A Survey of 4WD Traction Control Systems and Strategies

Traction Control Systems improve the general safety of a vehicle by providing better handling, directional stability and traction under various driving conditions. Consumers are becoming more aware of the benefits of traction control and the automobile manufacturers are responding with vehicles incorporating various kinds of traction control systems. This paper attempts to organize the various systems by the general principles used in their implementation and strategy. The basic elements of vehicle dynamics and the tire-patch mechanics are described. The influence of other subsystems like suspension and steering on vehicle dynamics is analyzed. The need for and the schemes used for the measurement of the various dynamic parameters are delineated. The advantages and limitations of the various control strategies are also described in relation to vehicle operating conditions. Driver expectations under low speed, high speed and off-road maneuvers vary and different strategies address these expectations differently. Several examples of the major traction control systems made by both US and international auto manufacturers are described in some detail. Both active as well as passive control systems are included and these are discussed as they relate to the principles developed earlier in the paper.