Silicon multimode coriolis vibration gyroscope with high-order rotationally symmetric mechanical structure and32electrodes
阅读说明:本技术 具有高阶旋转对称机械结构和32个电极的硅多模科里奥利振动陀螺仪 (Silicon multimode coriolis vibration gyroscope with high-order rotationally symmetric mechanical structure and32electrodes ) 是由 洛根·D·索伦森 阮勋 拉维夫·佩拉西亚 黄莲欣 大卫·T·常 于 2018-06-08 设计创作,主要内容包括:一种角度传感器,包括科里奥利振动陀螺仪(CVG)谐振器,该谐振器能够沿着包括第一法向模态和第二法向模态的第一对法向n=1模态以及包括第三法向模态和第四法向模态的第二对法向n=2模态振荡;传感器还包括:一个驱动电极和一个感测电极,它们沿着每个模态的反节点轴线对齐;以及一对偏置调谐电极,如果没有驱动和感测电极对与每个模态的反节点轴线对齐,则该对偏置调谐电极与所述反节点轴线对齐。(An angle sensor comprising a Coriolis Vibration Gyroscope (CVG) resonator that is capable of oscillating along a first pair of normal n-1 modes comprising a first normal mode and a second pair of normal n-2 modes comprising a third normal mode and a fourth normal mode; the sensor further includes: a drive electrode and a sense electrode aligned along the anti-node axis of each mode; and a pair of offset tuning electrodes aligned with the anti-node axis of each mode if no pair of drive and sense electrodes is aligned with the anti-node axis.)
1. An angle sensor, comprising:
a Coriolis Vibration Gyroscope (CVG) resonator capable of oscillating along the following modes:
a first pair of normal n ═ 1 modes comprising a first normal mode and a second normal mode, each of said first and second normal modes having an anti-node axis; and
a second pair of normal n-2 modes comprising a third normal mode and a fourth normal mode, each of the third and fourth normal modes having two anti-node axes;
at least one of a drive electrode and a sense electrode aligned along the anti-node axis of each of the first and second normal modes;
at least one of a drive electrode and a sense electrode aligned along a first anti-node axis of each of the third and fourth normal modes; and
a pair of offset tuning electrodes aligned with the second anti-node axis of each of the third and fourth modes if no drive or sense electrode is aligned with the second anti-node axis.
2. The angle sensor of claim 1, wherein the at least one of the drive and sense electrodes aligned along the first and second anti-node axes is each part of a pair comprising one sense electrode and one drive electrode.
3. The angle sensor of claim 1, further comprising:
a first pair of biased quadrature electrodes aligned with the 360/(8 x n) degree off-axis if no drive or sense electrode or no biased tuning electrode pair is aligned with an axis that is 360/(8 x n) degrees off-axis from the axis of the at least one of the sense and drive electrodes of each modality; and
a second pair of biased orthogonal electrodes aligned with the 360/(8 x n) degree off-axis if no drive or sense electrodes or no pair of biased tuning electrodes are aligned with an axis that is 360/(8 x n) degrees off-axis from the axis of the biased tuning electrode of each mode.
4. The angle sensor of claim 2, comprising:
a coarse readout circuit configured to:
the first pair of modes is driven,
measuring the motion of the first pair of modalities with a first sensitivity, and
deriving a coarse measure of true angular rate of the CVG resonator from the measured motion of the first pair of modes; and
a fine readout circuit configured to:
the coarse measurement values are received and the coarse measurement values,
the second pair of modalities is driven such that,
measuring motion of the second pair of modalities at a second sensitivity higher than the first sensitivity; the measurement is compensated by the coarse measurement value, and
deriving a fine measurement of a true angular rate of the CVG resonator from the measured motion and the received coarse measurements of the second pair of modes.
5. The angle sensor of claim 4, wherein to said drive the first pair of modalities, the coarse readout circuit comprises:
a first frequency reference configured to generate a first reference signal; and
a first phase control circuit configured to:
measuring a first phase difference between first phase targets and a difference between a phase of the oscillation of the first normal mode and a phase of the first reference signal,
applying a first phase correction signal to the CVG resonator to reduce the first phase difference; and
a second phase control circuit configured to:
measuring a second phase difference between second phase targets and a difference between a phase of the oscillation of the second normal mode and a phase of the first reference signal, and
applying a second phase correction signal to the CVG resonator to reduce the second phase difference.
