Adopting Supervisor for Bolt Loosening Detection by Using Smart Washer

Abstract

The objective of this study is the loosening detection of bolted joints without human involvement by applying the concept of structural health monitoring. The smart washer consists of a cantilevered plate bonded to a piezoelectric material, which provides self-sensing and actuation functions. The basic principle of how to detect bolt loosening is that the dynamics of a smart washer system vary depending on bolt tightening axial tension. The natural frequency of the smart washer was identified by using the sub-space state space identification algorithm in previous papers. However, the previous method has the problems that the fault detection accuracy deteriorates due to the influence of identification error and modeling error. This paper propose to apply the supervisor based on the model-based Fault Detection and Isolation technique for the detection of bolt loosening by using multiple observer. The numerical simulations and the experimentations were performed to verify the possibility of the observer-based loosening detection by using the smart washer. Improvement of bolt loosening detection accuracy was confirmed by comparing the proposed method with the previous method.