(a) Quarter-car models of the passive (left)
and the semi-active (right) configuration
(b) Test rig for an upperclass
vehicle suspension
Fig. 1. Quarter-car models and Quarter-car test rig, [15]
The quarter-car models of a passive (le.) and of a semiactive
suspension configuration (ri.) are depicted in Fig. 1(a).
By maintaining a constant value of the damper current, a
passive reference, i. e. dc(t) = dc, is obtained, where a
comfortable suspension setting is chosen in this work. The
control objective with respect to ride comfort is to minimize
the root mean square (rms) value of the vertical chassis
acceleration ¨xc. In order to incorporate human perception,
that is most sensitive to vertical mechanical vibrations in the
frequency range between 4 to 8Hz, the weighted acceleration
signal ¨xc,comf is derived by a shaping filter, [5]. Its rms-value
is used as comfort index. Due to the existing trade-off in
suspension control, an improvement in ride comfort calls