Optically sensed wire gyroscope apparatus and system, and methods for manufacture and cursor control

• US 5,594,169 A
• Filed: 11/04/1994
• Issued: 01/14/1997
• Est. Priority Date: 11/04/1994
• Status: Expired due to Term

• Current Assignee: Gyration, Inc. (SMK Corporation)
• Original Assignee: Gyration, Inc. (SMK Corporation)
• Inventors: Hotelling, Steven P., Field, John
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US08/334,675
• Time in Patent Office: 802 Days
• Field of Search: 73/504.14, 73/503.3, 73/504.01, 73/504.08, 73/504.18, 73/514.39, 73/514.16, 73/514.19, 73/514.26, 74/5.46, 74/5.6 A
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5635 using vibrating wires or strings
• CPC Class Codes: Y10T 74/1264 Optical

Abstract

Single and dual wire gyroscopes determine the orientation and attitude of a device using optical sensing of radiation interrupted by current-carrying, vibrating tensioned wires within a magnetic fields. The tensioned wires vibrate between end nodes within the respective magnetic fields to provide both sustaining oscillatory drives and the sensing of velocity in the directions perpendicular to the respective magnetic fields. Lateral displacements of tensioned wires in directions parallel to the associated magnetic fields are sensed using radiant illumination of the wires and radiation sensing below the wires to provide displacement signals. Precession of wires in vibratory trajectories out of planes perpendicular to respective magnetic fields are controlled by selectively twisting and bending the tensioned wires between mounting ends.

Claims

1. A gyroscopic device for sensing motion and comprising:

a frame;

a first tensioned wire having first and second ends suspended by the frame and including a suspended wire portion therebetween;

a first pair of magnets mounted on the frame and having opposite poles spaced apart about the first tensioned wire for forming a first gap and a first magnetic field therein oriented across the first gap with the suspended wire portion of the first tensioned wire disposed within the first magnetic field;

a first oscillator connected to the first tensioned wire for supplying a first oscillating signal to the first tensioned wire to vibrate the first tensioned wire within the first magnetic field in substantially perpendicular orientation thereto and at a selected vibration frequency;

a source of radiation spaced above the first tensioned wire for radiantly illuminating a selected portion thereof;

a detector spaced beneath the first tensioned wire for producing a first output proportional to lateral displacement of a portion of the first tensioned wire along the first magnetic field in response to variations in the radiant illumination received thereby caused by the vibrating first tensioned wire; and

a first circuit connected to the first tensioned wire and responsive to back potential on the first tensioned wire for producing a second output proportional to velocity of vibration of a portion of the first tensioned wire in a direction substantially perpendicular to the first magnetic field.

2. A device as in claim 1 wherein the device comprises:

a demodulating circuit connected to the first circuit and to the detector for combining the first and second outputs to produce an output indication of magnitude and direction of displacement of the first tensioned wire.

3. A device as in claim 1 wherein the frame comprises:

a pair of opposing sides with openings therein for supporting the first and second ends of the first tensioned wire; and

a pair of insulators disposed in the openings for supporting the first tensioned wire under tension in the frame and for electrically insulating the first tensioned wire therefrom.

4. A device as in claim 1 comprising:

a second tensioned having first and second ends suspended by the frame and including a suspended wire portion therebetween disposed in skewed orientation relative to the suspended wire portion of the first tensioned wire;

a second pair of magnets mounted on the frame and having opposite poles spaced apart about the second tensioned wire for forming a second gap and a second magnetic field therein oriented across the second gap with the suspended wire portion of the second tensioned wire disposed within the second magnetic field;

a second oscillator connected to the second tensioned wire for supplying a second oscillating signal to the second tensioned wire to vibrate the second tensioned wire within the second magnetic field in substantially perpendicular orientation thereto and at a selected vibration frequency;

the source of radiation spaced above the second tensioned wire for radiantly illuminating a selected portion of the second tensioned wire;

a detector spaced beneath the second tensioned wire for producing a third output proportional to lateral displacement of a portion of the second tensioned wire along the second magnetic field in response to variations in the radiant illumination received thereby caused by the vibrating second tensioned wire; and

a second circuit connected to the second tensioned wire and responsive to back potential on the second tensioned wire for producing a fourth output proportional to velocity of vibration of a portion of the second tensioned wire in a direction substantially perpendicular to the second magnetic field.

