Abstract: An electronic controlled fluid suspension system in which a change in a vehicle attitude is expected in advance by an advance control means responsive to a driving state detected by a driving state detection means, and the current vehicle attitude is feedback-controlled by a feedback control means. The shares of the advance control amount and the feedback control amount are calculated by a share determination means so that final control amount is determined based on the shares. Fluid flow to and from the fluid suspension is controlled by a fluid flow control means in response to the final control amount. In such control system, the advance control and the feedback control are smoothly switched, which results in improved maneuverability and stability of the vehicle.

Abstract: An electronic controlled suspension system detects a load on the fluid actuators and calculates a torsional load on the vehicle. Responsive to the calculated torsional load, corrective control is executed on the fluid flow to and from the fluid actuators, eliminating torsional load on the vehicle. Therefore, the driving characteristic is prevented from changing due to an unbalanced load on the vehicle. On the other hand, the electronic controlled suspension system detects a vehicle's cornering state. Responsive to the cornering state detected, control signals are output to increase the roll stiffness distribution to the front wheels. As a result, the roll stiffness distribution to the front wheels while the vehicle is about to corner becomes larger than that while the vehicle is steadily cornering. Responsive to the control signals, the vehicle attitude is controlled by supplying and discharging fluid to and from fluid actuators.

Abstract: In controlling roll and pitch of a vehicle body responsive to a displacement signal produced at each wheel of the vehicle, each signal is low-pass-filtered with a certain threshold frequency to prevent hunting of the control due to an excessively high frequency component (such as noise or a component corresponding to road irregularities) of the signal. According to this invention, the threshold frequency is changed to a higher value in order to get quick attitude control when the roll or pitch of the body is expected, while it is set at a lower value when no such attitude change is expected in order to prevent hunting of the control.