High Q angular rate sensing gyroscope

Abstract

A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.

1. A gyroscope comprising:
 a resonating element arranged and constructed to oscillate at a resonant frequency; 
 a voltage pick-off conductor applied to a predetermined area of said resonating element so as to sense net voltage signals proportional to a rate of rotation of said gyroscope when said gyroscope is rotated; and 
 a voltage balancing conductor applied to a predetermined area of said resonating element and in conductive communication with said pick-off conductor, said balancing conductor being arranged and constructed to zero net voltage signals sensed by said voltage pick-off conductor when said gyroscope is rotationally stationary. 
 
     
     
       2. The gyroscope of  claim 1  wherein said element exhibits piezoelectric properties and comprises one of a cylinder, a ring, and a bar. 
     
     
       3. The gyroscope of  claim 2  wherein said resonating element comprises a triangular prism having three longitudinal sides, each longitudinal side having applied thereto a conductive element. 
     
     
       4. The gyroscope of  claim 3  wherein two of said conductive elements are pick-off conductors. 
     
     
       5. A method of improving the uniform voltage response of a piezoelectric resonating element at a predetermined location upon said resonating element, said resonating element having a first surface and a second, opposing surface, said resonating element being solid between said first and second surfaces, the method comprising steps of:
 applying a first applied film conductor to the entire first surface of said resonating element; 
 applying a second applied film conductor to the entire second surface of said resonating element; 
 connecting said first and second thin film conductors to a DC voltage source; and 
 applying a DC voltage of predetermined strength to said first and second applied film conductors so as to create a voltage differential between said first and second applied film conductors, said voltage differential uniformly modifying the voltage response of the piezoelectric material of the resonating element over substantially the entire area of the piezoelectric material located between the first and second thin film conductors. 
 
     
     
       6. The method of improving the uniform voltage response of a piezoelectric resonating element at a predetermined location of  claim 5  further comprising a step of removing predetermined portions of said first and second thin film conductors to create a plurality of discrete thin film conductors arranged upon a surface of said resonating element in a predetermined arrangement. 
     
     
       7. In a gyroscope comprising an axi-symmetrical resonating element having a plurality of applied film conductors applied to a surface of an upper portion of said resonating element, said upper portion being supported upon a base portion, said base portion being substantially vibration free, an improvement comprising a plurality of applied film conductor leads, each of said plurality of conductor leads extending from one of said plurality of applied film conductors arranged upon said surface of said resonating element to said base portion of said element, each of said conductor leads being arranged to electrically connect said plurality of applied film conductors to circuitry for operating said gyroscope. 
     
     
       8. In an angular rate sensor comprising a tuning fork type structure composed of vibrator components which include a pair of parallel piezoelectric drive elements and a pair of parallel piezoelectric sensing elements joined together into a tuning fork configuration where said drive and sensing elements lie lying in respectively orthogonal planes, a plurality of leads electrically connected to said pairs of drive and sensing elements; and a plurality of lead terminals electrically connected to said leads for communicating said sensed voltage signals to circuitry which operates said gyroscope, an improvement comprising voltage a plurality of pick-off conductor conductors, each being on a surface separate surfaces of each said sensing element, said pick-off conductors being arranged and constructed to sense stress-induced voltage signals outputted by said sensing elements, said sensed voltage signals being indicative of a rate of rotation of said angular rate sensor, said pick-off conductors being applied to areas of the surface of said sensing elements that are subject to substantially zero stress when said angular rate sensor is rotationally stationary, each voltage pick-off conductors conductor being interposed between one of the sensing elements and at least one of the leads to provide an electrical pathway from said sensing element to said lead. 
     
     
       9. In the improved angular rate sensing gyroscope of  claim 8 , an additional improvement comprising a voltage balancing conductor applied to said sensing elements and in conductive communication with said pick-off conductors, said voltage balancing conductor being arranged and constructed to zero net voltage signals sensed by said pick-off conductors when said angular rate sensor is rotationally stationary. 
     
     
       10. In an angular rate sensing gyroscope comprising a resonating element having a polygonal cross-section defining a plurality of faces, the resonating element being supported above a base upon a plurality of support members secured respectively to said base, a plurality of conductive pads formed on the base, a plurality of conductive elements secured to a predetermined number of the plurality of faces of the resonating element and having a plurality of wires which connect the conductive elements to the conductive pads, an improvement comprising arranging said conductive elements so as to sense net voltage signals proportional to a rate of rotation of said element when said element is rotated, by applying said conductive elements to said predetermined number of faces of said resonating element on an area of said faces subjected to substantially symmetric stress when said angular rate sensing gyroscope is rotationally stationary. 
     
