RU2308682C1 - Method of adjusting resonance frequency of suspension of movable mass of gyroscope - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: method comprises determining mean value of the production of signals from the movement pickups in the axes of primary and secondary vibrations and measuring voltage at the additional electrode until the mean component of the production becomes zero. The gyroscope has movable mass that is provided with double-axes resonance suspension, two capacitive pickups of movement of the mass, two interface units, and phase detector, adder, and integrator connected in series.

EFFECT: simplified design enhanced precision.

2 cl, 2 dwg

Description

The invention relates to the field of micromechanics, in particular to micromechanical gyroscopes (MMGs) of vibration type and to schemes for adjusting the parameters of the vibrational loops of the suspension in these gyroscopes.

In MMG, the moving mass (PM) is attached to the base using at least a biaxial resonant suspension. The resonant frequency of the suspension along the axis of the primary vibrations is selected below the resonant frequency of the suspension along the axis of the secondary vibrations. MMG operating modes are possible both with coincidence of the resonant frequencies of the suspension, and work with a small shift of the resonant frequencies of these suspensions. In both cases, the adjustment of the resonant frequencies is carried out by using the so-called negative stiffness and is achieved by applying a voltage of a certain value to the electrodes, which are located on the axis of the secondary vibrations. An example of the implementation of such a adjustment is given on pages 412-413 in the book of V. Raspopov. Micromechanical devices, 2nd edition. Tool Gos. University, Tula, 2004, 475 pages. An example of MMG working with detuning the resonant frequencies of suspensions is given on page 451 of Fig.5.5.3. this book.

In the work [Peshekhonov V.G. et al. Results of the development of a micromechanical gyroscope. XII St. Petersburg International Conference on Integrated Navigation Systems May 23-25, 2005, pp. 268-274] describes an MMR of the RR type, in which electrodes located on the cover are used for control. The same electrodes can be used to reduce the resonant frequencies of suspensions, as was proposed in US Pat. US No. 6067858.

MMG, which is the adjustment of the resonant frequency of the suspension along the axis of the secondary vibrations by applying voltage to the corresponding electrodes, is described in US Pat. US No. 6067858 (see fig 23, column 22 of the description).

A method for adjusting the resonance frequency of the suspension along the axis of secondary vibrations in MMR RR-type and MMG itself are described in US Pat. US No. 6553833.

This method consists in generating voltages at the electrodes located along the axis of the secondary vibrations, moreover, two additional signals are generated to generate said voltage, the frequencies of which differ by + Δf and -Δf from F _{1 the} frequency with which the PM oscillates, which are supplied to the electrodes, located along the axis of the secondary vibrations. These additional signals cause PM vibrations along the axis of secondary vibrations, respectively, with frequencies F ₁ ± Δf. If the resonant frequency of the suspension along the axis of the secondary oscillations coincides with the frequency F ₁ , then the amplitudes of the PM vibrations at the frequencies F ₁ ± Δf are equal; if, for example, the resonant frequency of the suspension along the axis of the secondary vibrations is higher than F ₁ , then the amplitude of the PM vibrations at the frequency F ₁ + Δf is greater than F ₁ -Δf. As indicated in paragraphs 60-65 of column 4 of the patent description, Δf may be 100 Hz. Further, in accordance with the method described in the patent, the amplitudes of the signals of these frequencies obtained at the output of the capacitor-voltage 2 converter are isolated by detection (see FIG. 3 of the description), and depending on the difference of the extracted amplitudes, voltages are generated. To adjust the resonant frequency, the values of the generated voltages are changed until the amplitudes of these signals are equal.

A device that implements the described method for adjusting the resonant frequency of the suspension along the axis of secondary vibrations is shown in FIG. 3 of the description of US patent No. 6553833. It is a micromechanical gyroscope containing a moving mass on a biaxial resonant suspension, the first capacitive PM displacement sensor formed by electrodes located on the axis of the primary oscillations, and the first interface device (C / U 10 transducer in Fig. 3), the inputs of which are connected to these electrodes, a second capacitive PM displacement sensor formed by electrodes located on the axis of the secondary vibrations, and a second interface device (C / U 2 converter in FIG. 3), the inputs of which are connected to these Electrode electrodes disposed on the secondary oscillations axis, the synchronous demodulator (7), the test signal generator (6), the output of which through the voltage generating circuit (9) connected to the electrodes disposed on the axis of the secondary oscillations. MMG also contains an adaptive quadrature compensator (8), which provides reduction or suppression of quadrature interference.

