Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1990-09-05
1992-03-24
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
G01P 900
Patent
active
050977075
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to rotation sensors of the kind sometimes referred to as solid state or vibrational gyroscopes. These differ from conventional gyroscopes in having no movable components.
2. Description of Related Art
One such vibrational gyroscope is described in U.K. Patent No. 2164749 which employs a cylindrical shell with a radial skirt or flange. The shell is driven to vibrate by electrodes positioned on a piezo-electric material deposited on the flat base. Transverse acoustic bending waves are thus transmitted around the shell in opposite directions and a standing wave pattern is set up. Rotation of the shell in conjunction with the travelling bending wave produces a Coriolis force which displaces the vibration nodal pattern to an extent which is related to the rate of rotation.
Such a sensor is ideal for `strap down` applications where movements are large and sudden. Relatively low sensitivity is therefore required but with considerable frequency response.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a rotation sensor with greater sensitivity, albeit with lower frequency response. A particular application for such a high sensitivity device is in a stabilised gimbal mounted system where correction movements are likely to be small and slow.
According to the present invention, a rotation sensor comprises a strip of elastic material wrapped about an axis to form a coil, means for producing transverse acoustic waves in the strip travelling in each of two opposite directions around the strip and means responsive to the speed of wave transmission in the two directions to provide an output indicative of the rate of rotation of the coil about an axis aligned with or parallel to the coil axis.
The coil is preferably of spiral form.
There are preferably wave transmitting means coupled to the strip at spaced positions along the strip, and wave receiving means coupled to the strip at spaced positions along the strip. In particular there may be a transmitting means and a receiving means positioned at each end of the strip.
The sensor may include means responsive to the phase difference of signals received by the respective receiving means.
The strip may be mounted between plate members. It may also, or alternatively, have edge portions thicker than the central portion to maintain spacing of adjacent turns of the coil. The strip may comprise an active central portion supported by periodic sideways extensions. It may have a series of holes along each edge, the strip area between adjacent holes providing the sideways extensions.
The coil may comprise two coaxial spiral strips the inner ends of the two spirals being coupled together, wave transmitting means and wave receiving means being coupled to the outer ends of each of the two spiral strips. The inner ends of the spiral strips may be continuous each with the other by means of a helical section between the two spiral strips. The strip may be, at least at one end, divided across its width into sections, the transmitting means being coupled to a first of the sections and the receiving means being coupled to second and third sections, the divisions between the sections being such as to provide leakage paths from the first to the second and from the first to the third sections which leakage paths differ in path length by half a wavelength at the operating frequency so tending to suppress the locally transmitted signal in the receiver sections.
According to a further aspect of the invention, in a rotation sensor as aforesaid, the means for producing transverse acoustic waves may be adapted to operate in conjunction with the length of the strip in such manner as to produce a respective resonant frequency for each direction of the signal transmission, and means are provided for detecting the difference between the two resonant frequencies, this difference being representative of the rate of rotation of the coil.
The means for producing transverse acoustic waves may then compris
REFERENCES:
patent: 3307409 (1967-03-01), Newton
patent: 4384409 (1983-05-01), Lao
Chapman John E.
GEC--Marconi Limited
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