JP2514529B2 - Optical interference gyro - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis function of a closed loop type optical interference angular velocity meter (also referred to as an optical fiber gyro, hereinafter also referred to as a FOG), and is provided when the function and performance of the FOG is impaired due to a failure or the like. The present invention relates to a function of sending a signal to an external device for judging a failure and notifying or diagnosing the external device.

[0002]

2. Description of the Related Art A conventional FOG will be described with reference to FIG.
The light I from the light source 11 passes through the optical coupler 12, the polarizer 13, and the optical coupler 14 and is input to both ends of the optical fiber coil 17. Left and right light (CW) propagating through the optical fiber coil 17
The light and CCW light) are phase-modulated by the phase modulator 15 arranged at one end of the coil 17 of the optical fiber. The two lights subjected to the phase modulation are combined by the optical coupler 14 and interfere with each other, and again pass through the polarizer 13 and the optical coupler 12 to the light receiver 1
It branches to 8. The output V _P of the light receiver 18 at this time is a signal wave (modulation wave) that modulates the phase of light, P (t) = Asi
Let nω _P t be V _P = (I / 2) · K _OPT · K _PD {1 + cos ΔΦ (Σε _n · (−1) ⁿ · J _2n (X) · cos ₂ nω _P t ′) −sin ΔΦ (2Σ (−1 ) ^N · J _{2n + 1} (X) · cos (2n + 1) ω _P t ′)} (1) where Σ is from n = 0 to ∞, and t ′ = t−τ / 2 ε _n = 1; n = 0 2; n ≧ 1 K _OPT : The light I emitted from the light source 11 is the optical fiber coil 1
Optical loss from 7 to the light receiver 18 K _PD : Constant determined by photoelectric conversion coefficient and amplifier gain I: Light emitted from the light source 11 I _O : Maximum light amount reaching the light receiver 18 (I _O = K _OPT
I) J _n : Bessel function of the first kind X: 2Asin πf _P τ ΔΦ: Phase difference between the left and right lights in the optical fiber coil ω _P : Angular frequency of the modulated wave (ω _P = 2πf _P ) τ: Propagation in the optical fiber coil It is represented by the propagation time of the light that travels. Then, the output of the light receiver 18 is the synchronous detection circuit 1
9 into which the same component as the phase modulation frequency ω _P ,
That is, the first-order component in the equation (1) receives the reference signal S _r from the clock circuit 24 and is extracted. The DC component output V _O of the synchronous detection circuit 19 at this time is expressed by the following equation.

V _O = I · K _OPT · K _PD · J ₁ (x) · K _A1 · sin ΔΦ = K ₁ · sin ΔΦ (2) K ₁ , K _A1 : Gain Here, the phase difference ΔΦ between the two lights is ΔΦ = ΔΦ _s + ΔΦ _f (3) ΔΦ _s is the Sagnac that occurs when the rotational angular velocity Ω is applied to the optical fiber coil.
It shows the phase difference and is expressed by the following equation.

ΔΦ _s = (4πRL / Cλ) · Ω (4) where C: high speed, λ: wavelength of light in vacuum, R:
Radius of optical fiber coil, L: length of optical fiber coil. On the other hand, the phase difference ΔΦ _f is a phase difference generated by shifting the phase at a constant rate by the feedback phase difference generator 16 arranged at one end of the optical fiber coil 17. In practice, the feedback phase difference generator 16
The sawtooth wave signal R is applied to to shift the phase of light. The sawtooth wave signal R is fed to the feedback phase difference generator 16.
Is applied, CCW light is generated as shown by the solid line in FIG. 5A, while CW light is delayed by the propagation time τ of the light propagating through the optical fiber coil as shown by the broken line, and undergoes the same phase shift. As a result, the phase difference between the two lights occurs as shown in FIG. 5B. Here sawtooth wave phase shift up shift [Phi _R is 2πk of: Given that the (k integer), the phase difference .DELTA..PHI _f between both light to the frequency of the sawtooth wave signal R and f _R, .DELTA..PHI _f = (2πn _a L / C) · k · f _R (5) n _a is the refractive index of the optical fiber. Where ΔΦ
_When the output of the synchronous detection circuit 19 is applied to the sawtooth wave generation circuit 21 through the integrator 20 so that _f has a polarity opposite to the phase difference ΔΦ _s generated by the Sagnac effect and has the same magnitude or a difference of 2 mπ, the integration is performed. The input of the device 20, that is, the output of the synchronous detection circuit 19, that is, the expression (2) converges to zero, and a closed loop can be achieved.