     
       11. In the improved angular rate sensing gyroscope of  claim 10 , an additional improvement comprising a voltage balancing conductor applied to a predetermined number of said faces of said resonating element and in conductive communication with said conductive elements, said balancing conductor being arranged and constructed to zero net voltage signals sensed by said conductive elements when said angular rate sensing gyroscope is rotationally stationary. 
     
     
       12. An oscillating gyroscope having a single sensitive axis comprising:
 an axi-symmetric resonating element arranged and constructed to output voltage signals proportional to a level of stress induced therein, the resonating element being characterized by a stable oscillatory mode defining a plurality of nodes and anti-nodes; 
 a ground conductor applied to a first side of the resonating element; 
 an actuator conductor applied to a second side of the resonating element symmetrically about one of the anti-nodes of the resonating element, the ground and actuator conductors being constructed and arranged such that a voltage differential may be created therebetween for the purpose of driving the stable oscillatory mode of the resonating element; and 
 a pick-off conductor applied to the second side of the resonating element symmetrically about one of the nodes of the resonating element, the pickoff conductor sensing signals from the resonating element due to rotation of the gyroscope about the sensitive axis. 
 
     
     
       13. The oscillatory gyroscope having a single sensitive axis of  claim 12 , wherein the stable oscillatory mode of the resonating element is defines two distinct nodal diameters. 
     
     
       14. The oscillating gyroscope having a single sensitive axis of  claim 13 , wherein the nodes and anti-nodes of the stable oscillatory mode of the resonating element are spaced 45° apart. 
     
     
       15. The oscillating gyroscope having a single sensitive axis of  claim 14 , wherein the actuator conductor has an upper boundary and a lower boundary that are substantially congruent to stress gradient contour lines that identify respective predetermined levels of stress present in the resonating element. 
     
     
       16. The oscillating gyroscope having a single sensitive axis of  claim 15 , in which the upper boundary of the actuator conductor is congruent to a stress gradient contour line that identifies a magnitude of stress that is at most 87 percent of the maximum stress present in the resonating element along the anti-node over which the actuator conductor is arranged, the lower boundary of the actuator conductor being substantially congruent to a stress gradient contour line that identifies a magnitude of stress that is at least 75 percent of the maximum stress present in the resonating element along the anti-node about which the actuator conductor is arranged. 
     
     
       17. The oscillating gyroscope having a single sensitive axis of  claim 12 , wherein the actuator conductor symmetrically spans no more than 50° about the anti-node of the resonating element. 
     
     
       18. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the pick-off conductor senses a voltage signal that is substantially zero when the gyroscope is rotationally stationary. 
     
     
       19. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the actuator conductor induces deflections in the resonating element substantially toward an anti-node defined by the stable oscillatory mode of the resonating element. 
     
     
       20. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the actuator conductor measures approximately 20% of the diameter of the resonating element between an upper boundary and a lower boundary. 
     
     
       21. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the actuator conductor laterally spans approximately 40% of the diameter of the resonating element. 
     
     
       22. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the actuator conductor is an applied film conductor. 
     
     
       23. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein each of said actuator and pick-off conductors further includes a thin film conduction path formed on the surface of the resonating element that electrically connects respective actuator and pick-off conductors with a drive and sensing means at a location subject to substantially no vibration. 
     
     
       24. The oscillating gyroscope having a single sensitive axis of  claim 23  wherein the width of the conduction path is between approximately 1% and 4% of the diameter of the resonating element. 
     
     
       25. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the width of the pick-off is between 4% and 8% of the diameter of the resonating element. 
     
     
       26. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein the pick-off conductor has a balancing conductor electrically connected thereto. 
     
     
       27. The oscillating gyroscope having a single sensitive axis of  claim 12  wherein at least one actuator is symmetrically divided into two halves that are symmetrically arranged about the anti-node. 
     
     
       28. An oscillating gyroscope having a single sensitive axis comprising:
 an axi-symmetric resonating element characterized by a stable oscillatory mode defining a plurality of nodes and anti-nodes, the axi-symmetric resonating element being suspended within a magnetic field; 
 an actuator conductor applied to the resonating element symmetrically about an anti-node thereof, such that an electrical current passed through the actuator conductor will cause a deflection of the resonating element, the deflections inducing the stable oscillatory mode of the resonating element; and 
 a pickoff conductor applied to the resonating element symmetrically about a node thereof such that movement of the pickoff conductor relative to the magnetic field induces an electrical current therethrough; the electrical current being indicative of rotation of the gyroscope about the sensitive axis. 
 
