1. Design Purpose and Significance

1.1Suspension Overview and Design Purposes

Under the rapid development of the economy, people's lifequality has greatly improved, and vehicles have become an indispensable meansof transportation. Therefore, people are paying more and more attention tocomfort, safety, control and steering ability, the development of moderntechnology, production methods, and the need for vehicle smoothness. Thesuspension system has been greatly improved, making vehicles more than just ameans of transportation, but a better place for people to live ^[2][3].Suspension systems have also evolved into different structures and functions.The suspension includes independent suspension and non-independent suspension,passive suspension, active suspension and semi-active suspension. The activesuspension includes an active hydraulic suspension, an active air suspension,and the like. Different suspensions have different characteristics, but thebasic structure is similar.

The suspension consists of components mainly include elasticelements, guiding mechanisms and dampers. Suspensions commonly found intwo-axle vehicles have independent suspensions and non-independent suspensions.Among the independent suspensions, the single trailing arm type and singleinclined arm type independent suspension are simple in structure and low incost, and are often used in the rear suspensions, but there are stilldisadvantages such as small lateral stiffness and small roll angle stiffness ^[4][5].

For the vehicle, comfort, stability, and controlability is all related to the basic design of the suspension system. Thesuspension system of a vehicle refers to the entire force transmission systemcomposed of a shock absorber and a spring and a guiding mechanism between thevehicle body and the tire. It elastically connects the frame (or body) to theaxle (or wheel). Its functions are to transfer all the forces or momentsbetween the wheel and the frame (or the body), and to alleviate the impact loadtransmitted by the road surface to the frame (or the body), attenuate thevibration caused by the vehicle, and ensure the smooth running of the vehicle ^[6][7].

This design is the front suspension design of Toyota'seighth-generation Camry. The front suspension is chosen to be the McPhersonindependent suspension. The McPherson suspension has good responsiveness andhandling ability, and is simple in structure, small in space, low in cost andlight in weight, suitable for arranging large engines and assembling on smallbodies. It has a large spring stroke, saves three supports, and is easy toconstruct the shape of the front car floor. It has gradually become the mediumand high-end commercial vehicle and the preferred front suspension for racingcars. However, the McPherson suspension is not conducive to steeringperformance. For example, when driving on uneven roads, the wheels are easy toautomatically turn, so the driver must force the direction of the steeringwheel. When subjected to severe impact, the sliding column is easy to bend,thus affecting the steering performance. The stability is also poor, anti-rolland brake nodding ability is weak, after the stabilizer bar is increased. Butthe problem cannot be solved fundamentally, the durability is not good enough,and the shock absorber is easy to leak oil, so it needs to be replacedregularly ^[10].

In summary, the basic purpose of designing thissuspension is to optimize the actual parameters of different mechanisms, tomaximize the basic functions of the suspension itself, such as connection, forcetransmission and vibration reduction, and to design other necessary structuresand accessories, in order to reduce the weakening of steering performance ofMcPherson suspension on uneven road surface and other factors. Disadvantage,ultimately achieve the optimization of the vehicle's power performance,stability performance and control performance.

1.2Domestic and International Analysis Progress of Research

Widely used automotive suspensions are multi-linkindependent suspensions, MacPherson independent suspensions, etc. With thecontinuous innovation of the suspension mechanism, there are new suspensionstructures, such as active suspension ^[8][9]. The special kinds ofsuspension in the active suspension includes air suspension, electromagneticsuspension and CDC hydraulic suspension, and “magic carpet” suspension.However, the car suspension is a breakthrough in terms of comfort, stability,and NVH working ability in the car.