Mc pherson

Proceedings of the World Congress on Engineering 2009 Vol II WCE 2009, July 1 - 3, 2009, London, U.K.

Design Sensitivity Analysis and Optimization of McPherson Suspension Systems
Hee G. Lee, Chong J. Won, and Jung W. Kim

of vehicle suspension systems is presented. The design process of suspension systems consists of pre-processing design stage, analysis stage and post-processing stage. Forkinematic modeling of suspension systems, McPherson strut suspension system is adopted, where suspensions are assumed as combinations of rigid bodies and ideal frictionless joints. Constraint equations for displacement, velocity and acceleration using displacement matrix method and instantaneous screw axis theorem, sensitivities of static design factor and optimum design are obtained. Thevalidity and usefulness of the method employed are demonstrated to yield the effective suspension layout at early design stage. Index Terms— Design sensitivity analysis, McPherson suspension, optimization, static design factor

Abstract—Design sensitivity analysis and optimization

system. Tak [7] obtained the dynamic optimum design through sensitivity analysis and Min [8] carried out the sensitivityanalysis for kinematic static design factor using direct differentiation. In this paper, sensitivity analysis for kinematic static design factor determining the motion characteristics of suspension systems and sensitivity analysis and optimization for reaction at each joint are carried out with which the designers can consider the riding quality and steering stability in suspension system designand predict the change of suspension factors required depending on the vehicle characteristics. This may help the designers to determine layout of the suspension system and to develop the integrated optimum design system of suspension.

II. DESIGN PROCESS OF SUSPENSION SYSTEMS I. INTRODUCTION Some important characteristics of suspension systems in vehicle dynamics are mainly kinematic motionsand reactions to the forces and moments transmitted from tires through chassis [1]. Design requirements for such suspension systems are to determine the design variables to meet the behavior of wheels defined through dynamic analysis and to meet the requirements for forces and moments transmitted from tires, which is very difficult for designers to determine since the suspension systems consist ofdifferent kinds of 3-dimensional mechanical elements kinematically and the behaviors are highly non-linear. In spite of the difficulties, it may be possible to design the vehicle suspension systems effectively to meet the requirements simultaneously mentioned above. Conventional design studies of suspension systems are mainly focused on displacement and velocity. Suh [2]-[4] carried out theanalyses of displacement and velocity of suspension systems using displacement matrix and the analysis of instantaneous screw axis during bump and rebound using velocity matrix. Also, he carried out the force analysis at each joint using displacement matrix and system reduction method by treating the suspension system as single mass dynamic system. Kang et al. [5] carried out the analyses ofdisplacement, velocity and acceleration for McPherson strut suspension system using displacement matrix. Lee [6] carried out the sensitivity analysis of instantaneous screw axis through velocity analysis of multi-link suspension
Manuscript received March 3, 2008. H. G Lee is with Korea Military Academy, Seoul 139-799 Korea.(phone: +82-2-2197-2953; fax: +82-2-2197-0198; e-mail: hklee@ kma.ac.kr). C. J. Won iswith Kook-min University, Seoul 136-702 Korea (e-mail: cjwon@kookmin.ac.kr). J. W. Kim is with JATCO, Seoul 153-803 Korea (e-mail: miri1218@hanmail.net).

The design optimization process of vehicle suspension systems consists of pre-processing, analysis and post-processing stages. In pre-processing stage, the suspension systems are modeled as links of kinematic elements and simple joints and...