KR100846481B1 - Signal processing apparatus for a vibratory gyroscope with high SNR and method thereof - Google Patents

Abstract

Disclosed is a low noise signal processing apparatus and method for a vibratory gyroscope. The signal processing apparatus of the vibration type gyroscope according to the present invention includes a self oscillation unit, a phase control unit, a signal demodulation unit, and an angular velocity signal generation unit. The self oscillation unit receives a horizontal displacement signal of a vibratory gyroscope and generates a drive signal that is out of phase with the horizontal displacement signal by a horizontal self-oscillation angle, and the phase controller controls a phase difference between the drive signal and the first demodulation phase. A first demodulation phase signal and a second demodulation phase signal that is out of phase with the driving signal and a second demodulation phase, and the signal demodulation unit demodulates the demodulation signal according to the vertical displacement signal of the gyroscope and the first demodulation phase signal; A second demodulated signal demodulated according to the signal and the vertical displacement signal and the second demodulated phase signal, and the angular velocity signal generation unit receives the first demodulated signal and the second demodulated signal as inputs of the gyroscope. Generate an angular velocity signal proportional to the angular velocity. By generating two demodulation phase signals with a difference in demodulation phase angle and generating an angular velocity signal with the difference, the noise components of the same frequency band as the vertical displacement signal, that is, the noise components due to the driving signal and the demodulation phase signal, etc. are effectively removed. The signal-to-noise ratio (SNR) can be maximized.

Description

Signal processing apparatus for a vibratory gyroscope with high SNR and method

1 is a block diagram showing a signal processing apparatus of a conventional vibration type gyroscope.

2 is a conceptual diagram of a vibratory gyroscope.

3A and 3B are graphs showing frequency resonance characteristics of a vibrating gyroscope.

4 is a circuit diagram illustrating a capacitance model of a vibratory gyroscope.

5 is a block diagram showing an embodiment of a signal processing apparatus of a vibrating gyroscope according to the present invention.

6 (a) to 6 (e) are waveform diagrams of signals obtained as a result of simulation performed for comparing the conventional signal processing apparatus with the signal processing apparatus according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus of a vibration type gyroscope, and more particularly, to a low noise signal processing apparatus and method for reducing a bias component caused by noise.

In general, a gyroscope is known as an angular velocity measuring device using the characteristics of a rotating body. By the way, the conventional rotary gyroscope is bulky, high price for high precision, and has the disadvantage of being easily damaged by shock and vibration, a small volume and low-cost vibration type gyroscope is widely used.

1 is a block diagram showing a conventional signal processing apparatus for a vibratory gyroscope. For convenience of description, in FIG. 1, capacitance / voltage converters 110 and 120 (hereinafter referred to as C / V converters) for converting the vibratory gyroscope 100 and the capacitance signals C _Y and C _Z of the gyroscope into voltage signals are shown. Shown together.

Referring to FIG. 1, the signal processing device includes a self oscillator 200 and a demodulator 210. The self oscillator 200 generates a drive signal V _D from the horizontal displacement signal Vc _y obtained by C / V conversion of the horizontal displacement capacitance C _Y of the gyroscope. The demodulator 210 demodulates the vertical displacement signal Vc _{z obtained} by C / V conversion of the vertical displacement capacitance C _Z of the gyroscope to generate an angular velocity signal V _R. Ideally, when the horizontal self oscillation angle of the self oscillator 200 is π / 2 radians, the angular velocity signal V _R follows the input angular velocity signal Ω _x applied to the gyroscope.

However, due to the presence of various parasitic capacitances, the actual signal is mixed with various noises. The main noise sources are noise 31 caused by the driving signal V _D and noise 32 caused by signals generated by the self oscillator 200. These noises cannot be removed by band filtering because their frequency bands are similar to those of the vertical displacement signal Vc _z and affect the final output angular velocity signal V _R. As a result of the noise, the signal appearing in the angular velocity signal V _R is represented by a constant DC bias component, and thus it is called a zero rate output (ZRO). In addition, such a bias component is a main cause of the drift, which changes in characteristics with time. That is, in the presence of noise, since the angular velocity signal V _R is represented by the sum of the pure angular velocity signal component and ZRO, the pure angular velocity signal cannot be obtained only, and there is a problem in that a drift occurs in which characteristics vary with time.

SUMMARY OF THE INVENTION The present invention provides a signal processing apparatus and method of a vibrating gyroscope having a high signal-to-noise ratio (SNR) by removing noise, particularly noise in a frequency band such as a vertical displacement signal, in a signal processing of a vibrating gyroscope. To provide.

