Physics-of-failure assessment of a cruise control module

The purpose of a cruise control system is to accurately maintain the driver 's desired set speed, without intervention from the driver, by actuating th e throttle-accelerator pedal linkage. Over the past five years, owners of a particular cruise control have complained that it did not operate properly . Complaints ranged from not engaging upon command, to the cruise unexpecte dly accelerating past the desired speed. A common thread among all the comp laints was the intermittent nature of the problems. More than 96% of the re ported failed modules removed from vehicles and returned to the company, pa ssed bench tests. This paper presents a physics-of-failure process to identify, induce and an alyze failure mechanisms causing intermittent failures, high warranty retur ns and cannot duplicate (CND) problems of the digital electronic cruise con trol module (CCM). In addition, we explain why the manufacturer's tests wer e not representative of the actual automotive environments, nor were they c onducted in a manner to access actual failures. We conclude with a recommen dation for a physics-of-failure approach for future product development. (C ) 1999 Elsevier Science Ltd. All rights reserved.