As a result, the operating point of the closed loop is the position of ΔΦ = 0 ± 2mπ. The value of m is an integer,
Normally, it is operated at the position of m = 0. Therefore, si in equation (2)
nΔΦ = 0, and ΔΦ _s = −ΔΦ _f . Substituting the expressions (4) and (5) into this relational expression, the following relational expression holds. f _R = - by measuring the frequency f _R of _{(2R / n a λk) ·} Ω (6) Thus sawtooth signal, 2
Since R / (n _a λk) is a proportional constant, the input angular velocity Ω
You can know Note that k is usually "1". Therefore equation (6), f _R = - a _{(2R / n a λ) ·} Ω (7).

In FIG. 4, the sawtooth wave generation circuit 21 generates a sawtooth wave signal R having a repetition frequency f _R = R _RG V _d proportional to the output V _{d of the} integrator 20 when R _RG is its gain. The ROG output signal R _out having a rectangular wave of the same frequency is supplied to the output terminal 22 while being supplied to the feedback phase difference generator 16. The output V _{d of the} integrator 20 is also supplied to the output terminal 23 as needed. In addition, the integrator 2
0 and the sawtooth wave generation circuit 21 provide a feedback circuit 27.
Is configured.

From the clock circuit 24, the phase modulation frequency f _P
A rectangular wave signal having the same frequency as is supplied to the synchronous detection circuit 19 as a reference signal S _r . Further, the rectangular wave of the phase modulation frequency f _P is supplied from the clock circuit 24 to the phase modulation drive circuit 25, converted into a sine wave signal, and the level thereof is adjusted and supplied to the phase modulator 15 as the drive signal S _P.

[0008]

As described above, the FO
When the function of each part of G is operating normally, if the level of the output V _d of the integrator 20 and the frequency f _R of the FOG output R _out are measured, the rotational angular velocity Ω input by the equation (6) or (7) can be calculated. I can know. However, in the case of the conventional technology, FO
Somewhere in G fails and outputs V _d and R _out are not output, the frequency of R _out remains abnormal, and the level of output V _d drops or increases abnormally. Even then, the FOG output alone cannot determine whether the FOG itself is normal or abnormal, and the system using the FOG may be put in danger. An object of the present invention is to make it possible to judge whether the FOG is normal or abnormal by a diagnostic command.

[0009]

According to the present invention, in a closed-loop FOG, a reference signal of the synchronous detection means is switched to a reference signal having a phase shift of 180 ° in accordance with a diagnostic command, and the stable point of the closed loop is changed to the above-mentioned. The phase difference between right-handed light and left-handed light is shifted to 180 ° or a position that is an odd multiple of 180 °, and the output of the FOG at that time is sent to the diagnostic circuit as a diagnostic signal to determine whether the frequency (bias frequency) is within the specified value. By doing so, it is determined whether the FOG is normal or abnormal.

The order of the frequency of the reference signal of the synchronous detection means is switched according to a diagnostic command to synchronously detect the component of an even multiple of the phase modulation frequency, and the stable point of the closed loop is detected by the clockwise light and the counterclockwise light. The phase difference of 90 ° or an odd multiple thereof, the output of the FOG at that time is sent to the diagnostic circuit as a diagnostic output, and it is determined whether the frequency (bias frequency) is within the specified range.
Determine whether G is normal or abnormal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIG.
You. In this figure, the parts corresponding to those in FIG.
A duplicate description is omitted. Switch 28 is connected to side a
In the state, the phase modulation frequency f_pSignal of the same frequency as is synchronized
Reference signal S of the detection circuit 19 _rIs applied as. That conclusion
As a result, the first-order component contained in the interference light is synchronously detected and the product
It is applied to the divider 20. The output of the synchronous detection circuit 19 at that time
The force is expressed by equation (2), and the FOG output R_outFrequency f_R
Is a regular value shown in the equation (6).

