MEMS switches for impact threshold detection

Nithin Raghunathan, Purdue University

Abstract

A number of defense and commercial applications require monitoring of acceleration events from 100s-10,000s g with a bandwidth of at least 100 kHz. Such acceleration levels are typical in impact and pyroshock phenomena. They are also prominent in the analysis of structure destruction, rupture and collision processes. Current accelerometer designs offer very limited redundancy and high noise output. Furthermore they have latency in detection and are known to fail under lower than designed loads. The focus of this study is on the threshold detection of such events using arrays of single crystal silicon micro g-switches. These switches respond to different acceleration levels by making solid-to-solid contacts at a discrete acceleration level. This has the potential to offer high redundancy and promises an adequate confidence level in the measured data. The g-switches in this study are designed for two categories, high-g switches for acceleration levels up to 40,000 g and low-g switches (in the order of 100 g) both surviving impact conditions. The high-g switches were tested using a modified Hopkinson bar setup and successfully demonstrated up to 45,000 g. Experimental and modeling results are used to examine the dynamic behavior of the switches. The modeling results found to be in close agreement with the experiment results with deviations below 9 μs (<20%) for contact times. A prediction algorithm is developed to estimate acceleration prole and is found to have a maximum variation of 10.7% from simulations. The low-g switches show responses to accelerations in the order of 60 -172 g and survivability up to 20,600 g.

Degree

Ph.D.

Advisors

Peroulis, Purdue University.

Subject Area

Computer Engineering|Electrical engineering|Mechanical engineering

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