KEYWORDS – Steering Feel, Transition, Automated Driving, Driving Simulator ABSTRACT – The present publication addresses driving situations where control authority with regard to steering is transferred between a human driver and an automated lane centering system and vice versa. Besides visual and acoustic perception of the vehicle control state, haptic steering wheel feedback provides the driver with immediate state information. Incoherent steering feel leads to inconvenience and rejection of driving features originally designed to improve comfort and safety. Therefore, two research questions are addressed: Firstly, what are suitable strategies to shape steering feel during transitions between manual and assisted steering, and secondly, how can optimal transition steering feel be achieved. The chosen methodology comprises an empirical approach where steering transition scenarios are simulated in a controlled driver-in-the-loop environment. Three types of transition scenarios are considered, which are driver induced steering take-over (e.g. path correction, lane change), driver induced steering hand-over (e.g. upon system activation, return to path) and system induced steering hand-over (e.g. operational limit, failure). A set of different parametrizable transition strategies was developed and implemented in a static driver-in-the-loop simulator in order to be evaluated by experienced probands within the predefined scenarios. The evaluation concept consists of subjective rating criteria as well as objective key parameters. Based on the introduced approach, suitable transition strategies could be identified with respect to the actual transition scenario. Time and driver torque dependent strategies have shown the highest applicability. In order to answer the second research question, a correlation analysis between subjective and objective results enabled an estimation towards optimal transition strategies and parametrizations. Even with a high level of immersion, the experimental static driver-in-the-loop simulation environment cannot recreate the dynamic vehicle responses in terms of accelerations acting on the driver. The Vehicle responses have an influence on the driver’s judgement on steering feel and therefore need to be considered in subsequent research. Furthermore, the limited number of probands is not fully representative compared to a study of larger scale. Unique to this research is the dedicated focus on driver’s steering feel in terms of steering wheel dynamics during transition scenarios, while other aspects, such as visual and acoustic information concepts have been investigated before. It closes the gap between well explored conventional steering feel and steering feel of continuously operating driver assistance systems for lateral guidance. The investigation of transition strategies between manual and assisted steering has contributed valuable insights into the perception and design of steering feel as a whole. A scenario based selection of transition strategies enables the implementation of advanced lateral control approaches without unsettling the driver during the interaction process and thus increasing comfort and safety.
Mr. Matthias Becker, Project Manager ADAS/Steering, MdynamiX AG