Apparatus and methods for time domain measurement of oscillation perturbations

• US 9,705,450 B2
• Filed: 06/24/2011
• Issued: 07/11/2017
• Est. Priority Date: 06/24/2011
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Swanson, Paul D., Waters, Richard L.
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): McAndrew, Christopher
• Application Number:
  US13/168,603
• Publication Number:
  US 20120326700A1
• Time in Patent Office: 2,209 Days
• Field of Search: 324 7611
• CPC Class Codes: G01C 19/5705 using masses driven in reciprocating rotary motion about an axis
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03K 17/955 using a capacitive detector

Abstract

An oscillatory apparatus and methods of utilizing the same. In one embodiment, the apparatus comprises a force sensor having a proof mass, with one or more sensing electron tunneling electrodes disposed thereon, and a frame comprising one or more reference electron tunneling electrodes. Conductive plates disposed on the sensor base and capping wafers induce oscillations of the proof mass. The sensing and the reference electrode pairs are disposed in a face-to-face configuration, thus forming a digital switch characterized by one or more closed states. In the closed state, the switch generates triggering events, thereby enabling the sensing apparatus to generate a digital output indicative of the mass position. The time period between consecutive trigger events is used to obtain mass deflection due to external forcing. Time separation between the triggering events is based on the physical dimensions established during fabrication, thus not requiring ongoing sensor calibration.

Claims

1. A method comprising the steps of:

generating a triggering event when a first element of a switch passes a second element of the switch, wherein the first element is disposed on a proof mass assembly and the second element is disposed on a frame fixed in location with respect to the proof mass assembly, wherein the first element is an oscillator in harmonic oscillation, wherein when the oscillator is displaced from a reference position the oscillator experiences a restoring force proportional to the displacement, and the second element is located at a fixed trigger position of one or more fixed trigger positions within the amplitude range of the oscillation, wherein the fixed trigger positions are predefined physical locations with respect to a reference position of the first element;

determining at least one time period between successive triggering events; and

using the at least one time period and the fixed trigger position of the second element to determine one or more parameters of the oscillation.

2. The method of claim 1, wherein the first element and the second element comprise electron tunneling electrodes and the triggering event is a tunneling current between the first element and the second element.

3. The method of claim 1, wherein the parameters of oscillation include parameters caused by an external force acting upon the first element.

4. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using a time period between successive triggering events with respect to the same fixed trigger position.

5. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using more than one time periods between successive triggering events with respect to the same fixed trigger position.

6. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using a time period between successive triggering events with respect to a first fixed trigger position and using a time period between successive triggering events with respect to a second fixed trigger position.

7. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using the time period to estimate a deflection of the first element.

8. The method of claim 7 further comprising the step of using the estimated deflection of the oscillation to determine an acceleration of the oscillation.

9. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using the time period to estimate an amplitude shift of the oscillation.

10. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using the time period to estimate a phase shift of the oscillation.

11. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using the time period to estimate a change in period of the oscillation.

12. The method of claim 1, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using the time period to estimate damping of the oscillation.

13. A method comprising the steps of:

generating a triggering event each time a first element of a switch passes a second element of the switch, wherein the first element is disposed on a proof mass assembly and the second element is disposed on a frame fixed in location with respect to the proof mass assembly, wherein the first element is an oscillator in harmonic oscillation and the second element is located at one of more than one fixed trigger positions within the amplitude range of the oscillation, wherein when the oscillator is displaced from a reference position the oscillator experiences a restoring force proportional to the displacement, wherein the fixed trigger positions are each at a fixed predefined physical location with respect to a reference position of the first element of the switch;

determining at least one time period between successive triggering events; and

using the at least one time period and the physical locations of the fixed trigger positions to determine one or more parameters of the oscillation including parameters caused by an external force acting upon the oscillator.

14. The method of claim 13, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using a time period between successive triggering events with respect to the same fixed trigger position.

15. The method of claim 13, wherein the step of using the at least one time period to determine one or more parameters of the oscillation comprises using more than one time periods between successive triggering events with respect to the same fixed trigger position.

16. The method of claim 13, wherein a first fixed trigger position is a reference trigger position, a second fixed trigger position is a positive trigger position, and a third fixed trigger position is a negative trigger position, wherein the parameters comprise a deflection of the oscillator'"'"'s oscillation, wherein the deflection of the oscillator'"'"'s oscillation comprises a positive deflection d₊ around an oscillation maximum, where

17. The method of claim 16, wherein the step of estimating a deflection of the first element'"'"'s oscillation comprises separately using both d₊ and d₋

for each cycle of oscillation to provide two separate deflection estimates per cycle of oscillation.

18. The method of claim 16, wherein the step of estimating a deflection of the first element'"'"'s oscillation comprises averaging d₊ and d₋

for each cycle of oscillation to provide one deflection estimate per cycle of oscillation.

19. A method comprising the steps of:

generating a triggering event when a first element of a switch passes a second element of the switch, wherein the first element is disposed on a proof mass assembly and the second element is disposed on a frame fixed in location with respect to the proof mass assembly, wherein the first element is a harmonic oscillator in oscillation, wherein oscillations of the harmonic oscillator are substantially harmonic, wherein when the oscillator is displaced from a reference position the oscillator experiences a restoring force proportional to the displacement, wherein the second element of the switch is located at a fixed trigger position of one or more fixed trigger positions within the amplitude range of the oscillation, wherein the fixed trigger positions are predefined physical locations with respect to a reference position of the first element;

determining at least one time period between successive triggering events; and

using the at least one time period and the fixed trigger position of the second element to determine one or more parameters of the oscillation.