Page - 122 - in Maximum Tire-Road Friction Coefficient Estimation

6 Results and conclusion 6.5. Comparison of results with requirements of an AEB The aim of the presented algorithm is to provide an estimate of the friction potential for adapting the intervention strategy of an AEB, cf. Section 1.3.2. By having an estimate before a possibly critical situation is being detected by the system, different intervention strategies can be evaluated (e.g. braking or steering) and warning and activation times aswell as themagnitudeofdecelerationduringthebrakingphasescanbeadaptedonthe current friction potential. The proposed algorithm depends on the dynamic excitation during the manoeuvre, thus a phase with e.g. partial braking during the AEB interven- tion will deliver better estimates than a low dynamic driving state before AEB may be necessary. However, this information is available only very late in terms of adapting the intervention strategy. Figure 1.8 in Section 1.3.2 shows the relation between the tolerable deviation ∆µ and the time delay τM for two different friction potentials in order to not exceed a certain impact speed when approaching a standstill object. When not considering a time delay τM, the tolerable deviation ∆µ can be expressed as a function of the reference valueµ ref and the initial speed vx,0 for the same requirements in terms of maximum impact speed, [LKE13a]. Figure 6.16 shows the limits for ∆µ in dependence ofµref and vx,0. 0 1 0 −0.1 −0.2 −0.3 −0.4 0.2 0.4 0.6 0.8 1.2 140 kph 120 kph 100 kph 80 kph 60 kph 40 kh µref Figure 6.16.: Tolerable deviation ∆µ in dependence on the real valueµref of the friction potential and for different initial longitudinal speed vx,0, [LKE13a] The error results in Table 6.1 and Table 6.2 show that for many conditions, an MAE below 0.2 can be achieved, which fulfils the requirements of an estimate of µmax for inner-city speeds up to a reference road condition of µref ≈ 0.4. Since current AEB 122