The method of adjusting the resonant frequency of the suspension along the axis of the secondary vibrations in MMG and MMG, which uses the method described in US Pat. US No. 6553833, taken as a prototype.

Thus, to adjust the resonant frequency in the prototype, two additional signals are introduced that cause the PM to move along the axis of the secondary vibrations, and the PM movements caused by these signals are estimated, and the resonance frequencies of the suspension are matched by changing the voltage across the electrodes. Moreover, in the prototype, the quadrature component of the PM displacements is suppressed.

The disadvantages of the prototype method include the complexity for realizing the adjustment of the resonant frequency of the PM suspension in MMG, due to the fact that additional signal sources must be introduced into the prototype device, the frequencies of which should be tied to the resonant frequency of the suspension along the axis of primary oscillations, and additional demodulators for highlighting these signals. In addition, the presence of additional signals in a high-Q system, which is the PM suspension, leads to excitation of oscillations at the frequency of these signals, which narrows the dynamic range of MMG operation and reduces its accuracy. In addition, the criterion for fine tuning the resonant frequency is the equality of the amplitudes of the low-level signals, which limits the accuracy of this tuning. The presence of noise and interference in the amplification and signal conversion channel of the secondary oscillation circuit degrades this accuracy. An increase in the amplitudes of test signals to increase the accuracy of tuning by increasing the signal-to-noise ratio can lead to large disturbances of the PM from auxiliary test signals and, ultimately, to a deterioration in the accuracy of the MMG.

The disadvantages of the prototype device: insufficiently high accuracy and high complexity of the electronic part are due to the method used to adjust the resonant frequency.

The objective of the invention is to increase the accuracy of tuning the resonant frequency of the PM PMMG suspension along the axis of secondary vibrations. In addition, the object of the invention is to improve the accuracy of MMG and simplify its design.

The task is achieved in that in order to generate voltage on the electrodes used when adjusting the resonant frequency, the average component of the product of the signals of the moving mass displacement sensors along the axes of primary and secondary vibrations is determined and the generated voltage is changed until the obtained average component of the product becomes equal to zero

In addition, the task is achieved by the fact that in an MMG containing a moving mass on a biaxial resonant suspension, the first capacitive moving mass displacement sensor, formed by the first pair of electrodes located on the axis of the primary oscillations, and the first device for distinguishing the difference of currents flowing through the first pair of electrodes the inputs of which are connected to the first pair of electrodes, a second capacitive moving mass displacement sensor, formed by a second pair of electrodes located on the axis of the secondary vibrations, and the second With the aid of isolating the difference of currents flowing through the second pair of electrodes, the inputs of which are connected to the second pair of electrodes, additional electrodes located along the axis of the secondary vibrations are connected in series with the second phase detector, a summing device and an integrator, while the inputs of the phase detector are connected to the outputs of the capacitive sensors and the output with one input of the summing device, to the second input of which a constant voltage source is connected, the output of the summing device is connected to the input ntegratora, the output of which is connected to at least one of the additional electrodes.

Essentially, in the proposed method, instead of two test signals that are used in the prototype, a quadrature interference signal is used as a test signal. Due to the phase shift introduced by the resonant circuit by 90 ° at the resonant frequency, the quadrature noise when the resonant frequencies coincide is orthogonal to the signal of the PM displacement sensor along the axis of the primary oscillations. For a given zero value of the product of these orthogonal signals, an exact adjustment of the resonant frequencies is achieved. Due to the fact that the definition of the detuning of the resonant frequencies is determined by the phase difference, and due to the fact that the phase characteristic of the high-quality circuit has a large slope, the proposed method achieves a higher accuracy of tuning the resonant frequencies. And due to the fact that the quadrature interference, which is already present in the MMG, is used as a test signal, the MMG design simplification is achieved. An additional effect that provides an increase in the accuracy of MMG is the fact that due to the adjustment of the resonant frequency, the phase of the reference signal is adjusted relative to the useful one (component due to the action of Coriolis acceleration). This leads to a more accurate selection of the useful signal and the suppression of quadrature interference in the selection of the useful signal using a phase detector.

