For suspension control purposes, only the measurement
signals of the body and wheel accelerations (¨xc, ¨xw), the
suspension deflection (xcw = xc−xw) and the damper valve
currents for rebound and compression (i∗=[i∗
r , i∗
c ]T) are used.
All quantities, that are not available from measurements,
are estimated by means of filter-based methods already employed
in [8]. Using only the chassis and wheel accelerations
as well as the suspension deflection signal, the damper’s
relative velocity, the absolute velocities of the sprung and
unsprung masses and also the tire deflection – all needed
for suspension or damper control – are obtained. However,
for reasons of analysis immediate knowledge of the acting
damper force is needed, which can be directly gained from
the total force between body and wheel mass. Therefore, a
load cell is built into the suspension strut between the strut
mount and the chassis. For the performance evaluation of the
suspension control concepts, both the dynamic wheel load
Fdyn and the road displacement xg are measured. Based on
Fig. 1(a), the equations of motion of the semi-active quartercar
model can be derived as