5. A device as in claim 1 wherein the oscillator comprises:

an amplifier having an input connected to the first tensioned wire, and having an output for supplying to the first tensioned wire the first oscillating signal responsive to the back potential applied to the input in response to vibration of the portion of the first tensioned wire in a direction substantially perpendicular to the first magnetic field; and

a feedback circuit connecting the output of the amplifier to the input of the amplifier.

6. A device as in claim 1 wherein the source of radiation comprises:

a light emitting diode (LED) connected to a signal source for emitting radiation toward the detector.

7. A device as in claim 6 wherein the detector comprises:

a reference photosensor disposed beneath the first tensioned wire for receiving unobstructed radiation from the source for producing a reference electrical signal in response to the radiation; and

a controller connected to the signal source and to the LED for moderating signal supplied to the LED from the signal source in response to the reference electrical signal.

8. A device as in claim 7 wherein the controller comprises:

an operational amplifier having a first input connected to the signal source, and having a second input connected to the reference photosensor for receiving the reference electrical signal, and having an output connected to the LED for supplying an output signal representative of the relation between signal supplied to the LED from the signal source and the reference electrical signal.

9. A device as in claim 1 wherein the detector includes

a photodiode positioned in relation to the source of radiation for receiving radiation therefrom that varies in response to lateral displacement of the first tensioned wire along the first magnetic field.

10. A device as in claim 1 wherein

a demodulating circuit including a first mixer connected to receive a first portion of the second output and a first portion of the first output for producing a first signal as a combination of the portions of the first and second outputs applied thereto;

a phase shifter connected to receive the second output for shifting phase of a second portion of the second output by 90 degrees to produce a first displacement signal proportional to a first displacement of the first tensioned wire in a first direction;

a second mixer connected to receive the first output and the first displacement signal for producing a second signal as a combination of a second portion of the first output and the first displacement signal;

a differentiator connected to receive the second signal for producing a derivative signal as the derivative of a portion of the second signal; and

an adder connected to receive the first signal, the second signal and the derivative signal for producing an angular rate signal therefrom proportional to an angular rate of rotation of the frame.

11. A device as in claim 1 wherein the first end of the first tensioned wire is twisted in relation to the second end thereof in order to reduce an anisoelastic effect.

12. A device as in claim 1 wherein the first and second ends of the first tensioned wire are disposed with respect to the frame for introducing a bending moment of selected orientation and magnitude upon each end of the first tensioned wire;

the bending moment and the orientation thereof varying according to an amount of anisoelasticity compensation desired.

13. A device as in claim 1 wherein the first end of the first tensioned wire is twisted an angle theta about a longitudinal axis of the first tensioned wire with respect to the second end thereof in order to reduce precession of the vibrating first tensioned wire for providing an indication of rotation of the device from a reference orientation.

14. A device as in claim 1 wherein rotation of the device from a reference orientation is determined according to the expression:

space="preserve" listing-type="equation">K1*theta+K2*d(theta)/dt+K3*B;

where

theta=the angle between a central plane of the frame and a major elliptical axis of the cross section of the path of vibration of the first tensioned wire;

B=a minor elliptical axis of the cross section of the path of vibration of the first tensioned wire; and

K1, K2, and K3 are selected constants.

