Dissertation > Transportation > Road transport > Automotive Engineering > Automotive structural components > Travel System > Suspension

Research on Designed Method of Car Independent Suspension

Author LiangJingWen
Tutor YaoGuoFeng
School Jilin University
Course Solid Mechanics
Keywords Independent suspension Stiffness matrix Screw axes Elasto-kinematic performance Equivalent Elastic Mechanism
CLC U463.33
Type Master's thesis
Year 2009
Downloads 381
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Suspension is one of the important components of an automobile. It takes the function of transferring the forces and torques and defining the relative motion between wheel carrier and structure of the vehicle. It can also alleviate the impact load on uneven surfaces and attenuate bearing system vibration caused by impact load to simultaneously achieve both ride comfort and handling performance at an optimal level. Therefore designing automobile suspension system and making the research on suspension system which affects vehicle performance are of important significance.This paper gives a detailed introduction to Equivalent Elastic Mechanism and has proposed both an analysis tool and a design methodology, based on certain type car independent suspension of China FAW Group Corporation Technology Center. The simplified model of car independent suspension is established by software ADAMS, and the total stiffness matrix of independent suspension system are extracted,which . The structure of car independent suspension is analyzed and designed by applying Equivalent Elastic Mechanism and mathematical computation software MATLAB. The structure of car independent suspension designed by Equivalent Elastic Mechanism can also be assessed with the elasto-kinematic performance to draw the conclusion that the structure of car independent suspension meets practical requirements. The main contents in the paper are as follows:(1) This paper makes a research on car independent suspension by means of Equivalent Elastic Mechanism. Equivalent Elastic Mechanism is a simple and readily imagined compliant mechanism that can always be configured to replicate perfectly the elasto-kinematic behavior of any elastic system. Although the form of the mechanism never changes, its specific properties are computed from the stiffness matrix of the system to be analyzed. Consequently it represents a perfect synthesis of the entire linear compliant behavior of the original suspension system, but encapsulated in a very simple mechanism whose behavior is very intuitive and easy to visualize. Not only does the methodology provide greater insight into the function of the compliant suspension, it also results in significantly reduced design times and greater confidence in optimizing design.(2) This paper elaborates compliance matrix. According to the relations between stiffness matrix and compliance matrix compliance matrix is obtained. Simultaneously Equivalent Elastic Mechanism is introduced, which makes it possible to gain an insight into the ability of any suspension architecture to meet a given specification, and a feel for the proximity of a chosen configuration to the ideal solution that meets all the specification requirements. Suspension system can be simplified to three perpendicular screw axes and three purely translational compliances, whose characteristics are elaborated separately, obtaining their directions, their compliance properties and their positions in space.(3) This paper describes the module, software characteristic and function of software ADAMS. Certain type car independent suspension of China FAW Group Corporation Technology Center can be simplified to model which has been established with software ADAMS. The model mainly includes suspension system and tire. Suspension system consists of kingpin, upper wishbone, lower wishbone, pulling arm, steering linkage and steering knuckle. When force/torque is imposed on independent suspension in the Global Co-ordinate System, suspension produces displacement and rotation. Therefore stiffness matrix of independent suspension is obtained in the Global Co-ordinate System.(4) This paper presents the response of the Equivalent Elastic Mechanism to forces and torques applied to it, relating Equivalent Elastic Mechanism to the elasto-kinematic performances. This is possible as, in the same way that the theory can be viewed as a property of a suspension linkage; it can also be viewed as a property of the e-k specification. At the same time, this paper describes properties of cornering forces and longitudinal forces. Firstly stiffness and Euler angle of three perpendicular screw axes and three purely translational compliances with an example of certain type car independent suspension of China FAW Group Corporation Technology Center. Independent suspension is designed by calculating decomposition of the force and displacement. Then suspension designed should be evaluated with the elasto-kinematic performances. Self-aligning torque steer, traction force steer, braking force castor change and lateral force camber change are calculated, which are applied to assess ride comfort and handling performance. It reaches a conclusion that independent suspension designed by Equivalent Elastic Mechanism meets practical requirements. At last the structure of suspension is analyzed and the elasto-kinematic performances can be visualized realizing the connection between the Equivalent Elastic Mechanism and elasto-kinematic performances.(5) This paper has discussed architecture definition of Equivalent Elastic Mechanism. Clearly it is not the case that any architecture can exhibit any Equivalent Elastic Mechanism, as it is not the case that any architecture can fulfill any elasto-kinematic specification. Suspension architecture imposes constraints on the properties of the Equivalent Elastic Mechanism that it can potentially exhibit. Therefore it is possible to examine the constraints imposed by architecture in a simple and intuitive way. In doing so, it is possible to gain a feel for whether a given architecture will be able to reproduce a desired Equivalent Elastic Mechanism, and if so which configuration from the set of possible Equivalent Elastic Mechanism would be most suited to the architecture.

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