ROAD SURFACE FRICTION COEFFICIENT (MUE) DETERMINATION FOR TRACTION CONTROL SYSTEM

摘要

Traction Control system (TCS) provides better drivability and acceleration performance on low friction surfaces. The TCS typically tries to maintain the slip to an optimum value, to maximize traction force by modifying engine torque and/or brake force intervention. However the optimum slip is not a constant value and varies depending upon the road surface and tire conditions. It is a challenging task to predict this value dynamically and adapt TCS under all driving situations. Typically, TCS operates around fixed set point for slip. This will be achieved by controlling the brakes and torque independently. This system will not be efficient since the target slip may differ for different road friction coefficient. Hence, it is important to determine the Coefficient of Friction (Mue) of the road, to set the target slip value at an optimum level, so that the maximum tractive force can be derived under all road conditions. This paper describes the method used for development of Traction Control System for an Indian SUV and the methodology used to test it in simulation environment. The defining step in this development program was to estimate the surface friction of road under various vehicle running conditions. The Mue detection strategy and TCS controller are developed using Model Based Development (MBD) approach in MATLAB Simulink. Strategy is validated in Model In Loop (MIL) environment. The results obtained are presented in the subsequent sections.