Controller design and evaluation for vehicle run-off-the-road and recovery

Run-off-the-road (ROR) and unsuccessful recovery events account for a significant percentage of fatal vehicle crashes. Changes to roadway infrastructure have reduced the severity of automotive crashes; however, it is driver performance which remains a primary contributing factor to these incidents. An on-board vehicle control system, using combined steering and differential braking, provides enhanced safety by removing driver error from the recovery process once the ROR event has been identified. In this study, two control algorithms, based on sliding mode and state flow theories, have been designed to automatically recover a vehicle from this dangerous scenario. A driver model was also developed based on experimental data gathered at a tire manufacturer's test track. The controllers were numerically evaluated for a common road departure and return situation with comparison to the empirical driver model. The results show that both controllers safely recovered the vehicle and outperformed the driver steering model. Specifically, the state flow controller reduced recovery time by 40% compared to the sliding mode controller, while the driver model resulted in vehicle spin out.