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In modern society the automobile is an essential companion in everyday life. Be it commuting to and from work or during our leisure time - every week most of us spend many hours sitting in their car. In this context the seat is the main interface between the human being and the automobile itself. Functioning well, this close relationship can foster the well-being of the passenger and raise his spirit; being flawed it can otherwise cause severe pain in the back after a longer journey. Thus, for car manufacturers, the aspects of seat comfort are becoming more and more prominent in distinguishing themselves from their competitors. Despite its importance the development of comfort parameters in automotive seating is still being consigned to the subjective judgements of a poor number of seating experts or randomly selected test subjects.

For car manufacturers, seating comfort is becoming more and more important in distinguishing themselves from their competitors. There is a simultaneous demand for shorter development times and more comfortable seats. Comfort in automobile seats is a multi-dimensional and complex problem. Many current sophisticated measuring tools were consulted, but it is unclear on which factors one should concentrate attention when measuring comfort. The goal of this paper is to find a model in order to predict the overall seating discomfort based on body area ratings. Besides micro climate, the pressure distribution appears to be the most objective measure comprising with the clearest association with the subjective ratings. Therefore an analysis with three different test series was designed, allowing the variation of pressure on the seat surface. In parallel the subjects were asked to judge the local and the overall sensation.

To describe feelings of discomfort while sitting, many experiments have been conducted to find a link between interface pressure on the seat and the feelings of discomfort of test subjects. Most of these experiments found no relation or correlation between discomfort and pressure while others actually found a relation. A question which arose was how sensitive the human body is to pressure differences during sitting. The attempt of this study was to determine the sensitivity to pressure for an area of the thigh. Therefore a test stand was designed allowing the variation of pressure on an area of a thigh during sitting. In parallel, the subjects were asked to judge the pressure sensation. By analyzing the frequencies of answers given by the test subjects, a curve could be derived which describes the sensitivity of pressure sensation. In this paper the test stand, the test procedure, the results and further experiments will be discussed.

Often, pressure distributions on seats are referred to as an objective method to quantify seat comfort. However, the reliability of seat pressure measurement is yet unknown. Therefore, it is important to know how reliable these pressure measurements are, before using them effectively as a means to predict seat comfort based on pressure measurements. Experiments were conducted to determine the inter-individual and intra-individual variation in pressure distribution. The obtained variation ranges of the mean pressure in defined body areas are presented.

In this paper a project is described on finding a relationship between discomfort and contact force distribution between human and seat. In the first step experiments were conducted to find correlations between pressure and discomfort. In the second step these findings were validated for long term discomfort. The gained knowledge provides the possibility to check the long term riding properties of a car seat by taking the pressure distribution which takes only a few minutes. Furthermore, pressure distributions which are computed by digital human models can be evaluated with this knowledge.

The development times of car seats decrease while the demand for more comfortable seats increases at the same time. To fulfill this trade-off, numerical simulation of the body/seat interaction could be used. Therefore numerical models of the sitting human are needed. For this reason a 3D-FE-model of the thigh and pelvis of a 50th percentile male has been developed. The surfaces of the thigh and of the bones were gathered by a laser scanner. For the undeformed outer shape a test subject was chosen who has the anthropometry of a 50th percentile male. The geometry of the bones was scanned from a skeleton of a 50th percentile male. From the scanned data 3D CAD surfaces were derived. Within the CAD-system the bony structures were positioned inside the outer shape of the thigh and pelvis using computer tomography images. The biomechanic properties of the soft tissue were determined through indentation tests on test subjects.