The oscillation gyroscope signal processing apparatus according to the present invention for achieving the above technical problem is a self-oscillating unit for generating a drive signal having a phase difference by the horizontal displacement signal and the horizontal magnetic oscillation angle by inputting the horizontal displacement signal of the gyroscope, A phase control unit for generating a first demodulation phase signal out of phase with the drive signal and a first demodulation phase and a second demodulation phase signal out of phase with the drive signal and the second demodulation phase, a vertical displacement signal of the gyroscope and a first demodulation A gyroscope using a signal demodulator and a first demodulated signal and a second demodulated signal for generating a first demodulated signal demodulated according to a phase signal and a second demodulated signal demodulated according to a vertical displacement signal and a second demodulated phase signal; Preferably it includes an angular velocity signal generation unit for generating an angular velocity signal proportional to the input angular velocity.

In accordance with another aspect of the present invention, there is provided a signal processing method of a vibrating gyroscope according to an embodiment of the present invention, the method comprising: generating a drive signal having a phase difference equal to a horizontal displacement signal of a gyroscope by a horizontal magnetic oscillation angle, and retarding the drive signal by a first demodulation phase Generating a first demodulation phase signal and a second demodulation phase signal out of phase with the driving signal and the second demodulation phase, the first demodulation signal demodulated according to the vertical displacement signal of the gyroscope and the first demodulation phase signal, and Generating a demodulated second demodulated signal according to the vertical displacement signal and the second demodulated phase signal; and generating an angular velocity signal proportional to the input angular velocity of the gyroscope by inputting the first demodulated signal and the second demodulated signal. It is preferable to include.

Hereinafter, a signal processing apparatus of a vibrating gyroscope according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a conceptual diagram of a vibratory gyroscope.

Referring to Fig. 2, when the inertial mass m vibrates horizontally at the amplitude y _o and the oscillating angular frequency ω _y in the y-axis direction (horizontal direction), the displacement y (t) and the horizontal direction in the horizontal direction (y direction) The velocity v _y (t) in the (y direction) may be expressed as in Equation 1 below.

In this state, if a rotational angular velocity Ω _x (t) with an amplitude R _m and an angular frequency ω _R around the x axis is applied, the magnitude of 2 * v _y (t) * Ω _x (t) in the z-axis direction (vertical direction) Of Coriolis acceleration a _c (t) occurs, and the inertial force (Coriolis force) F _c (t) = m * a _c (t) causes the inertial mass m to vibrate in the z direction (vertical direction). do. Ω _x (t) and F _c (t) are represented by Equations 2 and 3, respectively.

By measuring the displacement z (t) in the z direction (vertical direction), the Coriolis acceleration a _c of the form demodulated by the angular velocity input can be detected. By demodulating this at a linear velocity in the y direction (horizontal direction) and low pass filtering, a signal (angular velocity signal) proportional to the input angular velocity Ω _x (t) can be obtained.

The signal processing device of the vibratory gyroscope measures the displacement y (t) in the horizontal direction and the displacement z (t) in the vertical direction and generates an angular velocity signal therefrom. However, in general, the small vibration type gyroscope has a very small Coriolis force, so the output displacement z (t) is also very weak. Therefore, in order to increase the sensitivity, the resonance characteristic of the vibration system with small attenuation is used. In other words, the oscillating gyroscope acts as a vibrometer having a natural frequency f _y in the horizontal direction (y direction) and a natural frequency f _z in the vertical direction (z direction).

Figure 3a is a graph showing the distribution of Coriolis acceleration according to the frequency change in the vibration type gyroscope. As shown in FIG. 3A, Coriolis forces are formed in both bands of f _y . The vibrometer in the z direction has a sense mode transfer function whose inertial mass m, the spring constant k _z , and the damping constant C are determined by the mechanical properties of the gyroscope, and the Coriolis force F _c (t). And the second order vibrometer as a transfer function between the displacement z (t) in the vertical direction. Here, the sense mode means a vibration mode in the vertical direction (z direction).

3B is a graph showing a change in the displacement z (t) in the vertical direction according to the frequency change. As shown in FIG. 3B, the displacement z (t) in the vertical direction is amplified by the quality factor Q- _z of the vertical vibration system and easily measured.

Since the actual oscillation gyroscope operates in a range of ω _y <ω _z and ω _R << ω _y , the vertical displacement z (t) can be expressed as Equation 5 below.

In order to perform electrical signal processing outside of the gyroscope, the above-described vertical displacement signal and horizontal displacement signal must be converted into electrical signals. From this point of view, the physical signal inside the vibratory gyroscope can be modeled as a capacitance.

