TURN RATE SENSOR
First Claim
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1. Rate of rotation sensing apparatus comprising:
- a mechanically resonant system including a pair of mass elements and spring suspension means coupling said elements for opposed oscillation generally along a first axis, said suspension including also electrically energizable forcing means for varying the relative alignment of said oscillatory mass elements with respect to said first axis;
means for driving said resonant system into vibration;
means for detecting angular oscillation of said system around a second axis which is perpendicular to said first axis;
means, controlled by said detecting means and responsive to the component of detected angular oscillation which is in-phase with the vibration of the resonant system, for energizing said forcing means to form a servo loop tending to minimize said component, the quadrature component of the detected angular oscillation being indicative of the rate of rotation of said mechanically resonant system around said second axis.
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Abstract
The turn rate sensing apparatus disclosed herein employs a sensor of the vibratory tuning fork type in which a rotation about an axis parallel to the tines of the fork is sensed by means of the resultant oscillator torque generated around this same axis by the Coriolis forces acting on the vibrating tines. In order to minimize similar oscillatory torques caused by residual misalignment of the tine motions, one of the tines is selectively distorted, e.g. by heating, under servo loop control so as to dynamically minimize such misalignment. Imbalances of the tines and the amplitude of fork vibration are also controlled dynamically so as to also minimize errors.
35 Citations
7 Claims
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1. Rate of rotation sensing apparatus comprising:
- a mechanically resonant system including a pair of mass elements and spring suspension means coupling said elements for opposed oscillation generally along a first axis, said suspension including also electrically energizable forcing means for varying the relative alignment of said oscillatory mass elements with respect to said first axis;
means for driving said resonant system into vibration;
means for detecting angular oscillation of said system around a second axis which is perpendicular to said first axis;
means, controlled by said detecting means and responsive to the component of detected angular oscillation which is in-phase with the vibration of the resonant system, for energizing said forcing means to form a servo loop tending to minimize said component, the quadrature component of the detected angular oscillation being indicative of the rate of rotation of said mechanically resonant system around said second axis.
- a mechanically resonant system including a pair of mass elements and spring suspension means coupling said elements for opposed oscillation generally along a first axis, said suspension including also electrically energizable forcing means for varying the relative alignment of said oscillatory mass elements with respect to said first axis;
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2. Rate of rotation sensing apparatus comprising:
- a tuning fork having a pair of generally parallel tines adapted to vibrate in opposition along an axis lying generally in the plane of said tines;
means for driving said tuning fork into vibration at a predetermined amplitude;
heater means for selectively distorting one of said tines to deflect it transversely with respect to said plane;
means for detecting angular oscillation of said fork around an axis generally paralleling said tines;
means, controlled by said detecting means and responsive to the component of detected oscillation which is in-phase with the vibration of the resonant system, for energizing said heater means to form a servo loop tending to minimize said component, the quadrature component of the detected oscillation being indicative of the rate of rotation of said tuning fork around said tine paralleling axis.
- a tuning fork having a pair of generally parallel tines adapted to vibrate in opposition along an axis lying generally in the plane of said tines;
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3. A turn rate sensing gyroscope system for sensing an externally impressed rate of angular displacement of said system, comprising:
- a vibrating element;
a servo controlled feedback loop for providing constant amplitude oscillations of said vibrating element;
a servo controlled feedback loop for offsetting static and dynamic imbalances about a first plane of symmetry and translation of said vibrating element;
a servo controlled feedback loop for offsetting static and dynamic imbalances about a second plane of symmetry of said vibrating element;
a servo controlled feedback loop for offsetting inertial forces externally impressed on said vibrating element.
- a vibrating element;
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4. Rate of rotation sensing apparatus comprising:
- a tuning fork having a pair of generally parallel tines adapted to vibrate in opposition along an axis lying generally in the plane of said tines and a central post also in said plane;
means for driving each of said tuning fork tines into vibration;
means responsive to the composite amplitude of said vibration for controlling the energization of said driving means to obtain vibration of predetermined amplitude;
means responsive to translational vibration of said post for differentially controlling the energization of said driving means so as to minimize said translational vibration;
heater means for selectively distorting one of said tines to deflect it transversely with respect to said plane;
means responsive to angular oscillation of said fork around said post;
means responsive to the component of angular oscillation of said fork around said post which is in-phase with the vibration of the resonant system for energizing said heater means to form a servo loop tending to minimize said component, the quadrature component of the detected oscillation being indicative of the rate of rotation of said tuning fork around said tine paralleling axis.
