Longitudinal vehicle dynamics control for improved vehicle safety

• A fully nonlinear Adams model of a Land Rover Defender is expanded to include supply and demand forces.
• A method of path planning that minimises the curvature of the trajectory followed is described.
• A reference vehicle speed is formulated following a model-based design approach.
• By not exceeding reference speed the vehicle will not exceed a pre-set lateral acceleration limit.
• The control system’s performance was evaluated through simulation and experimentally.

The aim is to investigate the improvements in vehicle safety that can be achieved by limiting the vehicle speed based on GPS path information. The control strategy is aimed at reducing vehicle speed before a potentially dangerous situation is reached, in contrast with widely used stability control systems that only react once loss of control by the driver is imminent. An MSC.ADAMS/View simulation model of an off-road test vehicle was developed and validated experimentally. A longitudinal speed control system was developed by generating a reference speed based on the path information. This reference speed was formulated by taking into account the vehicle’s limits due to lateral acceleration, combined lateral and longitudinal acceleration and the vehicle’s performance capabilities. The model was used to evaluate the performance of the control system on various tracks. The control system was implemented on the test vehicle and the performance was evaluated by conducting field tests. Results of the field tests indicated that the control system limited the acceleration vector of the vehicle’s centre of gravity to prescribed limits, as predicted by the simulations, thereby decreasing the possibility of accidents caused by rollover or loss of directional control due to entering curves at inappropriately high speeds.