Evaluation of driver's discomfort and postural change using dynamic body pressure distribution

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Abstract

The main objective of this study is the application of body pressure distribution measurements for the prediction of the driver's posture and its change. This requires quantitative analyses of dynamic body pressure distribution, which is the change of body pressure distribution with time. To investigate the relationship between dynamic body pressure data with driver's posture, 16 male subjects performed a simulated driving task for 45 min in a seating buck. During driving, the body posture and body-seat interface pressure were measured continuously, and the discomfort ratings were surveyed at the prescribed interval. For the statistical analyses, driving period, stature group, and lumbar support prominence were selected as independent variables, whereas subjective ratings of driver discomfort, driving posture, and body pressure values were selected as dependent variables. In this study, newly defined dynamic body pressure distribution variables were proposed, and the relationship between these pressure variables with subjective discomfort ratings were analyzed. The close correlations between the body pressure change variables and subjective discomfort ratings supported the possibility of using dynamic pressure data as a tool for the assessment of driver discomfort.

Relevance to industry

Since dynamic body pressure distribution data provide quantitative and objective indices in measuring driver's postural changes and discomfort while driving, the proposed method can be used for more effective automobile seat design and its evaluation.

Introduction

Drivers’ comfort is as important as the functional and aesthetic design of automobiles since consumers are more and more concerned about safety and comfortable driving. Progress in car seat development depends on the ergonomic research for seat design and on the assessment criteria used to analyze the interactions between driver and car (Yamazaki, 1992). One of the most important contributions that ergonomics can provide to the automobile design process is information of the physical size of driver, and his/her preferred postures (Porter and Gyi, 1998). The objective measures or indices affecting driver's comfort and related posture are needed to investigate (Gyi et al., 1998; Guenaelle, 1995).

Many researchers have been interested in drivers’ preferred postures. Porter and Gyi (1998) conducted an experiment to investigate observed optimum driving postures and positions and they developed the guidelines for optimum postural comfort. The study of Park et al. (2000) investigated the relationships among Korean drivers’ body dimensions, their driving postures and preferred seat adjustments after collecting data concerning the preferred driving postures and adopted seat adjustment levels. Reed et al. (2000) collected data on 68 subjects’ preferred driving postures in 18 combinations of seat height, steering wheel position, and seat back angle. Andreoni et al. (2002) used an optoelectronic system to capture the driving postures. However, these experiment times were not over 15 min. It would not be long enough to investigate postural changes and drivers’ discomfort that happen often in real driving situations. Hence, in this study, we investigated drivers’ discomfort and movement using dynamic body pressure distributions measured for a relatively long time, about 45 min.

The information of the pressure patterns are very useful for the design of seats (Andreoni et al., 2002). However, a clear and consistent relationship between interface pressure and driving comfort was not identified (Gyi and Porter, 1999). Lee and Ferraiuolo (1993) evaluated 16 car seats with 100 subjects. The author concluded that the results did not show enough correlation between subjective comfort and body pressure distributions. Andreoni et al. (2002) analyzed sitting posture and interaction of the driver body pressure with the cushion and the backrest. In this study, postures are measured by motion capture camera. Koyano et al. (2003) analyzed the static seating comfort of motorcycle seats using seated body pressure distribution data. These studies were performed in the static situation and used the body pressure distribution measured only at specific time. To investigate the pressure patterns, the body pressure distribution at specific times could provide enough information. However if the body pressure distributions are analyzed serially, it might provide more valuable information.

Lee et al. (1995) stated that the driver tends to move more frequently when he/she feels discomfort in order to adjust the posture and improve the discomfort situation. Previous studies relating to drivers’ movements used 3D motion cameras and CCTV's to measure the frequency of postural change. However, the application of these methods in small simulators or real cars is not practical. Therefore Park et al. (2001) limitedly checked the movement of the left leg in a passenger car with the automatic transmission.

The body pressure distribution is sensitive to movements and is relatively simple to measure even in a small space. Therefore, this study suggests the analysis method using serial or dynamic body pressure distribution to investigate the driver's movement.

The main objectives of this study are (1) to propose a method for using body pressure distribution data in order to measure driver's postural change during driving and (2) to investigate the relationships among the dynamic body pressure distribution and driver's postural changes and discomfort. For the prediction of drivers’ posture and its change using body pressure, dynamic data regarding changes over time in body pressure distribution and driving posture should be captured and analyzed. In this study, we suggest new body pressure variables by using the dynamic body pressure distribution, and investigate the relationship between these variables and changes in driver's posture.

Section snippets

Subjects

Sixteen healthy college students, all paid volunteers, participated in the experiment. All had driving experience and none had a history of musculoskeletal diseases. All subjects were male to minimize anthropometric differences. Their mean (SD) age, height, weight and driving experience were 25.5 (2.6) years, 172.8 (5.4) cm, 72.3 (9.8) kg, and 2.38 (2.4) years, respectively.

Experimental environment

The experiment was conducted in a seating buck. The seat of a mid-size sedan in Korean automobile market was used. The

Subjective discomfort ratings

ANOVA analysis was performed for whole body discomfort and the six body part discomforts. The summary of ANOVA results about subjective discomfort ratings is shown in Table 5 (α=0.05). Driving period was found to have a systematic effect on all subjective discomforts. All subjective discomfort ratings increased as the driving period increased. Fig. 3(a) shows the change of whole body discomfort according to the driving periods and letters in the bar indicate Student–Newman Keuls test results (α=

Discussion

The result of ANOVA for subjective discomfort showed that along with whole body discomfort, all body part discomfort levels increased as the driving period increased. The mean whole body discomfort before driving was 1.78, and that after driving was 4.37. El Falou et al. (2003) evaluated driver discomfort during 150 min of car driving. Despite the subjective increase in discomfort level, performance and SEMG did not show a significant effect. The mean peak discomfort at the end of the experiment

Conclusion

The objective of this study was the application of body pressure distribution data for the prediction of the driver's posture and its change. We suggested new body pressure variables, to which the dynamic body pressure distribution was applied, and investigated their relationship to the driver's posture and its change. body pressure change variables and subjective discomfort ratings were found to increase as the driving period increased. The driver tends to move more frequently when he/she

References (22)

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