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This paper will present a method of estimating tyre friction force using an extended Kalman filter (EKF). A review of current and proposed methods for tyre force estimation from the literature will be given. The EKF developed will estimate vehicle motions and tyre forces as state estimates from a noisy measurement set. The tyre forces will be compared to those from a high order vehicle model with non-linear tyres, which is subjected to the same tests as the measured vehicle, in order to validate the estimated forces. The robustness of the estimator to noise and input errors will be tested. The ultimate aim of this work is to provide estimates of tyre forces to a controller such as ABS or TCS.

This paper proposes an advanced control strategy to improve vehicle handling and directional stability by integrating either Active Front Steering (AFS) or Active Rear Steering (ARS) with Variable Torque Distribution (VTD) control. Both AFS and ARS serve as the steerability controller and are designed to achieve the improved yaw rate tracking in low to mid-range lateral acceleration using Sliding Mode Control (SMC); while VTD is used as the stability controller and employs differential driving torque between left and right wheels on the same axle to produce a relatively large stabilizing yaw moment when the vehicle states (sideslip angle and its angular velocity) exceed the reference stable region defined in the phase plane. Based on these stand-alone subsystems, an integrated control scheme which coordinates the control actions of both AFS/ARS and VTD is proposed. The functional difference between AFS and ARS when integrated with VTD is explained physically.