Adaptive Rollover Control Algorithm Based on an Off-Road Tire Model
Hopkins, Brad Michael
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Due to a recent number of undesired rollovers in the field for the studied vehicle, rollover mitigation strategies have been investigated and developed. This research begins with the study of the tire, as it is the single component on the vehicle responsible for generating all of the non-inertial forces to direct the motion of the vehicle. Tire force and moment behavior has been researched extensively and several accurate tire models exist. However, not much research has been performed on off-road tire models. This research develops an off-road tire model for the studied vehicle by first using data from rolling road testing to develop a Pacejka Magic Formula tire model and then extending it to off-road surfaces through the use of scaling factors. The scaling factors are multipliers in the Magic Formula that describe how different aspects of the force and moment curves scale when the tire is driven on different surfaces. Scaling factors for dirt and gravel driving surfaces were obtained by using an existing portable tire test rig to perform force and moment tests on a passenger tire driven on these surfaces. The off-road tire model was then used as a basis for developing control algorithms to prevent vehicle rollover on off-road terrain. Specifically, a direct yaw control (DYC) algorithm based on Lyapunov direct method and an emergency roll control (ERC) algorithm based on a rollover coefficient were developed. Emergency evasive maneuvers were performed in a simulation environment on the studied vehicle driven on dry asphalt, dirt, and gravel for the controlled and uncontrolled cases. Results show that the proposed control algorithms significantly improve vehicle stability and prevent rollover on a variety of driving surfaces.
- Masters Theses