Seite - 13 - in Maximum Tire-Road Friction Coefficient Estimation

1 Introduction 0 0.1 0.2 0.3 -0.2 -0.18 -0.16 -0.14 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 0 0.1 0.2 0.3 -0.2 -0.18 -0.16 -0.14 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 τ M in s µref = 1 140 kph 120 kph 100 kph 80 kph 60 kph 40 kph µref = 0.2 τ M in s Figure 1.8.: Tolerable deviation ∆µ versus tolerable time delay τM of the friction po- tential estimate when applied in an AEB to keep the impact speed below 4.2 m/s when approaching a standstill object and assuming hard braking (near physical limits), based on Lex et al., [LKE13a]. These requirements depend on the initial velocity and the actual valueµref of the friction poten- tial, shown here forµref = 1 (left) andµref = 0.2 (right). Requirements for pre-firing airbag With this system, the airbag is deployed before the collision occurs. This allows less ag- gressivedeploymentandcouples theoccupants’heads to thedeceleratingvehiclealready in the pre-collision phase. These measures can decrease the probability of head injuries, according to Eichberger, [Eic11, p.162-163]. Nevertheless, it has to be assured that the predicted collision is imminent in order to avoid false firing. Also, the two parameters stopping distance and impact speed must be calculated accurately in order to derive the necessary pre-fire times. Without information on the friction potential and the driver input, these two parameters cannot be predicted accurately and the pre-fire time can- not be calculated. For a friction potential of 0.8, the theoretically required accuracy of 13