CN100561126C - Micromachined Vibratory Gyroscope Using Electrostatic Coupling - Google Patents

Abstract

A micromachined vibratory gyroscope having two or more coplanar movable masses suspended on a planar substrate. Two perpendicular axes (x and y) are defined in the plane of the substrate, while a third axis, the z-axis or input axis, is defined perpendicular to the plane of the substrate. The movement of the two masses along the x-axis is coupled by an electrostatic coupling device such that the natural resonant frequencies of the resonances of the in-phase and anti-phase modes along the x-axis are separated from each other. When the two masses are driven to vibrate in anti-phase mode along the x-axis, and the above device is rotated about the z-axis, Coriolis forces act differentially on the masses in the Y direction, causing the two masses to move in The anti-phase mode vibrates along the y-axis. The anti-phase vibration along the y-axis can be directly detected by the velocity sensor to measure the rotational speed of the rotation about the z-axis. Optionally, the anti-phase vibrations of the first and second bodies along the y-axis can be transmitted to other movable bodies (ie, speed detection blocks), and then the movement of the movable body can be detected to measure the vibration around the z-axis. The speed of rotation. The test body is preferably suspended in such a way that, in the absence of Coriolis forces, movement of the vibrating mass along the x-axis does not affect the test body. This prevents the detection volumes from moving in response to linear accelerations in the plane of the substrate, but allows the volumes to readily respond to movement about an axis perpendicular to the plane of the substrate caused by Coriolis forces.

Description

Micromachined Vibratory Gyroscope Using Electrostatic Coupling

Cross References to Related Applications

Priority is claimed to Provisional Application No. 60/453,033, filed March 16, 2003.

technical field

This invention relates generally to inertial sensors and the like, and more particularly to micromachined vibratory gyroscopes.

Background technique

Vibrating gyroscopes work by detecting Coriolis-induced motion caused by the rotation of the gyroscope about a sensitive axis. When the drive mass vibrates along a given axis and rotates about an axis perpendicular to the axis of vibration, a Coriolis force is generated and exerted on the mass along a response axis perpendicular to the axis of vibration and the axis of rotation. By detecting changes in movement of the mass along the response axis caused by Coriolis forces, rotational speed can be measured.

Since the Coriolis force is proportional to velocity, the Coriolis force on the vibrating mass is in phase with the velocity of the mass. Any undesired coupling of movement along the primary or drive axis of vibration with the response axis will cause parasitic movement of the mass along the response axis. This undesired coupling is usually in phase with the mass's displacement rather than velocity, and is often referred to as quadrature error.

One method of detecting changes in movement of a mass caused by Coriolis forces is capacitive detection, which typically includes fixed and movable electrodes. In such devices, it is important to minimize the movement of the movable electrode without applying rotation, i.e. any movement of the mass along the response axis that is not caused by Coriolis forces. In addition, an undesired quadrature signal appears, which is the same frequency as the velocity signal but shifted in phase by 90 degrees. This quadrature signal is superimposed into the desired output signal. Although partially quadrature signals can be rejected electronically, for example using phase sensitive demodulation, it is still easy to degrade the performance of the gyroscope.

Another source of error for vibratory gyroscopes is sensitivity to linear acceleration, which can move the mass and produce undesired outputs.

When the gyroscope is mounted on a support in a particular application, any unbalanced momentum of the vibrating mass will cause some of the drive energy to be injected into the support, and possibly then couple that energy back into the device. Energy feedback in this manner can lead to offset errors and make the performance of the device sensitive to installation conditions.

In prior art micromachined vibratory gyroscopes, the vibrating masses are usually mechanically coupled together. This coupling is important to ensure that the masses vibrate at the same resonant frequency. Uncoupled blocks are prone to different resonant frequencies, detrimental to the practicality of the sensor.

While mechanical coupling does ensure that the mass vibrates at a single resonant frequency, such coupling has certain limitations and drawbacks. For example, their dimensions are liable to vary with manufacturing tolerances, which will result in variations in the degree of coupling. Additionally, many of the mechanical couplings are folded-beam designs, which increase the required substrate area and device size. Furthermore, the degree of coupling is determined by fixed mechanical properties of the coupling structure and is therefore not adjustable.

Contents of the invention

It is an object of the present invention to provide a new and improved micromachined vibratory gyroscope.

Another object of the present invention is to provide a gyroscope of the above character which does not require mechanical coupling between vibrating masses.

Another object of the present invention is to provide a gyroscope of the above character in which the vibrating mass is electrostatically coupled.