15. A method for measuring motion comprising the steps of:

suspending a wire having ends under tension within a magnetic field perpendicular to it longitudinal axis of the wire;

applying a fluctuating current to the wire to induce vibration thereof within the magnetic field;

sensing a counter-potential across the wire as a function of vibrational velocity thereof within the magnetic field;

forming from the counter-potential sensed across the wire a first velocity signal representative of a first direction of vibrational movement of the wire perpendicular to the magnetic field;

radiantly illuminating the wire substantially in a plane of vibrational movement of the wire within the magnetic field for forming a shadow of the wire on a surface spaced from the wire;

detecting variations in radiation upon the surface indicative of movement of the wire in a second direction parallel to the magnetic field; and

,

forming a first displacement signal as a function of the variation in radiation upon the surface.

16. A method as in claim 15 comprising the step of:

combining the first displacement signal and the first velocity signal to produce indications of magnitude and direction of displacement of the wire.

17. A method as in claim 15 wherein the step of applying the fluctuating current includes the steps of:

generating an amplified output current in response to an applied input;

applying a first portion of the output current to the wire;

sensing across the wire a counter-potential that is representative of the velocity of the vibrating wire within the magnetic field; and

forming the applied input as feedback from the counter-potential.

18. A method as in claim 15 wherein a source of radiation illuminates the wire and comprises the steps of:

powering the source of radiation to illuminate the wire and form a shadow thereof on a surface spaced away from the wire in a direction perpendicular to the magnetic field;

detecting a portion of radiation incident upon the surface substantially unaltered by the wire;

generating a reference electrical signal in response to the incident radiation detected on the surface; and

altering the power provided to the source in response to the reference electrical signal.

19. The method as in claim 16 comprising the steps of:

multiplying a first portion of the first velocity signal and a first portion of the first displacement signal to produce a first signal;

shifting the phase of a second portion of the first velocity signal by 90 degrees to produce a second displacement signal proportional to a second displacement of the wire in the first direction;

multiplying a second portion of the first displacement signal and the first displacement signal to produce a second signal;

differentiating a portion of the second signal with respect to time to produce a derivative signal; and

adding the first signal, the second signal and the derivative signal to produce an output indicative of an angular rate of rotation.

20. A method as in claim 15 wherein the step of suspending the wire includes twisting the wire along the longitudinal axis of the wire to reduce anisoelastic effects thereof.

21. A method as in claim 15 wherein the step of applying the fluctuating current includes imposing a bending moment upon each end of the wire varying according to the anisoelasticity of the wire.

22. A method as in claim 15 comprising the step of:

relatively twisting the ends of the wire by an angle theta about a longitudinal axis of the wire to reduce precession thereof and determine an amount of motion from a reference orientation around a longitudinal axis of the wire.

23. A method as in claim 15 comprising the steps of:

relatively twisting the ends of the wire until precession thereof is substantially eliminated.

24. The method as in claim 15 comprising the step of:

determining angular motion of the vibrating wire in a direction about the longitudinal axis thereof, according to the expression;

space="preserve" listing-type="equation">K1*theta+K2*d(theta)/dt+K3*B;

where

theta=the angle between a plane of the magnetic field and a major elliptical axis of the cross section of the path of vibration of the wire;

B=a minor elliptical axis of the cross section of the path of vibration of the wire; and

K1, K2, and K3 are selected constants.

25. A device for measuring orientation and attitude including

a frame;

first tensioned wire and second tensioned wire supported on the frame and axially disposed perpendicularly with respect to each other;

a source of oscillating electrical signal for each wire connected to supply oscillating current through respective first and second wires;

first and second magnetic field sources positioned in fixed relation to the frame for developing first and second magnetic fields about portions of the first and second wires for producing vibrations of the first and second wires in respective first and second directions perpendicular to the respective first and second magnetic fields in response to the oscillating current supplied to the respective first and second wires;

first and second sensors connected to the respective first and second tensioned wires for sensing counter-potentials thereon that are representative of vibrating velocities of the first and second tensioned wires, respectively, in the first and second directions for producing first and second velocity signals therefrom;

a light source for illuminating the first and second wires and casting a shadow image thereof onto a plane spaced away from the first and second tensioned wires; and

a light sensor disposed on the plane to receive the shadow image for developing first and second sensor signals indicative of fluctuations of the shadow images of the first and second tensioned wires, respectively, the first and second sensor signals being proportional to the deflections of the respective first and second tensioned wires in directions parallel to the respective first and second magnetic fields.