4 is a circuit diagram illustrating a capacitance model of a vibratory gyroscope. Referring to FIG. 4, the vibratory gyroscope includes a driving capacity C _D , an inertial mass M, a horizontal displacement capacity C _Y , and a vertical displacement capacity C _Z. For convenience of description, the horizontal C / V converter 110 and the vertical C / V converter 120 are shown together in FIG. 4.

Referring to FIG. 4, the vibration type gyro horizontal displacement signal Vc _y is a signal obtained by converting a horizontal displacement capacitor C _Y having a horizontal displacement y (t) value through the horizontal C / V converter 110. In addition, the vertical displacement signal Vc _z is a signal obtained by converting the vertical displacement capacitor C _Z having the vertical displacement z (t) value through the vertical C / V converter 120. The horizontal displacement signal Vc _y and the vertical displacement signal Vc _z are shown in Equations 6 and 7, respectively.

5 is a block diagram showing an embodiment of a signal processing apparatus of a vibrating gyroscope according to the present invention. Referring to FIG. 5, a signal processing apparatus of a vibrating gyroscope according to a preferred embodiment may include a first preprocessor 440, a self oscillator 400, a phase controller 410, a second preprocessor 450, and a signal demodulator ( 420 and the angular velocity signal generator 430. For convenience of description, the vibrating gyroscope 100, the horizontal C / V converter 110, and the vertical C / V converter 120 are illustrated together.

Referring to FIG. 5, the first preprocessor 440 amplifies and band filters the horizontal displacement signal Vc _y to remove noise. It is preferable to include a band filter 442 and an amplifier 444 for this purpose.

The self oscillator 400 receives the horizontal displacement signal Vc _y preprocessed by the first preprocessor 440 to generate a drive signal V _D having a phase difference equal to the horizontal displacement signal Vc _y by the horizontal self oscillation angle α. To this end, the self oscillator 400 includes a phase shifter 402 for phase shifting the horizontal displacement signal Vc _y by a horizontal self oscillation angle α and an amplifier 404 for amplifying the phase shifted signal to generate a drive signal V _D. It is desirable to.

A phase control section 410 includes a first phase shifter 411 and second phase shifter 412 is configured and the drive signal first demodulation phase to enter the V _D respectively, and the drive signal V _D Ψ _first and second demodulation including It produces a phase by a phase difference Ψ ₂ the I-phase signal V _Ψ1 first demodulation and second demodulation phase signal V _Ψ2.

The second preprocessor 450 amplifies and band filters the vertical displacement signal Vc _z to remove noise. It is preferable to include a band filter 452 and an amplifier 454 for this purpose.

Sinhobok demodulator 420 includes a first demodulation phase signal V _Ψ1 Vc _z vertical displacement signal by demodulating the vertical displacement signal Vc _z to produce a first demodulated signal V _dm1, and using a second demodulation phase signal V _Ψ2 using Demodulation generates a second demodulation signal V _dm2 . Preferably, the signal demodulator 420 includes a first and second phase-sensitive detector (PSD), and the first synchronous detector 421 generates a first demodulated signal V _dm1 , and a second The sync detector 422 generates a second demodulated signal V _dm2 .

The angular velocity signal generator 430 differentially and low-pass filters the first demodulated signal V _dm1 and the second demodulated signal V _dm2 to generate an angular velocity signal V _R proportional to the input angular velocity of the gyroscope. Preferably, the angular velocity signal generation unit 430 is composed of a difference 432 and a low pass filter 434, and the difference 432 separates the first demodulation signal V _dm1 and the second demodulation signal V _dm2 . generating a difference signal demodulated V _dm, and a low-pass filter 434 produces the angular velocity signal V _R by the difference between low-pass filtering the demodulated signal V _dm.

Because of the various parasitic capacitances present in signal processing devices, different noises are mixed into the signal. As the main and representative parasitic capacitances, there is noise caused by the drive signal V _D and the first demodulation phase signal _VΨ1 and the second demodulation phase signal _VΨ2 , which are added to the vertical displacement capacitance C _Z and incorporated into the vertical displacement signal Vc _z . do. These noises belong to the same frequency band as the vertical displacement signal Vc _z and are noises that cannot be removed by the second preprocessor 450.

Hereinafter, with reference to FIG. 5, the effect of noise in the signal processing device of the vibration type gyroscope according to the present invention and the removal of the noise due to the operation of the device will be described in detail.

The vertical displacement signal Vc _z of Equation 7 may be expressed as Equation 8 including noise.

