| Off-road vehicle stability has been a serious problem for a long time. The stability problem is mostly caused by vehicle overturn. Every year many people are injured, die and have property damage because of vehicle overturns. In the past most of our effort has been put on the dynamic analysis of the vehicle motion and on the design of the driver protection system. Unfortunately the protection system only reduces the degree of injury and damage but such system does nothing to prevent the accidents.;In applying this concept, an active off-road vehicle instability prevention system has been developed. A control map concept has been used to simplify the real time computation during the vehicle operation. The active overturn prevention system not only can prevent the accidents, save lives, and eliminate the equipment damage, but it can also increase the productivity of the vehicle. The system provides two operational modes. The first is the automatic control mode which regulates the vehicle speed below and close to the safe operation boundaries. The second is the manual mode which controls the vehicle speed only when the vehicle speed is close to the safe operation boundaries but the operator fails to slow it down. After the vehicle speed is low enough for safe operation, the control system hands back the speed control to the operator.;An information display has also been designed, constructed and tested in this study. The display may be used to train the operators and improve the operator's skill.;Since vehicle motion can be simulated and predicted using mathematical models and computer programs with given initial conditions and ground characteristics, the overturn of the vehicle can be completely determined so that the overturning boundaries can be set up according to the conditions of operation, such as vehicle velocity, heading angle, slope angle, height of bumps on the ground surface, and the reactions of operator in the form of steering, braking, and throttle control. These overturning boundaries can consist of a group of curves that give the maximum travel speed, slope angle, degree of ground roughness, and turning rate for which there is stable vehicle operation. Based on the group of overturning boundary curves and the comparison between those curves and the states of the vehicle motion, it is possible to predict whether the vehicle is stable or not if it continues its present motion. It is also possible to decide whether braking, steering, and throttle control are necessary. |
