Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-09-11
2002-10-01
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504160, C310S369000, C310S370000
Reexamination Certificate
active
06457358
ABSTRACT:
TECHNICAL FIELD
The present invention relates to piezoelectric systems, and more particularly to a generally tubular shaped, coriolis force drive, piezoelectric gyroscope system, and method of its use. The primary embodiment of said present invention system is of a generally elongated tubular shape having inner and outer radially polarized annular region defining surfaces, with an inner electrode present on the inner surface thereof, and four electrodes on the outer surface, said four electrodes on the outer surface ideally being oriented at substantially ninety degree intervals. In use said system is caused to rotate about an essentially centrally located longitudinally oriented axis while a flex inducing driving voltage is applied across two of said four electrodes which are oriented substantially 180 degrees with respect to one another, while an output voltage which is related to the rotation rate is sensed across the other two electrodes.
BACKGROUND
Piezoelectric gyroscopes are well known in the art. For instance, generally elongated rectangular solid shaped Piezoelectric gyroscopes which serve to produce a voltage at sensing electrodes thereof which is proportional to an angular rotation velocity of said piezoelectric-gyroscope about a longitudinally oriented axis therethrough are known, in which the mechanism of operation involves Coriolis force mediated flexure in a direction which is perpendicular to both said longitudinal axis, and a direction of an applied driving voltage effected flex.
One known embodiment of a piezoelectric gyroscope, as viewed in front elevational cross-section, typically has, at one longitudinally disposed side thereof, two vertically stacked, (ie. one atop the other), regions of vertically oriented polarized direction material sandwiched between driving voltage electrodes attached thereto at upper and lower surfaces. One of said vertically stacked regions of vertically oriented polarized direction material has an upward polarized direction and the other a downward polarized direction. On an opposite longitudinally disposed side thereof, and as viewed in side elevation there are present two adjacent regions of horizontally oriented polarized direction material, (ie. one in front of the other as viewed in frontal elevation), sandwiched between sensing voltage electrodes attached thereto at front and back vertically oriented surfaces. One said adjacent region of horizontally oriented polarized direction material having, as viewed from atop thereof, a horizontal laterally to the right projecting polarized and the other said adjacent region of horizontally oriented polarized direction material having a horizontal laterally to the left oriented polarized direction. That is, the polarized plane and polarized directions on said second longitudinally disposed side are simply rotated ninety (90) degrees, (eg. horizontally oriented), from the plane of the polarized directions, (eg. vertically oriented), on said first laterally disposed side about said longitudinally oriented axis therethrough.
Another prior art embodiment of a piezoelectric gyroscope is comprised of a long solid but flexible elongated rod with piezoelectric ceramics affixed thereto on side faces thereof. Said long solid but flexible rod can be triangular or rectangular in cross-section and have three or four electrodes mounted on side faces thereof. Where only three electrodes are present, both driving and sensing circuits share on of the electrodes. References which describe such piezoelectric gyroscope systems are, respectively:
“Vibrating Angular Rate Sensor May Threaten The Gyroscope”, Gates, Electronics, 41, 103-134 (1968); and
“Piezoelectric Vibratory Gyroscope Using Flexural Vibration Of A Triangular Bar”, Fujishima et al., IEEE 45th Annual Symp. On Frequency Control, 261-265 (1991).
Another prior art embodiment of a piezoelectric gyroscope is comprised of a solid but flexible, long, circular cross-section, piezoelectric elongated rod, with multiple electrodes affixed on the outer surface thereof. Such an embodiment is described in U.S. Pat. No. 5,336,960 to Fujishima et al., which is titled “Gyroscope Using Circular Rod Type Piezoelectric Vibrator”.
Another prior art embodiment of a piezoelectric gyroscope is comprised of a short flexible tubular shaped element, to an outer surface of which are affixed numerous piezoelectric ceramics. Application of driving voltage across some electrodes thereof cause a shape change from essentially circular cross-section toward essentially elliptical cross-section, which shape change, in combination with rotation effected Coriolis force, causes an output voltage to appear at other of said electrodes. Such a gyroscopic system is described in “The Dynamics Of A Thin Film Piezoelectric Cylinder Gyroscope”, Burdess, Proc. Inst. Mech. Engrs. 200 (C4), 271-280 (1986).
Yet another prior art embodiment of a piezoelectric gyroscope is described in an article by the inventor herein, titled “A Cylindrical Shell Piezoelectric Gyroscope”, Yang, Intl. J. of App. Electromagnetics and Mechanics, 8, 259-271, (1997). Said article describes a short tubular shaped piezoelectric gyroscope system in which radial and torsional vibration modes are utilized to realize a rotation detecting system.
Disclosed in a related Application by the present Inventor, (Ser. No. 09/271,791), is a piezoelectric gyroscope system comprising a generally longitudinally elongated three dimensional mass of piezoelectric material having first and second longitudinally disposed sides, said piezoelectric gyroscope system being distinguished in that a sensing electrode is present at one terminal end thereof, said sensing electrode being affixed so that it is oriented other than on a longitudinally oriented side of said piezoelectric gyroscope. Typically, said terminal end of said present invention piezoelectric gyroscope system, whereat said sensing electrode is affixed, is accurately described as oriented in a direction perpendicular to the direction of longitudinal elongation, and the generally longitudinally elongated three dimensional mass of piezoelectric material is a selected to be of a rectangular solid shape. Said invention couples the voltage amplification benefits of piezoelectric (Rosen) transformers to the angular velocity measuring capabilities of piezoelectric-gyroscopes, by placing a sensing electrode in a piezoelectric- gyroscope much as is done in piezoelectric-transformers, (eg. as viewed in elevation, at a vertically oriented end of a longitudinally disposed side of a present invention piezoelectric-gyroscope at which is present two regions of horizontally longitudinally oriented polarized direction material). That is, the two sensing electrodes in a conventional piezoelectric-gyroscope, described above as adjacent to regions of horizontally, laterally oriented polarized direction material, (ie. one in front of the other as viewed in frontal elevation), sandwiched between sensing voltage electrodes attached thereto at front and back surfaces, are, in the preferred embodiment of the present invention, replaced by a single electrode at a vertically oriented end of the longitudinally disposed side of the present invention piezoelectric-gyroscope at which is present the two adjacent regions of horizontally longitudinally oriented polarized direction material. Said single electrode can reference to one of the driving electrodes, or to a second sensing electrode. A preferred embodiment of said related invention Piezoelectric Gyroscope, which serves to couple the voltage amplification benefits of piezoelectric (Rosen) transformers to the angular velocity measuring capabilities of conventional piezoelectric gyroscopes, can be described as comprising a generally elongated, typically rectangular solid shaped block of piezoelectric material having first and second longitudinally disposed sides and a longitudinally oriented axis which projects essentially centrally therethrough from said first longitudinally disposed side to said second longitudinally disposed side thereof. At the first
Board of Regents of the University of Nebraska
Kwok Helen
Welch James D.
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