Tire/road friction estimation for front wheel driven vehicle

Abstract: Vehicles of today are equipped with several driving enhancing systems. The Electronic Stability Program (ESP) controls the brakes of the vehicle to prevent undesirable vehicle behavior. The Anti-lock Braking System (ABS) prevents the wheels to lock up while braking hard. Many vehicles are also equipped with advanced All Wheel Drive (AWD) systems or Limited Slip Differentials (LSD) allowing for the drive torque to be almost freely distributed among the wheels. Knowing the coefficient of friction to the road is extremely beneficial for all of these systems, especially for the AWD and LSD systems to be able to optimize the control. In this master thesis a method for estimating the tire/road friction coefficient will be developed. Focus will be put on Front Wheel Driven (FWD) vehicles equipped with an electronic Limited Slip Differential (eLSD). The eLSD in question is a newly launched product by BorgWarner AB called FXD (Front Cross Differential). This is an eLSD based on their well known fifth generation electro hydraulic clutch. Today it’s controlled by a complex control algorithm to be able to handle several driving situations. It’s desirable to know the tire/road friction coefficient to improve the control algorithm further. This is especially important when estimating the torque transfer through the differential.