6. The angle sensor of claim 5, wherein to said drive the second pair of modalities, the fine readout circuit comprises:
a second frequency reference configured to generate a second reference signal;
a third phase control circuit configured to:
measuring a third phase difference between a third phase target and a difference between the phase of the oscillation of the third normal mode and the phase of the second reference signal, and
applying a third phase correction signal to the CVG resonator to reduce the third phase difference; and
a fourth phase control circuit configured to:
measuring a fourth phase difference between fourth phase targets and a difference between a phase of an oscillation of the fourth normal mode and the phase of the second reference signal, and
applying a fourth phase correction signal to the CVG resonator to reduce the fourth phase difference.
7. The angle sensor of claim 4, wherein the fine readout circuitry is configured to drive the third normal mode at a first drive frequency and to drive a fourth normal mode at a second drive frequency, and
wherein the fine readout circuit is configured to derive a fine measurement of the true angular rate of the CVG resonator by: adjusting the first drive frequency and the second drive frequency such that a difference between the first drive frequency and the second drive frequency is proportional to the coarse measurement.
8. The angle sensor of claim 4, wherein the fine readout circuit is configured to derive the fine measurement of the true angular rate of the CVG resonator by: adjusting the natural frequency of the third normal mode and the natural frequency of the fourth normal mode such that a difference between the natural frequency of the third normal mode and the natural frequency of the fourth normal mode is proportional to the coarse measurement.
9. The angle sensor of claim 8, wherein the fine readout circuitry is configured to adjust a natural frequency of the third normal mode by adjusting a bias voltage applied to a tuning electrode coupled to the third normal mode.
10. The angle sensor of claim 1, wherein the resonator has rotational symmetry N, N being a power of 2 and at least equal to 8.
11. The angle sensor of claim 1 wherein each electrode comprises a set of sub-electrodes having at least one pair of differential sub-electrodes.
12. The angle sensor of claim 11, comprising at least 32 sub-electrodes.
13. The angle sensor of claim 11, wherein each electrode comprises a set of sub-electrodes having at least two pairs of interdigitated differential sub-electrodes.
14. The angle sensor of claim 11, wherein the two sub-electrodes of each sub-electrode pair are arranged to receive or transmit differential signals 180 degrees out of phase with respect to each other.
15. The angle sensor of claim 5, wherein the frequency reference comprises an atomic frequency reference, or an oven controlled crystal oscillator (OCXO) or a temperature controlled crystal oscillator (TCXO).
16. The angle sensor of claim 15 wherein the atomic frequency reference is a rubidium, cesium or hydrogen or strontium based clock.
17. The angle sensor of claim 15, wherein the atomic frequency reference is a chip-scale atomic clock (CSAC).
18. The angle sensor of claim 5, wherein the first phase control circuit is configured to apply a first phase correction signal to the CVG resonator by adjusting a natural frequency of the first normal mode.
19. The angle sensor of claim 5, wherein the first phase control circuit is configured to adjust the natural frequency of the first normal mode by applying a bias voltage to a first tuning electrode of the CVG resonator.
20. The angle sensor of claim 5, wherein the second phase control circuit is configured to adjust the natural frequency of the second normal mode by applying a bias voltage to a second tuning electrode of the CVG resonator.
21. The angle sensor of claim 4, wherein the fine readout circuit is configured to generate a measurement of the difference between the true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
22. The angle sensor of claim 4, wherein the coarse readout circuit is configured to generate a measurement of a difference between a true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
23. The angle sensor of claim 22, wherein the fine readout circuitry is configured to generate a measurement of the difference between the true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
24. The angle sensor of claim 4, wherein the coarse readout circuitry is configured to drive the first pair of modalities such that a magnitude of motion of a first normal modality is about 10 times a magnitude of motion of the second normal modality.
25. The angle sensor of claim 4, wherein the coarse readout circuitry is configured to drive the first pair of modalities such that a phase of motion of a first normal modality differs from a phase of motion of the second normal modality by approximately 90 degrees.
26. The angle sensor of claim 4, wherein the fine readout circuitry is configured to drive the first pair of modalities such that a magnitude of motion of the third normal modality is about 10 times a magnitude of motion of the fourth normal modality.
27. The angle sensor of claim 4, wherein the fine readout circuitry is configured to drive the first pair of modalities such that a phase of motion of the third normal modality differs from a phase of motion of the fourth normal modality by approximately 90 degrees.
28. The angle sensor of claim 4, wherein the fine readout circuitry is configured to drive the third normal mode at a first drive frequency and the fourth normal mode at a second drive frequency, and
wherein the fine readout circuit is configured to derive a measure of a difference between a true angular rate of the CVG resonator and the coarse measure by: adjusting the first drive frequency and the second drive frequency such that a difference between the first drive frequency and the second drive frequency is proportional to the coarse measurement.
