Research On Simulation Fidelity Of Equivalent Prismatic Suspension Model

The automobile is a complicated non-linear organization which includes such dynamics characteristics as inertia , elasticity , damping ,etc. The characteristic of the vehicle system is that includes many movement parts and complicated force. If we want to accurately describe the movement characteristic of automobile and build the exact mathematics model, we must consider the movement parts as many as possible , thus we can achieve the detailed dynamics equation . However, too complicated model equation brings the enormous difficulty in solving, and can not get the correct result. So, the scholar in different countries simplified every automobile subsystem through testing and the factitious method , can appear to collect the essence characteristic of the systems and assemblies , set up simpler mathematics model and receive solving . Of all subsystem of the automobile, suspension system always can be regarded as the key assemblies of the automobile chassis, its characteristic will influence many kinds of automobile serviceability such as handling stability , braking quality. Through analysis suspension structure and the ability of it transfer force, we can deeply analysis the force acting on the automobile body and conclude the rule of the automobile pitch and roll , provide the theoretical foundation for setting up more logical vehicle model . Main purpose of this paper is to analysis the fidelity of using equivalent prismatic suspension model simulate the force acting on the vehicle body transfer by the suspension links of the single-arm suspension. The suspension of modern cars has many kinds of structure, but generally be made up of the spring, shock absorber, suspension links some and auxiliary elastic components such as horizontal stabilizer. Usually substitute the true and complicated system of suspension with the spring and damping device structure while building the vehicle dynamics model that has less degree of freedom, but that simplified the structure of models and totally neglected force and moment that the suspension links transmits to the automobile body, so it must reduce the precision of the l model ; Utilize the method of dynamics of multibody system can build suspension model according to actual space structure totally, improve the precision of the model greatly . But this method must cause the increase of the degree of freedom of the model , increase artificial calculation, reduce operation speed, and difficult to satisfied with the real-time demanding. When building the real-time model of automobile dynamics of the simulator, in order to give consideration to both the demand for considering meeting real-time and demand of the commonability at the same time, put forward the concept of equivalent prismatic suspension model. Use the equivalent prismatic suspension model we can transfer the force of the suspension links and spring force into the vertical force acting on the centroid of the unspring mass. Thinking about some factitious agreement and simplify of the model, accuracy of the model simulation operation become the question that we care about. This paper go on some research of theory at this point. Analysis the fidelity of using equivalent prismatic suspension model simulate the force acting on the vehicle body transfer by the suspension links of the single-arm suspension. This paper has reviewed and summarized the concept of roll center and moment center and the concept of the system of equivalent single arm at first. Conclude the method of using the concept of roll center simplify double wishbone suspension and MacPherson strut type suspension as the independent single arm structure suspension. Then choose the suitable generalized coordinate , build the mechanics model of vehicle system with the independent single arm suspension, and according to the basic principle of mechanics induce five degree of freedom dynamics equation. Through solving Newton -Euler equation, it get every position coordinate and speed acceleration characteristic of movement component of the system, and write the procedure of the corresponding model with Matlab. In order to validate the veracity the vehicle model with single-arm suspension, utilize multibody systems dynamics analyse software ADAMS, build the contrast model of the vehicle model with single arm suspension , compare the heave response and roll response number simulation curve, thus verified the veracity of Matlab simulation procedure. Utilize single arm suspension vehicle model analyse normal load transfer and wheel trace change under the different rolling operating mode. This paper use the method of the equivalent mechanics calculate the equivalent vertical force of the equivalent prismatic suspension model that transfer by the suspension links, spring and damping and unspring mass inertia force. Build the vehicle model with the equivalent prismatic suspension model and write the procedure of the corresponding model with Matlab. Finally, compare the difference of the heave response and roll response between the vehicle model with single arm suspension and the vehicle model with equivalent prismatic suspension model under the lateral step force inspiriting, validate the veracity of using equivalent prismatic suspension model simulate the force acting on the vehicle body transfer by the suspension links of the single-arm suspension.