• Research and/or engineering questions/objective In autonomous vehicles, if the driving operation patterns of a self-driving vehicle differ from the driving operation patterns that drivers are accustomed to performing, there is a possibility that the passengers may feel anxiety and discomfort. In automated braking, not only safety but also ride comfort is considered to be important. Therefore, in this study, the relationship between human body behavior and ride comfort was studied in order to clarify the factors that affect individual differences in ride comfort during braking, and the effects of changes in situations were also investigated. • Methodology In the experiment conducted in this study, twenty-three subjects were asked to ride in the front passenger seat and to look ahead while wearing a seatbelt during the evaluation. Four types of braking were performed to simulate automatic driving by human driver operation from an initial speed of 50 km/h, and physical behavior and questionnaire evaluations were conducted. The order of the braking was randomized, and the participants experienced three sets of braking. A seven-level questionnaire was used to obtain the comfort scores, and the movements of the head and shoulders were measured by motion capture. The subjects for whom both shoulder movements and questionnaires could be measured were divided into groups for each of the most highly rated braking, and analyses were performed for each group. This was done in two patterns, with and without obstacles in front of the vehicle. • Results The group was found to be divided into two main groups. Shoulder angle contributes to the ride comfort evaluation of braking, and we found that questionnaire scores tend to be higher for braking conditions where the change in shoulder angle is smaller. The results also suggest that individual differences in ride comfort evaluation may be affected by differences in the timing of the body posture with respect to braking g-force. Furthermore,some subjects showed a change in their tendency to evaluate braking depending on changes in the situation, suggesting that the timing of the body posture may change. • Limitations of this study Even if we look at individual results based on the present results, the results of a very small number of subjects cannot be explained by the relationship between braking evaluation and shoulder angle change. Therefore, it is considered necessary to conduct an integrated analysis based on the results of psychological analysis as well as behavioral analysis. • What does the paper offer that is new in the field in comparison to other works of the author? Difficulties in human research include the fact that it is difficult to obtain a unified view of individual tendencies due to their diversity, and the fact that psychological effects are subjective and difficult to quantify. Against this backdrop, focusing on passenger comfort in automatic braking, the approach of this research will be divided into two parts: behavior analysis and psychoanalysis. We will consider classifying human sensitivity to braking during automatic driving and quantifying the characteristics of each group. • Conclusion In this paper, the relationship between human body behavior and ride comfort was studied in order to clarify the factors that affect individual differences in ride comfort during braking, and the effects of changes in situations were also investigated. The obtained results suggested the following:(1) Shoulder angle contributes to the ride comfort evaluation of braking, (2) Individual differences in ride comfort evaluation may be affected by differences in the timing of the body posture with respect to braking g-force, (3) Changes in the situation may change the timing of the body posture for braking.
Mr. Masanori Matsuoka, Section Head, ADVICS Co., Ltd.; Mr. Yoshihide Onishi, employee, ADVICS Co Ltd; Mr. Yu Sugiura, employee, ADVICS Co Ltd; Prof. Shoichiro Takehara, professor, Sophia University