Vehicle suspension system

A suspension unit of a wheeled vehicle comprising:

• a hydraulic actuator of which the displacement is variable by control of the flow of hydraulic fluid to at least one side of the piston and cylinder thereof;
• means to connect the actuator to the body and a wheel hub of the vehicle so that variation of the displacement of the actuator controls the height of the body above the wheel hub;
• transducers on the vehicle which generate signals, each transducer providing a signal indicative of at least one of force applied to the body by the actuator, longitudinal acceleration of the vehicle, lateral acceleration of the vehicle, speed of vehicle and yaw rate of the vehicle;
• control means to control the flow of fluid to and from the actuator, in response to the signals generated by the transducers, to control the vehicle suspension, said control means comprising a processor which generates a velocity demand signal which corresponds to a velocity required of the actuator and a hydraulic control circuit controlled by the velocity demand signal;
• displacement detector means to detect when the actuator displacement approaches a desired maximum/minimum value and to generate a control signal when the actuator displacement approaches the desired maximum/minimum value;
• and
• means to modify the velocity demand signal which operates in response to the control signal generated by the displacement detector means to being the extension/contraction of the actuator gradually to a stop as the desired maximum/minimum value is reached.