The implementation of the proposed method requires the introduction of only three additional elements: a phase detector, a summing device and an integrator, and essentially two elements of a phase detector and amplifier that are simple to implement, because summation of the signals can also be obtained in the amplifier, which, when feedback is introduced using a capacitor, can be converted into an integrator.

The claimed method and device are illustrated by drawings.

Figure 1 shows the amplitude-frequency and phase-frequency characteristics (frequency response and phase response) of the resonant suspension along the axis of the secondary vibrations.

Figure 2 shows the block diagram of MMG.

In figure 2, the following notation:

1 - PM

2,3 - the first pair of electrodes located along the axis of the primary oscillations

4,5 - the second pair of electrodes located along the axis of the secondary vibrations

6,7 - the first and second devices for distinguishing the difference of currents flowing respectively through the first and second pairs of electrodes

8 - phase shifting device

9 - phase detector

10 - low-pass filter (low-pass filter)

11,12 - electrodes of the comb engine

13 - control device of the comb engine

14 - alternating voltage generator

15 - an additional electrode located along the axis of the secondary vibrations

16 - constant voltage source

17 - second phase detector

18 - summing device

19 - integrator

The proposed method is as follows.

In figure 1. (upper part) shows the frequency response of the resonant suspension of PM MMG along the axis of secondary vibrations for two different Q factors (Q ₁ and Q ₂ , Q ₁ ≥Q ₂ ).

The frequency response corresponding to a lower value of Q (Q2) is depicted by a thin line. On the lower part of figure 1 shows the phase response corresponding to the specified values of the quality factor (Q ₁ and Q ₂ ). Three cases of MMG operation are possible: when the frequency of primary PM oscillations (or the frequency with which the drive operates) F _{d is} less than the resonance frequency of the PM MMG suspension along the axis of secondary oscillations F _p (case F _d1 ), greater than (case F _d2 ) and is equal to this frequency .

According to these cases, as can be seen from the graph for the phase response, the phase shift introduced by the suspension will be less than 90 °, more than 90 °, or equal to 90 °. On the PM along the axis of secondary vibrations, forces act, one of which is due to the action of Coriolis acceleration, and the other is due to manufacturing manufacturing errors that cause the appearance of quadrature interference. The quadrature interference at zero phase shift introduced by the resonant suspension of the PM MMG along the axis of the secondary oscillations (i.e., when F _d is much lower than the resonance frequency, for example, the value of F _d1 for Q ₂ , as shown in the phase response curve), is in phase with the signal at the output of the PM displacement sensor along the axis of the primary vibrations. The output signal of the PM displacement sensor along the axis of secondary vibrations with a stationary MMG is a quadrature noise. When multiplying the signals of the sensors for moving the moving mass along the axes of primary and secondary vibrations with a stationary MMG and highlighting the average component, the values of the latter will depend on the position F _d relative to the resonant suspension frequency of the PM MMG suspension along the axis of the secondary vibrations F _p .

In accordance with the three cases considered above, the value of this average component will be larger, smaller, and equal to zero. Therefore, by increasing the voltage at the electrodes located on the axis of secondary vibrations (or at least on one of them), due to the phenomenon of "negative stiffness", it is possible to reduce the resonance frequency of the PM MMG suspension along the axis of secondary vibrations and come to the case when the frequency F _p becomes equal with F _d1 . The arrow on the upper part of figure 1 shows the direction of movement of the resonant frequency F _p in the direction of F _d1 . For the second case, with a negative value of the average component of the product of the signals, the voltage at the electrodes located along the axis of the secondary oscillations decreases and the resonance frequency of the PM MMG suspension along the axis of the secondary oscillations increases. The arrow on the lower part of figure 1 shows the direction of movement of the resonant frequency F _p in the direction of F _d2 . In both the first and second cases, a change in the voltage at the electrodes until the average component reaches zero leads to a fine tuning of the resonance frequency of the PM MMG suspension along the axis of the secondary vibrations to the frequency F _d , i.e. the frequency with which the primary oscillations occur, which are chosen equal to the resonant frequency of the PM MMG suspension along the axis of the primary oscillations. If the resonant frequencies coincide (the third case), then the voltage at the electrodes does not change.