     
     
       29. The oscillating gyroscope of  claim 28  wherein the nodes and anti-nodes of the axi-symmetric resonating element are spaced 45° apart from one another. 
     
     
       30. The oscillating gyroscope of  claim 29  wherein the actuator conductors symmetrically span no more than 25° to either side of the anti-node. 
     
     
       31. The oscillating gyroscope of  claim 28  wherein the pick-off conductors conduct substantially no current when the oscillating gyroscope is rotationally stationary. 
     
     
       32. The oscillating gyroscope of  claim 28  wherein the stable oscillatory mode of the resonating element is defined by two nodal diameters. 
     
     
       33. The oscillating gyroscope of  claim 32  wherein the deflections induced by the current passing through the actuator conductor are directed toward an anti-node defined by the stable oscillatory mode of the resonating element. 
     
     
       34. The oscillating gyroscope of  claim 28  further comprising a plurality of flexible legs, the flexible legs being coupled to the resonating element so as to support the resonating element in the magnetic field. 
     
     
       35. The oscillating gyroscope of  claim 34  wherein the flexible legs are coupled to the resonating element adjacent the nodes defined by the stable oscillatory mode of the resonating elements. 
     
     
       36. A ring gyroscope comprising:
 a ring suspended from a support structure and in a magnetic field by a plurality of leg member pairs, said ring being capable of vibrating at a resonant oscillation frequency defined by a plurality of vibratory nodes and a plurality of vibratory anti-nodes,   a plurality of pick-off conductor loops, each arranged to pass through at least a portion of said magnetic field, each pick-off conductor loop being disposed on one of said leg member pairs and on a node portion of said ring whereupon one of said plurality of vibratory nodes is located when said ring is vibrating and rotationally stationary about a sensitive axis, said node portion being bracketed by the one of said leg member pairs, the pick-off conductor loop being arranged symmetrically about said node portion; and   a plurality of actuator conductor loops, each arranged to pass through at least a portion of said magnetic field, each actuator conductor loop being disposed on adjacent leg members of said leg member pairs that are adjacent each other and on an anti-node portion of said ring whereupon one of said plurality of vibratory anti-nodes is located when said ring is vibrating and rotationally stationary about said sensitive axis, said anti-node portion being bracketed by the adjacent leg members, the actuator conductor loop being arranged symmetrically about said anti-node portion.   
     
     
       37. An oscillating gyroscope having a sensitive axis comprising:
 an axi-symmetric resonator element arranged and constructed to output signals proportional to a level of stress induced therein, said axi-symmetric resonator element being capable of vibrating with a stable oscillatory mode that defines a plurality of stationary node locations and stationary anti-node locations when said axi-symmetric resonator element is rotationally stationary;   a ground conductor applied to a first side of said axi-symmetric resonator element;   an actuator conductor applied to a second side of said axi-symmetric resonator element, said actuator conductor being positioned symmetrically about one of said plurality of stationary anti-node locations, said ground conductor and said actuator conductor being constructed and arranged so that a voltage differential between said ground and said actuator conductors will drive said stable oscillatory mode of said axi-symmetric resonator element; and   a pick-off conductor applied to said second side of said axi-symmetric resonator element, said pick-off conductor being positioned symmetrically about one of said plurality of stationary node locations, said pickoff conductor sensing signals being produced when said axi-symmetric resonator element is vibrating and rotated about said sensitive axis.   
     
     
       38. A method of operating an angular rate sensing gyroscope comprising:
 providing a resonator comprising a polygonal cross section that defines a plurality of faces and having a plurality of conductive elements secured to a predetermined number of said plurality of faces on areas of said faces characterized by substantially symmetric stresses when said angular rate sensing gyroscope is rotationally stationary relative to a sensitive axis;   operatively connecting said angular rate sensing gyroscope to a control circuit to determine a rate of rotation of said resonator about said sensitive axis based at least in part on signals received from said plurality of conductive elements.   
     
