Rotational accelerometer

• US 5,251,484 A
• Filed: 04/03/1992
• Issued: 10/12/1993
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Mastache, Mark D.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): BROCK, MICHAEL J
• Application Number:
  US07/862,909
• Time in Patent Office: 557 Days
• Field of Search: 73/517 A, 73/517 R, 324/661, 324/676
• US Class Current: 73/514.02
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration

Abstract

A rotary accelerometer has capacitively coupled rotary and fixed thin film electrodes fixed to a substrate. The rotary electrode is angularly flexible and has a central hub secured to the substrate and spoke electrodes radially extending from the hub. Elongated electrodes are fixed to the substrate in circumferential positions on each side of each spoke electrode and in the same plane as the spoke electrodes. The rotary electrode, having a mass and being angularly flexible, responds to angular acceleration to differentially change the gaps between its spoke electrodes and the adjacent fixed electrodes. The fixed electrodes are energized with rectangular wave voltages of opposite phase. The sum of these voltages in the spoke electrodes is a function of the difference in the gaps which, in turn, is a function of the angular inertia of the rotary electrode.

Claims

1. A rotary accelerometer, comprising:

a substrate;

an angularly flexible, rotary electrode comprising a central hub having an axis, and a least one pair of, substantially radially disposed spoke electrodes projecting in opposite directions from said central hub, substantially along a common diameter, each spoke electrode having opposite sides;

means attaching said central hub to said substrate, and

an elongated electrode fixedly attached to said substrate, respectively on the same side of said opposite sides of each spoke electrode and defining with each spoke electrode respective circumferential gaps which are substantially equal.

2. The rotary accelerometer according to claim 1, comprising:

a flexible connection between the distal end of each spoke electrode and said substrate.

3. The rotary accelerometer according to claim 1, comprising:

a second elongated electrode fixedly attached to said substrate on the remaining side of said opposite sides of each spoke electrode and defining with each spoke electrode respective second, substantially equal circumferential gaps which are substantially equal to said first circumferential gaps.

4. The rotary accelerometer according to claim 3, in which:

said angularly flexible rotary electrode is balanced about said axis.

5. The rotary accelerometer according to claim 1, in which:

said angularly flexible rotary electrode is balanced about said axis.

6. The rotary accelerometer according to claim 1, in which:

each elongate electrode and said rotary electrode are thin film electrodes.

7. The rotary accelerometer according to claim 6, comprising:

a flexible thin film connection between the distal end of each spoke electrode and said substrate.

8. The rotary accelerometer according to claim 7, in which:

said thin film connection is integral with said spoke electrode.

9. The rotary accelerometer according to claim 6, in which:

said thin film electrodes are disposed in the same plane.

10. The rotary accelerometer according to claim 1, in which:

said substrate is of a monocrystaline-silicon material and said rotary electrode and each elongated electrode are of a polycrystaline material.

11. The rotary accelerometer according to claim 10, in which:

said rotary electrode and each elongated electrode are attached to said substrate at n+ regions in said substrate.