Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1990-12-18
1994-04-19
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
G01P 900
Patent
active
053035887
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a sensor for determining angular velocity which operates in the manner of the vibratory gyroscopes. Known vibratory gyroscopes with the same field of application generally work with low-frequency flexural vibrations which, as a result of the Coriolis forces occurring in rotation, produce a resonance vibration perpendicularly relative to the primary vibration and accordingly provide a measurement of the angular velocity. However, vibratory gyroscopes have also been proposed which proceed from a thickness shear vibration. In this case, the natural frequency of the oscillator is already substantially higher (>100 Khz). Moreover, the excitation of a resonance vibration by Coriolis forces is deliberately dispensed with in the interest of a low temperature dependency of the signal. The Coriolis forces in this case effect a forced longitudinal thickness vibration.
In the present invention, however, a different measurement principle is used: the effect of the Coriolis forces on an ultrasonic wave in a rotating medium. In so doing, a new oscillation form is not brought about. The deflection of the ultrasonic wave in the rotating medium, which is proportional to the angular velocity, produces a measurement signal.
SUMMARY OF THE INVENTION
The sensor for determining angular velocity, according to the invention, has the advantage over vibratory gyroscopes in that it has a low sensitivity to shaking and temperature. It has a simple, mechanically stable construction. The use of a high frequency enables a suppression of low-frequency interference signals which are otherwise caused by shaking or vibrations of the sound conductor installed in the motor vehicle. Since there is no transition to another oscillation form, the same piezoceramic shear oscillators are used in forming the measurement signal as are used in the transmitter. The wide spatial separation of the sensor and signal source facilitates the suppression of the disturbing influences of the excitation voltage on the measurement signal.
It is particularly advantageous for the construction of the sensor that the selected sound frequency be as high as possible based on the sound absorption in order to achieve a good bundling (directionality) of the sound ray. The sound absorption should be high enough so that a continuous acoustic wave is made possible in closest approximation. The bundling (directionality) and accordingly the sensitivity can be further improved through the use of a cylindrical wave instead of a plane wave. The sound velocity should be as low as possible for a high sensitivity, which is achieved substantially through the use of a transverse acoustic wave. ZERODUK is optimally suited as material for the sound conductor.
Embodiment examples of the invention are shown in the drawing and explained in more detail in the following description of preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1 and 2 show a longitudinal section through an embodiment example of the sensor according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A sensor for determining the angular velocity .OMEGA. of a rotating system, designated by 10 in FIG. 1 comprises a sound conductor 11 with length 1, width b and thickness d. A transmitter 12, particularly a planar piezoceramic shear oscillator by means of which an ultrasonic wave 13 is radiated into the sound conductor 11, is arranged at one end face of the sound conductor 11. Two receivers 14, 15 are located at the other end face of the sound conductor 11, a gap 16 extending parallel to the x direction is located between the two receivers 14, 15. The indicated directions have reference to the system of coordinates plotted in the drawing, wherein the x direction extends orthogonal to the drawing plane and the drawing plane is the yz plane. The vector of the angular velocity .OMEGA. to be determined is orthogonal to the yz plane, i.e. directed parallel to the x direction, so that a ray deflection is effected in the yz plane.
The excitation p
REFERENCES:
patent: 3145572 (1964-08-01), Brindley
patent: 4516427 (1985-05-01), Carey
patent: 4672848 (1987-06-01), Gohin et al.
Boruschewitz Manfred
Hamisch Hansjoachim
Chapman John E.
Robert & Bosch GmbH
Striker Michael J.
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