Validity of Comfort Assessment in RAMSIS 1999-01-1900

This paper describes the validation of the Comfort Assessment function of RAMSIS performed at Saab Automobile AB. The purpose was to find out if the effects of a change in design on comfort can be predicted by RAMSIS.

An interior mock-up of a car was used, in which seat, steering wheel, accelerator pedal, brake pedal and clutch pedal could be adjusted independently. In this mock-up 21 test subjects (10 men, 11 women) were told to adjust the steering wheel and the seat in the way that they obtained a good driving position. Pedals were fixed at a pre-defined position. The test subjects were told to judge the discomfort of the driving position on a scale from 1 to 10 with 1 meaning “not at all comfortable” and 10 meaning “very comfortable”. Then the test subjects were told to adjust the pedals and seat to improve the driving position, and asked to judge the discomfort of the new driving position. The seat, steering wheel and pedal positions were recorded for the two driving positions. Also, some anthropometric key dimensions were measured.

A CAD model of the interior mock-up was created and transferred to RAMSIS. The anthropometric measures of the 21 test subjects were used to create RAMSIS manikins corresponding to each test subject. The manikins were positioned in the previously recorded seating position with the pre-defined pedal position. A task defining which points on the manikin should touch which surfaces in the model was created so that the manikin was positioned in a driving position. RAMSIS was used to calculate the comfort values. The pedals were repositioned according to the individual pedal arrangement for each manikin and the manikin was repositioned to the second driving position. The same task was used to calculate a new driving position, and the comfort values were calculated.

For three manikins RAMSIS determined a worse comfort rating in the second driving position while the test subject specified a better comfort rating. In ten cases RAMSIS predicted a better comfort while also the test subjects rated the driving position as better. In the rest of the cases either RAMSIS predicted a better comfort while the test subject did not find the second driving position better (but not worse) or vice versa.