ISSN: 2319- 8753 International Journal of Innovative Research in Science, Engineering and Technology (An ISO 3297: 2007 Certified Organization) Vol. 3, I ssue 5, May 2014 Copyright to IJIRSET www.ijirset.com 12047 Analysis of Optimum Suspension Parameters of a Semi-Independently Suspended Automobile Anirudh R. Iyer 1 , R. Venkatachalam 2 , A. Balaraju 3 1 P G Student, Dept. of Mechanical Engineering, National Institute of Technology, Warangal, India 2 Professor, Dept. of Mechanical Engineering, National Institute of Technology, Warangal, India 3 Research Scholar, Dept. of Mechanical Engineering, National Institute of Technology, Warangal, India Abstract: Suspension system of an automobile not only supports the body of the vehicle, engine and passengers but also absorbs shocks arising from the roughness of the road. Most of the present day cars are provided with independent suspension for the front wheels and conventional suspension for the rear wheels. Such a suspension system is referred in this paper as semi-independent suspension system. When the automobile is moving, the roughness of the road keeps giving excitations to the suspension system through tyres. The stiffness and damping of the suspension system play an important role in absorbing the shocks and provide comfort to the passengers. In this paper, an attempt is made to obtain the optimum values of these parameters for providing maximum comfort to the passengers. Keywords: Semi-independent suspension system, Full car model, Optimum suspension parameters I. INTRODUCTION The suspension system is one of the most important systems of an automobile. Its main purpose is not only to support the engine, its components, passengers, but also to isolate them from shocks arising due to roughness of the road. It has been a practice from the beginning to have a frame called chassis which is being supported through springs and dampers by the front and rear axles. This type of suspension system is called Conventional Suspension System. There is yet another type of suspension called Independent Suspension System, in which the axle of a wheel is hinged to the body and is held in position by springs and dampers which are placed in between axle and the body. There is no separate chassis and the body of the vehicle itself acts as chassis. Many of the present day cars use independent suspension for the front wheels and conventional suspension for the rear wheels. In this paper, such a system is referred as Semi-independent Suspension System. The study of suspension systems has been a subject of interest for many researchers. A suspension system may be modelled as a quarter car model or a half car model or a full car model. The quarter car model or half car model yield the results very quickly but they are not accurate because they do not represent the system in a realistic way because the roll and/or pitch motions cannot be taken into account by these models. Full car model considers the entire vehicle as it is. The results can be considered to be accurate and realistic. However, the analysis becomes more complex. Hedrick [1] considered a quarter car model with hydraulic actuator acting under the effect of coulomb friction. An absorber based nonlinear controller and adaptive nonlinear controller are proposed. Employing two sensors, one for displacement and other for velocity measurements, Majjad [2] considered a quarter car model and estimated the nonlinear damping parameters. Gobbi and Mastin [3], Wei Gao et al. [8] studied dynamic behaviour of passively suspended vehicles running on rough roads. The road profile is considered to give random inputs to the suspension system. Rajalingam and Rakheja [4] studied the dynamic behaviour of quarter car model under nonlinear suspension damper. Ahmed Faheem [5] studied the dynamic behaviour using quarter car model and half car model for different excitations given by the road. Jacquelien et al. [6] used electrical analogy in conjunction with quarter car model and studied the control scheme of the suspension system. Wei Gao et al. [7] also studied the dynamic characteristics