Controlling an Autonomous Racing Vehicle: Using Feedforward and Feedback to Control Steering and Speed

This paper describes the algorithms used for controlling an autonomous vehicle that operates at the limits of tire adhesion. The controller is designed to imitate a racecar driver by using both feedforward and feedback to command the steering, throttle, and brakes of the vehicle. The feedforward steering is based on the vehicle handling diagram, while the lanekeeping steering feedback is added to ensure vehicle stability and reduces tracking errors caused by disturbances or modeling errors. The feedforward speed is estimated based on the available friction, while the proportional speed feedback is introduced to mimic a race-car driver modulating the speed to trim the vehicle orientation. Two different speed feedback designs based on lookahead error and heading error are compared. The experiments demonstrate the superiority of heading error feedback, which enables the vehicle to operate at its limits while maintaining minimal lateral and heading errors from the desired trajectory.