Vehicle Dynamics Control for Rollover Mitigation

Abstract: Characterized by a high ratio between the height of center of gravity and the track-width, commercial vehicle dynamics differ from passenger car dynamics. The roll stability limit, measured in terms of lateral acceleration, is much lower, while longitudinal and lateral load transfer during braking and cornering reduce the yaw stability, resulting in roll motion. Rollovers are dangerous and possible lethal accidents. This master's thesis proposes how to detect and prevent untripped rollovers on commercial vans. Two methods to predict and detect rollover are examined. An analytical one, which uses the spring deflection sensors to measure the load distribution and therefore detects wheel liftoff as an indication of possible rollover. The other one, which is used in the developed controller, considers the potential and kinetic roll energy of the vehicle. A new control system is introduced to stabilize the roll and slip dynamics of the vehicle. It is based on an energy-related Lyapunov function, which controls the yaw rate to accomplish the objectives. The controller outputs the desired braking forces on each wheel that will stabilize the vehicle. Finally, differential braking is used to take out energy from the system. Simulations of extreme maneuvers show that the control system prevents the vehicle from rollover and skidding. They also indicate that the controller is robust against uncertainties in the load conditions. Comparisons with an existing LQ-controller confirm further the promising results of the Lyapunov controller.