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An accelerated seat durability test was developed to identify potential problems in areas with traditionally high warranty cost and customer dissatisfaction: squeak & rattle and mechanism looseness & efforts. The test inputs include temperature, humidity, road vibration, occupant movements, and mechanism cycling. These inputs were combined into a single 14-day test profile that simulates 10 years and 250,000 km. (approximately 150,000 miles) of 95th percentile customer usage. Various components of the seat assembly are tested together as a system. The test was performed on two current production programs. The test produced issues similar to those found in warranty repair data and evaluations of used seats from high-mileage customer-owned vehicles.

Currently one OEM requires seat system to pass a fatigue test consisting of a varying load applied to the seat back for a large number of cycles. The test was derived from a seat occupant study documented in SAE paper 840509, Passenger Car Seating Loads; A Human Factors Engineering Problem. This test takes an average of two weeks to complete for a given program. The purpose of our study is to develop an equivalent fatigue test that shortens the required test time and provides the same results and confidence.

This paper is the second in a two-part series that provides an overview of four objective methods for measuring Seat Comfort. It provides a detailed description of three of the four concepts, Electromyography (EMG), Spinal Loading, and Body Motion. Each of these methods is discussed in terms of Theory, Test Technique, and Test Data that are strictly linked to measurable biological parameters. Graphs are included to show the nature of the specific biological activity being measured and how these activities change in response to environmental stimuli acting on the human body. A comparison of the four techniques is provided. Suggestions are made to help future efforts in developing these objective measures of Seat Comfort.

As customer expectations rise, automotive seat comfort is becoming an increasingly important design goal. This paper explores the application of two objective measurables to the design of automotive seats. These measurables are EMG (electromyograph) data and seat pressure distribution data. An attempt is made to correlate these measurables with subjective comfort. An experiment is designed to collect the required analytical and subjective data. This data is then analyzed statistically to discover any correlations that may exist. The resulting correlations found in the statistical analysis are not large enough to be the basis for seat design, but indicates that with further work seat comfort may be measured objectively. The results of this research will lead the direction for further work.