International Journal of Modern Engineering Research (IJMER) www.ijmer.com Vol.3, Issue.3, May-June. 2013 pp-1377-1381 ISSN: 2249-6645 www.ijmer.com 1377 | Page A.Purushotham Department of Mechanaical Engineering, SreeNidhi Institute of Science and Technolgy Ghatkesar, Hyderabad, A.P. India-501 301 Abstract: Most of automobiles these days are using two suspension systems namely: double wishbone suspension system and McPherson suspension due to their good dynamic performance and higher passenger comfort. The MacPherson strut setup is still being used on high performance cars such as the Porsche 911, several Mercedes-Benz models and lower BMW models due to its light weight, design simplicity and low manufacturing cost. This paper proposes a systematic and comprehensive development of a two-dimensional mathematical model of a McPherson suspension. The model considers not only the vertical motion of the chassis (sprung mass) but also rotation and translation for unsprung mass (wheel assembly). Furthermore, this model includes wheel mass and its moment of inertia about the longitudinal axis. The paper offers an implementation of the model using Matlab- Simulink, whose dynamics have been validated against a realistic two dimensional model developed with the Ansys software. Keywords: Simulink, ANSYS, suspension, active and passive system I. INTRODUCTION Some common types of independent suspensions are: Swing axle, Sliding pair, McPhersonstrut, Upper and lower A-arm (double wishbone), Multi-link suspension, Semi-trailing arm suspension, Swinging arm, Leaf springs. The McPherson strut is a type of car suspension system which uses the axis of a telescopic damper as the upper steering pivot. It is widely used in modern vehicles and named after Earlie S. MacPherson, who developed the design. MacPherson struts consist of a wishbone or a substantial compression link stabilized by a secondary link which provides a bottom mounting point for the hub or axle of the wheel. This lower arm system provides both lateral and longitudinal location of the wheel. The upper part of the hub is rigidly fixed to the inner part of the strut proper, the outer part of which extends upwards directly to a mounting in the body shell of the vehicle. Fig. 1.1:Model of MacPherson To be really successful, the MacPherson strut required the introduction of unibody (or monocogue) construction, because it needs a substantial vertical space and a strong top mount, which uni bodies can provide, while benefiting them by distributing stresses. The strut will usually carry both the coil spring on which the body is suspended and the shock absorber, which is usually in the form of a cartridge mounted within the strut. The strut also usually has a steering arm built into the lower inner portion. The whole assembly is very simple and can be preassembled into a unit; also by eliminating the upper control arm, it allows for more width in the engine compartment, which is useful for smaller cars, particularly with transverse -mounted engines such as most front wheel drive vehicles have. It can be further simplified, if needed, by substituting an anti-roll bar (torsion bar) for the radius arm. For those reasons, it has become almost ubiquitous with low cost manufacturers. Furthermore, it offers an easy method to set suspension geometry. The McPherson suspension is widely used in small and medium size vehicles due to its light weight, compact size and low cost. Fig 1.1 shows a McPherson suspension system which consists of a suspension arm or control arm plus a spring-damper assembly (strut) firmly attached to the wheel assembly. Large and systematic changes in kinematic parameters, such as camber angle and track width are a major problem in modeling and controlling this type of suspension. The quarter-car linear model is commonly used to analyze the suspension dynamic behavior. However, this model does not Comparative Simulation studies on MacPherson Suspension System