Experimental Verification of a Drift Controller for Autonomous Vehicle Tracking: a Circular Trajectory Using LQR Method
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ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
Experimental Verification of a Drift Controller for Autonomous Vehicle Tracking: a Circular Trajectory Using LQR Method Mincheol Park and Yeonsik Kang* Abstract: This study develops an autonomous vehicle control method that enables it to perform a drift maneuver which is an expert driving technique consisting of sliding the rear wheel intentionally for fast cornering. By developing an autonomous control algorithm for such an agile maneuver, the safety of the future autonomous vehicle on extreme conditions such as slippery road, will be increased. Drift equilibrium states are derived to find the suitable feedforward control input for the scale car to enter the drifting region. In addition, a feedback controller is designed based on the linear quadratic regulator method in order to track the circular trajectory and maintain drift equilibrium states. To validate the performance of the developed control algorithm a 1:10 scale car experimental platform is developed with on-board control and sensor system. The feasibility of the developed method for the autonomous vehicle is confirmed through both simulation and experiments following circular trajectories while maintaining the desired equilibrium states. Keywords: Autonomous race car, drift control, drift equilibrium, linear quadratic regulator, scale car.
1.
INTRODUCTION
1.1. Research motivation Safety is one of the most important factors influencing the commercialization of autonomous vehicles. There have been a number of studies on the safety of autonomous vehicles under normal driving conditions. However, in order to ensure safety, there is a need for control strategies which can maneuver the vehicle safely under harsh conditions such as bad weather or slippery roads. This paper investigates a vehicle control problem in extreme conditions such as tire saturation on a slippery road. Drift control is a technique employed by professional drivers under slippery road conditions such as unpaved, wet, or icy roads. In order to control the behavior of the vehicle under such extreme conditions, vehicle dynamics, including nonlinear tire dynamics, should be carefully taken into account. Professional drivers apply the drift control technique when a vehicle enters sharp corners by intentionally sliding the rear tires of the vehicle in order to turn the vehicle heading quickly and exit the corner without reducing the speed. Counter-steering is a typical manipulation which steers the front wheels in the opposite direction to
the turning direction. During the drift maneuver, the profession driver carefully regulates the vehicle turn rate and side slip angle around the desired values which are chosen based on his experience. Implementation of such professional driver skill on autonomous vehicle can help increase the safety of autonomous driving expecially when the vehicle is sliding its wheels and losing control. This study develops a control method which allows the autonomous vehicle to perform the drift maneuver, ta
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