29. The angle sensor of claim 4, wherein the fine readout circuit is configured to derive a measure of a difference between a true angular rate of the CVG resonator and the coarse measure by: adjusting the natural frequency of the third normal mode and the natural frequency of the fourth normal mode such that a difference between the natural frequency of the third normal mode and the natural frequency of the fourth normal mode is proportional to the coarse measurement.
30. The angle sensor of claim 4, wherein the fine readout circuitry is configured to adjust a natural frequency of the third normal mode by adjusting a bias voltage applied to a tuning electrode coupled to the third normal mode.
[ technical field ] A method for producing a semiconductor device
The present description relates to MEMS gyroscopes, in particular to MEMS gyroscopes using resonators having high order mechanical symmetry and preferably having at least 32electrodes for controlling and sensing resonator oscillation.
[ background of the invention ]
Gyroscopes may be used in a wide range of applications, including guidance of aircraft, spacecraft, missiles, and the like. Gyroscopes (or "gyro") measure angular rate, i.e., the rate at which the gyroscope rotates about one or more axes. The output of the gyroscope may be a digital data stream. The rate resolution of the gyroscope (i.e., the ability of the gyroscope to detect low angular rates or small changes in angular rate) may be limited in part by the resolution (i.e., the number of bits) and the scaling factor of an analog-to-digital converter (ADC), which may be part of the signal chain that connects the physical sensing element to the digital output of the gyroscope. The range of the gyroscope (i.e., the maximum angular rate it can measure) may also be related to the resolution and scale factor of the ADC. It follows that gyroscopes designed to operate at high angular rates may have poor resolution, while high resolution gyroscopes may have relatively limited range. However, certain applications may require gyroscopes that have both high range (e.g., in airplanes or missiles designed to be highly maneuvered) and high resolution to provide accurate guidance.
MEMS gyroscopes may be vibrating structure gyroscopes, or "coriolis vibrating gyroscopes," which use a vibrating structure to determine its rate of rotation, following the basic physical principles: even if the support of the vibration object rotates, the vibration object tends to continue to vibrate in the same plane. The coriolis effect causes a vibrating object to exert a force, for example, on its support, and by measuring this force, the rotation rate can be determined. Vibrating structure gyroscopes are simpler and less expensive than traditional rotating gyroscopes of similar accuracy. Inexpensive vibrating structure gyroscopes, fabricated with MEMS technology, are widely used in smart phones, gaming devices, cameras, and many other applications.
Known MEMS gyroscopes, such as disclosed in US7168318 (ISOLATED planmesylroscope by Challoner et al), remain sensitive to their environment (temperature, vibration).
Environmentally robust high performance inertial sensors with attractive CSWaP (cost size weight and power) are in strong demand in weapons, space and vehicle systems. There is a need for a MEMS gyroscope that is less environmentally sensitive than known MEMS gyroscopes.
[ summary of the invention ]
The present description relates to a Coriolis Vibration Gyroscope (CVG) whose electrodes are arranged to simultaneously maintain and measure the oscillation of the CVG resonator along a pair of n-1 normal modes and along a pair of n-2 modes. Where appropriate, the CVG comprises electrodes arranged to fine-tune the respective frequencies of oscillation of the CVG resonator along said modes. Where appropriate, the CVG may comprise electrodes arranged to generate a dynamically induced static torque with respect to each of said modalities.
According to an embodiment, the CVG resonator exhibits N-th order rotational symmetry, where N is a power of 2 greater than or equal to 8. According to an embodiment of the present description, the electrodes of the CVG comprise 16 pairs of differential electrodes arranged around the perimeter of the CVG resonator at a predetermined distance of said perimeter, for example a predetermined distance of 100nm to 30 μm in radial direction, preferably of 2 μm to 30 μm in radial direction.
According to an embodiment of the present description, the CVG includes a control circuit that maintains a first target phase difference between oscillations in the first pair of modes and a second target phase difference between oscillations in the second pair of modes.
According to an embodiment of the present description, the CVG comprises a control circuit that uses rotation measurements with coarse sensitivity by using sensing of oscillations in a first pair of modes as a bias for rotation measurements with higher sensitivity by using sensing of oscillations in a second pair of modes.
According to the present described embodiment, the two n-1 modes ideally or nominally degenerate. According to the present described embodiment, the two n-2 modes ideally or nominally degenerate.
