Time-Optimal Lane Change for Tractor-Semitrailer on Varying Road Friction: Performance Bounds for Autonomous Driving

Emergency maneuvers for autonomous tractor-semitrailer combinations have been studied in previous works, but questions remain in order to demonstrate safety in all weather and road conditions. By formulating a lane change maneuver in different road conditions as a numerical optimal control problem, an upper performance bound can be established and subsequently used as a benchmark in the development of autonomous driving or advanced driver assistance-systems. The resulting optimal maneuver indicates that the time-optimality of a maneuver is strongly linked to the force direction of the trailer axle. Comparing the optimal lane change maneuvers with optimal straight line braking indicates that the decision of whether to brake or evade in emergency situations should be informed by the available tire-road friction. The results can be used to inform safe autonomous vehicle behaviors in low-friction conditions.