The safety of vehicles has become the main concern of vehicle designers. Many researchers developed sophisticated mathematical models of vehicles to achieve maximum safety in vehicle design. Later it has been known that this models can't be utilized widely in the simulation of transient manoeuvres because the performance of transient manoeuvres mainly depends on drivers. To solve this problem, it is necessary to study die driver-vehicle-environment closed-loop system. In this paper, a new mathematical model using fuzzy control theory for driver-vehicle-environment system of handling and stability is developed. The research efforts are mainly on die mathematical model of three degrees of freedom of a vehicle, on the method of establishing a driver fuzzy control model, on the computer simulation of driver-vehicle-environment system and on the comparison of simulation results with running experiment results. A block diagram for the driver -vehicle-environment system used in this study is shown in Fig. 1. This study is applicable to describe transient manoeuvres of vehicles and evaluate vehicle handling characteristics.