Embodiments of the present description include an angle sensor having: a Coriolis Vibration Gyroscope (CVG) resonator capable of oscillating along the following modes: a first pair of normal n ═ 1 modes comprising a first normal mode and a second normal mode, each of the first normal mode and the second normal mode having an anti-node axis; and a second pair of normal n-2 modes comprising a third normal mode and a fourth normal mode, each of the third normal mode and the fourth normal mode having two anti-node axes; at least one of drive and sense electrodes aligned along an anti-node axis of each of the first and second normal modes; at least one of drive and sense electrodes aligned along a first anti-node axis of each of a third and fourth normal mode; and a pair of offset tuning electrodes aligned with the second anti-node axis of each of the third and fourth modes if no drive or sense electrode is aligned with said second anti-node axis.
According to an embodiment of the present description, at least one of the drive electrode and the sense electrode aligned along the first and second anti-node axes is each part of a pair comprising one sense electrode and one drive electrode.
According to an embodiment of the present description, the angle sensor further comprises: a first pair of biased quadrature electrodes aligned with the 360/(8 x n) degree off-axis if either no drive or sense electrodes or no pair of biased tuning electrodes are aligned with an axis that is off-axis from the 360/(8 x n) degree axis of at least one of the sense and drive electrodes of each modality; and a second pair of biased quadrature electrodes aligned with the 360/(8 x n) degree offset axis if no drive or sense electrode or no pair of biased tuning electrodes is aligned with an axis offset from the axis of the biased tuning electrode of each mode by 360/(8 x n) degrees.
According to an embodiment of the present description, the angle sensor further comprises: a coarse readout circuit configured to: driving the first pair of modes, measuring motion of the first pair of modes at a first sensitivity, and deriving a coarse measure of the true angular rate of the CVG resonator from the measured motion of the first pair of modes; and a fine readout circuit configured to: receiving a coarse measurement, driving a second pair of modalities, measuring motion of the second pair of modalities at a second sensitivity higher than the first sensitivity (the measurement being offset from the coarse measurement), and deriving a fine measurement of the true angular rate of the CVG resonator from the measured motion of the second pair of modalities and the received coarse measurement.
According to an embodiment of the present introduction, for said driving the first pair of modes, the coarse readout circuit comprises: a first frequency reference configured to generate a first reference signal; a first phase control circuit configured to: measuring a first phase difference between the first phase targets and a difference between the phase of the oscillation of the first normal mode and the phase of the first reference signal, and applying a first phase correction signal to the CVG resonator to reduce the first phase difference; and a second phase control circuit configured to: a second phase difference between the second phase targets and a difference between the phase of the oscillation of the second normal mode and the phase of the first reference signal are measured and a second phase correction signal is applied to the CVG resonator to reduce the second phase difference.
According to an embodiment of the present description, for said driving the second pair of modes, the fine readout circuit comprises: a second frequency reference configured to generate a second reference signal; a third phase control circuit configured to: measuring a third phase difference between the third phase targets and a difference between the phase of the oscillation of the third normal mode and the phase of the second reference signal, and applying a third phase correction signal to the CVG resonator to reduce the third phase difference; and a fourth phase control circuit configured to: a fourth phase difference between the fourth phase targets and a difference between the phase of the oscillation of the fourth normal mode and the phase of the second reference signal are measured, and a fourth phase correction signal is applied to the CVG resonator to reduce the fourth phase difference.
According to an embodiment of the present introduction, the fine readout circuit is configured to drive the third normal mode at the first drive frequency and to drive the fourth normal mode at the second drive frequency, and the fine readout circuit is configured to derive the fine measure of the true angular rate of the CVG resonator by: the first drive frequency and the second drive frequency are adjusted such that a difference between the first drive frequency and the second drive frequency is proportional to the coarse measurement.
According to an embodiment of the present description, the fine readout circuit is configured to derive a fine measure of the true angular rate of the CVG resonator by: the natural frequency of the third normal mode and the natural frequency of the fourth normal mode are adjusted such that the difference between the natural frequency of the third normal mode and the natural frequency of the fourth normal mode is proportional to the coarse measurement.
According to an embodiment of the present description, the fine readout circuit is configured to adjust the natural frequency of the third normal mode by adjusting a bias voltage applied to a tuning electrode coupled to the third normal mode.
According to an embodiment of the present description, the resonator has a rotational symmetry of degree N, N being a power of 2 and at least equal to 8.
According to an embodiment of the present description, each electrode comprises a set of sub-electrodes having at least one pair of differential sub-electrodes.
According to an embodiment of the present description, the angle sensor comprises at least 32 sub-electrodes.
According to an embodiment of the present description, each electrode comprises a set of sub-electrodes having at least two pairs of interdigitated differential sub-electrodes.
