January 6, 2008
Journal Article

Continuous Shock Monitoring for Damage Detection of Remote Systems

Abstract

For remote systems deployed in hazardous environments, a severe shock event can occur at any time. Personnel handling, transportation, storage, and deployment can expose equipment to high levels of shock during inadvertent drops or collisions. Even though delicate components are usually placed in robust containers with shock damping components, most remote systems are susceptible to shock damage. To address this need, engineers at the Pacific Northwest National Laboratory have developed a family of asset Health Monitors to detect if and when assets have been subjected to shock in excess of their design envelopes. The concept is embodied in a low cost, low power, battery powered Health Monitor mounted to the asset that is capable of measuring, recording, analyzing, and displaying if a shock event has occurred that puts the asset at risk of failure. By storing shock data along with a time stamp, the Health Monitor can be used to determine equipment readiness, flag potentially damaged equipment, and trace the root cause of equipment malfunction. Equipment shock limits are usually specified in terms of maximum shock level or maximum drop height, and both these limits have been employed on Health Monitors. Applying the maximum shock level criteria may be appropriate for assets with a known fragility level, whereas applying the maximum drop height criteria may be appropriate for assets in which drops during personnel handling is the most likely drop event. Implementing the maximum shock level criteria is straightforward, but assessing drop height from shock data is complicated by the fact that containers are three dimensional systems with different impact surfaces (corners, edges, and flat surfaces). The container impact surface can significantly affect the shock amplitude and frequency response of the container during a drop. This paper focuses on an analysis algorithm that was developed to determine drop height from a variety of drop orientations using shock data from a MEMS 3-axis accelerometer. When a shock event is higher than a defined threshold, an alarm light will be displayed when the Health Monitor status is queried. The algorithm has been successfully implemented as firmware running on the Health Monitor microprocessor. Drop testing and statistical analysis confirmed that the Health Monitor could accurately capture maximum shock levels and estimate drop height. The Health Monitor has been used for military applications on supply pallets, portable missile containers, and control systems, but could be readily adapted for use on crawlers, evacuation vehicles, or robotic arms.

Revised: July 22, 2010 | Published: January 6, 2008

Citation

Hatchell B.K., F.J. Mauss, J.R. Skorpik, and K.L. Silvers. 2008. Continuous Shock Monitoring for Damage Detection of Remote Systems. Transactions of the American Nuclear Society 99, no. 1:769-770. PNWD-SA-8058.