The Dynamics Simulation Model Of Macpherson Suspention Using Cartesian Coordinates

Suspension is an important part of the vehicle. It is composed of the elastic component, direction equipment and shock absorber. As a setting which pass the force between the wheel and the body ,it also pass the force and moment form the wheel to the body, and it can absorb the librateion and the impact come from the road surface,reduce the yawp in the cab,improve the comfort performance, keep the well operate performance and calm running perfoemance. The Suspension model, which gets the suspend characteristics based on the Roll_theory, only be used in the station that the wheel jumping in little range.It con't simulate the speed and the pase of the wheel nicety. Aimed at these disadvantages, in this paper, I use the theory of Cartesian coordinates for multibpdy system dynamics to build the Macpherson suspension.model base on the constrains,and make preparations for building the whole vehicle model. Dynamics of multibody systems is a subject branch which relate to both antiquity and high and new. It colligate many subject such as geostatics, analytical mechanics,computational mechanics, material mechanics, biomechanics and so on.combining with the computer and many years practice,it is working up. Modeling method and numerical method are the cores of dynamics of multibody systems. The Cartesian coordinate for multibpdy system dynamics is a modeling method which using the absolute coordinates to define the loctation and shape of the object. There are four parts in the dissertion. In Chapter one, I summarize the construction and the function of the suspension and the development of the multibody system dynamics. I also discuss the purpose and meaning of this dissertion, and put forward the contents of the dissertion. In Chapter tow, I particular expatiate the system info of the Cartesian coordinate for multibpdy system dynamics. In Chapter three,I deduce the constration equations of the common joints, such as revolute joint, spherical joint and translational joint.And then build the dynamics model of the Macpherson suspension without the resilient bushing.But in fact, there are resilient bushing between the suspension and the body, and the resilient bushing changes the suspensions dymactics characters,in order to show the fuction of the resilient bushing, I change the spherical joint with a spring to simulate the resilient bushing, and build the model of the Macpherson suspension with a the resilient bushing. In Chapter four, there are three parts. The first one is about numerical method. Numerical method is a key of the dynamics simulation. The choice for numerical method is very important. The dynamics equition is a set of algebra-differential equitions. In order to solving it, I complie some arithmetic: (1) Row pivot Gaussian elimination method for set of linear equations. (2) Adams Bashforth format for ordinary differential equation. (3) Direct default-amend method for amending the default of coordinate and velocity. This method can amend the default to the perfect range in one or tow times, and keep it in long time. In the second part, I programme the dynamics emulator based on the software engineering and OOP technic.In order to being transferred easily, some class libraries are designed, such as: (1) Model_define class: CQBody, CQJoint, CQForce, CQFElement. (2) Emulate_comput class: CQMatrix, CQEquation, CQList, CQFandT and...