Sensor for determining angular velocity with piezoceramic compon

Details Sensor for determining angular velocity with piezoceramic compon Sensor for determining angular velocity with piezoceramic compon

1991-01-29

1993-09-21

Snow, Walter E.

Electricity: measuring and testing

Electrical speed measuring

73505, G01C 1956

Patent

active

052472523

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a sensor for determining angular velocity and including at least one piezoceramic component such as oscillation gyrometer. Known oscillation gyrometers generally use low-frequency flexural oscillators, e.g. bar oscillators, cylindrical oscillators or tuning-fork oscillators. In gyrometers with bar oscillators and cylindrical oscillators, comparitively small piezoceramic components are mounted on larger, non-piezoelectric oscillating bodies. The bodies effect the excitation of oscillations, serve as sensor for the amplitude control, and convert the action of the Coriolis force on the oscillating body into the measuring signal. Since a component or a component pair is required for each individual function, the construction of this gyrometer is complicated. Furthermore, the different expansion coefficients of the oscillating body and of the piezoceramic components lead to thermally determined mechanical stresses, which can result in comparitively large temperature dependencies of the measuring signal.
In gyrometers with tuning-fork oscillators, use is made of a piezoelectric oscillating body on which no additional exciting components must be mounted. However, the coupled flexural oscillators are likewise excited to resonance by action of the Coriolis force, so that strong temperature dependencies exist for the measuring signal even with this gyrometer.
For all the gyrometers mentioned, the oscillation frequencies employed are relatively low, and are located in the region of the frequencies of vibrations or only slightly removed therefrom, so that the measuring signals obtained are relatively strongly influenced by these interference signals.


SUMMARY OF THE INVENTION

The object of the invention is a sensor for determining angular velocity which does not require additional oscillators and has a very simple, but mechanically stable construction.
The object of the invention is achieved by forming the piezoceramic component as a thickness shear oscillator. The absence of additional components on the oscillating body improves the performance in the case of temperature changes. Furthermore, the sensor has, a relatively low sensitivity to vibrations. This is achieved by large frequency spacing, which is obtained by forming the component as a thickness shear oscillator, between the signal frequency and the interference frequencies of vibrations. Such spacing enables an effective filtering with a high-pass filter in the signal path. This is supported by a considerable compensation of the interference charges, induced by vibration, in the case of parallel connection of two sensors with opposite orientation of their polar Z-axes, as shown in FIG. 5. At the same time, because of the addition of the useful signals, a higher measuring sensitivity is achieved.
The present invention both as to its construction so to its mode of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of the preferred embodiments when read in connection with the accompanying drawings.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view representing a measurement principle according to the invention with reference to a three-directional coordinate system;
FIG. 2 is a diagrammatic view representing the measurement principle according to the invention with reference to a two-dimensional coordinate system;
FIG. 3 is a cross-sectional view of a first embodiment of a sensor according to the invention;
FIG. 4 is a perspective view of a second embodiment of a sensor according to the invention;
FIG. 5 is a perspective view of a third embodiment of a sensor according to the invention;
FIG. 6 is a perspective view of a fourth embodiment of a sensor according to the invention; and
FIG. 7 is a schematic view showing electrical connection of the sensor with exciting voltage.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The measurement principle of the sensor 10, which consists in its simplest form of a pi

REFERENCES:
patent: 3842681 (1974-10-01), Mumme

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