In Equation 8, N _D , N _{Ψ 1,} and N _Ψ 2 are amplitudes of noise due to the driving signal V _D , the first demodulation phase signal V _Ψ 1, and the second demodulation phase signal V _Ψ 2, respectively.

Self-oscillation (400) to phase shift the horizontal displacement signal _y Vc, and generates the horizontal displacement signal and the driving signal Vc _y V _D having a phase difference of the horizontal oscillator by the magnetic angle α as shown in Equation (9).

A phase control section 410 the drive signal V _D for the first demodulation phase Ψ ₁ and the second demodulation phase Ψ _2, by phase-shifting by a first demodulation phase signal V _Ψ1 and second demodulation expressed as Equation 10a and 10b A phase signal V ₂ is generated and output to the signal demodulator 420.

The signal demodulator 420 generates a first demodulated signal V _dm1 and a second demodulated signal V _dm2 , and outputs the first demodulated signal V _dm2 to the angular velocity generator 430. Specifically, the first synchronous detector 421 of sinhobok demodulator 420 to produce a first demodulated signal V _dm1 is expressed as the following Equation 11a in synchronization with the detected vertical displacement signal Vc _z in the first demodulation phase signal V _Ψ1 do. In addition, the second synchronous detector 422 synchronously detects the vertical displacement signal Vc _z as the second demodulated phase signal V _Ψ2 to generate a second demodulated signal V _dm2 expressed as in Equation 11b.

The difference 432 of the angular velocity generating unit 430 generates a differential demodulation signal V _dm that is different from the first demodulation signal V _dm1 and the second demodulation signal V _dm2 , and the low pass filter 434 low-passes the differential demodulation signal V _dm . Filtering generates an angular velocity signal V _R as shown in Equation 12 below.

In Equation 12, N _{Ψ 1} ≒ N _{Ψ 2} is assumed.

In such a case, in order to have a high signal-to-noise ratio (SNR), it is necessary to reduce the ZRO acting as a bias and at the same time maximize the angular velocity output component. To do this, the conditions given in the following equation must be satisfied.

또한, 상기 수학식 13의 첫번째 식에서 두번째 식을 빼면, 다음 수학식 14를 얻을 수 있다. 따라서, 제 1 복조위상 Ψ1 과 제 2 복조위상 Ψ2 의 차이는 π/2 라디안이 되어야 한다.

Further, by subtracting the second equation from the first equation of Equation 13, the following equation (14) can be obtained. Therefore, the difference between the first demodulation phase Ψ 1 and the second demodulation phase Ψ 2 should be π / 2 radians.

That is, to obtain the maximum signal-to-noise ratio (SNR), the horizontal self-oscillation angle α = π / 4-φ _o radians, the first demodulation phase Ψ ₁ = π / 4 radians, and the second demodulation phase Ψ ₂ = -π / Most preferably, it has a value of 4 radians. At this time, the bias component of the angular velocity signal V _R is minimized, and thus the drift component is minimized. Therefore, the angular velocity signal V _R has only a V _Ro component proportional to the angular velocity input Ω _x (t) without noise. The self-oscillation section can be configured by setting the value of the horizontal self-oscillation angle α to a value other than π / 2 radians. That is, the value of the horizontal self oscillation angle α may have a value less than π / 2 radians.

In order to verify the contents of the present invention, a simulation was performed using a mathematical model of a vibratory gyroscope.

6 (a) to 6 (e) are output waveform diagrams of respective parts of the signal processing apparatus shown in FIGS. 1 and 5. Here, the value of each variable used in this experiment is the horizontal quality factor Q _y = 5,000, the horizontal natural frequency f _y = 5,000 [Hz], the vertical quality factor Q _z = 500, the vertical unique Frequency f _z = 5,100 [Hz], gyroscope inertial mass m = 2 X 10 ^-7 [kg], horizontal vibration amplitude y _o = 10 [μm], rotational angular velocity R _m = 1 [deg / sec ] And the frequency of rotational angular velocity f _R = 5 [Hz].

Fig. 6 (a) shows the angular velocity input Ω _x (t), Fig. 6 (b) shows the capacitance change C _z (t) due to Coriolis force, and Fig. 6 (c) shows the vertical displacement signal Vc _z (t) with noise added. 6 (d) is an angular velocity signal V _R (t) in the conventional signal processing apparatus shown in FIG. 1, and FIG. 6 (e) is an angular velocity signal in the signal processing apparatus according to the present invention shown in FIG. V _R (t) is shown, respectively.

