Latching Microelectromechanical Shock Sensor Systems: Design, Modeling, and Experiments

Abstract

Latching shock sensors are acceleration threshold sensors that trigger when the acceleration level exceeds the designed acceleration threshold. The latching mechanism provides a mechanical memory, which keeps the sensor in a triggered, or latched, state until the sensor is reset. The attractive feature of this type of sensor is that it does not require power during monitoring; power is only needed to query and reset the sensor. Several devices have been presented in the literature, but with limited experimental data and models that provide little to no insight into the dynamics of the latching event. The aim of this work is to further the understanding of the physics and design of micromechanical latching shock sensors by conducting a combination of careful experiments and development of original reduced-ordermodels. These efforts enable one to obtain a detailed picture of the latching dynamics for the first time. Latching shock sensors have been designed, fabricated, and experimentally evaluated in this work. The model predictions have been compared to the experimental results to verify the validity, including a quantitative comparison of the position of the shock sensor during a latching event captured via high-speed videography. This is the first time a latching event has been imaged in this class of sensors, and the first time, the model predictions of position versus time histories have been validated through experiments. The models have also been used to conduct detailed numerical studies of the shock sensor, amongst other things to predict a latch "bounce" phenomenon during an acceleration event. To understand more thoroughly how the various design parameters affect the latching threshold of the sensor, various parametric and optimization studies have also been conducted with the reduced-order models to guide designs of future latching acceleration threshold sensors.