Differential angular velocity sensor that is sensitive in only one degree of freedom

• US 5,243,278 A
• Filed: 02/08/1991
• Issued: 09/07/1993
• Est. Priority Date: 02/08/1991
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Hulsing, Rand H. II
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US07/653,585
• Time in Patent Office: 942 Days
• Field of Search: 324/173, 324/174, 324/207.15, 324/207.22, 324/207.25, 324/207.24, 73/505, 73/517 A
• US Class Current: 324/173
• CPC Class Codes: G01P 3/46 by measuring amplitude of generated current or voltage in general G01R19/00
• CPC Class Codes: G01P 3/52 by measuring amplitude of generated current or voltage
• CPC Class Codes: G01P 3/58 by measuring or comparing amplitudes of generated currents or voltage amplitude comparators H03K5/24

Abstract

The invention comprises a velocity sensor (10, 30, 50, 60, 70, 110) that measures velocity in only one degree of freedom and is insensitive to the other five degrees of freedom. The velocity sensor uses differential flux splitting, and by sensing changes in flux, common mode effects are removed. In practising the invention, a permanent magnet (17, 33, 55, 65, 71, 131) is used to create a flux field, and multiple return paths are used to split the flux. A plurality of pole pieces (20-21, 39-40, 58-59, 66-67, 72-73, 111-112) simultaneously move an equal amount in relation to the return paths for differentially varying the amount of flux carried by each return path (13-14, 34-36, 52-53, 63-64, 73A-C and 75A-C, to thereby induce a differential voltage in secondary coils (15-16, 37-38, 56-57, 68-69, 80-83 and 90-93, 140-143 and 150-153). Detection means (not shown) is used to sense the change in voltage and provide an indication of the sensed velocity. The pole pieces and return paths are overlapped by an amount to ensure that one may move relative to the other a limited extent in directions not parallel to the sensitive axis without effecting a change in the net overlapped area, and the coils are arranged in series-connected, oppositely wound pairs so that common mode error signals are cancelled.

Claims

1. An angular velocity sensor comprising:

means for generating a flux field;

a first X-shaped pole piece disposed proximate a north pole of said means for generating a flux;

a second X-shaped pole piece disposed proximate a south pole of said means for generating a flux, said first and second X-shaped pole pieces being in vertical alignment with one another;

a rotor disposed between said first and second X-shaped pole pieces, said rotor having a plurality of return path steps, said return path steps being rotatable with respect to said first and second X-shaped pole pieces about a sensing axis, said return path steps and said first and second pole pieces forming multiple flux paths, arms of said first and second X-shaped pole pieces overlying and extending radially a distance beyond respective return path steps, said return path steps and said arms of said first and second pole pieces being dimensioned and positioned with respect to one another so that the magnitude of flux flowing through respective flux paths is sensitive to relative motion of said pole pieces and said return path steps about said sensing axis

flux responsive means respectively associated with each of said multiple flux paths for generating a signal indicative of the rate of change of flux through the respective flux path thereby to indicate the angular velocity of the relative motion between said pole pieces and said return path steps about said sensing axis, said flux responsive means being generally insensitive to common mode motion of said rotor with respect to said pole pieces;

whereby said angular velocity sensor is sensitive to angular velocity about said sensing axis while being generally insensitive to velocity in other degrees of freedom.

2. An angular velocity sensor as claimed in claim 1 wherein said flux responsive means comprises:

a coil respectively wound about each of said arms of said first and second pole pieces, said coils being wound and interconnected with one another so as to generate a voltage indicative of sensed velocity in response to flux changes which occur when said rotor rotates with respect to said first and second pole pieces about said sensitive axis while generally cancelling any voltages which would otherwise result from flux changes occurring as a result of common mode motion of said rotor with respect to said pole pieces.

3. A differential angular velocity sensor comprising:

a base plate;

counter-rotating rotors positioned on opposite sides of said base plate and mounted for equal but opposite counter-rotation with respect to one another about a sensing axis, said rotors having raised return path steps formed thereon;

means for generating a flux along said sensing axis;

first and second pole pieces fixed at respective opposite poles of said means for generating a flux and on the side of the respective rotors opposite the base plate, each of said pole pieces having a plurality of radially projecting arms arranged in diametrically opposed pairs, each of said arms extending into overlying relationship with a respective one of the raised return path steps to form spaced flux return paths, said raised return path steps and said arms being dimensioned and positioned with respect to one another so as to result in a differential flux split between opposed pairs of said arms, each of said arms extending radially beyond the respective raised return path step, said arms of said first pole piece being in vertical alignment with said arms of said second pole piece;

said counter-rotating rotors being rotatable about said sensing axis with respect to said first and second pole pieces;

flux responsive means respectively associated with each of said multiple flux paths for generating a signal indicative of the rate of change of flux through the respective flux path thereby to indicate the angular velocity of the relative motion between said pole pieces and said return path steps about said sensing axis, said flux responsive means being generally insensitive to common mode motion of said rotors with respect to said pole pieces;

whereby said differential angular velocity sensor is sensitive to differential angular velocity about said sensing axis while being generally insensitive to velocity in other degrees of freedom.

