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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.

During early phases of interior car layout a lot of different aspects have to be considered like crashworthiness, regulations, philosophy of the company etc.. Ergonomic aspects do not always play the most important role in these cases. Since aspects of comfort in cars are getting more and more important in nowadays these aspects should be taken into account very early in the interior car layout process. This paper shows a way to design the interior layout of a car from scratch for a good postural comfort for all anthropometries with the aid of a digital human model (RAMSIS). The novelty of this approach is to use the digital human model to design the interior and not to verify or correct an existing one.

This paper concerns a former experimental study of the Lehrstuhl für Ergonomie of TU München, where in the first step correlations between pressure and discomfort were found for the seat pan. In the second step these findings were validated for long term discomfort. Now an additional correlation for the back should be found, which is essential for later research. In this context tests conducted before should now be confirmed and validated by another seat comfort model with a higher number of subjects and a long term test, too. Interesting part of this study will be the intercorrelation between seat pan and back.

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 lack of measured data is a problem that often occurs when modeling physical human properties. This problem also occurs when trying to describe the human thigh with a finite element model. In this pilot study, an experimental chair was used to gather the required information. Each cushion of the chair consists of 81 pistons. Each piston is controlled individually by a computer. This experimental chair was used in two experiments. In the first experiment, the chair was used to measure the force length characteristics of deformed human thighs during unsupported sitting. In the second experiment, the measurement of the characteristics of undeformed thighs deformed by one piston was attempted. In this paper the test stand, the test procedures, the results und 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.

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.