Research On Optimal Slip Control Of Vehicle Traction System

The driven wheels of vehicle are often skidding or spinning when the vehicle is runningon a low friction road. This phenomenon is possibly to lead the vehicle lose its stabilityand safety, and also influence the acceleration performance and braking performance ofthe vehicle. The traction control system is emerging to solve this problem. Recently,the traction control system (TCS/ASR) is becoming a standard configuration of almostall the middle-class and high-class vehicles. It plays an important role on improving thevehicle stability, safety and the acceleration or braking performance.The working principle of the traction control system in this thesis takes use of therelationship between the slip and road friction coefcient, to regulate the driven torqueon the wheel for obtaining the optimal slip to realize the maximum traction force perfor-mance. Due to the high nonlinear character and the uncertain of the parameters of thevehicle system, the controller of the traction control system needs to have high robustnessand high adaptive.Based on the analysis above, the controller adapted in this thesis is sliding modecontroller which is not depend on the exact system dynamic model and performs goodrobustness and adaptive performance. Meanwhile, feedback linearization controllers forthe acceleration and deceleration cases are also designed, which is used for comparisonwith the sliding mode controller. The result shows that the sliding mode controller hasbetter robust performance and more easy to be applied to the real system. Besides, therelationship between slip and friction coefcient is diferent under diferent road conditions.Hence, the aim of the optimal slip changed according to the diferent road condition, thisproblem has widely be researched in the vehicle dynamic research area and many methodshas been proposed and applied, for instance, EKF method and sliding mode observer, etc.This thesis focuses the work on the designing and simulating of the nonlinear controllerof the traction control system. Hence, the control aim of the optimal slip is calculatedbased on the Burckhardt tire model with known experiment parameters for typical roadconditions.For the need of simulation, a8-DoF vehicle dynamic model and an Uni-Tire model are established. Diferent simulation conditions such like acceleration and decelerationdriving, varying road adhesion coefcient test, split road test and vehicle parameter inter-ference test are designed and the designed controllers are used in the simulation systemto test the controller performance.In the last, the future research of this issue include two aspects: designing an optimalslip observer for any unknown road condition to create an entire traction control systemfor all roads; establishing a hardware-in-the-loop simulation platform and test the controlsystem on this platform. All this future works are take advantages to improve the tractioncontrol system performance.