According to an embodiment of the present introduction, the two sub-electrodes of each sub-electrode pair are arranged to receive or transmit differential signals 180 degrees out of phase with respect to each other.
According to an embodiment of the present description, the frequency reference comprises an atomic frequency reference, an oven controlled crystal oscillator (OCXO) or a temperature controlled crystal oscillator (TCXO).
According to an embodiment of the present description, the atomic frequency reference is a rubidium, cesium or hydrogen or strontium based clock.
According to an embodiment of the present description, the atomic frequency reference is a chip-scale atomic clock (CSAC).
According to an embodiment of the present description, the first phase control circuit is configured to apply the first phase correction signal to the CVG resonator by adjusting a natural frequency of the first normal mode.
According to an embodiment of the present description, the first phase control circuit is configured to adjust the natural frequency of the first normal mode by applying a bias voltage to the first tuning electrode of the CVG resonator.
According to an embodiment of the present description, the second phase control circuit is configured to adjust the natural frequency of the second normal mode by applying a bias voltage to the second tuning electrode of the CVG resonator.
According to an embodiment of the present introduction, the fine readout circuit is configured to generate a measurement of the difference between the true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
According to an embodiment of the present introduction, the coarse readout circuit is configured to generate a measurement of the difference between the true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
According to an embodiment of the present introduction, the fine readout circuit is configured to generate a measurement of the difference between the true angular rate of the CVG resonator and the coarse measurement at a resolution of 19 bits.
According to an embodiment of the present description, the coarse readout circuitry is configured to drive the first pair of modes such that the amplitude of motion of the first normal mode is about 10 times the amplitude of motion of the second normal mode.
According to an embodiment of the present description, the coarse readout circuit is configured to drive the first pair of modes such that the motion phase of the first normal mode differs from the motion phase of the second normal mode by approximately 90 degrees.
According to an embodiment of the present description, the fine readout circuit is configured to drive the first pair of modes such that the amplitude of motion of the third normal mode is about 10 times the amplitude of motion of the fourth normal mode.
According to an embodiment of the present description, the fine readout circuit is configured to drive the first pair of modes such that the motion phase of the third normal mode differs from the motion phase of the fourth normal mode by approximately 90 degrees.
According to an embodiment of the present introduction, the fine readout circuit is configured to drive the third normal mode at the first drive frequency and to drive the fourth normal mode at the second drive frequency, and the fine readout circuit is configured to derive the measure of the difference between the true angular rate of the CVG resonator and the coarse measure by: the first drive frequency and the second drive frequency are adjusted such that a difference between the first drive frequency and the second drive frequency is proportional to the coarse measurement.
According to an embodiment of the present introduction, the fine readout circuit is configured to derive a measure of the difference between the true angular rate of the CVG resonator and the coarse measure by: the natural frequency of the third normal mode and the natural frequency of the fourth normal mode are adjusted such that the difference between the natural frequency of the third normal mode and the natural frequency of the fourth normal mode is proportional to the coarse measurement.
According to an embodiment of the present description, the fine readout circuit is configured to adjust the natural frequency of the third normal mode by adjusting a bias voltage applied to a tuning electrode coupled to the third normal mode.
These and other features and advantages will become more apparent from the following detailed description and the accompanying drawings. In the drawings and the description, reference numerals indicate various features; like reference numerals refer to like features throughout both the drawings and the description.
[ description of the drawings ]
Fig. 1 shows a picture of a section of an angle sensor according to an embodiment of the present description, as well as a section of a detailed view of a CVG resonator of the sensor and a very detailed view of a section of a CVG resonator.
Fig. 2 shows a schematic diagram of a sensing circuit that may be used in an angle sensor according to embodiments of the present description.
FIG. 3 illustrates the operation of a sensing circuit such as illustrated in FIG. 2.
Fig. 4A and 4B show schematic diagrams of modal phase control circuits that may be used in an angle sensor according to embodiments of the present description.
Fig. 5 shows a schematic diagram of a differential electrode control circuit that may be used in an angle sensor according to embodiments of the present description.
Fig. 6 illustrates the anti-nodal axis of the CVG resonator of the angle sensor according to an embodiment of the present description.
Fig. 7 illustrates an ideal position of the control and sensing electrodes of the CVG resonator of the angle sensor according to the embodiments presented.
Fig. 8 illustrates the actual positions of the control and sensing electrodes of the CVG resonator of the angle sensor according to an embodiment of the present description.
Fig. 9A illustrates the first n-1 oscillation mode of the CVG resonator of the angle sensor according to the embodiment of the present description.