On the other hand, when the switch 28 is connected to the side b by the diagnostic command, the reference signal S _r1 is applied to the synchronous detection circuit 19 with the phase shifted by 180 ° by the inverter 29. As a result, the synchronous detection circuit 19 outputs an output having a polarity opposite to that of the output expressed by the equation (2), and the operating point of the closed loop becomes the position of ΔΦ = mπ or −mπ. m
Is an integer of 1, 3, 5, ..., And here, it is operated at the position of m = 1. That is, ΔΦ = π, and as a result, Δ
Φ _f = π−ΔΦ _s . Since ΔΦ _s = 0 in a state where the input angular velocity Ω is not applied, the frequency f _R of the sawtooth wave signal R at that time is expressed by the following equation from the equation (5). F _R when the input angular velocity Ω is not applied is called a bias frequency and is represented by f _b .

F _b = C / 2n _a L (8) In the equation (8), C is the speed of light, n _a is the refractive index of the optical fiber, and L is
Is the length of the optical fiber, and both are elements with a small temperature coefficient. Therefore, f _b is almost constant when the operating state of the FOG is normal, and can be used as an accurate diagnostic signal. Therefore, in FIG. 1, the output R _{out is set} to the diagnostic circuit 30.
Is input to monitor whether or not the bias frequency f _b is within the allowable range, and when it is out of the range, the alarm signal ALM is sent to the outside. The frequency divider 33 _divides the frequency 2f _p of the secondary reference signal S _r2 input from the clock circuit 24 into ½ to generate a primary reference signal S _r1 .

In FIG. 2, when the switch 28 is connected to the side a, the signal S _r1 having the same frequency as the phase modulation frequency f _P is applied as the reference signal S _r of the synchronous detection circuit 19. As a result, the primary component included in the interference light is synchronously detected and applied to the integrator 20. The output of the synchronous detection circuit 19 at that time is shown by the equation (2), and the frequency f _R of the FOG output R _OUT is a normal value shown by the equation (6).

On the other hand, when the switch 28 is connected to the side b by the diagnostic command, the secondary reference signal S _r2 having the frequency 2f _p is applied to the synchronous detection circuit 19 as the reference signal S _r . As a result, the output Vp 'of the synchronous detection circuit 19 is expressed by the following equation. V _o ′ = K ₂ · cos (ΔΦ) (9) This output is supplied to the feedback circuit 27 including the integrator 20 and the sawtooth wave generator 21.

As a result, the system is closed loop negative feedback.
The operation point is ΔΦ = mπ / 2 or −m depending on the operation.
The position is π / 2. m is an integer of 1, 2, 3 ...
Then, in this case, it is operated at the position of m = 1. That is, ΔΦ =
π / 2, resulting in ΔΦ _f= Π / 2-ΔΦ_sTona
You. Here, when the input angular velocity Ω is not applied,
ΔΦ_s= 0, the bias frequency f at that time is_bIs
It is expressed by the following equation from the equation (5).

F _b = C / 4n _a L (10) That is, the bias frequency f _b shown in the equation (10) is generated in the state where the input angular velocity Ω = 0. Since this f _b is composed of elements having a small temperature coefficient as is clear from the equation (10), it can be used as a highly accurate diagnostic signal because it is almost constant if the FOG operation is normal. .

