Vehicle Traction Control and Its Applications

Control of vehicle traction is of utmost importance in providing safety and obtaining desired vehicle motion in longitudinal and lateral vehicle control. Vehicle traction control systems can be designed to satisfy various objectives of a single vehicle system or a platoon of vehicles in an automated highway system, which include assuring ride quality and passenger comfort. Other objectives are aimed at providing desirable longitudinal and lateral motion of the vehicles. Vehicle traction force directly depends on the friction coefficient between road and tire, which in turn depends on the wheel slip as well as road conditions. From control point of view, we may influence traction force by varying the wheel slip. Wheel slip is a nonlinear function of the wheel velocity and the vehicle velocity. In this paper, a robust adaptive sliding mode controller is designed to maintain the wheel slip at any given value. Different objectives of traction control, give different target slips to be followed. Simulation study shows that longitudinal controllers, which do not take traction into account explicitly (termed as tractionless or passive controllers), cannot handle external disturbances well; on the other hand, longitudinal traction controllers (termed as active controllers) give satisfactory results with the same disturbances. Simulations show how some of the vehicle performance objectives are met by using traction controllers.