Integrated Control Between Active Suspention and 4 Wheel Steering System

Integrated Control Between Active Suspention and 4 Wheel Steering System

INTRODUCTION

FEW YEARS HAVE PASSED since the electronic control suspension to improve both the stability and ride comfort, was introduced.  The electronic control suspension has been continuously produced since then.  The active suspension has been studied since earlier times than the semi-active suspension.  However, the active suspension system has not actually been used for cars until early 1987, when it was used for Formula-1 racing cars, and that too for a short time.  And then later during the same year, when the system was used to actively control only the attitude using pneumatic pressure as a power source.  Meanwhile, for application of electronic control technique to steering system, the speed sensitive type electronic control power steering was introduced way back in 1974.  Further, the system to electronically control the steering characteristics of rear wheels was introduced in 1985.
    Though the possibility of 4 wheel steering system (4WS) has been discussed since the 1960’s, it was mounted on passenger cars in the year 1987.  Even though, the mentioned system have independently been developed and produced, the possibility of the so called integrated control system made by integrating these systems has only been discussed.

NEED FOR THE INTEGRATED SYSTEM

The active control suspension makes it possible to control the vertical moving performance including the control of attitude, ride comfort, stability and vehicle height, and partially control the lateral and longitudinal maneuverability.
    Also, 4WS makes it possible to improve stability and controllability, which
 are the lateral maneuverability.  Each of these systems greatly improves performances and greatly influences performances other than the intended ones.  This is because the functions of vehicle dynamics such as driving, braking, turning and vertical movement are closely related to each other through the road contact force of tires which are the sole contact point between a vehicle and ground surface.
    As the improvement effect of more performances is expected by increasing each control system gain, the effect other than the desired ones or the influence on other systems cannot be ignored.