26. A device as in claim 25 comprising:

a first demodulating circuit connected to receive the first velocity signal and the first sensor signal to produce an output therefrom indicative of magnitude and direction of displacement of the first wire in a direction parallel to the magnetic field therefor; and

a second demodulator connected to receive the second velocity signal and the second sensor signal to produce an output therefrom indicative of magnitude and direction of displacement of the second wire in a direction parallel to the magnetic field therefor.

27. A device as in claim 25 wherein each of the wires includes first and second ends;

the frame including first and second pairs of opposing sides with openings therein for supporting the first and second ends of each wire; and

first and second pairs of insulators holding the wires under tension and insulating respective said ends of the wires from the frame.

28. A device as in claim 25 wherein the first and second magnetic field sources have pole faces that are disposed on the frame for developing third and fourth magnetic fields;

the first and second tensioned wires including first and second suspended areas, respectively, that are suspended between pole faces of respective said third and fourth magnetic fields.

29. A device as in claim 25 wherein each of said source of the oscillating signal includes an oscillator comprising:

an amplifier having an input and having an output connected to supply fluctuating current to a respective one of the first and second tensioned wires in response to a signal applied to the input thereof; and

the input connected to the respective wire for receiving counter potential generated across such wire by the vibrational movement of the wire in a magnetic field associated therewith.

30. A device as in claim 25 wherein the light source comprises:

a light emitting diode positioned to illuminate the first and second tensioned wires and the light sensor disposed on the plane that is spaced away from the first and second tensioned wires; and

a source of electrical signal connected to power the light emitting diode.

31. A device as in claim 25 wherein the light sensor comprises:

a reference photosensor for receiving unobstructed illumination from the light source for generating a reference electrical signal in response to illumination received thereby;

a source of electrical signal for supply to the light source; and

a circuit for moderating the electrical signal supplied to the light source in response to the reference electrical signal.

32. A device as in claim 31 wherein the circuit comprises:

an operational amplifier having first and second inputs, and an output;

the first input of the operational amplifier being connected to the source of electrical signal supplied to the light source for receiving the electrical signal therefrom;

the second input of the operational amplifier being connected to the reference photosensor for receiving the reference electrical signal; and

the output of the operational amplifier being connected to the light source for supplying power thereto representative of a combination of said electrical signal and said reference electrical signal.

33. A device as in claim 25 wherein the light sensor comprises:

first and second photodiodes, each positioned in relation to the light source for receiving illumination therefrom of varying intensity indicative of positions of respective ones of the first and second tensioned wires along the direction of the respective first and second magnetic fields.

34. A device as in claim 26 wherein each of the source of oscillating signal includes:

an oscillator output connected to supply respective one of the velocity signals to the respective demodulating circuit; and

each demodulating circuit includes;

a first mixer connected to receive a first portion of respective velocity signals and a first portion of respective sensor signals for producing a first signal therefrom;

a phase shifter connected to receive a second portion of the respective velocity signal for shifting the phase thereof by 90 degrees to produce a first displacement signal proportional to a first displacement of the respective tensioned wire in the first direction;

a second mixer connected to receive a second portion of the respective sensor signal and the first displacement signal for producing a second signal therefrom;

a differentiator connected to receive the second signal for producing a derivative of a portion of the second signal as a derivative output signal; and

an adder connected to receive the first signal, the second signal and the derivative signal to produce an angular rate signal therefrom that is proportional to an angular rate of rotation of the frame around a longitudinal axis of at least one of the first and second tensioned wires.

35. A device as in claim 25 wherein each of the first and second tensioned wires includes first and second ends;

each of the first ends being twisted in relation to the respective second ends for reducing anisoelastic effects in the respective first and second tensioned wires.

36. A device as in claim 25 wherein each of the first and second tensioned wires includes first and second ends supported on the frame;

and

mounts for each end of each wire supported on the frame to impose a bending moment upon each end of each of the wires;

the bending moment at each end varying according to the respective anisoelasticity of each of the wires.

