In a suspension control system, a controller previously stores damping
force maps (an ordinary road map, a rough road map, and an extremely rough
road map) corresponding to road surface conditions (an ordinary road, a
rough road, and an extremely rough road) defined by frequency and
amplitude of vertical acceleration. The frequency and amplitude of the
vertical acceleration are detected, and a damping force map (the ordinary
road map, the rough road map, or the extremely rough road map)
corresponding to the detected information is selected. Damping force
control is effected on the basis of the selected damping force map.
Selection of a damping force map according to the frequency and amplitude
of the vertical acceleration is also made when a change in the vertical
acceleration, i.e. a change in piston speed, is predicted during running
on an ordinary road, a rough road or an extremely rough road.