4. A differential angular velocity sensor as claimed in claim 3 and further comprising means for dithering said counter-rotating rotors about said sensing axis with respect to said first and second pole pieces.

5. A differential angular velocity sensor as claimed in claim 3, wherein said first and second pole pieces are X-shaped.

6. A differential angular velocity sensor as claimed in claim 3, wherein:

the rotors are connected to each other and to the base plate by flexible means extending therebetween to limit relative movement of the rotors about said sensing axis.

7. A differential angular velocity sensor as claimed in claim 6 wherein:

said flexible means comprises a plurality of elongate, spring-like flexures fixed at their opposite ends to the rotors and fixed intermediate their ends to the base plate, said flexures permitting rotational movement of the rotors relative to one another but generally preventing relative translational movement therebetween.

8. A differential angular velocity sensor as claimed in claim 7, wherein:

said flexible means further includes a plurality of links connected between the rotors to permit said counter-rotating motion but to prevent axial displacement of one relative to the other.

9. A differential angular velocity sensor as claimed in claim 3 wherein said means for generating a flux comprises:

a magnet carried by said base plate and extending into proximity with said rotors at respective opposite poles of said magnet.

10. A differential angular velocity sensor as claimed in claim 3 wherein said flux responsive means comprises:

a coil respectively wound about each of said arms of said first and second pole pieces, said coils being wound and interconnected with one another so as to generate a voltage indicative of sensed velocity in response to flux changes which occur when said rotor rotates with respect to said first and second pole pieces about said sensitive axis while generally cancelling any voltages which would otherwise result from flux changes occurring as a result of common mode motion of said rotor with respect to said pole pieces.

11. A differential angular velocity sensor as claimed in claim 3, wherein said first and second pole pieces are X-shaped.

12. A differential angular velocity sensor comprising:

a base plate;

a counter=-rotating rotors positioned on opposite sides of said base plate and mounted for equal but opposite counter-rotation with respect to one another, said rotors having raised return path steps formed thereon;

a magnet carried by said base plate and extending into proximity with said rotors at respective opposite poles of said magnet;

first and second pole pieces fixed at respective opposite poles of said magnet and on the side of the respective rotors opposite the base plate, each of said pole pieces having a plurality of radiallly projecting arms arranged in diametrically opposed pairs, each of said arms extending into overlying relationship with a respective one of the raised return path steps to form spaced flux return paths, said raised return paths steps and said arms being dimensioned and positioned with respect to one another so as to result in a differential flux split between opposed pairs of said arms, each of said arms extending radially beyond the respective raised return path step, said arms of said first pole piece being in vertical alignment with said arms of said second pole piece;

said counter-rotating rotors being rotatable abut a sensing axis with respect to said first and second pole pieces;

a coil respectively associated with each of said arms of said first and second pole pieces, said coils being wound and interconnected with one another so as to generate a voltage indicative of sensed differential velocity in response to differential flux changes which occur when said counter-rotating rotors rotate with respect to said first and second pole pieces about said sensitive axis while generally cancelling any voltages which would otherwise result from flux changes occurring as a result of common mode motion o said counter-rotating rotors with respect to said pole pieces;

whereby said differential angular velocity sensor is sensitive to differential angular velocity about said sensing axis while being generally insensitive to velocity in other degrees of freedom.

13. A differential angular velocity sensor as claimed in claim 12 and further comprising means for dithering said counter-rotating rotors about said sensing axis with respect to said first and second pole pieces.

14. A differential angular velocity sensor as claimed in claim 12, wherein said first and second pole pieces are X-shaped.

15. A differential angular velocity sensor as claimed in claim 12, wherein:

the rotors are connected to each other and to the base plate by flexible means extending therebetween to limit relative movement of the rotors about said sensing axis.

16. A differential angular velocity sensor as claimed in claim 15 wherein:

said flexible means comprises a plurality of elongate, spring-like flexures fixed at their opposite ends to the rotors and fixed intermediate their ends to the base plate, said flexures permitting rotational movement of the rotors relative to one another but generally preventing relative translational movement therebetween.

17. A differential angular velocity sensor as claimed in claim 16, wherein:

said flexible means further includes a plurality of links connected between the rotors to permit said counter-rotating motion but to prevent axial displacement of one relative to the other.