Abstract
A feasibility study of an active controlled vehicle is carried out so as to improve performances of the vehicle safety and comfortability remarkably. The purposes of this study are to develop a basic technology for realizing an actively controlled vehicle and to predict its effect on these performances.
An experimental vehicle is constructed with a front active steering system and independent hydropneumatic suspension systems which are integrated control elements and hydraulic power sources for individual wheel. A design procedure utilizing a modern control theory and a sophisticated element technique using each actuator and multi-microprocessors are also applied to the vehicle. The active steering control strategy is based on the optimal control theory including a driver-vehicle closed control system. It is possible to improve the vehicle controllability and stability at high speeds by a slight front steering angle control. On the other hand, the characteristic of the suspension system is functional integrations in each suspension unit. These systems are expected reductions of generated noise from oil pipes and spending energy to compress the oil. The active suspension control system uses combined methods of feedforward and feed back controls corresponding to various running conditions.
Experiments by real running tests show that every performance like controllability, stability, roll motion and riding comfort is improved. Comparing with controlled and noncontrolled vehicle, as well as the reduction of generated rolling angle below 50% due to steering, especially in the lane-change maneuver tests, settling time of the lateral motion of the vehicle is improved to 25% reduction and integral value of squared steering angle which show the amount of driver's steering operation is improved to 35% reduction according to simultaneously controls of both steering and suspension. The easiness of steering in driver-vehicle closed loop is derived from these results.
