An MR(Magneto-Rheological) fluid damper is designed and applied to a semi-a
ctive suspension system of a quarter car model. The damping constant of the
MR damper changes according to the input current and the time delay of the
damper is included in the system dynamics. The passive method, LQ control
and frequency shaped LQ control are compared in experiments. The advantage
of the proposed frequency shaped LQ control is that the ride comfort improv
es in the frequency range of 4 and 8 Hz where a human is most sensitive and
the driving safety improves around the resonance frequency of unsprung mas
s, 11 Hz. The experiments using a quarter car model show the effectiveness
of the algorithm.