Active vehicle suspension system

An active vehicle suspension system, comprising:

• a hydraulic actuator disposed between a wheel and a vehicle body, said actuator including a cylinder and a piston slidably received therein, said piston dividing an interior of said cylinder into first and second chambers which are defined by first and second pressure receiving surfaces of said piston, respectively, in cooperation with said cylinder;
• a pressure source;
• a first line connecting said pressure source to said first chamber;
• a control valve for controlling a pressure supplied from said pressure source to said first chamber of said cylinder;
• a second line connecting said pressure source to said second chamber;
• pressure reducing means provided in said second line for reducing a level of pressure supplied from said pressure source to said second chamber during all normal operations of the active vehicle suspension system to a level lower than a maximum pressure which said control valve can supply to said first chamber;
• and
• an accumulator connected to said second line;
• said first pressure receiving surface being substantially smaller than said second pressure receiving surface;
• and
• said control valve being adapted to control said pressure applied to said first chamber of said cylinder over a range defined between an output pressure of said pressure source anti a zero pressure.