     
       39. A method of operating an angular rate sensing gyroscope comprising:
 providing an angular rate sensing gyroscope comprising:   a pair of piezoelectric drive elements and a pair of piezoelectric sense elements configured in a tuning fork type configuration,   a plurality of lead terminals,   a plurality of leads operatively connected to said pair of piezoelectric drive elements, said pair of piezoelectric sense elements, and said plurality of lead terminals,   a plurality of pick-off conductors, each being applied to areas on the surfaces of said pair of piezoelectric sense elements characterized by substantially zero stress when said angular rate sensor is rotationally stationary relative to a sensitive axis, said pick-off conductors being arranged and constructed to sense stress-induced signals outputted by said pair of piezoelectric sense elements, each of said plurality of pick-off conductors being interposed between one of said pair of piezoelectric sense elements and at least one of said plurality of leads to provide an electrical pathway from each of said pair of piezoelectric sense element to said lead; and   connecting a circuitry that operates said gyroscope to said plurality of lead terminals, said circuitry indicating a rate of rotation of said angular rate sensor about said sensitive axis based on signals received from said plurality of lead terminals.   
     
     
       40. A method of operating a gyroscope comprising:
 selecting a ring gyroscope comprising:
 a ring suspended from a support structure and in a magnetic field by a plurality of leg member pairs, said ring being capable of vibrating at an oscillation frequency that defines a plurality of vibratory nodes and a plurality of vibratory anti-nodes, 
 a plurality of pick-off conductor loops, each arranged to pass through at least a portion of said magnetic field, each pick-off conductor loop being disposed on one of said leg member pairs and on a node portion of said ring whereupon one of said plurality of vibratory nodes is located when said ring is vibrating and rotationally stationary about a sensitive axis, said node portion being bracketed by the one of said leg member pairs, the pick-off conductor loop being arranged symmetrically about said node portion; and 
 a plurality of actuator conductor loops, each arranged to pass through at least a portion of said magnetic field, each actuator conductor loop being disposed on adjacent leg members of said leg member pairs that are adjacent each other and on an anti-node portion of said ring whereupon one of said plurality of vibratory anti-nodes is located when said ring is vibrating and rotationally stationary about said sensitive axis, said anti-node portion being bracketed by the adjacent leg members, the actuator conductor loop being arranged symmetrically about said anti-node portion; and 
   operatively connecting said ring gyroscope to a control circuit to determine a rate of rotation of said ring gyroscope about said sensitive axis based at least in part on signals received from said plurality of pick-off conductors.   
     
     
       41. A method of operating an oscillating gyroscope comprising:
 selecting a gyroscope comprising:
 an axi-symmetric resonator element suspended within a magnetic field and capable of vibrating with a stationary oscillation when said axi-symmetric resonator element is rotationally stationary with respect to a sensitive axis, said stationary oscillation defining a plurality of node locations and anti-node locations on said axi-symmetric resonator element, 
 at least one actuator conductor, each applied to said axi-symmetric resonator element symmetrically about a corresponding one of said plurality of anti-node locations such that an electrical current when passed through the at least one actuator conductor will cause a deflection of said axi-symmetric resonator element and induce a stable oscillatory mode of said axi-symmetric resonator element, and 
 at least one pickoff conductor, each applied to said axi-symmetric resonator element symmetrically about a corresponding one of said plurality of node locations such that when there is movement of said corresponding one of said plurality of node locations relative to the magnetic field a signal is induced in the at least one pickoff conductor; and 
   operatively connecting said gyroscope to a control circuit to determine a rate of rotation of said axi-symmetric resonator element about said sensitive axis based at least in part on signals received from said at least one pickoff conductor.   
     
     
       42. A method of operating a gyroscope comprising:
 selecting an oscillating gyroscope comprising:
 an axi-symmetric resonator element having a sensitive axis and arranged and constructed to output signals proportional to a level of stress induced therein, said axi-symmetric resonator element being capable of vibrating with a stable oscillatory mode that defines a plurality of stationary node locations and stationary anti-node locations when said axi-symmetric resonator element is rotationally stationary, 
 a ground conductor applied to a first side of said axi-symmetric resonator element, 
 an actuator conductor applied to a second side of said axi-symmetric resonator element, said actuator conductor being positioned symmetrically about one of said plurality of stationary anti-node locations, said ground conductor and said actuator conductor being constructed and arranged so that a voltage differential between said ground and said actuator conductors will drive said stable oscillatory mode of said axi-symmetric resonator element, and 
 a pick-off conductor applied to said second side of said axi-symmetric resonator element, said pick-off conductor being positioned symmetrically about one of said plurality of stationary node locations, said pickoff conductor sensing signals being produced when said axi-symmetric resonator element is vibrating and rotated about said sensitive axis; and 
   operatively connecting said oscillating gyroscope to a control circuit to determine a rate of rotation of said axi-symmetric resonator element about said sensitive axis based at least in part on signals received from said pickoff conductor.