Abstract
Keywords: seating comfort, discomfort, pressure distribution
In recent years comfort has become more important for car manufactures to distinguish themselves from their competitors. The seat comfort or discomfort is very important because the seat is the main interface between user and car. However, seat discomfort can only be evaluated very late in the product development process by physical prototypes. It would be a big advantage for the developer to be able to check the seat discomfort by virtual seat tests. One component of virtual testing is to utilize a digital human model to simulate the contact forces between human and seat. The other part is to have a tool to interpret the results gained from simulation, especially the contact force distribution. For the first part human models already exist, for example Verver (2003) or Mergl et al. (2004).
Several studies have also been performed on interpreting pressure distributions: Gyi, Porter (1999) published experiments on the relationship between interface pressure and driving discomfort. They conducted experiments with fourteen test subjects on a static rig in the laboratory. Each subject conducted a two and a half hour test ride on seven seats. "A clear, simple and consistent relationship between interface pressure and driving discomfort was not identified". Only a relationship between pressure under the ischial tuberosties and discomfort for very tall males could be found.
Bubb & Estermann (2000) conducted long term experiments with 20 test subjects. The subjects drove for six and a half hours under realistic conditions in a car with one setting. Additional tests were performed with 51 test subjects, who drove two hours with two different seat settings. They could not find a relation between interface pressure and subjective evaluations.
In the study published by Reed et al. (1991) the long term discomfort for car seats was evaluated. Eight test subjects evaluated four different seats during three hour test rides in a static seating buck. Among other objective parameters, Reed et al. took the pressure on the interface between seat and human and the deflection profile of the seat. "Seat indentation contours, combined with the pressure sensor measurements, helped to explain the two areas of discomfort reported on the test seats." Furthermore, the short term seat evaluations resulted in different discomfort evaluations for the seats than the three hour test rides. They concluded that a short term evaluation is insufficient to predict the comfort performance in actual conditions of daily use.