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First, this paper describes a measurement of the human back-backrest interface contours and a reduction procedure of the measured contours to reconstruct the statistical back contours of American 50 and 95-percentile male. Second, the paper illustrates the difference of the back contour between the statistical male drivers and SAE 3-D Manikin. Finally, the advantage of using the back contour model in experiment is given. The AM 50 back contour model was used as a loader to obtain the backrest pressure distribution and proved an excellent tool for backrest comfort evaluation.

Drivers' fatigue during long hour driving comes from various causes. The purpose of this study is to clarify the mechanisms of drivers' fatigue in relation to seat performance. The drivers' posture was examined on the assumption that an optimal seating posture against fatigue should exist. As a first step, laboratory test was conducted to grasp fatigue analysis viewpoints. Then, as a next step, road test with seat pressure distribution (S.P.D.) and Electromyogram (EMG) was implemented to clarify fatigue process. Results show that seat support condition is found to be one of the factors behind uncomfortable postures and physical burdens, which leads to subjectively felt fatigues.

For an automobile seat, lateral support is considered to be one of the most essential elements for comfort. This report examines lateral support with two selected seats. Driver's movement while cornering was observed by seat pressure distribution (S.P.D.), and muscle activity was simultaneously recorded in electromyogram (EMG). S.P.D showed larger lateral movement of driver and EMG showed higher muscle activity on a poor lateral support seat than on a good lateral support seat. The higher muscle activity on the poor seat was explained as an effort to compete against the larger lateral movement of the body. Thus, poor lateral support was proved to lead to heavier physical burden.

Seat lumbar support is thought to be essential for seating comfort as it plays important role in the driver's fatigue during long term driving. We tried to evaluate the lumbar support performance objectively with Seat Pressure Distribution. First, the tolerance in the measurement was eliminated by application of ASPECT manikin that reproduced a human seating torso posture [1, 2]. Second, an analysis method to visualize the seat support balance on the human back was developed. Third, a hypothesis for the optimal support balance to minimize the fatigue was proposed according to the fatigue growing mechanisms. Examining the deviation of each seat result from the optimal support, the performances were quantitatively evaluated. In addition to that, the effect of the lumbar support adjuster was taken into consideration to predict the market evaluation more precisely.