This paper shows the influence on dynamic behavior of the car when it is equipped with
magneto-rheological dampers controlled by a feedback. The feedback is built up in two ways; the
first is implemented by a switch on/off control that is characterized by the injection of magnetic
field with a constant value. It happens when a certain value of relative speed between the sprung
and unsprung mass is exceeded. The second feedback is characterized by the H-infinity control
which is based on the relative displacement in order to vary the magnetic field signal in a
continuous manner. At the same time the H-infinity control of vehicle is maintained by taking into
account the exceeding of speed signal in order to consider the substantial differences with the
switch on/off control. These differences are evaluated in terms of relative displacement and speed
between the unsprung and sprung mass. The exogenous excitation is the road disturbances which
are introduced as a square wave input in order to emulate those that are commonly encountered on
the road. All simulations and results are performed by MATLab-Simulink and Mathematica
