Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1996-09-24
1999-04-20
Oda, Christine K.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
7350402, G01P 904
Patent
active
058958509
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to a micromechanical resonator of a vibration gyrometer for detecting the rate of rotation (absolute angular velocity).
BACKGROUND INFORMATION
A vibration gyrometer, in which two resonating (vibrating) masses are patterned out of a silicon semiconductor crystal, is described in German Published Unexamined Application No. DE-OS 40 22 495. When working with the known vibration gyrometer, the problem occurs that the oppositely phased vibration of the two resonating masses of the vibration gyrometer does not remain stable in phase, e.g., when subjected to a temperature change. The Coriolis force that arises in response to a rotational pulse can not always be measured precisely enough in this case, so that this sensor is not able to demonstrate the high level of operational dependability required in certain applications, e.g., in motor vehicles.
Another vibration gyrometer is known from the publication, "A Micromachined Comb-Drive Tuning Fork Rate Gyroscope", IEEE, Feb. 93, pp. 143-148. Two resonating masses that oscillate in phase opposition are suspended so as to allow them to move normally to the substrate under the influence of Coriolis forces. These movements are detected electrostatically with the aid of fixed counter-electrodes situated on the substrate. However, this gyrometer is not so suited for use in an environment which is replete with vibrations, e.g. in a motor vehicle, since the resonator structure not only carries out the excitation vibration of the resonating structure, but also takes up movements coupled in from the remaining degrees of freedom. This can distort the measuring result.
SUMMARY OF THE INVENTION
An advantage of the micromechanical resonator of a vibration gyrometer according to the present invention is that the suspension springs are so designed that the two resonating masses, which are mechanically coupled across the coupling region and, thus, mutually excite each other, vibrate in absolute phase opposition. This results in stable phase conditions, since parameter changes, such as temperature fluctuations or different masses of the two resonating masses, do not have a disruptive effect. This yields the advantage that the micromechanical resonator of the vibration gyrometer can be equipped with separate, exactly specified sensors, e.g., for measuring the Coriolis forces. By making one or more of the suspension springs soft in the direction of vibration of the resonating masses and substantially harder in all other degrees of freedom, the transfer of the moment of rotation of the rate of rotation to the resonating masses is facilitated. In manufacturing the resonator, the further advantage is attained that the manufacturing tolerances can be relatively large and a special adjustment is not necessary. Therefore, it is especially cost-effective to manufacture the micromechanical resonator according to the present invention.
An especially beneficial design approach can be achieved in that both the coupling region comprising the coupling mass and the resonating springs, as well as the resonating masses, are each joined via at least one suspension spring to the substrate. A configuration of this type is mechanically relatively stable, in particular at high accelerations, as can occur, for example, in applications in a motor vehicle.
To keep the influence of the suspensions springs as small as possible, their spring stiffness is very soft in comparison to that of the resonating springs.
A simple design approach is achieved by forming a frame around or at least partially around the resonating masses, and by designing the frame at the same time as a coupling mass to which the two resonating masses are mechanically coupled via resonating springs. A structure of this type is able to be simply etched using known methods, e.g., out of a silicon wafer.
When the frame is used as a coupling mass, the effective coupling mass is all the smaller, the smaller the parts of the frame are designed. Given very small frame parts, the mass of
REFERENCES:
patent: 4656383 (1987-04-01), Albert
patent: 4710668 (1987-12-01), Fima
patent: 5635638 (1997-06-01), Geen
patent: 5635640 (1997-06-01), Geen
Oda Christine K.
Robert & Bosch GmbH
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