Referring to FIG. 6 (d), it can be seen that the angular velocity signal V _R (t) by the conventional signal processing apparatus exhibits an output characteristic with respect to the angular velocity input to some extent, but has a bias of 1.28 volts. On the other hand, referring to FIG. 6 (e), the result of applying the signal processing of the present invention results in an angular velocity signal alternately based on zero without a bias component and following the angular velocity input Ω _x (t) of FIG. 6 (a). It can be seen that.

The present invention can be embodied as code that can be read by a computer (including all devices having an information processing function) in a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording devices include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

According to the vibration processing gyroscope signal processing apparatus and method of the present invention, by generating two demodulation phase signals having a difference in the demodulation phase angle and generating an angular velocity signal with the difference, the bias component caused by noise, in particular the vertical displacement signal Noise components due to the drive signal and the demodulation phase signal having the same frequency band as described above can be effectively suppressed, and the drift component drifted with time can be reduced by reducing the bias component. By reducing these noise components, the signal-to-noise ratio (SNR) can be maximized, and the parasitic capacitance can be minimized to simplify implementation.

In addition, since the self-oscillation unit can be configured by setting the value of the horizontal self-oscillation angle α to a value other than π / 2 radians, the phase angle of the drive signal V _D is not limited.

Claims (16)

In the signal processing device of a vibratory gyroscope, A self-oscillating unit configured to generate a drive signal having a phase difference from the horizontal displacement signal by a horizontal magnetic oscillation angle as a horizontal displacement signal of the gyroscope; A phase control unit generating a first demodulation phase signal out of phase with the driving signal by a first demodulation phase and a second demodulation phase signal out of phase with the driving signal by a second demodulation phase; A signal demodulator configured to generate a first demodulated signal demodulated according to the vertical displacement signal of the gyroscope and the first demodulated phase signal, and a second demodulated signal demodulated according to the vertical displacement signal and the second demodulated phase signal; And And an angular velocity signal generator configured to generate an angular velocity signal proportional to an input angular velocity of the gyroscope by receiving the first demodulated signal and the second demodulated signal as inputs. The signal processing apparatus of claim 1, further comprising a first preprocessor configured to amplify and band filter the horizontal displacement signal. The signal processing apparatus of claim 1, further comprising a second preprocessor configured to amplify and band filter the vertical displacement signal. The method of claim 1, wherein the signal demodulation unit, A first synchronous detector for synchronously detecting the vertical displacement signal with the first demodulation phase signal; And And a second synchronous detector for synchronously detecting the vertical displacement signal with the second demodulation phase signal. The apparatus of claim 1, wherein the angular velocity signal generation unit performs differential and low pass filtering on the first demodulated signal and the second demodulated signal. The apparatus of claim 1, wherein a difference between the first demodulation phase and the second demodulation phase is π / 2 radians. 7. The signal processing apparatus of claim 6, wherein the first demodulation phase and the second demodulation phase are π / 4 radians and -π / 4 radians, respectively. 2. The signal processing apparatus of claim 1, wherein the horizontal magnetic oscillation angle has a value less than [pi] / 2 radians. In the signal processing method of the vibration type gyroscope, (a) generating a drive signal that is out of phase with the horizontal displacement signal of the gyroscope by a horizontal magnetic oscillation angle; (b) generating a first demodulation phase signal out of phase with the drive signal by a first demodulation phase and a second demodulation phase signal out of phase with the drive signal by a second demodulation phase; (c) generating a first demodulated signal demodulated according to the vertical displacement signal of the gyroscope and the first demodulated phase signal, and a second demodulated signal demodulated according to the vertical displacement signal and the second demodulated phase signal; And and (d) generating an angular velocity signal proportional to an input angular velocity of the gyroscope by inputting the first demodulated signal and the second demodulated signal. 10. The signal processing method of claim 9, further comprising amplifying and band filtering the horizontal displacement signal. 10. The method of claim 9, further comprising amplifying and band filtering the vertical displacement signal. The method of claim 9, wherein step (c) comprises: (c1) generating a first demodulated signal by synchronously detecting the vertical displacement signal with the first demodulated phase signal; And and (c2) synchronizing the vertical displacement signal with the second demodulation phase signal to generate a second demodulation signal. The signal processing method of claim 9, wherein the step (d) performs differential and low pass filtering on the first demodulated signal and the second demodulated signal. 10. The signal processing method of claim 9, wherein a difference between the first demodulation phase and the second demodulation phase is π / 2 radians. 15. The signal processing method according to claim 14, wherein the first demodulation phase and the second demodulation phase are π / 4 radians and -π / 4 radians, respectively. 10. The signal processing method of claim 9, wherein the horizontal magnetic oscillation angle has a value less than [pi] / 2 radians.

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