According to the present invention, these and other objects are achieved by providing a micromachined vibratory gyroscope in which vibrating masses are electrostatically coupled, for example, by means of parallel plate capacitors. This coupling can be used between the blocks themselves, as well as between the blocks and other volumes used to detect the response to rotation. This type of coupling is less prone to change than mechanical coupling and can be adjusted when needed by changing the bias voltage.

Description of drawings

1-6 are top plan views roughly schematically illustrating different embodiments of micromachined vibratory gyroscopes incorporating the present invention.

Detailed ways

In the embodiment shown in Figure 1, the two blocks are directly coupled together using an electrostatic force that varies with the relative position of the two blocks. The coupling capacitors are asymmetrical in that their capacitance increases as the blocks move closer to each other and decreases as they move away from each other.

In this embodiment, blocks 101, 102 are suspended by beams 105-108 and 109-112, respectively, wherein one end of each beam is fixed to the base plate. Each beam is L-shaped with arms extending in the x and y directions. This suspension structure allows the blocks 101, 102 to move in the x-axis and y-axis directions. Block 101 preferably matches block 102 and beams 105-108 preferably match beams 109-112.

Plates 103, 104 connect the blocks 101, 102 in parallel and alternately, and form the electrodes or plates of the capacitor. When a voltage is applied, the electrostatic force between the plates varies with the relative position of the blocks 101, 102 along the x-axis direction. This force can be approximated as a spring with a negative spring constant between two blocks.

When the drive masses 101, 102 vibrate in phase along the x-axis, their resonant frequency is determined by the spring constants of the beams 105-108 and 109-112. When the drive masses 101, 102 vibrate in anti-phase mode along the x-axis, the two masses alternately move closer and further away from each other, thereby changing their relative positions. In this case, the resonant frequency is determined not only by the spring constant of the beam, but also by the negative spring constant caused by the electrostatic force applied between the two blocks. In this way, by applying a voltage difference between the two blocks, the resonance frequency of the anti-phase mode in the x-direction can be tuned and can be separated from that of the in-phase mode in the x-direction.

The embodiment shown in Figure 1a is similar to that of Figure 1, except that the coupling capacitors are symmetrical in that the change in capacitance is approximately equal for equal movements of the blocks towards and away from each other.

As in the embodiment shown in Figure 1, the attractive force between the two plates of the capacitor increases as the blocks approach each other, and in addition to providing an equal change in capacitance in either direction of movement, a symmetric capacitor produces a capacitance that is proportional to the mass A more linear relationship between the displacements of .

Optionally, the beam in the embodiment shown in Figures 1 and 1a can also be adjusted to allow movement in the z-axis direction, but not in the y-axis direction. Coriolis movement will also be oriented along the z-axis direction, while the y-axis will be the input axis about which rotation is detected. This way, the input axis lies in the plane of the device, rather than perpendicular to it.

The embodiment shown in Figure 1 b is also similar to that of Figure 1 , but with the addition of means for coupling the two masses together for movement along the y- and x-axes. The device comprises plates 103by, 104by extending from the blocks in the x-direction, spaced apart in the y-axis direction to form the plates of an electrostatic coupling capacitor coupling the blocks together to move. As with the embodiment shown in Figure 1, the plates 103bx, 104bx couple the two blocks together for movement along the x-axis.

In the embodiment shown in Figure 2, the blocks 201, 202 are electrostatically coupled with a third block 203 interposed therebetween. Block 201 is coupled to block 203 by means of plates 204, 205 affixed to both blocks, wherein plates 204, 205 are arranged in a spaced, opposing manner, and block 202 is connected in a similar manner by means of plates 206, 207 to Block 203 is coupled.

Blocks 201, 202 and 203 are respectively suspended by beams 208-211, 212-215 and 216-217, one end of each beam being fixed to the base plate. The beams 208-211 and 212-215 are L-shaped with arms extending in the x and y directions, allowing the blocks 201, 202 to move in the x and y directions. The beams 216, 217 only extend in the y-direction and only allow movement of the mass 203 in the x-direction. Preferably, the overall design is symmetrical about both the x-axis and the y-axis about the center of the structure.

A voltage is applied between blocks 201 , 203 and between blocks 202 , 203 . For the anti-phase resonant mode of the blocks 201, 202 in the x-direction, the overall spring constant of the resonance is given by the spring constants of the beams 208-211 and 212-215, and the force exerted by the capacitor plates 204, 205 and 206, 207, etc. The effective negative spring constant is determined. For in-phase resonant modes of the masses 201, 202 in the x-direction, the spring constants of the beams 216, 217 are also contributing factors to the overall spring constant and resonant frequency. Thus, the anti-phase mode resonance frequency can be separated from the non-phase mode resonance frequency.

