The paper addresses the driver-vehicle interaction in the event of an erroneous steering torque intervention of an EPS (Electric Power Steering) system. Based on an overview of pertinent empirical findings the question is raised whether and to what extent statements on the controllability of steering torque faults that have been obtained in a specific test vehicle are valid for other, different vehicles. Methodology and results of an experimental study are presented that utilised a test vehicle which, using a combination of EPS and AFS (Active Front Steering), allowed the independent variation of steering torque offsets and resulting yaw reactions. The vehicle response was modified by variations of steering ratio. N=30 normally practised drivers participated in the study. The results show that subjective evaluations of torque interventions are significantly affected by the dynamic response of the vehicle. The failure-induced maximum yaw rate proves to be an appropriate safety criterion which is relevant to the driver and which can be applied to vehicles with different dynamic characteristics. The comparison of the present EPS study with findings of a previous study on steering angle failures (AFS) supports the use of the yaw rate as a safety criterion that is independent of the actuator concept. The main empirical findings of our study are as follows: 1. A large variety of different steering wheel angle changes can occur within the same test vehicle for the same steering torque requests. Steering wheel angle changes depend on the grip- and hold force on the steering wheel at the time point where the fault occurs. The variance of the induced steering wheel angle and yaw rate changes increases significantly with growing requested torque amplitudes. This means that the prediction of the impacts of a failure becomes increasingly difficult. 2. Depending on vehicle characteristics, the same steering torque offsets are rated differently. Statements on amplitude limitations that have been derived from a specific test vehicle can therefore not simply be generalised. 3. The disturbance induced yaw reaction strongly determines the driver ratings. In contrast to the steering torque, this criterion can be transferred to other vehicles with different dynamic characteristics. 4. The comparison of the findings of the present EPS-study with results of a previous study on steering angle failures (AFS) demonstrates that the same lateral disturbances lead to comparable driver ratings. Overall, the results suggest that the yaw rate can be used not only as a vehicle independent safety criterion, but also as one that is independent of the actuator concept.
Controllability of erroneous steering torque interventions: Driver reactions and influencing factors
Regelbarkeit von fehlerhaften Lenkmomenteingriffen: Fahrerreaktionen und Einflussfaktoren
2010
13 Seiten, 8 Bilder, 15 Quellen
Aufsatz (Konferenz)
Englisch
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