Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1996-09-30
1998-06-09
Oda, Christine K.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
G01P 904
Patent
active
057637814
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to symmetrical mechanical resonators and in particular to vibratory or Coriolis type rate sensors employing the same.
BACKGROUND OF THE INVENTION
The terms "tuning forks" and "symmetrical mechanical resonators" are used herein as synonyms and both can be defined as signifying mechanical structures that include two masses that are counter-oscillating in such a manner that their common center-of-mass is ideally stationary and their total linear and angular momentums are zero at any time. The classical tuning fork includes two tines connected to a common stem, which in turn is connected to a stationary base. The purpose of the stem is to decouple the tines as much as possible from the base and to couple them to each other, so that they have a common resonance frequency and a minimum energy is dissipated to the stationary base.
Tuning forks have been used as frequency standards by employing piezoelectric crystalline quartz. They have also been used as angular inertial rate sensors, wherein the excited vibrational counter-motion of the tines combines with the inertial rotation of the tuning-fork base to induce in the tines so-called Coriolis accelerations which are perpendicular to the plane of the excited vibrations and of opposite sense in each of the two tines. These accelerations induce vibratory motions in the tines perpendicular to the excited vibrations, the difference of which is indicative of the input angular inertial rate. Although each of the tines responds to said inertial rotation, it also responds to vibratory motion of the mounting base that would lead to an output error that is indistinguishable from the rate signal; however, by processing the differential induced vibrations, the error is ideally eliminated. The earliest application of a tuning fork resonant structure for angular inertial rate sensing is described in "New space rate sensing instrument," by J. Lyman in Aeronautical engineering review, Vol. 12, pp. 24-30, 1953. A modified rate sensor that utilizes a double tuning fork is described in "Reduction of errors in vibratory Gyroscopes by Double Modulation" by R. W. Bush and G. C. Newton, Jr. in IEEE Transactions on automatic control, October 1964 pp. 525-535. Numerous other rate sensors are based on vibrating structures that are essentially constituted by two counter-oscillating masses of various structures. In order to decrease the cost of vibratory rate sensors, they are often manufactured as monolithic structures by employing photolithographic microfabrication techniques. All monolithic tuning fork geometries utilized in the prior art belong to either of the following three families:
Single tuning-fork, as in U.S. Pat. No. 5,343,749.
H-shaped structures that are essentially two tuning forks with a common base, as in U.S. Pat. Nos. 4,524,619 and 5,056,366.
Vibrating frame constructions that can be regarded as two tuning-forks with the ends of the ends of their corresponding tines connected, as in U.S. Pat. Nos. 4,654,663 and 5,349,855.
It is obvious to those skilled in the art that there are four main vibration modes in the conventional tuning fork, these being:
1. An in-plane, symmetrical, vibration mode depicted with short arrows in FIG. 1.
2. An asymmetrical, in-plane vibration mode depicted with long arrows in FIG. 1.
3. A symmetrical vibration mode perpendicular to the plane of the tuning fork.
4. An asymmetrical vibration mode perpendicular to the plane of the tuning fork.
The first and third modes are referred to as the excitation mode and the output or Coriolis mode, and are the only modes relevant to rate sensing. The second and fourth modes are parasitic and lead to sensitivities of the rate sensor to linear accelerations. It is well known, however, to those skilled in the art that, regardless of the specific geometry of the tuning fork, there are additional, higher order, vibration modes, that are, however, of little consequence to its applications as a rate sensor.
A shortcoming of all prior art implementations of the tunin
REFERENCES:
patent: 4654663 (1987-03-01), Alsenz et al.
patent: 4930351 (1990-06-01), Macy et al.
patent: 4958519 (1990-09-01), Whaley
patent: 5056366 (1991-10-01), Fersht et al.
patent: 5166571 (1992-11-01), Konno et al.
patent: 5349855 (1994-09-01), Bernstein
patent: 5367217 (1994-11-01), Norling
patent: 5600065 (1997-02-01), Kar
Friedman Mark M.
Oda Christine K.
LandOfFree
Coupled resonator vibratory rate sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coupled resonator vibratory rate sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coupled resonator vibratory rate sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2202113