- a tuning fork having a pair of generally parallel tines adapted to vibrate in opposition along an axis lying generally in the plane of said tines and a central post also in said plane;
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5. A vibratory tuning fork turn rate gyroscope system for producing an electrical signal proportional to an externally impressed rate of angular displacement of said system, comprising:
- a planar vibratory tuning fork having in the principal plane a center post and two tines extending from the base of said fork, said center post having a rectangular cross-section and extending from said base uniformly about the axis of symmetry of said tuning fork, said tines being positioned symmetrically on opposite sides of said center post, the first of said tines being slotted, having a slot in a plane parallel to the said principal plane and extending along a substantial length of said first tine from the inner to the outer boundary of said first tine, and the second of said tines being homogeneous;
a tine vibration amplitude servo controlled feedback loop comprising;
a. a capacitive proximity sensing means associated with each of said tines, each of said sensing means having a proximity reference sensor, respectively positioned on said center post and the associated one of said tines, b. a first tine control amplifier means having inputs connected to the respective ones of said proximity transmitting sensors for producing an output signal representative of the sum of the displacements of the ones of said tines with respect to said center post, c. a tine drive amplifier means associated with each of said tines, each of said drive amplifier means having a sum input connected to said first tine control amplifier means;
a tine imbalance servo controlled feedback loop comprising;
a. a piezoelectric strain detection means having two sensor means attached to said center post, b. a second tine control amplifier means having sum inputs connected to the respective ones of said sensor means for producing a common mode output signal representative of the sum of the strains detected by said torque sensor means, c. a tine drive amplifier means associated with each of said tines, a first of said drive amplifier means associated with said slotted tine having a difference input connected to said second tine control amplifier means, and a second of said drive amplifier means associated with said second tine having a sum input connected to said second tine control amplifier means, d. a piezoelectric tine drive motor means associated with each of said tines, each of said motor means having an input connected to the respective one of said tine drive amplifier means, each of said motor means positioned on the base of said tuning fork adjacent to the respective ones of said first and second tines;
a tine planar oscillation servo controlled feedback loop comprising;
a. said piezoelectric crystal torque sensing means, b. a third tine control amplifier means having a sum input connected to a first and a difference input connected to the second of said torque transmitting sensor means, for producing a differential mode output signal representative of the difference between the torque detected by said torque sensing means, c. multiplier means having a first input connected to said first tine control amplifier means and the second input connected to said third tine control amplifier means, d. a low pass filter mean having an input connected to said multiplier means, e. a heat generator means having an input connected to said low pass filter multiplier means, and positioned on an outside surface of said slotted tine overlapping said slot; and
a turn rate sensing servo controlled feedback loop comprising;
a. said piezoelectric crystal torque detection means, b. said third tine control amplifier means, c. an electromagnetic tine deflection means having an input connected to said third tine control amplifier means.
- a planar vibratory tuning fork having in the principal plane a center post and two tines extending from the base of said fork, said center post having a rectangular cross-section and extending from said base uniformly about the axis of symmetry of said tuning fork, said tines being positioned symmetrically on opposite sides of said center post, the first of said tines being slotted, having a slot in a plane parallel to the said principal plane and extending along a substantial length of said first tine from the inner to the outer boundary of said first tine, and the second of said tines being homogeneous;
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6. A method for producing in a planar vibratory tuning fork turn rate gyroscope system, an electrical signal proportional to an externally impressed rate of angular displacement of said system, including the steps of:
- maintaining constant amplitude tine oscillations by a first servo controlled feedback loop;
compensating for tuning fork imbalances about a first plane of symmetry perpendicular to the principal plane of said tuning fork by a second servo controlled feedback loop;
compensating for tuning fork imbalances about a second plane of symmetry parallel to said principal plane of said tuning fork by a third servo controlled feedback loop;
maintaining planar tuning fork tine oscillations in said second plane of symmetry of said tuning fork by a fourth servo controlled feedback loop; and
generating an electrical signal from signals provided by said first and fourth loops said electrical signal being proportional to said externally impressed rate of angular displacement of said gyroscope system.
- maintaining constant amplitude tine oscillations by a first servo controlled feedback loop;
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7. A method for producing in a planar vibratory tuning fork rate gyroscope system, an electrical signal proportional to an externally impressed rate of angular displacement of said system, wherein said system comprises a planar vibratory tuning fork having two tines in the principal plane, tine vibration amplitude sensing means, piezoelectric torque sensing means, a piezoelectric tine drive motor means, amplifier means, analog multiplier means, tine deformation means, tine deflection means, and phase shift means, including the steps of:
- maintaining constant amplitude tine oscillations by a first servo controlled feedback loop means, said first loop means comprising said amplitude sensing means, said amplifier means and said motor means;
compensating for tuning fork imbalances about the plane of symmetry perpendicular to said principal plane of said tuning fork by a second servo controlled feedback loop means, said second loop comprising said torque sensing means, said amplifier means and said motor means;
compensating for tuning fork imbalances abOut the plane of symmetry parallel to said principal plane of said tuning fork by a third servo controlled feedback loop means, said third loop comprising said torque sensing means, said amplifier means, said analog multiplier means and said tine deformation means;
maintaining planar tuning fork tine oscillation in said plane of symmetry parallel to said principal plane of said tuning fork by a fourth servo controlled feedback loop means, said fourth loop comprising said torque sensing means, said amplifier means and said tine deflection means; and
generating an electrical signal from said signals first and fourth loops by said phase shift means and said analog multiplier means, said electrical signal being proportional to said externally impressed rate of angular displacement of said gyroscope system.
- maintaining constant amplitude tine oscillations by a first servo controlled feedback loop means, said first loop means comprising said amplitude sensing means, said amplifier means and said motor means;
Specification