Comparing an Unbalanced Motor with Mechanical Vibration Transducers for Vibrotactile Forward Collision Warnings in the Steering Wheel

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A static driving simulator study was conducted to investigate an unbalanced actuator (UAK) and two mechanical vibration transducers (exciters) integrated in a steering wheel as vibrotactile warnings during manual driving. In a repeated-measures design, two vibration signal conditions (UAK vs. exciters) were presented to 32 subjects in two test routes with two forward collision warning scenarios. The effects of the vibration signals on driving behavior, reaction times, workload, acceptance, preference, and vibrotactile feel were examined in order to evaluate signal usability. The exciters led to lower SD speed and lower mean steering wheel angle acceleration and were preferred by 63% compared to the UAK. However, subjects showed longer reaction times and shorter time to collisions with the exciters. Due to its intense vibration, the UAK is more suitable for acutely dangerous situations requiring quick reactions. For less hazardous situations or incremental warnings, exciters are more suitable to avoid startle effects.