Design, Fabrication, and Testing of Time Delay Micromechanisms for Fuzing Systems
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Micromechanical sequential-leaf time delay mechanisms based on SOI/DRIE technology have been designed, fabricated, and characterized. The devices were designed as elements of a larger fuzing system for rifled munitions, in which a passive timing mechanism triggers at a predetermined rotational speed, followed by a desired delay time before the next element of the munition fuzing train is activated. Analytical models for the micromechanical timing mechanisms have been developed and a variety of designs was simulated from the linear and nonlinear models, and using dynamics simulation software. Fabricated mechanism arrays designed to initiate switching at centripetal accelerations from 44 to 263 g were characterized using a high-speed camera, with delay times of between 0.67 and 0.95 ms achieved for single elements within the arrays. Measured delay times and switching accelerations follow predicted trends based on analytical and numerical models. Runaway escapement mechanism was coupled with the sequential-leaf time delay mechanisms to increase the delay time of each mechanism element. Mechanism switching at 2,000 g have been designed and simulated. The predicted delay time of each mechanism element was approximately doubled with the coupled runaway escapement mechanism. Two types of locking mechanisms were developed to increase reliability of operation of the sequential-leaf time delay mechanisms. The fish-bone type locking mechanism had been successfully demonstrated. A generic testing method for rotational dynamics that could image small displacement of object with high-speed off axis rotation was developed, which demonstrated for the first time of real time monitoring for rotational time delay mechanism. Image processing technology was used to improve image quality of high-speed images and extend the capability of high-speed camera to adapt to high rotation speed tests and to assist in post image analyses.