Publication Detail

Design and Fabrication of a MEMS-ARRAY Pressure Sensor System for Passive Underwater Navigation Inspired by the Lateral Line

Stephen M. Hou
2012
241 pp.
MITSG 12-09
$75.00 DOM / $85.00 INT
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An object within a fluid flow generates local pressure variati ons that are unique and char- acteristic to the object’s shape and size. For example, a three-dimensional object or a wall-like obstacle obstructs flow and creates sharp pressure gradients nearby. Similarly, un-steady flow contains vortical patterns with associated unique pressure signatures. Detection of obstacles, as well as identification of unsteady flow features, is required for autonomousundersea vehicle (AUV) navigation. An array of passive underwater pressure sensors, withtheir ability to “touch at a distance” with minimal power consumption, would be able to resolve the pressure signatures of obstacles in the near field and the wake of objects in the intermediate field. As an additional benefit, with proper design, pressure sensors can alsobe used to sample acoustic signals as well. Fish already have a biological version of such a pressure sensor system, namely the lateral line organ, a spatially-distributed set of sensors over a fish’s body that allows the fish to monitor its hydrodynamic environment, influenced by the external disturbances. Throughits ability to resolve the pressure signature of objects, the fish obtains “hydrodynamic pictures”. Inspired by the fish lateral line, this thesis describes the development of a high-density array of microelectromechanical systems (MEMS) pressure sensors built in KOH-etched silicon and HF-etched Pyrex wafers. A novel strain-gauge resistor design is discussed, and standard CMOS/MEMS fabrication techniques were used to build sensors based on the strain-gauge resistors and thin silicon diphragms. Measurements of the diaphragm
deflection and strain-gauge resistance changes in respons to changes in applied external pressure confirm that the devices can be reliably calibrated for use as pressure sensors to enable passive navigation by AUVs. A set of sensors with millimeter-scale spacing, 2.1 to2.5V/Pa sensitivity, sub-pascal pressure resolution, and −2000 Pa to 2000 Pa pressurerange has been demonstrated. Finally, an integrated circuit for array processing and signal amplification and to be fabricated with the pressure sensors
is proposed

type: Full theses / dissertations

Parent Project

Project No.: 2006-R/RT-2/RCM-17
Title: Touch-at-a-Distance: Pressure Microsensor Arrays for AUV Navigation