A modified design and fabrication sequence has been devised to improve the performance of a cloverleaf vibratory microgyroscope that includes an axial rod or post rigidly attached to the center of the cloverleaf structure. The basic concepts of cloverleaf vibratory microgyroscopes, without and with rods or posts, were described in two prior articles in NASA Tech Briefs, Vol. 21, No. 9 (September 1997): "Micromachined Planar Vibratory Microgyroscopes" (NPO-19713), page 68 and "Planar Vibratory Microgyroscope: Alternative Configuration" (NPO-19714), page 70. As described in more detail in the second-mentioned prior article, the cloverleaf-shaped structure and the rod or post are parts of a vibratory element that senses rotation via the effect of the Coriolis force upon its vibrations.
Heretofore, the posts for devices of this type have been fabricated separately, then assembled manually onto the cloverleaf structures. The resulting imperfections in the assembled units have given rise to asymmetric stresses in the cloverleaf structures and, consequently, to changes in resonant frequencies of vibration and in shapes of vibration modes. These changes, in turn, have caused variations in performance among nominally identical devices.
The modified design provides for the fabrication of the upper half of the post as an integral part of the cloverleaf structure; this is accomplished by reactive-ion etching of a single-piece half-post-and-cloverleaf structure from a wafer of silicon. The lower half of the post and a baseplate are also a single piece made by reactive-ion etching from a wafer of silicon. The two pieces are bonded together (see figure) by a thermal-compression metal-to-metal bonding technique to form a cloverleaf gyroscope with
an integrated post structure.
This work was done by Tony K. Tang, Roman Gutierrez, and Damien Roger of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
Intellectual Property group
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109
(818) 354-2240
Refer to NPO-20688, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
Cloverleaf Vibratory Microgyroscope With Integrated Post
(reference NPO-20688) is currently available for download from the TSP library.
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Overview
This document presents a technical support package from NASA detailing advancements in the design and fabrication of a cloverleaf vibratory microgyroscope, specifically focusing on a modified design that integrates an axial rod or post into the structure. The work was conducted by researchers Tony K. Tang, Roman Gutierrez, and Damien Roger at the Jet Propulsion Laboratory (JPL) for NASA.
The cloverleaf vibratory microgyroscope operates based on the Coriolis force, which affects its vibrations to sense rotation. Previous designs required separate fabrication of posts that were manually assembled onto the cloverleaf structures. This assembly process often led to imperfections, resulting in asymmetric stresses that altered the resonant frequencies and vibration modes, causing performance variations among nominally identical devices.
To address these issues, the modified design incorporates the upper half of the post as an integral part of the cloverleaf structure. This is achieved through reactive-ion etching, allowing for the creation of a single-piece half-post-and-cloverleaf structure from a silicon wafer. The lower half of the post and a baseplate are also fabricated as a single piece using the same method. These two components are then bonded together using a thermal-compression metal-to-metal bonding technique, resulting in a more consistent and reliable cloverleaf gyroscope with an integrated post structure.
The document emphasizes that these modifications are expected to enhance unit-to-unit consistency, improving the overall performance of the microgyroscope. The work is part of ongoing efforts to advance microfabrication techniques and improve the reliability of sensors used in aerospace applications.
Additionally, the document includes a notice regarding the rights to the invention, stating that the contractor has elected to retain title to the invention under Public Law 96-517. Inquiries about commercial use rights are directed to the JPL Intellectual Property group.
Overall, this technical support package highlights significant progress in the field of microgyroscope technology, showcasing innovative design modifications that promise to enhance the performance and reliability of these critical devices in aerospace and other applications.
