Development of a method to predict occupied vehicle seat vibration and discomfort

Seat vibration is one of the known causes of discomfort in vehicle. The amount of vibration transmitted to occupant body is often associate with bad perception toward vehicle ride comfort. To evaluate the seat vibration and discomfort, automotive seating industry relies on subjective evaluation, however this method is complex because of several factors such as temperature, noise, and degree of tolerances can influence the perception of vibration. Moreover, the subjective method lacks repeatability and the results do not always lead to major improvement in the seat performance. Currently there is the ISO standard (ISO 2631-1 1997 and ISO 10326-1 1992) developed for assessing the vibration transmission to seated human body. The ISO 2631-1 (1997) specified the perception of human body to vibration whereas ISO 10326-1 (1992) specified the method and equipment used for evaluating the performance of the vehicle seat. Nevertheless, many researchers have shown that these ISO standard method may have underestimated the discomfort when used for evaluating vehicle seat vibration discomfort in high frequency (>10 Hz). It is worth to note that the ISO standard has developed for a wilder application and to assess the vibration emission to occupant, therefore the influence of vehicle seat structural dynamics (structural resonances and vibration mode shapes) was not considered. The vehicle seat structural resonance is found to be in the range that affect the health and comfort of human occupant (0.5 Hz - 80 Hz) and the transmission of vibration to occupant body is not well-investigated. Therefore, this research aims to characterise the influence of vehicle seat structural dynamics on vibration transmission of occupant body and to develop a new discomfort assessment method. The developed method show significant improvement over the current method in frequency up to 100 Hz.