The Development of a Sound Quality-Based End-of-Line Inspection System for Powered Seat Adjusters

In recent years, the perceived quality of powered seat adjusters based on their sound during operation has become a primary concern for vehicle and seat manufacturers. Historical noise targets based on overall dB(A) at the occupant's ear have consistently proved inadequate as a measure of the sound quality of a seat adjuster. Significant effort has been devoted to develop alternative sound quality metrics that can truly discriminate between “good” and “bad” seat adjusters. These new metrics have been successfully applied for some years by product development engineers in test labs. However, in the assembly plant the sound quality of the seat adjuster is still assessed subjectively by an operator at the end of the assembly line. The main problem with this approach is not only the lack of consistency and repeatability across large samples of seat tracks, but also the fact that the only feedback provided from the end-of-line to the product development team is of subjective nature. This subjective information is of little help for the engineers who have to diagnose and remedy the problem. Additionally, since sound quality has become one of the main reasons for rejection at the end of the assembly line, there is the need for integrating sound quality performance checks with the standard quality control or functional checks in the manufacturing environment. Therefore, the new challenge for the seat adjuster manufacturer is to implement at the end of the assembly line an automated Sound Quality-based inspection system that relies exclusively on objective parameters. The authors of this paper have devoted a lot of effort toward developing such a system, and this paper will describe and discuss the main issues related to its design, implementation and validation.