An active suspension apparatus is provided for a vehicle which includes an actuator being extensible and retractable and provided between a vehicle body and a wheel so that the force of the vehicle body to support the wheel is adjustable, a sprung G sensor or a vehicle height sensor for detecting a vibration input to the vehicle body, and a control valve and a controller for controlling the supporting force of the actuator in accordance with the vibration input detected by the sprung G sensor or the vehicle height sensor, and thereby restraining the stroke of the actuator. The suspension apparatus further comprises a forward road surface sensor for detecting the size of irregularities of a road surface in front of the vehicle, and the control valve and the controller are adapted to execute normal control such that the equivalent spring constant of the actuator is adjusted to a first spring constant when a surface irregularity of a size larger than a predetermined size is detected by the forward road surface sensor, and to execute inverse spring control such that the equivalent spring constant of the actuator is adjusted to a second spring constant lower than the first spring constant, and thereby lengthening the stroke of the wheel, when no surface irregularity of a size larger than the predetermined size is detected by the forward road surface sensor. As a result, the ride is greatly improved when the vehicle runs on a smooth road.

An actuator for adjusting a height of the vehicle body is provided for each of the wheels and the height of the body is adjusted for each of the wheels by supplying and discharging an operating fluid to and from the actuator. A vehicle-height detecting sensor is also provided on each wheel for detecting the height of the vehicle body and for control over a posture of the body, namely, control over a supply or discharge of the operating liquid to or from the actuator is implemented with respect to bouncing, pitching or rolling of the body on the basis of output from the vehicle-height detecting sensor. Furthermore, a plurality of vertical G sensors for detecting acceleration in a vertical direction are provided to sense bouncing, pitching and rolling components of acceleration in the vertical direction, and the posture control utilizing the vehicle-height sensor is corrected so as not to make the vertical acceleration for the three components larger. Three vertical G sensors are provided so as to define a virtual plane representing the body, and that, for instance, two of the three vertical G sensors are disposed on the front portion of the body at positions bilaterally symmetrical to each other and one thereof is disposed on the rear portion thereof at a middle position, thereby allowing the three vertical G sensors to enable a detection of the acceleration in the vertical direction with respect to the bouncing, pitching and rolling components.

An apparatus for controlling damping coefficients for respective vehicular shock absorbers is disclosed in which a plurality of shock absorbers are interposed between predetermined parts of a vehicle body and tire wheel and are provided with damping coefficient changing members, each changing member varying the coefficients of the damping shock absorbers at multiple stages by changing position of an associated actuator, the actuator receiving a signal to change the position of the damping coefficient changing member on the basis of an input signal derived from a sprung mass vertical G sensor. Particularly, a correction portion is provided in a control unit which varies a position change rate of the damping coefficient changing member according to a value of the input signal derived from an input signal sensor, e.g., the sprung mass vertical G sensor.

A suspension system for a vehicle which has a hydraulic cylinder that extends and retracts in accordance with a change in the distance between a vehicle body and an axle to vary the volumetric capacity of a working chamber defined therein, an accumulator connected to the working chamber in the hydraulic cylinder, a control valve controlling the flow rate of oil charged into and discharged from the accumulator and the hydraulic cylinder, and a vehicle level sensor detecting a change in the above-described distance. The suspension system further has a control unit that controls the control valve, on the basis of a flow control signal obtained by multiplying the detected signal from the vehicle level sensor by an amplification factor, so as to restore the vehicle to a neutral state. The control unit is arranged to increase the amplification factor when the amount of the extension or retraction of the hydraulic cylinder is close to the extent of the full stroke thereof. When the vehicle is running on a normal road surface, the suspension system absorbs any changes in the road surface, thereby stably maintaining the attitude of the vehicle body, and in the case of large irregularities, it is possible to prevent full rebound or full bump which would otherwise occur when the hydraulic cylinder performs a full-stroke operation.

An active suspension for a vehicle including cylinder-piston type actuators each supporting the vehicle body relative to each of front right, front left, rear right and rear left wheels, height sensors for detecting height Hfr, Hfl, Hrr and Hrl of the vehicle body at the front right, the front left, the rear right and the rear left wheel, and a calculation control device which calculates based on height signals from the height sensors a bounce amount B and a pitch amount P with respect to the road surface from a standard state of the vehicle body according to: (where Kb and Kp are positive coefficients, and H is the mean value of standard vehicle heights of the portions of the vehicle body corresponding to respective wheels at the standard state of the vehicle body), calculates based on the amount B and P the supporting force for the actuators necessary to reduce the bounce and the pitch amount, and controls the actuators based on the calculation results to increase or decrease the force acting between the wheels and the vehicle body through the actuators.