Page - 50 - in Integration of Advanced Driver Assistance Systems on Full-Vehicle Level - Parametrization of an Adaptive Cruise Control System Based on Test Drives

4. Measurements w Aβw βˆw [km/h]xvv3 12 1 0 0 Figure 4.3.: Weight functionswβA andwβˆ for the combined side slip angleβ value of the front steering angle δ and a steering of the rear axle towards the inside of the curve. In the model used, the steering angle is not modified, but the lateral tyre stiffness is modified reading fcy= fcy,0−cy,e for the front axle, where fcy,0 is the basic cornering stiffness, and cy,e is the influence of the kinematics and elasto-kinematics of the suspension on the cornering stiffness. The same approach is used at the rear axle, but there the basic stiffness is increased by cy,e reading rcy= rcy,0 +cy,e. The linear STM of eq. (B.8), which is used for the estimation of side slip angle, does not work at vvx = 0. Therefore, another algorithm is used to find β at low vehicle speeds. It is based on the assumption that at low speeds the side slip angles at the wheels are small,αf 1rad andαr 1rad. In general, the vehicle moves around the Instantaneous Centre of Rotation (ICR). With the assumption of small side slip angles, the ICR has nearly the same position as ICR-A, where A means Ackermann, see fig. B.1. Thus, for low vehicle speeds, the side slip angle is estimated by βA= arctan ( lr tan(δ) lf+ lr ) . (4.12) The combination of βˆ andβA is performed using the velocity-dependent weight function w(vvx) depicted in fig. 4.3. The equation for the combined side slip angle reads β=wβA βA+wβˆ βˆ. (4.13) For the validation of the observer, test drives with a specially equipped vehicle were carried out. One additional sensor was mounted at the front bumper of the vehicle, which measures the longitudinal Avvx and lateral speed A vvy in the vehicle coordinate system at sensor position A with its position vector Avs = [ A vx A vy ]T in the vehicle coordinate system. The transformation of the measured speed from the speed sensor pointA to the CG is done using vv=   AvvxA vvy 0   +   00 vωz   ×Avs, (4.14) 50