Fig. 9B illustrates the second n-1 oscillation mode of the CVG resonator of the angle sensor according to the embodiment described above.
Fig. 9C illustrates the first n-2 oscillation mode of the CVG resonator of the angle sensor according to the embodiment of the present description.
Fig. 9D illustrates the second n-2 oscillation mode of the CVG resonator of the angle sensor according to the embodiment of the present description.
Fig. 10 illustrates how the acceleration sensitivity can be introduced into the n-2 vibration mode of the angle sensor.
Fig. 11A and 11B illustrate how the oscillation frequency of a mode of a pair of modes may be controlled according to embodiments of the present description.
[ detailed description ] embodiments
In the following description, numerous specific details are set forth in order to provide a thorough description of various embodiments disclosed herein. However, it will be understood by those skilled in the art that the presently described invention may be practiced without all of the specific details discussed below. In other instances, well-known features have not been described in order not to obscure the invention.
Embodiments described herein relate to an angle sensor having a coriolis vibration gyroscope resonator configured to oscillate along a pair of n-1 and a pair of n-2 modes that preferably have rotational symmetry equal to or greater than 8 (i.e., powers of 2 (i.e., 8, 16, 32, 64, etc.)). Rotational symmetry (also referred to in biology as radial symmetry) is a property that a shape will have when it looks the same after a partial revolution of a certain rotation. The rotational symmetry of an object refers to the number of different orientations that it appears to be the same.
Fig. 1 shows a picture of a fragment of an angle sensor 10 according to an embodiment of the present description, comprising a
According to the embodiment of the present description, a plurality of electrodes 22 are arranged on the
According to the present presented embodiment and as detailed below, the
According to the present presented embodiment and as detailed below, the electrode 22 further comprises for each modality: a first pair of biased quadrature electrodes aligned with the 360/(8 x n) degree off-axis if no drive or sense electrodes or no biased tuning electrode pair are aligned with an axis that is 360/(8 x n) degrees clockwise off-axis from the anti-node axis of each mode; and a second pair of biased quadrature electrodes aligned with the 360/(8 x n) degree offset axis if no drive or sense electrodes or no biased tuning electrode pair are aligned with an axis that is 360/(8 x n) degrees counterclockwise offset from the anti-node axis of each mode.
According to embodiments of the present description and as detailed below, each of the electrodes (drive electrode, sense electrode, bias tuning electrode, bias quadrature electrode) described above may be a differential electrode comprising at least two electrodes arranged side by side. According to embodiments of the present description, the sensor may be sealed with a lid in a vacuum environment to maintain a high quality factor (Q).
Fig. 2 schematically illustrates elements of a sensing circuit 24 of the angle sensor 10 according to an embodiment of the present description, the sensing circuit 24 comprising a
According to embodiments of the present description, the
FIG. 3 illustrates the operation of the sensing circuit 24 according to embodiments of the present description: the
According to the present described embodiment, the output of the
According to the present described embodiment, the
According to an embodiment of the present description, the
According to embodiments of the present description, the drive frequency and phase of a mode may be determined by the signal sent to the drive electrode of that mode.
According to the embodiments presented, the
Fig. 4A shows a schematic diagram of a
According to the present described embodiment, the first
According to the present presented embodiment, the first
According to the present presented embodiment, the first
FIG. 4B shows a schematic diagram of a drive circuit 48 of the
For ease of reference, the
FIG. 5 illustrates
According to the present described embodiment, the
According to the present described embodiment, the
According to the present described embodiment, the
According to the present described embodiment, the input drive voltage is split into two halves that are out of phase, e.g., such that the
Because the
The
Fig. 6 illustrates a portion of the nodal and anti-nodal axes of the
The first n-2 mode of the
The second n-2 mode of the
The second anti-node axis 94 of the first n-2 mode is illustrated in fig. 6 at an angle of pi/2 relative to the anti-node axis 90 of the first n-2 mode. According to an embodiment of the present disclosure, offset tuning electrodes (not shown) are arranged on each side of the periphery of
