Use of integrated control to enhance the safety of vehicles in run-off-road scenarios


In this paper, an integrated vehicle control system (IC) is tested in run-off-road scenarios. The integrated control was used in order to manage the interaction between the Anti-Lock Brake System (ABS), Four-wheel Steering system (4WS), and Electronic Stability Programme (ESP). For all the simulations performed in this work, a virtual test driver, based on fuzzy control, is employed. By receiving the lateral position of an obstacle and vehicle’s relative yaw angle, the virtual driver must be able to make an avoiding collision maneuver. Nine fuzzy rules were established considering that the controller must not only perform the avoiding maneuver, but also to minimize the behavior difference between under-steering and over-steering tendencies. The vehicle without any control system is used as reference behavior. For testing the efficiency of the control systems, i.e. ABS, ESP and 4WS, the vehicle perform an avoidance maneuvers in off-road conditions. The ESP and 4WS systems were implemented in order to maintain the vehicle’s stability while performing off-road maneuvers. The run-off-road scenarios were built for simulating mu-split in order to evaluate the capability of ESP, 4WS and the IC to improve the vehicle's stability and keep its maneuverability. The ABS model was developed also using fuzzy control. The system receives information regarding the wheels’ current velocities for performing a slip-based control. The fuzzy database was composed only by three rules, which were enough to make the system work properly not only on surfaces with normal and reduced friction, but also in mu-split conditions. The 4WS system is used to improve the maneuverability at low velocities and the lateral response and stability at high velocities. The magnitude and orientation of rear steer angle was defined by the magnitude of the front wheels steer angles. The ESP is applied only when the tires are operating in the non-linear region, that means when the driver is no longer able to control the vehicle. A simple switch approach was used to model the ESP, where the yaw angular velocity and side slip angle errors, calculated using a simple handling model, were used as references. The simulations were done in a virtual environment that contains a fully non-linear vehicle model with a real suspension geometry and the TMeasy tire model, also used in commercial software. This environment is also capable to simulate 3D road profiles with different friction conditions and obstacles, e.g. bumps and holes as well as random profiles.

In XVII International Symposium on Dynamic Problems of Mechanics, DINAME.