Angular rate sensor

Abstract

An apparatus for measuring rate of turn employing a vibrating tuning fork type sensor in which the tynes vibrate in a coaxial manner. This arrangement eliminates reaction torques and forces at the base of the tuning fork which allows the tynes to freely deflect into an elliptical pattern during an input turn rate. Sensors are employed which monitor the shape of this elliptical pattern, this shape being proportional to angular turn rate.

What is claimed is: 
     
       1. An apparatus for measuring rate of turn, comprising: (A) mounting pedestal;   (B) common base mounted to said mounting pedestal;   (C) type one substantially fixed to said common base;   (D) tyne two substantially fixed to said common base such that vibration effects with said tyne one are virtually cancelled whereas said tyne one and said tyne two act as coaxial tynes of a tuning fork whereas there is virtually no movement in said mounting pedestal;   (E) drive means associated with said tyne one and said tyne two for oscillating said tyne one and aid tyne two in opposition to one another as in a tuning fork, at a selected frequency in a prescribed direction;   (F) first pickoff means for sensing relative motion of said tyne one to said tyne two whereas said first pickoff means senses a selected proportion of the motion in the driven oscillating direction as well as a selected proportion of the resultant force motion which is perpendicular to the driven oscillating direction;   (G) second pickoff means for sensing relative motion of said tyne one to said tyne two whereas said second pickoff means senses a selected proportion of the motion in the driven oscillating direction as well as a selected proportion of the motion in the resultant force direction which is perpendicular to the driven oscillating direction whereas the phase of either the said selected proportion of the motion in the resultant force direction or of said selected proportion of the motion in the driven oscillating direction is opposite to the corresponding selected proportion of said first pickoff means, for sensing any phase difference of said selected frequency related to said first pickoff means, whereas said phase difference corresponds to a measurement of rate of turn of the apparatus.   
     
     
       2. An apparatus according to claim 1, including detector means for measuring a phase difference between output of said first pickoff means and output of said second pickoff means at said selected frequency of oscillating said tyne one and said tyne two whereas said phase difference corresponds to a measurement of rate of turn of the apparatus. 
     
     
       3. An apparatus according to claim 1 wherein said first pickoff means senses essentially the same selected proportion of the motion in the driven oscillating direction as the said second pickoff means as well as essentially the same selected proportion of the motion in the force direction as the said second pickoff means, including detector means for measuring a phase difference between output of said first pickoff means and output of said second pickoff means at said selected frequency of oscillating said tyne one and said tyne two, whereas the tangent of one half the said phase difference corresponds to a measurement of the rate of turn of the said apparatus. 
     
     
       4. An apparatus according to claim 1, wherein said first pickoff means is comprised of a first sensing coil connected to said tyne one and a first sensing permanent magnet connected to said tyne two, said second pickoff means is comprised of a second sensing coil connected to said tyne one and a second sensing permanent magnet connected to said tyne two. 
     
     
       5. An apparatus for measuring rate of turn, comprising: (A) mounting pedestal;   (B) common base mounted to said mounting pedestal;   (C) tyne one substantially fixed to said common base;   (D) tyne two substantially fixed to said common base such that vibration effects with said tyne one are virtually cancelled whereas said tyne one and said tyne two act as coaxial tynes of a tuning fork whereas there is virtually no movement in said mounting pedestal;   (E) drive means associated with said tyne one and said tyne two for oscillating said tyne one and said tyne two in opposition to one another as in a tuning fork, at a selected frequency in a prescribed direction;   (F) first pickoff means for sensing relative motion of said tyne one to said tyne two whereas said first pickoff means senses motion in the driven oscillating direction;   (G) second pickoff means for sensing relative motion of said tyne one to said tyne two whereas said second pickoff means senses a selected proportion of the motion in the driven oscillating direction as well as a selected proportion of the motion in the resultant force direction which is perpendicular to the said driven oscillating direction for sensing any phase difference of said selected frequency related to said first pickoff means, whereas the tangent of said phase difference corresponds to a measurement of rate of turn of the apparatus.   
     
     
       6. An apparatus according to claim 5, including detector means for measuring a phase difference between output of said first pickoff means and output of said second pickoff means at said selected frequency of oscillating said tyne one and said tyne two whereas the tangent of said phase difference corresponds to a measurement of rate of turn of the apparatus. 
     
