Adjustable hydropneumatic active suspension apparatus

An active suspension apparatus using hydropneumatic springs for suspending a body of a vehicle on wheels by utilizing fluid and air pressures, comprising:

• acceleration detecting means, located at the floor of a passenger compartment, of a vehicle, for detecting an absolute acceleration Z of said floor corresponding to a vertical acceleration of the floor;
• displacement detecting means for detecting a relative displacement X between an axle of the vehicle and the body;
• a controller having a differentiator for differentiating the relative displacement X detected by said displacement detecting means and generating a rate X of change in relative displacement as a function of time, an absolute value circuit for calculating absolute values of the absolute acceleration Z, the relative displacement X and the rate X of change in relative displacement X, an operation circuit for multiplying the absolute values .vertline.Z.vertline., .vertline.X.vertline. and .vertline.X.vertline. from said absolute value circuit with predetermined coefficients, respectively, and producing an output signal from the sum of the absolute values which have been multiplied by the coefficients, and a comparator for comparing an output signal from said operation circuit with a reference value and generating a signal representing the state of the road surface on which the vehicle travels and the travel state of the vehicle;
• and
• driving means for controlling an opening of a restrictor arranged between each hydropneumatic spring chamber and a corresponding actuator in accordance with the signal from said controller,
• whereby damping force characteristics are controlled in accordance with the road surface state and the travel state.