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Vehicle Dynamics and Control for Active Safety
Published October 17, 1994 by Society of Automotive Engineers of China in China
On the general view of active safety, to understand interactive relations of driver's behavior with vehicle performance, road and its environmental conditions is very important. Presently vehicle dynamics and control technologies are expected to share greater roles in order to decrease driver's mental and physical load and to compensate road condition changes. This paper will discuss main contributions of remarkably improved vehicle dynamics technologies on many current subjects and future technologies to be achieved. For better feel of driving, handling, braking and also for possible safety, etc. vehicle dynamics should be analyzed including driver's maneuvers. Stability criteria and objective evaluation of a closed loop system for steering maneuver in lane change and against crosswind gust are derived theoretically, using a linear preview driver model. On the phase plane of vehicle response parameters, design parameters and chassis control gains, results are confirmed by evaluating excellently performing vehicles on the market. Furthermore, to achieve optimum design relations of driver's abilities and vehicle responses are analyzed and consequently a new 4WS strategy is found to minimize effects of external disturbances as well as to optimize steering response. When a vehicle approaches the limit of tire adhesions, each chassis system has to be controlled cooperatively. An integrated control strategy is proposed, i.e. control effects of distributions of roll stiffness on active suspension, and driving forces on 4 wheel drive, braking forces on anti-lock brake, etc. are analyzed theoretically using the effective cornering stiffness in consideration of tire non-linearity. Furthermore, concerning driving, braking and steering, contribution of each system to stability and controllability are investigated by the same measure. Thus this integrated control system enables drivers to expand limitations related to driving tasks and to achieve maximum dynamic performance and results are verified by experimental vehicles on dry and slippery roads. Finally, as new concepts of intelligent vehicles in future, many feasibilities and advanced technologies are discussed so that information of vehicle motions and tire adhesions or road conditions will be integrated and effectively combined for driver to obtain a margin of safety, i.e. prevent loss of control, be able to control quickly and decrease driver's effort for avoiding accidents, etc