37. A device as in claim 25 wherein each of the first and second tensioned wires includes first and second ends;

each of the first ends is twisted an angle theta about the longitudinal axis of the respective wire with respect to the respective second end in order to reduce precession of the respective wire in determining an amount of rotation of the device from a reference orientation.

38. A device as in claim 37 wherein the amount of rotation is determined according to the expression:

space="preserve" listing-type="equation">K1*theta+K2*d(theta)/dt+K3*B;

where

theta=the angle between a plane of the magnetic field and a major elliptical axis of the cross section of the path of vibration of the wire;

B=a minor elliptical axis of the cross section of the path of vibration of the wire; and

K1, K2, and K3 are selected constants.

39. A method for measuring motions with a vibrating wire comprising the steps of:

suspending the wire having ends, under tension within a magnetic field perpendicular to a longitudinal axis of the wire;

applying an oscillating current to the wire to vibrate the wire perpendicular to the magnetic field;

sensing counter-potential across the wire representative of vibrational velocity of the wire in the magnetic field;

forming from the counter-potential across the wire a first velocity signal representative of a first direction of movement of the wire perpendicular to the magnetic field;

illuminating the wire substantially in parallel with the plane of vibration toward a detection surface to cast a shadow of the wire onto the surface;

detecting variations in illumination upon the surface indicative of movement of the wire in a second direction parallel to the magnetic field; and

producing a first displacement signal representative of the variations in illumination upon the surface.

40. A method as in claim 39 comprising the seep of:

combining the first displacement signal and the first velocity signal to produce magnitude and direction of displacement of the wire.

41. A method as in claim 39 wherein the step of applying the oscillating current includes the steps of:

generating an amplified output current responsive to an applied input;

applying the output current to the wire to vibrate the wire within the magnetic field;

generating a counter-potential in response to vibrational movement of the wire within the magnetic field; and

forming the applied input as feedback from the counter potential.

42. A method as in claim 39 in which a light source provides the illumination, and wherein the illuminating step includes:

applying an electrical signal to power the light source for illuminating the wire;

detecting the illumination upon the surface unaltered by movement of the wire;

generating a reference electrical signal in response to incident illumination; and

moderating the electrical signal applied to the light source in response to the reference electrical signal.

43. The method as in claim 40 wherein in the step of producing magnitude and direction, the method comprises:

multiplying a first portion of the first velocity signal and a first portion of the first displacement signal to produce a first signal;

shifting the phase of a second portion of the velocity signal by 90 degrees to obtain a second displacement signal proportional to a second displacement of the wire in the first direction;

multiplying a second portion of the first displacement signal and the first displacement signal to produce a second signal;

differentiating a portion of the second signal with respect to time to produce a derivative signal; and

adding the first signal, the second signal and the derivative signal to produce an angular rate of rotation.

44. A method as in claim 39 wherein the step of suspending the wire includes:

twisting the wire along the longitudinal axis of the wire in order to reduce anisoelastic effects thereof.

45. A method as in claim 39 comprising:

imposing a bending moment upon each of the ends of the wire in magnitude and orientation according to the anisoelasticity of the wire.

46. A method as in claim 39 comprising the step of:

relatively twisting each of the ends by an angle theta about the longitudinal axis of the wire to reduce precession in determining an amount of rotation of the device from a reference orientation relative to a longitudinal axis of the wire.

47. A method as in claim 39 comprising the step of:

relatively twisting the ends until precession is substantially eliminated.

48. The method as in claim 39 comprising of:

determining the angle of rotation according to the expression;

space="preserve" listing-type="equation">K1*theta+K2*d(theta)/dt+K3*B;

where

theta=the angle between a plane of the magnetic field and a major elliptical axis of the cross section of the path of vibration of the wire;

B=a minor elliptical axis of the cross section of the path of vibration of the wire; and

K1, K2, and K3 are selected constants.