Similarly, the second anti-node axis 96 of the second n-2 mode is illustrated in fig. 6 at an angle of pi/2 relative to the anti-node axis 92 of the second n-2 mode. According to an embodiment of the present disclosure, if no sense and drive electrodes are aligned with axis 96, a bias tuning electrode (not shown) is disposed on each side of the periphery of
According to the present presented embodiment, a first offset quadrature axis 98 associated with the first n-2 mode is illustrated, at an angle of pi/8 counterclockwise with respect to the first anti-node axis 90; and illustrates a second offset quadrature axis 100 associated with the first n-2 mode, at an angle of pi/8 counterclockwise with respect to the first anti-node axis 94. According to the embodiment of the present description, if no sense or drive or bias tuning electrodes of the modes of the
According to the present presented embodiment, a third offset quadrature axis 102 associated with the second n-2 mode is illustrated, at an angle of pi/8 counter-clockwise with respect to the second anti-node axis 92; and illustrates a fourth offset quadrature axis 104, also associated with the second n-2 mode, at an angle of pi/8 counterclockwise with respect to the first anti-node axis 96. According to the embodiment of the present description, if no sense or drive or bias tuning electrodes of the modes of the
Fig. 7 illustrates the positions of electrodes corresponding to the two n-2 modes illustrated in fig. 6 in an embodiment where each electrode includes only two sub-electrodes. For example, the drive electrode at position D1 may include two drive sub-electrodes 22', 22 "at positions D1+, D1-, respectively, symmetrically arranged on the periphery of the
Similar to the above, the drive electrode 22 at position D2 may include two drive sub-electrodes 22 ', 22 "at positions D2+, D2-, respectively, which are symmetrically arranged on the periphery of the
As illustrated in fig. 7, the electrodes 22 at positions BT1, BT2, BX1, and BX2 may each include two sub-electrodes 22', 22 "symmetrically arranged on each side of the periphery of the
Note that the combination of the electrode 22, the
1/applying an AC voltage signal at or near the resonant frequency of the n-2 mode of vibration on the D1 or D2 electrodes will excite mechanical vibratory motion of the CVG mechanical resonator disk in the first n-2 mode or the second n-2 mode, respectively; and
2/vibrational motion along the first or second n-2 mode of the CVG
In both cases, a DC voltage must be applied across the electrostatic gap to polarize it so that either the drive function or the sense function of a particular electrostatic transducer can be performed. To eliminate electrostatic feedthrough as disclosed, for example, in U.S. application No.14/836462, which is hereby incorporated by reference, the drive and sense electrodes are divided into positive (+) and negative (-) sub-electrodes, respectively. Differential AC voltage signals (equal in amplitude but opposite in phase/polarity) are applied to the sub-electrodes in positions D1+ and D1-, respectively. This excites oscillatory motion of the CVG
According to the embodiment of the present description, when the disk or ring gyroscope or
In a similar manner, the BX 2electrode may pull the first n-2 mode Clockwise (CW) toward the BX2 electrode.
According to the present presented embodiment, the effect on the second n-2 mode is exactly the opposite for BX1 and BX2 (i.e., BX1 pulls the second n-2 mode clockwise/CW and BX2 pulls the second n-2 mode counter clockwise/CCW). However, if the first n-2 mode is driven with a constant amplitude (e.g. using a phase locked loop or PLL and Automatic Gain Control (AGC) circuit in the driven mode) and the second n-2 mode is not driven (open loop) or actively driven with zero motion (forced balance operation), the second mode amplitude will be very small and not significantly affected by the BX electrode. In this case, by using a combination of tuning voltages applied to BX1 and/or BX2 to properly align the drive mode shapes, the sense mode motion in response to the applied rotation will self-align because the force generated by the coriolis effect is the cross product of the radially oriented velocity and the vertically (out-of-plane) oriented axis of rotation. For the n-2 mode, the direction of this force is 45 ° to the drive axis, which is the sensing mode. In other words, if the first n-2 mode is driven with the D1 electrode on axis 90, and BX1 and BX2 are properly tuned to exactly align the second n-2 mode to axis 90, then the net driving force due to the coriolis effect under rotation is oriented along the n-2 mode 2 (sensing mode) axis, which is axis 92 in fig. 7. According to the embodiments of the present description, electrode GB may be biased to a non-zero DC value, and the BX1/BX 2electrodes may be held nominally at DC ground (until a tuning potential is applied to them), or the GB electrode may be held at ground potential, and then the BX1/BX2 may be DC biased.
