Page - 49 - in Maximum Tire-Road Friction Coefficient Estimation

3 Vehicle model acceleration manoeuvres, the mean relative deviation ∆ωfl exceeds the 5 % limit in some regions, as can be seen in Figure 3.4. At lower friction potentials, the wheels 0.2 0.4 0.6 0.8 1 1.2 2 4 6 8 0 2 4 6 8 10 12 Longitudinal velocity v x in m/sFriction potential µmax Figure 3.4.: Meanrelativedeviation∆ωflof the front leftwheel’s rotational speedduring an accelerating manoeuvre with varied wheel moment of inertia. It can be seenthat for lowµmax≤0.5, there isanabruptchange inthecharacteristics. This occurs as the front wheels start to spin in order to be able to follow the given speed profile. The variation of the moment of inertia results in different wheel rotational accelerations that influence ∆ωfl as shown. are more likely to spin. This high wheel rotational acceleration is responsible for the high influence of the wheel’s moment of inertia on ∆ωfl. By monitoring the wheel rotational speeds ∆ωi and the wheel rotational speeds ωi of the driven wheels during the sensitivity analysis, it can be assured that the deviation of the wheel speeds of the driven wheels remain within acceptable limits. This does not restrict the analysis, as situations with high wheel rotational speeds rarely occur and are prevented in vehicles with traction control systems (TCS). The influence on non-driven wheels can be entirely omitted due to low wheel rotational acceleration during acceleration manoeuvres, which is also confirmed by the results of this investigation. 49