1
Parameter
Unit Value
M
s
kg
300
M
u
kg 50
k
s
N
m
18000
k
t
N
m
180000
b
s
Ns
m
1200
b
t
Ns
m
0
Quarter Car Modeling - Active Suspension System
easy-simulink.com
Problem:
“For road vehicle users, comfort is an important issue. To move from one place to another,
road vehicles usually encounter various vibrations and shocks from ground, for instance, in
traveling on a bumpy surface, or crossing over an obstacle. Prolonged exposures to vibrations
cause some problems, such as pain and fatigue, for the passengers. To alleviate these problems,
momentary loads from ground should be absorbed and damped out. Automotive suspension
systems are intended to absorb and decrease the shocks and vibrations transferred from the
ground to the passengers as well as the vehicle body. Passive suspension systems which
consist of spring and damper components have been traditionally utilized on different types
of vehicles, such as motorcycles, passenger cars, trucks and even bikes. Active suspension
systems with separate actuators to apply controlled forces provide better ride A quarter-car
model of a passenger sedan with active comfort and improved handling. The suspension system
shown below represents the vehicle system at each wheel. It consists of a spring k
s
, a damper b
s
and a hydraulic actuator F
a
. The tire stiffness and damping properties are also shown by k
t
and b
t
,
respectively. The effective vehicle body mass is shown by M
s
(sprung mass), and M
u
(unsprung
mass) represents the effective mass for the wheel and axle. The vertical displacements from the
static equilibrium for M
u
and M
s
are shown by x
u
and x
s
, respectively. The road profile is
represented by x
r
. The suspension travel x
s
- x
u
is measured and compared to the set point (r = 0).
The required actuator force is determined by the controller to eliminate the error, and thus, to
reduce the vehicle oscillations. The actuator can provide a maximum force of 3000.”
x
s
M
s
F
a
b
s
k
s
x
u
M
u
b
t
k
t
x
r
