem. It can automatically adjust the obliquity, the front angle and the rear wheel to get a certain angle of steering when the suspension is contracted by different connecting rod. The principle is that by designing the constraint angle of the connecting motion point, the suspension can be actively adjusted when the suspension is compressed, and the degree of freedom of the design is very large. It can match and adjust the vehicle completely. Therefore, multi link suspension can maximize the tire grip to maximize the vehicle's handling limit. But because of its complex structure and high cost, both the cost of research and development and the cost of manufacturing are the highest, but the performance is the best in all suspension designs. This design will only be used in medium and large cars, but usually only for rear wheels. The reason is that the multi link mechanism is very complex and occupies large space, making it difficult to arrange. Therefore, it can only be used on the rear bridge with larger space. But there is one exception: the Audi series.

We know that Audi is using the front engine design, the engine is arranged before the front axle, so more space is made in the front axis, so it is possible to arrange the front axle of the multi connecting rod, thus greatly improving the control performance of the vehicle; and the Mercedes BMW has the balance of the weight distribution of the whole vehicle, and the engine is arranged in the layout of the engine. After the front axle, there is not enough space to design multi link suspension, so we can only choose to occupy less space Mcpherson and double fork test suspension. So comparing Audi and BMW models also has their advantages and disadvantages. < subsection > because of the complexity of the multi link suspension structure, the multiple components, and the weight must be higher than the double fork suspension, so the Audi A4 chose to use the aluminum alloy to make the suspension to reduce the weight increase response and the rebound speed to achieve the perfect balance of comfort and manipulation.