To detect rotation about an axis lying in the plane of the device, rather than perpendicular to it, the beams 208-215 can be tuned to allow movement in the z direction while maintaining electrostatic coupling between the blocks along the x axis. Coriolis movement is thus oriented along the z-axis direction, while the y-axis becomes the input axis about which rotation is detected. In this modified embodiment, the electrodes for detecting Coriolis movement are arranged above and/or below the block along the z-axis.

The embodiment shown in Figure 3 is similar to that shown in Figure 1, with electrodes 313-316 for detecting the response to Coriolis shift along the y-axis. As with the embodiment shown in FIG. 1 , blocks 301 and 302 , beams 305 - 308 and 309 - 312 , and capacitor plates 303 and 304 are suspended on substrate 300 . Electrodes 313-316 are mounted at fixed positions on the substrate and distributed above and below the block in the y-direction.

When the drive masses 301, 302 vibrate in the x-direction in anti-phase mode and the device rotates about the z-axis, a Coriolis force is differentially induced on the masses 301, 302, causing the mass 302 to differentially move in the y-direction. vibration. The rotational speed is measured by detecting this movement through the capacitor formed by the electrodes 313-316 and the vibrating mass.

Electrodes 313-316 arranged on opposite sides of the block constitute with the block a differential capacitive detector. The differential detection is advantageous for canceling interference from linear acceleration, since this interference is seen as a common mode signal rather than a differential signal.

As shown in Figure 3, embodiments therein are sensitive to rotation about the z-axis by detecting movement along the y-axis. This embodiment can also be adapted to detect rotation about the y-axis if desired, in which case the capacitor plates 313-316 are positioned above and/or below the block in the direction of the z-axis.

The embodiment shown in Figure 3a is similar to that in Figures 1b and 3, in that capacitor plates 303ax, 304ax provide coupling for movement in the x-direction between blocks 301a, 302a, and plates 303ay, 304ay provide Coupling for movement in the y-direction, and the plates 313a-316a form capacitors with the block for detecting movement of the block in the y-direction.

Figure 4 shows another embodiment where two blocks are electrostatically coupled together with a third block placed in between. In this embodiment, the change in movement along the y-axis caused by the Coriolis force is transmitted to the movable detection element by a mechanical beam, which is then detected preferably using a capacitive detector to measure rotational speed. In the absence of Coriolis forces caused by rotation, the sensing element is relatively stationary and unaffected by vibrations of the mass along the x-axis, minimizing quadrature error.

As with the embodiment shown in FIG. 2 , blocks 401 , 402 and 403 , capacitor plates 404 , 405 and 406 , 407 , and beams 408 - 411 , 412 - 415 and 416 , 417 are suspended on substrate 400 . In addition, detection blocks 418, 419 are also suspended from the substrate by beams 420, 421 and 422, 423 and connected to blocks 401, 402 by beams 424, 425 and 426, 427 to move in the y direction. Fixed detection elements 428-431 are affixed to the substrate adjacent to the detection block and are capacitively coupled to the detection block.

When the drive masses 401, 402 are vibrated in the x-direction in anti-phase mode, and the device is rotated about the z-axis, Coriolis forces are differentially induced on the masses 401, 402, causing the masses to differentially move in the y-direction The ground vibrates. This vibration is transmitted to the detection blocks 418,419 through the beams 424,425 and 426,427. Since the beams 420, 421 and 422, 423 only extend in the x-direction, the detection mass is held in such a way that they are minimally affected by vibrations of the vibrating mass in the x-direction where there is no Coriolis force. Movement of the detection blocks 418, 419 is detected by a change in capacitance between them and the electrode plates 428-431.

Figure 5 shows another embodiment of a gyroscope in which two blocks are electrostatically coupled together by a third block and coupled to the movable sensing element. As in the previous embodiment, blocks 501 , 502 and 503 , capacitor plates 504 , 505 and 506 , 507 , and beams 508 - 511 , 512 - 515 and 516 , 517 are suspended on substrate 500 .

A detection element or block 522 in the form of a rigid rectangular frame is suspended from the substrate by beams 523-526 and connected to blocks 501,502 by beams 518,519 and 520,521. Fixed detection elements 527-530 are fixed on the substrate adjacent to the detection block and are capacitively coupled with the detection block.

