The automobile industry has reached a major turning point, which is said to be once every 100 years. In this conversion, the technology related to CASE (Connected, Autonomous / Automated, Shared, Electric) is attracting particular attention, but along with this, the way of making the car body / chassis and the way of developing the car itself are also large. It is about to change, and we engineers / researchers involved in mechanical engineering are working on that research every day. One example of this is research on model-based development (MBD). In model-based development, emphasis is placed on functional design, and the functions required for a single vehicle are incorporated into individual systems and parts, and based on that, model-based design is carried out. This model-based development has spread rapidly in the automobile industry in recent years, but its spread is relatively slow in fields that are greatly influenced by human sensibilities and sensations, such as the field of vibration and noise. It is considered that this is largely because there are no absolute evaluation indexes or numerical indexes required for functional design. Against this background, automobile manufacturers are currently widely conducting research and development focusing on the quantification and modeling of human sensibilities, and in recent years, seats focusing on the behavior of the pelvis of the seated person is being developed and put into practical use. In addition, the author's research group has been conducting research on the relationship between vehicle noise and human stress.In this study, to achieve a human-adaptive vibration design in a vehicle cabin based on the sensory characteristics of the passengers, the psychological stress of the passengers by the vibration of the seat of the commercial vehicle were studied. As an initial study, the measurement of the vibrational acceleration and its modal analysis of the seat were performed. We measured 22-points and 10-points vibrational acceleration for 3-directions (vertical, longitudinal, and lateral) of the seat and occupant in a commercial vehicle, respectively. Then, we performed modal analysis with obtained data. Results showed that the seat had four distinct vibrational modes in the idle state: vertical; horizontal; folding; rising. The amplitude of the folding mode vibration was 24 Hz and it was consistent with the 2nd order vibration of the engine of the vehicle. It was the biggest vibration of the seat. We also performed the measurement of the brain wave and pulse wave of the occupant seating on the seat to estimate his psychological stress caused by the seat vibration. Results showed that the psychological stress could be estimated by using his brain wave. However, the pulse wave was not suitable to estimate the psychological stress of the occupant due to the negative influence of the noise caused by the engine to his pulse wave. In addition, we also found that the sensitivity of the occupant to the seat vibration can be predicted from the results of spectral analysis of the gravity center of the occupant.

On the Vibration Transfer Characteristics From the Seat of the Vehicle to the Occupant

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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