RU2714870C1 - Micromechanical gyroscope - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: invention relates to the field of accurate instrument making, in particular to the vibration micromechanical gyroscopes (MMG), which measures the angular velocity. Invention consists in the fact that in MMG with built-in temperature sensor, quadrature electrodes and controlled voltage sources, outputs of which are connected to quadrature electrodes, signal conversion device, which output is connected to inputs of controlled voltage sources, at that output of built-in temperature sensor is connected to input of signal conversion device, signal conversion device realizes functional dependence of voltage on quadrature electrodes compensating for quadrature noise from output signal of built-in temperature sensor.

EFFECT: higher MMG accuracy.

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Description

The invention relates to the field of precision instrumentation, in particular to vibratory micromechanical gyroscopes (MMG), measuring angular velocity.

In these MMGs, a conductive moving mass (PM) is suspended from a support fixed to the base using an elastic resonant suspension. The electrodes located on different PM suspension axes provide measurement of PM motions and the formation of forces (moments) for controlling PM motions, including the formation of PM vibrations along the axis of primary vibrations and the measurement of PM motions along the secondary vibrations axis. To excite PM oscillations along the axis of primary oscillations in MMG, an electronic unit is used, called the primary oscillation excitation unit at a frequency f ₁ (for modern MMG f ₁ > ₁₀ kHz). To form the forces acting on the PM and measure the displacements of the PM along the axis of primary vibrations, electrodes are used that are in the form of combs, while some electrodes are located on the PM (moving electrodes), and others, stationary, on the base. Such electrodes are called comb electrodes.

PM oscillations along the axis of secondary vibrations occur under the action of Coriolis forces arising from the rotation of the MMG base around the MMG sensitivity axis. In this case, the axis of sensitivity and the axis of primary and secondary oscillations are orthogonal to each other. Vibrations of the PM caused by the Coriolis force contain information about the measured angular velocity ΩMM, they are useful.

These PM oscillations are measured using electrodes located along the axis of the secondary oscillations; changes in the capacitances of these electrodes are converted in the secondary oscillation channel into a signal proportional to Ω.

However, harmful vibrations of PM are superimposed on them, which are caused by forces acting on the PM, due to manufacturing errors of the sensitive element (SE) MMG.

The indicated errors may include deviations from the given sizes of the PM suspension elements and electrodes, the presence of residual pressure in the CE chamber, etc.

The amplitude of harmful PM vibrations can significantly exceed the amplitude of PM vibrations caused by Ω, which makes it difficult to measure the useful component of vibrations and, accordingly, reduces the accuracy of MMG. Harmful PM vibrations, phase-shifted relative to useful by ± 90 °, or forces orthogonal to the Coriolis force, are called quadrature noise. To suppress it, various methods are used, in particular, synchronous detection of signals in the channel of secondary vibrations. For synchronous detection, a demodulator with a reference signal is used, the phase of which coincides with the phase of the useful signal. In this case, the amplitude of the useful signal is extracted, and the quadrature signal is converted into a high-frequency signal, the spectrum of which begins with a frequency of 2f ₁ . This component is filtered by a low-pass filter. However, if the phase of the reference signal is unstable, then the suppression of the quadrature signal by the demodulator is insufficient and, in high-precision MMGs, various methods of compensating for the quadrature interference are additionally applied.

The operation of vibrating MMGs is described in detail in the literature [1, 2]. In [2, p. 101], methods for suppressing quadrature interference are described, one of which is the formation of a constant voltage of a certain magnitude on the so-called quadrature electrodes.

Ways to suppress quadrature noise in MMG, including through the use of quadrature electrodes, are given in domestic and foreign publications [3-7].

In MMR of the RR type, quadrature electrodes can be flat electrodes in the form of sectors partially located above the tooth zone of the comb electrodes or holes in the PM [3, 4]. In MM-type LL-type quadrature electrodes are performed as comb electrodes with teeth displaced from the central position [5].

