Abstract: A shock absorber is connected between a vehicle body and a vehicle wheel. The shock absorber provides a variable damping force. A control apparatus for the shock absorber includes an actuator for adjusting the damping force provided by the shock absorber. A vibration detecting device serves to detect a relative vibration between a spring upper member and a spring lower member. A damping-factor estimating device serves to estimate a damping factor of the shock absorber. A speed estimating device serves to estimate an absolute speed of the spring upper member on the basis of the relative vibration detected by the vibration detecting device and the damping force estimated by the damping-force estimating device. A signal setting device serves to set a drive signal of the actuator on the basis of the absolute spring upper member speed estimated by the speed estimating device.

Abstract: A shock absorber damping force control system for a vehicle employs at least a high-frequency component included in sprung mass vibration as a factor to control a damping force of a shock absorber. The system provides a lower damping force of the shock absorber with a larger magnitude of the high-frequency component when signs of a sprung mass velocity and a relative velocity between a sprung mass and an unsprung mass coincide with each other. A low-frequency component may also be employed as a factor to control the damping force of the shock absorber. The system provides a lower damping force with a larger ratio of the high-frequency component relative to the low-frequency component when signs of the sprung mass velocity and the relative velocity coincide with each other.