Improvement of Ride Comfort by Preview Vehicle-Suspension System 920277
The adaptation of an active control suspension has remarkably improved the vehicle attitude and ride comfort characteristics. Such an active controlled suspension is controlled by actuators and hydro-dynamic equipments like servo valves. The control strategies are composed of feedback control with each cylinder oil pressure, suspension stroke and velocity. In the practical application of these systems, it must be taken into account that the effect of control is much dependent on the time delay of a controller as well as control elements.
The object of this study is to confirm preview effects on the response of the system. The aim of preview feedforward control is to compensate the system delay of active control suspension. The control system is constructed of an ordinary feedback loop and a feedforward loop based on a road preview signal. The control signal from a preview sensor is supplied to an oil control servo valve just before the road preview point arrives at the front tire or the rear one.
To confirm the control effects on this control system, calculations based on simulation were executed using a half car model with four degrees of freedom for sprung and unsprung masses. These calculations clarified the control condition that the compensation time range for the decrease of the vertical acceleration of sprung mass exist.
Finally, the preview control effects were confirmed experimentally using a test vehicle with an optical preview sensor installed at front bumper. The effectiveness of the preview feedforward control system was verified by the measurement of the vertical acceleration of sprung mass. Compared with a preview controlled vehicle and a non-preview controlled one, the vertical acceleration of the experimental vehicle during on downgrade road driving was decreased by about 25%, and the vertical acceleration in the frequency range from 1 to 8 Hz during on paved rough road driving was decreased by about 30% to 45%.