Quantifying the Visual Motion of an Automotive Seat Back

Visual movement of automotive components can induce a sense of poor quality and/or reliability to the customer. Many times this motion is likely to induce squeaks and rattles that further degrade customer opinion. For both of these reasons, it may be necessary to quantify the visual motion of certain components. This paper deals with a study in which the angular displacement from the observer to a passenger-side seat back was correlated to the subjective impression of seat back motion. Minutes Of Arc (MOAs) were found to correlate well to the perception of 17 subjects who evaluated the seat back motion of a seat mounted to a TEAM Cube in which road vibrations were played into a passenger seat and subjects were instructed that the evaluation surface was a “rough road” surface. This was confirmed for both the driver observing the unoccupied passenger seat from the side and a rear seat passenger viewing the unoccupied front seat from behind. In the first case the driver was observing fore-aft motion. In the second case the rear seat passenger was observing lateral motion. Another experiment was then conducted in which three of the same vibrations were evaluated, but this time subjects were instructed that the vehicle was traveling over a “smooth” road surface. As expected, subjective ratings generally deteriorated due to increased expectation for the smoother surface. Not expected, however, was that the decrease in subjective rating increased with stronger levels of excitation. The results show that at low MO levels expectations are nearly identical while higher MOA levels show an increasing expectation (i.e., lower subjective rating).