If compensating voltage U _{E is} formed on the quadrature electrodes, then due to a change in the overlap area during PM oscillations along the axis of the primary oscillations, the electrostatic force changes with the primary oscillation frequency between these electrodes and the PM. These changes depending on the position of the electrodes relative to the axis of sensitivity are in phase or out of phase with quadrature noise, their amplitude is proportional to (U _E ) ² [5]. Due to the choice of quadrature electrodes and the selection of U _E, it is possible to form electric field forces F _E (or moments) that are in antiphase to the forces (moments) that cause quadrature interference in the MMG and are equal in amplitude. In this case, the force F _e compensates for the forces causing the appearance of quadrature noise.

Thus, the compensation of the quadrature noise in the MMG described above, which are analogues of the proposed device, is achieved by connecting the voltage source with the quadrature electrodes, while the voltage required to suppress the quadrature noise is selected by calculation [5, formulas on pages 10, 11 ] or experimentally [Fig. 7 of patent 3].

The disadvantage of analogues is that the forces causing quadrature interference in the MMG can change with changing ambient temperature. This is noted in [2, p. 101]. Therefore, when choosing a fixed value of voltage U _E, compensation for quadrature interference in the entire range of operating temperatures is not provided, which affects the accuracy of MMG and, accordingly, narrows the scope of such MMG.

Known MMG with a built-in temperature sensor (VDT) and the temperature correction unit (BTK) of the output signal, the input of which receives signals from the output channel of the secondary oscillations and VDT [8-11]. The signal from the output of the secondary oscillation channel, in addition to the signal proportional to Ω, contains an additive component dependent on the ambient temperature. After calibrating the MMG, this component, which consists in determining this component at different angular velocities of rotation of the MMG and ambient temperatures, is compensated with an achievable error in the BTX.

Known MMG with quadrature electrodes and connected to them controlled voltage sources [6], which is selected as a prototype. The inputs for controlling voltage sources in this MMG are connected to a signal conversion device, which also depends on the gap (d) between the quadrature electrodes and the PM. A change in the quadrature interference caused by a change in the ambient temperature in this MMG, as well as in the MMG according to patents [3-5], leads to a deterioration in their accuracy.

The technical problem to be solved is the reduction of the influence of changes in ambient temperature on the degree of suppression of quadrature interference by quadrature electrodes.

Achievable technical result - improving the accuracy of MMG.

The essence of the invention lies in the fact that in MMG with a built-in temperature sensor, quadrature electrodes and controlled voltage sources, the outputs of which are connected to quadrature electrodes, a signal conversion device, the output of which is connected to the inputs of controlled voltage sources, while:

- the output of the built-in temperature sensor is connected to the input of the signal conversion device;

- the signal conversion device implements the functional dependence of the voltage on the quadrature electrodes, compensating for the quadrature noise, from the output signal of the built-in temperature sensor.

The proposed device can be used both in MMR RR- and LL-type.

In FIG. 1 shows a block diagram of the proposed MMR RR-type, in FIG. 2 - LL-type described in the patent [5].

In FIG. 1 and 2, the following notation is accepted:

1 - the base on which the PM is suspended;

2 - elastic resonant suspension (hereinafter referred to as elastic suspension);

3 - source of alternating voltage supplied to the PM (hereinafter - IPN);

4 - PM;

5, 6 - fixed comb electrodes of the angle sensor / displacement sensor;

7, 8 - fixed comb electrodes of the torque sensor / force sensor;

9, 10 - stationary flat electrodes of the angle sensor located on the cover of the MMG above the PM (hereinafter referred to as measuring electrodes);

11, 12 - fixed flat electrodes of the angle sensor located on the cover MMG partially above the tooth zone PM (hereinafter - the first pair of quadrature electrodes);

13 - controlled voltage source (UIN);

14 - device for the excitation of primary oscillations (UVPK);

15 - channel secondary oscillations (KVK), which includes a capacitance-voltage Converter and a demodulator;

16 - temperature sensor built into MMG (VDT);

17 - a signal conversion device that implements the dependence of the voltage on the quadrature electrodes, compensating for the quadrature noise, on the output signal of the VDT (hereinafter - UPS);

18, 19 - the second pair of quadrature electrodes;

U ₀ is the supply voltage of the controlled voltage source;

U _KV is the voltage compensating for the quadrature noise;

U _OUT - the output of MMG.