When the drive masses 501, 502 vibrate in anti-phase mode in the x-direction, and the device rotates about the z-axis, Coriolis forces are differentially induced on the masses 501, 502 and cause these masses to differentially move in the y-direction. vibration. This vibration is transmitted to detection mass 522 via beams 518-521. Since the beams extend in the y-direction and are relatively rigid in this direction, movements in the y-direction are easily transmitted without largely transmitting the differential vibrations of the masses in the x-axis to the detection mass.

The beams 523-526 shield the detection mass from vibrations of the mass 501, 502 in the x-direction where no Coriolis force exists. Beams 523-526 also hold mass 522 firmly and inhibit it from responding to changes in movement in linear acceleration along the x and y axes, but readily respond to any changes in rotational movement about the z-axis caused by Coriolis forces. Movement of the detection block 522 is detected by a change in capacitance between the block and the electrode plates 527-530.

Figure 6 shows another embodiment with a rigid detection element or block. In this embodiment, blocks 601, 602 are electrostatically coupled together by plates 603, 604, and are suspended from base plate 600 by L-shaped beams 605-608 and 609-612. The blocks are also electrostatically coupled via plates 613, 614; 615, 616; 617, 618 and 619, 620 to the surrounding detection block 621, which has the form of a rigid rectangular frame. The detection block is suspended on the substrate by beams 622-625, and electrode plates 626-629 are fixed to the substrate to capacitively couple with the detection block to detect its movement.

When the drive masses 601, 602 vibrate in anti-phase mode in the x-direction and the device rotates about the z-axis, Coriolis forces are differentially induced on the masses, causing the masses to differentially vibrate in the y-direction . This movement change is transmitted to the detection block 621 through the electrode plates 613 , 614 ; 615 , 616 ; 617 , 618 and 619 , 620 . These electrode pairs form parallel plate capacitors, and when a voltage is applied between them, the electrostatic force between each pair of plates varies with the relative position of the electrode pair in the y-direction.

Beams 622-625 keep mass 621 relatively stationary in the absence of Coriolis forces, thereby reducing quadrature error. They also hold mass 621 firmly, effectively resisting changes in movement caused by linear accelerations along the x and y axes, but still responsive to changes in rotational movement about the z axis caused by Coriolis forces. As in the previous embodiments, the movement of the detection block 621 is detected by the capacitance change between the detection block 621 and the electrode plates 626-629.

The present invention has many important features and advantages. The provided micromachined vibratory gyroscope overcomes deficiencies of prior art gyroscopes, including quadrature error, sensitivity to linear acceleration, momentum imbalance, and mechanical coupling effects.

The cancellation of the momentum imbalance is achieved by coupling the two masses and driving them in anti-phase mode to balance the driving momentum. The coupling is achieved by electrostatic forces that vary with the relative position of the two masses. This electrostatic force can be applied directly between the two masses, or through one or more intermediate masses between the two drive masses.

Since the two blocks are driven in anti-phase mode, the Coriolis forces on the two blocks are in opposite directions, so that the output signal can be detected differentially. The effects of linear acceleration are seen as common-mode interference and can be rejected by the electronics used to process the signal. Sensitivity to linear acceleration can thus be greatly reduced.

In some embodiments, changes in the movement of the vibrating mass caused by Coriolis forces are transferred to one or more other bodies (i.e., detection masses) via mechanical beams and/or electrostatic forces that follow the movement of the mass being driven. The relative position between the detection block and the change. Suspending the detection blocks in such a way that they are relatively stationary in the absence of Coriolis forces greatly reduces quadrature error.

The manner in which the detection masses are suspended as described above also prevents them from responding to changes in movement of linear acceleration along the x and y axes, but allows them to readily respond to differential movement along the response axis (y-axis) caused by Coriolis forces. This design significantly reduces sensitivity to linear acceleration.

A microfabricated gyroscope is fabricated on a planar substrate where two vibrating masses are coupled by an electrostatic force that varies with the relative position of the two masses. This electrostatic force can be generated directly between the two blocks, or it can be generated through one or more intermediate blocks. The coupling results in different resonant frequencies of the resonance along the vibration axis for anti-phase and in-phase resonant modes. This coupling technique can be easily extended to micromachined vibratory gyroscopes with more than two blocks.

Changes in movement caused by Coriolis forces are transferred to one or more other movable masses or detection bodies through mechanical beams and/or electrostatic forces that vary with the relative position between the vibrating mass and detection mass Variety.

The detection mass is suspended such that it remains relatively stationary in the absence of Coriolis forces and is not affected by vibrations of the vibrating mass along the vibration axis.

