Angular accelerometer

• US 6,393,914 B1
• Filed: 02/13/2001
• Issued: 05/28/2002
• Est. Priority Date: 02/13/2001
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Baney, William J., Christenson, John C., Zarabadi, Seyed R.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/782,708
• Time in Patent Office: 469 Days
• Field of Search: 73/514.02,514.04,514.32
• US Class Current: 73/514.04
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration

Abstract

An angular accelerometer having a substrate, a fixed electrode supported on the substrate and including a first plurality of fixed capacitive plates, and a ring-shaped rotational inertia mass substantially suspended over a cavity and including a plurality of movable capacitive plates arranged to provide a capacitive coupling with the first plurality of fixed capacitive plates. A central member is fixedly attached to the substrate. A plurality of support arms extend between the central member and the ring-shaped mass for supporting the mass relative to the fixed electrode during rotational movement of the mass. The angular accelerometer also includes an input electrically coupled to the fixed electrode for receiving an input signal, and an output coupled to the mass for providing an output signal which varies as a function of the capacitive coupling and is indicative of angular acceleration.

Claims

1. An angular accelerometer comprising:

a substrate;

a fixed electrode supported on the substrate and including a first plurality of fixed capacitive plates;

a rotational inertia mass substantially suspended over a cavity and including a plurality of movable capacitive plates arranged to provide a capacitive coupling with said first plurality of fixed capacitive plates, said rotational inertia mass configured as a substantially annular ring and rotationally movable relative to said fixed electrode;

a central member fixed to said substrate and located substantially in the center of said rotational inertia mass;

a plurality of support arms extending between said central member and said rotational inertia mass for supporting said rotational inertia mass relative to said fixed electrode and allowing rotational movement of the rotational inertia mass upon experiencing an angular acceleration;

an input electrically coupled to one of the fixed electrode and the rotational inertia mass for receiving an input signal; and

an output electrically coupled to the other of the fixed electrode and the rotational inertia mass for providing an output signal which varies as a function of the capacitive coupling and is indicative of angular acceleration.

2. The angular accelerometer as defined in claim 1, wherein each of said plurality of support arms comprises a radial extending arm.

3. The angular accelerometer as defined in claim 1, wherein each of said plurality of support arms comprises a curved arm.

4. The angular accelerometer as defined in claim 3, wherein said curved arm is substantially S-shaped.

5. The angular accelerometer as defined in claim 1, wherein each of said plurality of support arms comprises a folded arm.

6. The angular accelerometer as defined in claim 1, wherein said plurality of support arms are substantially equi-angularly located.

7. The angular accelerometer as defined in claim 1, wherein said rotational inertia mass is substantially centrally located, and said first fixed electrode is radially displaced from said rotational inertia mass.

8. The angular accelerometer as defined in claim 1, wherein said substrate comprises a silicon substrate.

9. The angular accelerometer as defined in claim 8, wherein said angular accelerometer is fabricated by a trench etching process.

10. The angular accelerometer as defined in claim 1, wherein said plurality of support arms comprises at least four equi-angular located arms.

11. The angular accelerometer as defined in claim 1, wherein each of said plurality of support arms are flexible so as to bend during angular acceleration about one axis, yet rigid to resist bending due to other accelerations about other axes.

12. The angular accelerometer as defined in claim 1, wherein an input signal is applied to said rotational inertia mass and a differential output signal is produced by the fixed capacitive plates.

13. An angular accelerometer comprising:

a first bank of variable capacitors formed of a first plurality of fixed capacitive plates and a first plurality of movable capacitive plates;

a second bank of variable capacitors formed of a second plurality of fixed capacitive plates and a second plurality of movable capacitive plates;

a rotational inertia mass configured as a ring that is rotatable in response to angular acceleration and is electrically coupled to said first and second plurality of movable capacitive plates and arranged so that said first and second movable capacitive plates form capacitive couplings with said first and second plurality of fixed capacitive plates;

a central member fixed to said substrate and centrally located within said rotational inertia mass and separated therefrom;

a plurality of support arms extending between said central mass and said rotational inertia mass for supporting said rotational inertia mass and movable capacitive plates relative to said first and second fixed capacitive plates and allowing rotational movement of the rotational inertia mass upon experiencing an angular acceleration;

a first input electrically coupled to said first plurality of fixed capacitive plates;

a second input electrically coupled to said second plurality of fixed capacitive plates; and

an output electrically coupled to said plurality of movable capacitive plates for sensing an output signal indicative of angular acceleration in response to rotation of said rotational inertia mass.

14. The angular accelerometer as defined in claim 13, wherein each of said plurality of support arms comprises a radial extending arm.

15. The angular accelerometer as defined in claim 13, wherein each of said plurality of support arms comprises a curved arm.

16. The angular accelerometer as defined in claim 15, wherein said curved arm is substantially S-shaped.

17. The angular accelerometer as defined in claim 13, wherein each of said plurality of support arms comprises a folded arm.

18. The angular accelerometer as defined in claim 13, wherein said plurality of support arms are substantially equi-angularly located.

19. The angular accelerometer as defined in claim 13, wherein said rotational inertia mass is substantially centrally located, and said first and second plurality of movable capacitive plates are radially extended from said rotational inertia mass.

20. The angular accelerometer as defined in claim 13, wherein said substrate comprises a silicon substrate.

21. The angular accelerometer as defined in claim 20, wherein said angular accelerometer is fabricated by a trench etching process.

22. The angular accelerometer as defined in claim 13, wherein said plurality of support arms comprises at least four equi-angular located arms.

23. The angular accelerometer as defined in claim 13, wherein each of said support arms are flexible so as to bend during angular acceleration about one axis, yet rigid to resist bending due to acceleration about other axes.

24. A micromachined angular accelerometer comprising:

a substrate;

a fixed electrode supported on the substrate and including a first plurality of fixed capacitive plates;

a rotational ring having a central opening and including a plurality of movable capacitive plates at the outer perimeter arranged to provide a capacitive coupling with the first plurality of fixed capacitive plates, said rotational ring being suspended over a cavity and rotationally movable relative to said fixed electrode;

a central member fixed to said substrate and located within the central opening of the ring;

a plurality of support arms extending between said central member and said rotational ring for supporting said rotational ring relative to said fixed electrode and allowing rotational movement of the rotational ring upon experiencing an angular acceleration;

an input electrically coupled to one of the fixed electrodes and the rotational ring for receiving an input signal; and

an output electrically coupled to the other of the fixed electrode and the rotational ring for providing an output signal which varies as a function of the capacitive coupling and is indicative of angular acceleration.

25. The angular accelerometer as defined in claim 24, wherein each of said plurality of support arms comprises a radial extending arm integrally extending between said rotational ring and said central member, and wherein said radial extending arm is formed by removing material on opposite sides of said radial extending arm.

26. The angular accelerometer as defined in claim 25, wherein each of said plurality of support arms comprises a curved arm.

27. The angular accelerometer as defined in claim 26, wherein said curved arm is substantially S-shaped.

28. The angular accelerometer as defined in claim 25, wherein each of said plurality of support arms comprises a folded arm.

29. The angular accelerometer as defined in claim 24, wherein each of said plurality of support arms comprises two pairs of oppositely opposed support arms, wherein said two pairs are arranged approximately ninety degrees relative to one another.