The quadrature electrodes of CE LL-type (11, 12 and 18, 19 in Fig. 2), in contrast to CE RR-type, are comb. For quadrature electrodes 11, 12, the teeth on PM 4 are displaced from the central position upward vertically, and for electrodes 18, 19 - downward vertically. Depending on the phase of the quadrature interference, either electrodes 12, 18 or 11, 19 can be connected to element 13.

PM 4 can oscillate along the X axis (primary axis) and the Y axis (secondary axis).

In FIG. Figure 3 shows the experimentally obtained dependences of the quadrature noise on the ambient temperature, measured with the aid of the RCCB, for two domestic-made RR-type MMGs.

In FIG. 3 are indicated:

q is the quadrature interference;

T is the temperature measured using RCC;

q (T) is the dependence of the quadrature noise on the ambient temperature;

1 - dependence q (T) for the first MMG;

2 - dependence q (T) for the second MMG.

In FIG. Figure 4 shows the experimentally obtained dependences of the phase change of the reference signal of the demodulator (which is part of KVK 15, not shown in Fig.) On the ambient temperature for two MMR RR-types of domestic design, in which the elements 14, 15 are implemented through the use of a specialized integrated circuit, described in [13].

In FIG. 4 are indicated:

Δϕ is the phase shift of the reference signal of the demodulator;

T is the temperature measured using RCC;

Δϕ (T) is the temperature dependence of the phase shift of the demodulator reference signal;

1 - dependence Δϕ (T) for the first MMG;

2 - dependence Δϕ (T) for the second MMG.

Conducting PM 4, which is made in the form of a disk, part of which sectors is made in the form of combs, is suspended from the base 1 by means of an elastic suspension 2 made in the form of torsion bars. PM 4 can move both around an axis perpendicular to the plane of the disk (axis of primary vibrations X) and around a horizontal axis (axis of secondary vibrations Y).

Fixed electrodes 5-8 are comb electrodes, some of which are used in the formation of the PM 4 angle sensor (elements 7, 8), and others as a moment sensor (elements 5, 6). These electrodes are connected to UVPK 14.

The AC voltage source 3 is connected to PM 4.

The inputs of the channel of the secondary oscillations 15 are connected to the measuring electrodes 9, 10, and one of the outputs UVPK 14.

The measuring electrodes 9, 10 are located symmetrically with respect to the horizontal axis. They are connected to the inputs of the capacitance-voltage converter (not shown in Fig. 1), which is part of the KVK 15. The options for constructing the secondary-oscillation channel are described in sufficient detail in various publications, for example, in [1, 2, 8].

The output of the UIN 13 is connected to the quadrature electrodes 11, 12.

The output of the VDT 16 through the UPS 17 is connected to the control input of the UIN 13. The proposed device works as follows: A current passes through the interelectrode capacitances formed by the PM 4 and electrodes 7-10, the magnitude of which is determined by the voltage and frequency of the IPN 3 and the values of the interelectrode capacitances, which depend on positions of PM 4. These currents are converted by UVPC 14 at moments causing PM 4 vibrations around the axis of primary vibrations, and in KVK 15 when the base rotates with an angular velocity Ω into a signal proportional to Ω.

To suppress the quadrature noise on the quadrature electrodes 11, 12 with the help of a UIN 13, the voltage is increased by observing the signal at the output of the capacitor-voltage converter KVK 15 at Ω = 0. If in this case the amplitude of the observed signal decreases, continue this procedure until the amplitude begins to increase, and the phase of the signal changes to the opposite. The voltage value at the electrodes 11 and 12, corresponding to the minimum of the observed signal, is a compensation voltage.

If, when the voltage at the quadrature electrodes 11, 12 increases, the signal at the output of the capacitor-voltage converter increases, then it is necessary to connect the output of the UIN 13 to another pair of quadrature electrodes, 18 and 19, located symmetrically to the electrodes 11, 12 relative to the Y axis.

By setting the ambient temperature, for example, when installing MMG in a heat chamber, measuring the signal at the output of the VDC 16 (U _T ) and repeating the above procedure for determining the compensation voltage U _E , you can obtain the data necessary to determine the dependence of the voltages compensating for the quadrature noise from the output signal VDT 16: U _E = f (U _T ). UPS 17, which implements this dependence, can be formed using digital (for example, a microcontroller with a digital-to-analog converter) or analog elements [12].