     
       7. A method of measuring .Iadd.a .Iaddend.rate of turn, comprising .Iadd.the steps of.Iaddend.: (A) .[.a vibrating element,.]. vibrating .Iadd.an element .Iaddend.at a selected frequency .Iadd.with .Iaddend.the vibratory pattern of said vibrating element being .[.deflected into.]. an elliptical pattern proportionally related to .Iadd.said .Iaddend.rate of turn of said vibrating element;   (B) .[.first pickoff means for.]. sensing .Iadd.with a first pickoff means the .Iaddend.motion of said vibrating element .[.whereas said first pickoff means senses motion.]. in .[.the.]. .Iadd.a .Iaddend.driven oscillating direction;   (C) .Iadd.sensing with a .Iaddend.second pickoff means .[.for sensing motion of said vibrating element whereas said second pickoff means senses.]. a selected proportion of the motion .Iadd.of said vibrating element .Iaddend.in .[.the.]. .Iadd.said .Iaddend.driven .[.oscillating.]. direction as well as a selected .[.proportion.]. .Iadd.portion .Iaddend.of the motion .Iadd.of said element .Iaddend.in .[.the resultant force.]. .Iadd.a reaction .Iaddend.direction which is perpendicular to the said driven .[.oscillating.]. direction .[.for sensing any phase difference of said selected frequency related to said first pickoff.].;   (D) .[.detector means for.]. measuring a phase difference between .Iadd.an .Iaddend.output .Iadd.signal .Iaddend.of said first pickoff means and .Iadd.an .Iaddend.output .Iadd.signal .Iaddend.of said second pickoff means at said selected frequency of oscillating said vibrating element .[.whereas.]. .Iadd.wherein .Iaddend.the tangent of said phase difference corresponds to a measurement of rate of turn of said vibrating element.   
     
     
       8. .[.A.]. .Iadd.The .Iaddend.method according to claim 7, wherein .[.said.]. .Iadd.the step of .Iaddend.vibrating .Iadd.said .Iaddend.element .[.is comprised of.]. .Iadd.comprises the step of vibrating at least .Iaddend. two .[.or more vibrating.]. tynes .[.vibrating.]. in opposition to each other. 
     
     
       9. .[.A.]. .Iadd.The .Iaddend.method according to claim 7 wherein .Iadd.the step of vibrating .Iaddend.said .[.vibrating.]. element .[.is comprised of.]. .Iadd.comprises the step of vibrating .Iaddend.a single tyne cantilever mounted from a rigid base. .Iadd. 
     
     
       10.  Apparatus for measuring an angular rate of turn comprising: a plurality of elongated vibratile elements,   drive means associated with said vibratile elements for controllably oscillating said elements in a driven direction;   said elements being responsive to said oscillation in said driven direction for oscillating in a reaction direction perpendicular to said driven direction by an amount controlled by an angular rate of turn of said apparatus,   first pickoff means responsive to said oscillation for sensing relative motion of said vibratile elements with respect to each other so that said first pickoff means senses a selected proportion of the motion of said elements in said driven direction as well as a selected proportion of a resultant motion of said elements in said reaction direction perpendicular to said driven direction;   said first pickoff means being responsive to said sensing for generating a first output signal,   second pickoff means responsive to said oscillation for sensing relative motion of said vibratile elements with respect to each other so that said second pickoff means senses a selected proportion of the motion of said elements in said driven direction as well as a selected proportion of the resultant motion of said elements in a said reaction direction perpendicular to said driven direction with the phase of said motions sensed by said first and second pickoff means in said reaction direction being opposite to each other, and   said second pickoff means being responsive to said sensing for generating a second output signal with said second output signal being phase shifted from said first output signal by an amount corresponding to the angular rate of turn of said apparatus. .Iaddend. .Iadd.11. Apparatus for measuring an angular rate of turn comprising:   a plurality of elongated vibratile elements;   a base;   each of said elements being affixed to said base;   drive means associated with said vibratile elements for oscillating said elements in opposition to one another in a driven direction;   said elements being responsive to said oscillation in said driven direction to oscillate in a reaction direction by an amount determined by an angular rate of turn of said apparatus,   said elements being affixed to said base such that vibration effects of said oscillation of said elements are canceled for both said driven direction and said reaction direction of vibration of said elements, and   means responsive to said oscillations for providing an output signal having a phase shift whose magnitude is indicative of said angular rate of turn of said apparatus. .Iaddend. .Iadd.12. Apparatus for measuring an angular rate of turn comprising:   a base,   a plurality of elongated vibratile elements,   drive means associated with said vibratile elements for controllably oscillating said elements in a driven direction;   said elements being responsive to said oscillation in said driven direction for oscillating in a reaction direction by an amount proportional to an angular rate of turn of said apparatus,   said elements being affixed to said base such that vibration effects of said oscillation of said elements are canceled for both said driven direction and said reaction direction of oscillation of said elements,   first pickoff means for sensing relative motion of said elements with respect to each other so that said first pickoff means senses a selected proportion of the motion of said elements in said driven direction as well as a selected proportion of the resultant motion of said elements in a reaction direction perpendicular to said driven direction;   said first pickoff means being responsive to said oscillations for generating a first output signal,   second pickoff means for sensing relative motion of said elements with respect to each other so that said second pickoff means senses a selected proportion of the motion of said elements in said driven direction as well as a selected proportion of the resultant motion of said elements in a said reaction direction perpendicular to said driven direction with the phase of said motions sensed by said first and second pickoff means in said reaction direction being opposite to each other, and   said second pickoff means being effective upon said sensing for generating a second output signal phase shifted from said first output signal by an amount corresponding to the angular rate of turn of said apparatus.   
     
