Sitting Strategy Analysis based on Driving Posture and Seating Pressure Distribution

Abstract

In the design of comfortable automobile seats, driving posture and seating pressure have been considered importantly. Automobile seats can be examined by driving posture analysis of whether drivers can control the steering wheel or the pedals with their preferred posture, and by the seating pressure distribution analysis of whether the seat supports a driver's body appropriately so that the driver doesn't feel fatigue easily. However, considering all the postures and seating pressure distributions of drivers negatively affect the efficiency of the design process. In order to overcome this situation, several studies which classified representative sitting strategies were conducted, but it is known that the classification of the sitting strategy had been done by visual observation, and it should be classified by a quantitative method to be used in the automobile seat design process.There are 3 objectives of the present research. First, sitting strategies were quantitatively classified by driving posture. Second, sitting strategies were quantitatively classified by seating pressure. Lastly, the relationship between the two types of sitting strategies was analyzed. Twenty female and twenty male participants were recruited and a seating buck which is reconfigurable into a coupe, sedan, or SUV type had been used to consider the effect of the occupant package layout (OPL) type of the seat. The driving postures were captured by a motion capture system, and the seating pressures were measured by two pressure mats attached on each seatback and seatpan of the seat.First, the sitting strategies by driving posture were classified, and the characteristics were found. The sitting strategies by driving posture were quantitatively classified by cluster analysis on 6 joint angles (head, neck, trunk, hip, knee, and ankle). As a result, 3 strategies (Reclined, Erect, and Slouched) for upper-body and 3 strategies (Knee bent, Knee extended, and Upper-leg lifted) for lower-body were extracted, and it is shown that there are gender effect on the upper-body strategy and the OPL type effect on the lower-body strategy.Second, the sitting strategies by seating pressure were classified, and the characteristics were found. The sitting strategies by seating pressure were quantitatively classified by cluster analysis on the body pressure ratio (BPR) data which is the pressure ratio on 17 body parts in comparison with the total pressure on the whole body. As a result, it is shown that the seating pressure based sitting strategies of the upper-body and lower-body were dependent to each other. Therefore, the combined sitting strategies for the upper-body and lower-body were classified into 5 types (Mid-back & Scapular, Hip

Mid-back & Scapular, Hip & Mid-thigh

Mid-back & Lumbar, Hip

Mid-back & Lumbar, Hip & Mid-thigh

and Lumbar, Hip & Mid-thigh). The OPL type effect was significant on the combined sitting strategy by seating pressure. Lastly, the relationship between the two types of sitting strategies by driving posture and seating pressure was analyzed. In order to analyze the relationship, a Chi-square test on 2 sets (driving posture and seating pressure) of 9 sitting strategies (combination of upper and lower body sitting strategy) was conducted. However, the result was not significant. It is assumed to be the effect of seat configuration, so a follow-up study is required.In summary, the sitting strategies by driving posture were classified into 3 types each for upper-body and lower-body, and the strategies by seating pressure were classified into 5 types for the whole body. Furthermore, the relationship between the two sitting strategy types is not significant.