Thus, it is shown that without introducing additional signals into the MMG, using only the quadrature noise signal, it is possible to adjust the resonance frequency of the PM MMG suspension along the axis of secondary vibrations F _p to the frequency F _d . Note that the proposed method can be applied in MMG, in which special measures are not introduced (for example, such as a two-mass suspension, or the introduction of mechanical restraints of PM along the orthogonal axis in the design, as was done in MMG f. Analog Devices ADXRS150) by suppression of quadrature interference. Note the additional advantages of the proposed method. Due to the fine tuning of the resonant frequencies of the PM suspensions, the reference signal of the demodulator emitting the Coriolis acceleration signal is exactly in phase with the Coriolis acceleration carrier, which ensures the maximum transmission coefficient of the demodulator for the useful signal and the complete suppression of quadrature interference.

In the MMG flowchart, in which the proposed method is implemented, in FIG. 2, on the two sides of the PM 1, a pair of electrodes 2, 3 are located along the axis of primary vibrations, a pair of electrodes 4, 5 are located along the axis of secondary vibrations. The first and second difference extraction devices currents flowing through pairs of electrodes (6 and 7, respectively) are connected by inputs to the first pair of electrodes 2, 3 and the second pair of electrodes 4, 5. The output of the first device for isolating the difference of currents 6 through a phase shifting device 8 is connected to one of the inputs of the phase detector 9. Phase output the tractor 9 is connected to the input of the low-pass filter 10, the output of which is the output of the MMG. The output of the second current difference device 7 is connected to the other input of the phase detector 9. The output of the first current difference device 6 is connected to the input of the comb motor control device 13, the outputs of which are connected to the electrodes of the comb motor located along the primary axis of PM 1. With PM 1 the output of the alternating voltage generator 14 is connected. The additional electrode 15 is located along the axis of the secondary vibrations. The second phase detector 17, the summing device 18 and the integrator 19 are connected in series between the output of the second current difference device 7 and the output of the electrode 15. The output of the constant voltage source 16 is connected to one of the inputs of the summing device 18.

MMG works as follows.

The alternating voltage generator 14 creates voltages between the PM 1 and the electrodes 2-5, through which a current flows, depending on the capacitance of the capacitors formed by these electrodes and the PM 1. Current difference devices 6, 7 distinguish the differences of the currents flowing through the pairs of electrodes 2, 3 and 4, 5. The distinguished differences in currents are proportional to the displacements of PM 1 along the corresponding axes. Thus, the devices for distinguishing the difference of the currents 6, 7 together with the pairs of electrodes 2, 3 and 4, 5 form respectively capacitive displacement sensors PM 1 along the axis of primary and secondary vibrations. The first device for distinguishing the current difference 6 together with the control device of the comb engine 13, a pair of electrodes 2, 3 and 11, 12, and PM 1 form a self-oscillating circuit on the resonant suspension, in which oscillatory movements of PM 1 along the axis of primary vibrations occur. Under the influence of Coriolis accelerations, PM 1 can oscillate with the frequency of primary oscillations or, as they say, with the frequency of a drive. The amplitude of these oscillations, which is proportional to Coriolis accelerations, is extracted by a phase detector 9, the input of the reference signal of which receives the output signal of the first current difference device 6 through the phase shifter 8. The low-pass filter 10 suppresses the high-frequency components of the output signal of the phase detector 9 and extracts a low-frequency component, which and is a useful signal. If the resonant frequency of the PM 1 suspension along the axis of secondary vibrations F _p coincides with the frequency F _{d of the} primary PM 1 oscillations, then the phase shift introduced by the device 8 can be set to zero. Note that in the case where F _d <F _p (case F _d1 ), the shift φ is set equal to 90 ° if the resonance frequencies are not tuned.

Consider how the introduced elements 17-19 provide automatic adjustment of F _p to F _d1 .

Let us denote the voltage at the output of the first current difference device 6 - U ₆ , and the voltage at the output of the second current difference device 7 - U ₇ . These stresses for the case F _d <F _p can be represented in the form of expressions:

where Uп (t), Uкв (t) are the useful signal and the quadrature noise, respectively.

