Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
1999-10-27
2001-06-12
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06244111
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a micromechanical gradient sensor.
BACKGROUND INFORMATION
Although applicable to any micromechanical gradient sensors, the present invention as well as its underlying problem are explained with respect to a gradient sensor which is manufacturable using the technology of silicon surface micromechanics.
Generally, gradient sensors can have many uses in the consumer goods and construction industries, for example, in self-adjusting spirit levels, self-adjusting construction lasers, zero-stable gravitational acceleration sensors for monitoring structures (bending of bridges, gradient of buildings, etc.), or, generally, in the alarm technology, for example, in vehicles such as ships, passenger cars, rail vehicles, or aircraft.
Described in the related art are micromechanical acceleration sensors having capacitive comb patterns. However, these cannot sense their own static orientation in the gravitational field, but only measure changes of their position in the gravitational field. However, these changes can only be determined if they take place within a certain time. Slower changes cannot be easily distinguished from operating point drifts which are typical of conventional sensors.
In the known approaches above, it has turned out to be a disadvantage that an extremely slow change, for example, during a bending of a support due to material fatigue, cannot be distinguished, for example, from a temperature-contingent zero drift.
SUMMARY OF THE INVENTION
The micromechanical gradient sensor according to the present invention has the advantage that it can measure its own orientation in the gravitational field, while it is stable in the zero point for the evaluation at the same time.
The basic idea of the present invention is that the direction of sensitivity of the gradient sensor is constantly changed relative to the gravitational field by rotary motions, for example, rotary oscillations according to a known time function. If the operating point changes by drifting, then the amplitude of the output signal indeed changes, but since the information about the gradient is not in the amplitude of the output signal of the acceleration sensor but in the phase relation of this signal relative to the motion of the ring body, this information is not influenced by drifting.
Therefore, this sensor does not indicate any false measured values either when the magnitude of the gravitational acceleration changes, for example, in the elevator. However, the sensor does deliver falsified measured values when it is moved on circular paths whose axis of rotation is located parallel to the center of the rotary motion of the sensor. Therefore, the main application lies in the fields indicated at the outset.
According to a preferred embodiment, a control device is provided which is designed in such a way that it continually regulates the excursion to zero, the angle of inclination of the sensor axis relative to the perpendicular being able to be determined from the control signal.
According to a further preferred embodiment, radially outwards directed extension bars are provided on the outer periphery, and the driving device is formed by a comb pattern of capacitor plates having fixed capacitor plates anchored to the substrate and movable capacitor plates attached to the extension bars.
According to a further preferred embodiment, the ring body is a circular ring body which is secured to a support pole provided on the substrate in the ring axis, using a plurality of, preferably four spring bars, which are spaced from each other by 90°.
According to a further preferred embodiment, the acceleration sensing device has at least one pair of mutually opposing acceleration sensors which are each secured to the ring body via a second spring device, each pair of mutually opposing acceleration sensors being designed in such a manner that, as a result of the centrifugal force acting due to the rotary motions, and as a result of the force acting against the spring tension of the two spring devices due to the gravitational acceleration, the pair is able to travel out in a coupled fashion along the sensor axis connecting the acceleration sensors, and running through the ring axis.
According to a further preferred embodiment, the acceleration sensors have frames, preferably U-frames, which are each secured to the ring body tangentially via a preferably U-shaped double spring, a comb pattern of capacitor plates being formed in these frames, which include fixed capacitor plates anchored to the substrate and movable capacitor plates attached to the frame.
According to a further preferred embodiment, the ring body is a circular ring body which, using a plurality of, preferably four spring bars, which are spaced from each other by 90°, is secured to a respective support pole provided on the substrate, the support poles being each provided in prolongation of the spring bars, spaced from each other by 90°.
According to a further preferred embodiment, the acceleration sensing device has an acceleration sensor which is arranged centrically to the ring body, and includes a bar which runs in the direction of the sensor axis, and is secured to the inner periphery of the ring body via four bar springs which run orthogonally to the bar and originate at its ends, the acceleration sensor having a comb pattern of capacitor plates having fixed capacitor plates anchored to the substrate and movable capacitor plates attached to the bar.
REFERENCES:
patent: 5872313 (1999-02-01), Zarabadi et al.
patent: 5889207 (1999-03-01), Lutz
patent: 5955668 (2000-05-01), Hsu et al.
patent: 6062082 (2000-05-01), Guenther et al.
Kenyon & Kenyon
Moller Richard A.
Robert & Bosch GmbH
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