Apparatus and Methods for Time Domain Measurement of Oscillation Perturbations

• US 20120326700A1
• Filed: 06/24/2011
• Published: 12/27/2012
• 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.
• Granted Patent: US 9,705,450 B2
• Time in Patent Office: Days
• US Class Current: 324/76.11
• 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 time-domain force sensing apparatus, comprising:

a first structure comprising;

a proof mass comprising a plurality of sides;

at least one position-sensing electrode disposed on the proof mass; and

at ground element disposed on a first side of the plurality of sides of the proof mass, and coupled to a ground plane;

a second structure comprising;

at least one position defining electrode; and

a first capacitive plate disposed along a first side of the second structure;

a driving circuit electrically coupled to the first capacitive plate and the ground plane, and configured to induce oscillatory motion of the proof mass relative to the at least one position-defining electrode at a first frequency; and

a sensing circuit coupled to the at least one position-defining electrode and to the at least one position-sensing electrode, the sensing circuit configured to output a signal indicative of at least one predetermined spatial configuration between the at least one position defining electrode and the at least one position-sensing electrode;

wherein;

the signal comprises at least a first pulse associated with a first time value, and a second pulse associated with a second time value; and

a difference between the second time value and the first time value is configured based at least in part on the first frequency and a displacement of the proof mass caused by the inertial force.

2. The apparatus of claim 1, wherein:

the at least one position-defining electrode comprises a first position-defining electrode and a second position-defining electrode;

the at least one predetermined spatial configuration comprises (i) a first spatial configuration between the first position-defining electrode and the at least one position-sensing electrode, and (ii) a second spatial configuration between the second position-defining electrode and the at least one position-sensing electrode; and

the signal further comprises at least a third pulse associated with a third time value, and a fourth pulse associated with a second time value, the third and the fourth pulses generated based at least in part on the second spatial configuration.

3. The apparatus of claim 1, wherein:

the at least one position-defining electrode comprises a first position-defining electrode and a second position-defining electrode;

the at least one position-sensing electrode comprise a first position-sensing electrode and a second position-sensing electrode;

the at least one predetermined spatial configuration comprises (i) a first spatial configuration between the first position-defining electrode and the first position-sensing electrode and a first spatial configuration between the second position-defining electrode and the second position-sensing electrode, (ii) a second spatial configuration between the second position-defining electrode and the first position-sensing electrode, and (iii) a third second spatial configuration between the first position-defining electrode and the second position-sensing electrode; and

the signal further comprises;

at least a third pulse associated with a third time value, and a fourth pulse associated with a second time value, the third and the fourth pulses generated based at least in part on the second spatial configuration; and

at least a fifth pulse associated with a fifth time value, and a sixth pulse associated with a sixth time value, the fifth and the sixth pulses generated based at least in part on the third spatial configuration.

4. The apparatus of claim 1, wherein:

the second structure comprises a second capacitive plate disposed along second side of the second structure, the second side substantially opposing the first side;

the driving circuit is electrically coupled to the second capacitive plate; and

the driving circuit configured to provide a first driving signal to the first capacitive plate and a second driving signal to the second capacitive plate, wherein the second driving signal is phase shifted relative the first driving signal.

5. An oscillation apparatus configured for sensing an external force, the apparatus comprising:

an oscillator;

a driving circuit configured to drive the oscillator;

a switch apparatus comprising a first element and a second element; and

a sensing circuit coupled to the switch;

wherein;

at least one of the first element or the second element is disposed on the oscillator;

the sensing circuit is configured to output a substantially digital signal indicative of a first closed state, the first closed state corresponding to the oscillator being placed substantially in a first reference position such that the first and second elements are aligned; and

the signal comprises a first event and a second event, the second event separated from the first event by a first time period, the first period of time being related at least in part to a frequency of oscillation of the oscillator and the external force.

6. The apparatus of claim 5, wherein the applied force is substantially irregular, and the oscillation of the oscillator is substantially non-sinusoidal.

7. The apparatus of claim 5, wherein

the oscillator motion is characterized by a displacement in a first direction;

and

the alignment of the first and the second elements is configured in a second direction that is substantially perpendicular to the first direction.

8. The oscillation apparatus of claim 7, wherein the first and the second elements each comprise a tunneling tip electrode pair separated by a gap along the second direction;

and

the alignment of the first and the second elements is configured to cause a tunneling electrode discharge current across the gap.

9. The oscillation apparatus of claim 7, wherein the first and the second elements each comprise a magnetic tip electrode pair separated by a gap along the second direction;

and

the alignment of the first and the second elements is configured to cause a magnetic pulse across the gap.

10. The oscillation apparatus of claim 7, wherein a first electrode of the tunneling tip electrode pair is at a different electrical potential relative to a second electrode of the tunneling tip electrode pair;

and

the alignment of the first and the second elements is configured to cause an electric pulse in at least one of the first electrode or the second electrode.

11. The oscillation apparatus of claim 5, wherein the external force comprises a Coriolis force.

12. The oscillation apparatus of claim 5, wherein the external force comprises an acceleration force.

13. A method for measuring an external parameter using an oscillator capable of undergoing an oscillatory motion with respect to a reference position, the motion characterized by a first time period, and a switch characterized by at least a first closed state, the method comprising:

inducing an oscillatory motion within the oscillator; and

using a sensing circuit coupled to the switch to output a signal indicative of the switch being in the at least the first closed state, and a first event and a second event, the second event separated from the first event by a second period, the second period being related at least in part to the first time period and the external parameter.

14. The method of claim 13, wherein the first time period substantially matches a natural resonance frequency of the oscillator.

15. The method of claim 13, wherein the oscillatory motion of the oscillator is substantially non-sinusoidal.

16. The method of claim 13, wherein the step of inducing comprises applying a sinusoidal driving force to the oscillator for a first time interval.

17. The method of claim 13, wherein the step of inducing comprises applying a substantially intermittent driving force to the oscillator.

18. The method of claim 13, wherein the step the step of using the sensing circuit comprises:

charging at least one side of the switch to a higher voltage potential relative to another side of the switch;

measuring an electrical property of the switch during a second time interval.

19. The method of claim 18, wherein the step of measuring comprises a first measurement and a second measurement, both the first and the second measurement occurring within one of said first time period.

said parameter to said oscillator to induce an influence thereon;

generating signals from electrodes associated with said oscillator, said signals corresponding to the position of said electrodes as a function of time, said position being related at least in part to said influence; and

estimating the parameter based at least on said generated signals.

20. A method of operating an oscillatory device, comprising:

inducing an oscillation in an oscillator of the device using a driving signal; and

generating a substantially digital output from said device using at least first and second electrodes, the output being generated based at least in part on a clock signal, the clock signal having a predetermined jitter;

wherein said jitter substantially eliminates aliasing of said output.