If β is denoted by the phase shift of the signal introduced by the PM1 suspension along the axis of secondary vibrations (the value of β can be determined from the phase response in Fig. 1), then at F _d ≈F _p expression (2) takes the form

Assuming that the measured angular velocity is a variable signal and changes, for example, according to a harmonic law, the value of the quadrature noise exceeds the useful signal, which often takes place in practice, i.e. the condition is satisfied

Assuming that the phase detector is implemented as a series-connected analog multiplier and low-pass filter, we obtain that at the output of the phase detector 17, the output signal will be proportional to the value of Cos (β-90 °). This means that for the case when F _d is to the left of F _p , the output voltage of the phase detector 17 will be of one sign (for example, positive), when F _d is to the right of F _p , the output voltage of the phase detector 17 will be of a different sign (for example, negative), and if these frequencies are equal, β = 0 and the output voltage of the phase detector 17 will be 0. At zero voltage of the source 16, the output signal of the summing device 18 is equal to the input. When the average component of the output signal of the phase detector 17 deviates from zero, the output voltage of the integrator 19 will change, respectively, the voltage at the electrode 15 will change. This change will lead to a change in the resonance frequency of the PM 1 MMG suspension along the axis of secondary oscillations F _p. In this case, the frequency will change until the phase difference of the signals at the input of the phase detector 17 becomes 90 °, i.e. until the resonant frequencies of the suspensions match.

In the case when it is necessary to work with some detuning Δf (Δf = F _p -F _d ) between the resonant frequencies (for example, to ensure a sufficiently wide MMG bandwidth), the desired detuning can be set by selecting the voltage of the source 16 (U ₀ ). It is selected as follows. The phase shift value (β ₀ ) corresponding to the desired detuning is determined from the phase response and the value is set in accordance with the expression

.

.

The magnitude of the phase shift introduced by the phase-shifting device 8 is chosen equal to (90 ° + β ₀ ) or (90 ° -β ₀ ). With this choice, the resonance frequency of the PM 1 MMG suspension along the axis of secondary oscillations F _p will stabilize and remain equal to Δf + F _d due to a change in the voltage at the output of the integrator 19 in the case when β ₀ changes due to a change in the frequency F _p (for example, due to temperature changes). The suppression of quadrature interference and the selection of the useful signal by the phase detector 9 occurs in the MMG shown in FIG. 2 in the same way as when Δf = 0.

Thus, the proposed method for adjusting the resonant frequency can be implemented in MMG operating both at reduced resonant frequencies and at diluted frequencies. Note that the implementation of elements 8-10 and 16-19 is possible without changing the essence of the invention on discrete elements, in the form of a microcontroller or a specialized chip, including elements 6, 7, 13, 14.

Claims (2)

1. The method of adjusting the resonant frequency of the suspension of the moving mass of the micromechanical gyroscope along the axis of secondary vibrations, which consists in generating voltage at least one of the electrodes located along the axis of the secondary vibrations, characterized in that they determine the average component of the product of the signals of the moving mass displacement sensors along the primary axes and secondary vibrations and change the generated voltage until the obtained average component of the product becomes equal to zero. 2. A micromechanical gyroscope containing a moving mass on a biaxial resonant suspension, a first capacitive moving mass displacement sensor formed by a first pair of electrodes located on the axis of the primary oscillations, and a first difference device for distinguishing currents flowing through the first pair of electrodes, the inputs of which are connected to the first pair electrodes, a second capacitive moving mass displacement sensor, formed by a second pair of electrodes located on the axis of the secondary vibrations, and a second difference extraction device currents flowing through the second pair of electrodes, the inputs of which are connected to the second pair of electrodes, and additional electrodes located along the axis of the secondary oscillations, while the output of the first difference extraction device is connected to the comb motor control input and connected to one of the inputs of the phase detector through a phase shifter the output of which is connected to the input of a low-pass filter, the output of which is the output of a micromechanical gyroscope, characterized in that it is connected in series the second phase detector, implemented as a series-connected analog multiplier and a low-pass filter, a summing device and an integrator, while the inputs of the second phase detector are connected to the outputs of the capacitive sensors, and the output with one input of the summing device, to the second input of which a constant voltage source is connected , the output of the summing device is connected to the input of the integrator, the output of which is connected to at least one of the additional electrodes.

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