Vibration sensitivity measurement of back and buttocks for effective seat vibration warning

Abstract: The study focuses on tactile sense as an additional modality for presenting information to drivers, alongside the visual displays and auditory sounds commonly used for driver assistance functions.Although many haptic warnings with built-in vibrators in the steering wheel and seats have been studied, there are few practical applications for seats, despite the steering wheel already being implemented. Vibration-based information presentation is an effective means of presenting information as it can present information solely to the driver without causing anxiety to passengers through display or sound warnings.Furthermore, as autonomous driving functions become more widespread, drivers can focus on other activities while in a hands-off state during Level 3 or higher levels. The presentation of information through tactile sense is considered highly effective when using a seat that maintains constant contact with a large area of the occupant during other activities.Many vibration warnings use eccentric motors to create vibrations, which limits the range of vibration characteristics that can be achieved. Additionally, there is insufficient knowledge regarding the optimal vibration characteristics and areas for stimulus. This study measured the vibration sensitivity of the back and buttocks in contact with the seat and investigated the vibration characteristics required for efficient warnings.Vibro-transducers were attached to the clothed human back surface of the body, and the minimum vibration output required to elicit a response was recorded for each frequency (30 to 150 Hz, in 10 Hz increments) at various sites on the back and buttocks. The resulting data was used to create a vibration sensitivity map of the back side of the body.First, in a preliminary experiment, 39 points on the back of the body from the 7th cervical vertebra to the back of the knee were comprehensively measured at 80 mm intervals for seven participants (4 males and 3 females), and the measurement points were narrowed down by examining regional differences, left-right differences, and individual differences. Finally, 22 measurement points were selected based on the skeleton and vibration sensitivity was measured. The buttocks, which have different pelvic positions inside the body, were measured in the supine and sitting positions.In the experiment, measurements were taken on a total of 14 subjects, 7 male and 7 female adults, and a vibration sensitivity map of the backside of the body was created.Based on the sensitivity maps, the effectiveness of the warning stimulus will be tested using a seat vibration warning with driving simulator.

Keywords: Tactile sense, Vibratory Waring, HMI

DOI: 10.54941/ahfe1005256

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