When the ambient temperature changes, a corresponding change in the signal at the output of the VDC 16 leads to such a change in the signal at the output of the UPS 16, which generates a voltage on the quadrature electrodes, corresponding to the value at which the quadrature noise is compensated.

An analysis of the experimentally obtained dependences q (T) and Δϕ (T) shown in FIG. 3, 4 demonstrates that:

- the change in the quadrature interference q (T) in the operating temperature range can be ≈10% of its average level. This shows that the suppression of quadrature interference by a fixed value of the compensation voltage on the quadrature electrodes is not effective enough;

- taking into account the change in Δϕ at the level of 0.5-1 °, the component of the MMG output signal due to the quadrature noise can be estimated as 0.5-1 ° / s. MMG error (zero signal instability) when the ambient temperature changes in the range of 125 ° C, is three orders of magnitude greater than the error at constant temperature.

- the nature of the dependences q (T) shows that they can be approximated in the UPS with an error of 1%. This allows, due to the implementation of the q (T) dependence in OOPS 17, to reduce the residual change in the quadrature interference in the operating temperature range to 0.005-0.01%, i.e., to reduce the MMG error (zero signal instability) by 2 orders of magnitude. Thus, by maintaining a high level of interference suppression during MMG operation over a wide temperature range, MMG accuracy is improved.

The claimed technical result is confirmed by a calculation carried out in the evaluation of the components of the MMG errors obtained in experimental studies of sensor samples.

Literature

1. Raspopov V.Ya. Micromechanical devices: Textbook / Tula: Grif and K., 476 p.

2. Acar S., Shkel A., MEMS Vibratory Gyroscopes: Structural Approaches to Improve Robustness, Springer, 2008, 262 pp.

3. RF patent No. 2344374.

4. RF patent No. 2320962.

5. US patent No. 8104364.

6. RF patent No. 2626570.

7. Belyaeva T.A. Compensation methods for quadrature interference in an RR-type micromechanical gyroscope / The dissertation for the degree of candidate of technical sciences, Concern Central Research Institute Elektropribor, 126 s, St. Petersburg, 2009, inv. No. 141187.

8. V.G. Peshekhonov et al. Test results for an installation batch of rr-type micromechanical gyroscopes / Gyroscopy and Navigation, No. 1 (72), 2011, pp. 37-48.

9. P. Prikhodko et al. Compensation of drifts in high-Q MEMS gyroscopes using temperature self-sensing, Sens.Actuators A: Phys. (2013), http://dx.doi.org/10.1016/j.sna2012.12.024.

10. Nekrasov Ya.A., Moiseev H.B., Lyukshonkov P. G., Pavlova SV., Improving the operational characteristics of the domestic RR-type micromechanical gyroscope / XXI St. Petersburg International Conference on Integrated Navigation Systems, 2014, pp. 226-235.

11. Results of the study of a MEMS gyroscope with temperature self-compensation / Y. A. Nekrasov, R. G. Lukshonkov // XX II St. Petersburg International Conference on Integrated Navigation Systems, 2015 - C288 - 293.

12. Handbook of nonlinear circuits: Designing devices based on analog function modules and integrated circuits. Ed. Sheingold D.Kh. / M.: Mir, 1977.

13. A. Ismail et al A HIGH PERFORMANCE MEMS BASED DIGITAL-OUTPUT GYROSCOPE. Transducers, 2013, Barcelona, 16-20 June 2013.

Claims (1)

A micromechanical gyroscope containing a support on the base to which a conductive moving mass is suspended on an elastic resonant suspension, capable of oscillating in two mutually perpendicular directions along the axes of primary and secondary vibrations, comb electrodes connected to the primary oscillation excitation device, the secondary oscillation channel with measuring electrodes, located along the axis of secondary oscillations, quadrature electrodes, controlled voltage source connected to quadrature electrodes, sun a triple temperature sensor, a signal conversion device, the output of which is connected to the input of a controlled voltage source, characterized in that the output of the built-in temperature sensor is connected to the input of a signal conversion device, which implements the experimentally determined dependence of the voltage on the quadrature electrodes, which compensates for the quadrature noise, from the output signal of the built-in temperature sensor.

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