     
        .Iaddend. .Iadd.13.  Apparatus for measuring an angular rate of turn comprising: a plurality of elongated vibratile elements,   drive means associated with said vibratile elements for controllably oscillating said elements in a driven direction;   said elements being responsive to said oscillation in said driven direction for oscillating in a reaction direction perpendicular to said driven direction by an amount controlled by an angular rate of turn of said apparatus, and   means for generating a plurality of output signals in response to said oscillations with said output signals being phase shifted from said each other by an amount controlled by said angular rate of turn of said apparatus. .Iaddend. .Iadd.14. The apparatus of claim 13 wherein said apparatus further comprises a common base; and   wherein each of said vibratile elements has an end affixed to said common base so that the vibration effects of said oscillations are canceled for said driven and reaction directions. .Iaddend. .Iadd.15. The apparatus of claim 14 wherein said base is affixed to a mounting pedestal. .Iaddend. .Iadd.16. The apparatus of claim 13 wherein each of said elements comprises an inverted substantially U-shaped tyne having an open end portion affixed to a common base. .Iaddend. .Iadd.17. The apparatus of claim 16 wherein said inverted substantially U-shaped tynes share a common elongated axis parallel to legs of said inverted substantially U-shaped tynes and wherein a first one of said tynes is positioned and rotated 90 degrees about said axis from a second one of said tynes. .Iaddend. .Iadd.18. The apparatus of claim 13 wherein said means for generating a plurality of output signals comprises:   a first motion detector which senses motion of said vibratile elements in said driven direction and creates a first drive component signal;   a second motion detector which senses motion of said vibratile elements in said reaction direction and creates a first reaction component signal;   a summing means;   wherein said first drive component signal and said first reaction component signal are added by said summing means to generate a first pickoff signal which is phase displaced from said first drive component signal by an amount controlled by said rate of turn. .Iaddend. .Iadd.19. The apparatus of claim 13 wherein said means for generating a plurality of output signals comprises:   a first motion detector which senses motion of said vibratile elements in said driven direction and creates a first drive component signal;   a second motion detector which senses motion of said vibratile elements in said reaction direction and creates a first reaction component signal;   a summing means;   wherein said first drive component signal and said first reaction component signal are added by said summing means to generate a first pickoff signal;   a third motion detector which senses motion of said vibratile elements in said reaction direction and creates a second reaction component signal wherein said second reaction component signal is in opposite phase to said first reaction component signal;   a fourth motion detector which senses motion of said vibratile elements in said driven direction to create a second drive component signal,   wherein said second reaction component signal and said second drive component signal are added by said summing means to generate a second pickoff signal which is phase displaced from said first pickoff signal by an amount proportional to said rate of turn of said apparatus. .Iaddend.   
     
     
        .Iadd.20.  Apparatus for measuring an angular rate of turn comprising: a plurality of elongated vibratile elements,   drive means associated with said vibratile elements for controllably oscillating said elements in a driven direction;   said elements being responsive to said oscillating in said driven direction for oscillating in a reaction direction perpendicular to said driven direction by an amount controlled by an angular rate of turn of said apparatus, and   means for generating an output signal in response to said oscillations with said output signal having a phase shift controlled by said angular rate of   
     
     
        turn of said apparatus. .Iaddend. .Iadd.21.  A method for measuring an angular rate of turn of apparatus comprising the steps of: controllably oscillating a plurality of elongated vibratile elements in a driven direction;   said elements being responsive to said oscillation in said driven direction for oscillating in a reaction direction perpendicular to said driven direction by an amount controlled by an angular rate of turn of said apparatus, and   generating an output signal in response to said oscillations with said output signal being phase shifted by an amount controlled by said angular rate of turn of said apparatus. .Iaddend. .Iadd.22. A method for measuring an angular rate of turn of apparatus comprising the steps of:   mounting a plurality of elongated vibratile elements on a base,   operating drive means associated with said vibratile elements for oscillating said elements in opposition to one another in a driven direction;   said elements being responsive to said oscillation in said driven direction to oscillate in a reaction direction by an amount proportional to said angular rate of turn of said apparatus,   said elements being affixed to said base such that the vibration effects of said oscillation of said elements are canceled for both said driven direction and said reaction direction of vibration of said elements, and   generating an output signal having a phase shift whose magnitude is indicative of said rate of turn. .Iaddend.