Suspending the detection mass in the manner described above significantly prevents its movement in response to linear acceleration in the plane of the substrate, but allows the detection mass to readily respond to changes in movement caused by rotation about an axis perpendicular to the plane of the substrate.

Electrostatic coupling between blocks can be symmetrical or asymmetrical and can be used along both the detection axis and the drive axis.

Although the gyroscope in this preferred embodiment is sensitive to rotation about the z-axis, its drive mode electrostatic coupling is also applicable to gyroscopes with an input axis along the y-axis.

Although the invention has been described with specific reference to microfabricated gyroscopes, it is to be understood that it is equally applicable to other means of electrostatically coupling vibrating masses together.

From the foregoing it is apparent that the present invention provides a new and improved micromachined vibratory gyroscope. It will be apparent to those skilled in the art that, although only certain presently preferred embodiments have been described in detail herein, certain changes and modifications can be made without departing from the scope of the invention as defined in the appended claims. Revise.

Claims (20)

1. little processing gyrotron, comprise: first and second, it is installed by this way, make to allow to move and respond differential mobile along second by the Coriolis force that produces around the 3rd rotation along first vibrate in opposite phase, described second perpendicular to described first, described the 3rd perpendicular to described first and second; And be used for by electrostatic force described device that is coupled, described electrostatic force changes with described relative position.

2. little processing gyrotron as claimed in claim 1, wherein said electrostatic coupling power is oriented as along described first, makes described anti-phasely to move and have different resonance frequencies with phase shift along described first.

3. little processing gyrotron as claimed in claim 1, wherein said by simultaneously along described first and described second electrostatic coupling, make each anti-phase in described along described first and second move and have different resonance frequencies with phase shift.

4. little processing gyrotron as claimed in claim 1, wherein said be used for described device that is coupled comprise an a plurality of and described connection with the described consistent parallel plate electrode that moves.

5. little processing gyrotron as claimed in claim 4 wherein connects described first pole plate and is equidistantly separated and connecting between described second pole plate, make described mutually near and away from the electrostatic force that equates substantially of mobile generation.

6. little processing gyrotron as claimed in claim 1 wherein is used for described device that is coupled comprised by electrostatic coupling the 3rd between described first and second.

7. little processing gyrotron as claimed in claim 1 also comprises a plurality of sensors, and itself and described first and second capacitive couplings are to monitor described along described second moving.

8. little processing gyrotron as claimed in claim 1, also comprise with the detecting element of described first and second couplings and with the capacitively coupled a plurality of sensors of described detecting element, to monitor described along described second moving.

9. little processing gyrotron as claimed in claim 8, wherein said detecting element and described electrostatic coupling.

10. little processing gyrotron as claimed in claim 1, wherein said is suspended above on the planar substrates, described first and second are positioned at the plane that is parallel to described substrate, described the 3rd perpendicular to described substrate.

11. little processing gyrotron as claimed in claim 1, wherein said is suspended above on the planar substrates, and described first and the 3rd is positioned at the plane that is parallel to described substrate, described second perpendicular to described substrate.

12. little process velocity sensor, comprise by together first and second of electrostatic coupling, it is installed by this way, make to allow to move and respond differential mobile along second by the Coriolis force that produces around the 3rd rotation along first vibrate in opposite phase, described second perpendicular to described first, described the 3rd perpendicular to described first and second.

13. little process velocity sensor as claimed in claim 12, wherein said first and second intercouple by electrostatic force, and described electrostatic force changes with described relative position.

14. little process velocity sensor as claimed in claim 13, wherein said electrostatic coupling power is oriented as along described first, makes described anti-phasely to move and have different resonance frequencies with phase shift along described first.

15. little process velocity sensor as claimed in claim 12, wherein said by simultaneously along described first and described second electrostatic coupling, make each anti-phase in described along described first and second move and have different resonance frequencies with phase shift.

16. little process velocity sensor as claimed in claim 12 also comprises a plurality of sensors, itself and described first and second capacitive couplings are to monitor described along described second moving.

17. little process velocity sensor as claimed in claim 12, also comprise with the detecting element of described first and second couplings and with the capacitively coupled a plurality of sensors of described detecting element, to monitor described along described second moving.

18. little process velocity sensor as claimed in claim 17, wherein said detecting element and described electrostatic coupling.

19. little process velocity sensor as claimed in claim 17, wherein said detecting element comprises rectangular frame, described framework around described first and second and with its coplane.

20. little process velocity sensor as claimed in claim 12, wherein said first and second orthogonal and perpendicular to described the 3rd.

Images