Fig. 8 illustrates the actual position of the control and sensing electrodes of the
According to the present described embodiment, the drive electrode for the first normal mode may comprise two drive sub-electrodes 22', 22 "at positions labeled N1D1+, N1D1-, respectively, which are symmetrically arranged on the periphery of the
According to the present described embodiment, the drive electrodes for the second normal mode may comprise two drive sub-electrodes 22', 22 "at positions labeled N1D2+, N1D2-, respectively, which are symmetrically arranged on the periphery of the
According to an embodiment of the present introduction, the sensor of fig. 8 comprises sensing and driving sub-electrodes as disclosed in fig. 7 at positions N2D1+, N2D1-, N2S1+, N2S1-, N2D2+, N2D2-, N2S2+, N2S 2-for driving and sensing oscillations along normal modes with anti-node axes 90 and 92. According to the present described embodiment, the positions of the drive electrodes and the sense electrodes for the modes may be switched to one side or the other of the periphery of the
According to the embodiments of the present description and as illustrated in fig. 8, there is no biasing tuning electrode of the first or second normal mode on the periphery of the
According to the embodiment of the present description and as illustrated in fig. 8, because the anti-node axis 94 (along axis 90) of the third n-2 normal mode of the
According to the present described embodiment and as illustrated in fig. 8, because the direction of the pi/8 clockwise deviation from the anti-node axes 90 and 94 of the third n-2 normal mode of the
According to the present presented embodiment, having the
The electrodes having the arrangement shown in fig. 8 allow simultaneous operation of both n-1 and n-2 pairs of modes of the CVG
Fig. 9A illustrates the maximum deformation of the resonator when the
Fig. 9B illustrates the maximum deformation of the resonator when the
Fig. 9C illustrates the maximum deformation of the resonator when the
Fig. 9D illustrates the maximum deformation of the resonator when the
For the sake of clarity, the magnitude of the deformation of the
Fig. 10 illustrates the physical mechanism by which acceleration sensitivity would be introduced to the n-1 vibration mode used in the high precision rotation sensor disclosed herein if the n-1 vibration mode was not corrected by a loop as illustrated in, for example, fig. 4A. The n-1 mode is highly sensitive to linear acceleration in the face (X as shown, inferred as Y). Due to non-linear effects (geometry and material), a non-zero strain field is generated due to Ax acceleration or Ay acceleration. This non-zero strain then disturbs the n-2 mode in frequency, which causes them to measure an artificial apparent rotation, which leads to gyroscope errors. This introduction discloses the simultaneous application of multi-modal control of the type disclosed in U.S. application No.15/253694 to both the n-1 and n-2 modalities (as opposed to the n-2 and n-3 modality control disclosed in U.S. application No. 15/253694). By applying the forced balancing technique as disclosed in U.S. application No.15/253704 to the n-1 mode, the amount of strain generated by in-plane acceleration is greatly reduced, which minimizes the impact on the high-precision n-2 mode. At the same time, a coarse estimate of the rotation rate is obtained from the n-1 modal controller and combined with a high accuracy n-2 modal rotation rate readout to create a higher dynamic range rotation measurement system, as disclosed in U.S. application No.15/253694 (again after the n-2 and n-3 modal pairs are replaced by n-1 and n-2 modal pairs in U.S. application No. 15/253694).
Fig. 11A and 11B illustrate how the oscillation frequency of a mode of a pair of modes may be controlled according to embodiments of the present description. Without using a control loop as illustrated in fig. 4 to operate a
Having now described the invention in accordance with the requirements of the patent statutes, those skilled in the art will understand how to make changes and modifications to the invention to meet the specific requirements or conditions thereof. Such changes and modifications can be made without departing from the scope and spirit of the present invention as disclosed herein.
For purposes of illustration and disclosure, the foregoing detailed description of exemplary and preferred embodiments has been presented as required by the law. It is not intended to be exhaustive or to limit the invention to the precise form described, but only to enable others skilled in the art to understand how the invention may be adapted for a particular use or embodiment. The possibilities of modifications and variations will be apparent to a person skilled in the art.
The description of the exemplary embodiments is not intended to be limiting, and these embodiments may have included tolerances, feature dimensions, specific operating conditions, engineering specifications, etc., and may vary from embodiment to embodiment or from prior art to prior art, and no limitation should be implied therefrom. The applicant has made this disclosure in relation to the current state of the art, but advances are also contemplated and future adaptations may take these into account, i.e. in accordance with the current state of the art at the time.
Preferably comprising all of the elements, parts and steps described herein. It will be understood that any of these elements, parts and steps may be replaced or deleted entirely by other elements, parts and steps as will be apparent to those skilled in the art.
Broadly, this document discloses at least the following: an angle sensor comprising a Coriolis Vibration Gyroscope (CVG) resonator that is capable of oscillating along a first pair of normal n-1 modes comprising a first normal mode and a second pair of normal n-2 modes comprising a third normal mode and a fourth normal mode; the sensor further includes: a drive electrode and a sense electrode aligned along the anti-node axis of each mode; and a pair of offset tuning electrodes aligned with the anti-node axis of each mode if no pair of drive and sense electrodes is aligned with the anti-node axis.