OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Semi-active suspension system performance is dependent on the controllability of smart part known as
magnetorhelogical (MR) or electro-rheological (ER) dampers. Magneto-rheological (MR) dampers provide a
base for promising future related to vibration control of semi-active suspension systems. Power requirement by
this controllable MR damper is low while response is quick to provide output results is a few milliseconds. The
alignment behavior of magnetizable suspended particles is related to the application of electric current to MR
damper [Fig. 2].
Fig. 2: Illustration of MR Fluid Activation behavior:
(a) Without Magnetic Field (b) Initial stage during Magnetic Field application (c) Fully developed stage
Latest technological developments in the field of MR fluids have forced the automotive manufactures to choose
the concerned fluid compared to electro-rheological fluid for the application in MR dampers [2-4]. Several
attractive characteristics of MR damper which make them suitable for semi-active suspension system are quick
response to the applied controllable magnetic field, compact size and reliability i.e. can act as a fail safe device in
form of passive damper in case of power failure.
Many researchers have presented the data related to the useful and effective performance of MR damper
assembled in semi-active suspension system [5-7]. Duym studied the physical model of a shock absorber related
to the automotive dynamic simulation [8]. Guclu presented his study results about the dynamic property of a
vehicle model by considering effect of dry friction on the dampers [9]. Choi et al. studied the practical
applicability of a cylindrical MR damper using hardware-in-loop simulation method [10].Nguyen et al. used
finite element analysis technique to study an optimal design of a MR damper [11].
2. Mathematical Modeling of Quarter Car Model
In present study, a simple quarter-car suspension model with two-degree-of-freedom (2DOF) system
representing one-fourth mass of car body, suspension parts and single tyre with wheel is analyzed (Fig. 3) by
considering vertical movement but neglecting pitching and rolling motion of mentioned system. It shows an
unsprung mass, indicating the quarter body mass of car, the lower unsprung mass and the wheel mass.
Fig.3: Semi-active Quarter car suspension model
The equations of vertical direction motion for the quarter car suspension system i.e. sprung mass (quarter car
body mass) and unsprung mass (suspension parts) can be represented by applying Newton’s second law of
motion with the help of following mathematical equations:
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