In FIG. 3, the switch 28 is connected to the side b by the first diagnosis command CTL ₁ , and the FOG output terminal 22 is
The output R _OUT of the frequency f _b shown in the equation (10) is sent out, the switch 34 is connected to the b side by the second diagnostic command signal CTL ₂ , and as a result, the system is operated from the closed loop negative feedback operation to the operating point. Stabilizes at a position shifted by π (radian) from the previous phase difference. The output R _OUT of the FOG at this time is the previous FOG output R under the condition of ΔΦ _s = 0.
A signal whose absolute value is equal to _OUT and whose polarity is opposite to that of _OUT is obtained, and a more reliable and accurate diagnostic signal is obtained by these signals. In the above, the output of the sawtooth generation circuit 21 is used as a diagnostic signal in both equations (8) and (10), but the gain of the sawtooth wave generation circuit 21 is set to K _RG (Pulse / Volts), the sawtooth wave generation circuit 21. Let V _{d be} the input voltage of V _d =
It can be expressed as f _b / K _RG and V _d can be used as a diagnostic signal. Further, the diagnostic circuit 30 for judging whether or not the frequency f _b of the feedback signal R is within a specified value from the diagnostic signals R _OUT , V _d is, for example, an external FOG.
May be provided in the parent device using.

The check of the bias frequency f _b by the diagnostic circuit 30 is carried out before the departure of an aircraft equipped with this optical interference angular velocity meter, for example.

[0020]

As described above, according to the present invention, by adding a diagnostic function to the FOG, when the performance function is impaired due to a failure or the like of the FOG, it is possible to judge the failure by itself or to provide a signal for diagnosis. Is sent to an external diagnostic circuit, the device using the FOG can be avoided from a dangerous state.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of claim 1 of the present invention.

FIG. 2 is a block diagram showing an embodiment of claim 2 of the present invention.

FIG. 3 is a block diagram showing an essential part of an embodiment of claim 3 of the present invention.

FIG. 4 is a block diagram of a conventional optical interference angular velocity meter.

5 is a waveform diagram of a feedback phase Φ _f and a feedback phase difference ΔΦ _f between CCW light and CW light generated in the feedback phase difference generator 16 of FIG.

Claims (3)

(57) [Claims] 1. An optical path that makes at least one round, branching means for passing clockwise light and counterclockwise light with respect to the optical path, and interference means for interfering the clockwise light and counterclockwise light propagating through the optical path. A phase modulation means arranged between the branching means and one end of the optical path to apply phase modulation to the clockwise light and the counterclockwise light; and between the branching means and the other end of the optical path. Feedback phase difference generating means arranged to generate a phase difference between the clockwise light and the counterclockwise light, a light receiver for detecting the light intensity of the interference light obtained by the interference means as an electric signal, and from the light receiver Of the output of the phase modulating means, or a synchronous detecting means for synchronously detecting a component of an odd multiple thereof, and a feedback phase difference generating means for generating a feedback signal by the output of the synchronous detecting means. In a closed loop type optical interference gyro consisting of a feedback signal generating means for supplying, a phase of a reference signal supplied to the synchronous detecting means is shifted by 180 ° by a diagnostic command, and a stable point of the closed loop is controlled by the clockwise light. The phase difference between the counterclockwise light and the counterclockwise light is shifted to a position of 180 ° or an odd multiple thereof, and the output of the optical interference angular velocity meter obtained from the feedback signal generating means at that time is sent to the diagnostic circuit as a diagnostic signal to obtain the feedback signal. An optical interference angular velocity meter characterized in that the frequency is monitored. 2. An optical path that makes at least one round, branching means for passing clockwise light and counterclockwise light with respect to the optical path, and interference means for interfering the clockwise light and counterclockwise light propagating through the optical path. And a phase modulation unit arranged between the branching unit and one end of the optical path to apply phase modulation to the clockwise light and the counterclockwise light, and arranged between the branching unit and the other end of the optical path. Feedback phase difference generating means for generating a phase difference between the clockwise light and the counterclockwise light, a light receiver for detecting the light intensity of the interference light obtained by the interference means as an electric signal, and an output from the light receiver Among these, a synchronous detection means for synchronously detecting the modulation frequency of the phase modulation means or a component of an odd multiple thereof, and a feedback signal generated by the output of the synchronous detection means and supplied to the feedback phase difference generation means. In a closed loop type optical interference gyro consisting of feedback signal generating means, the order of the frequency of the reference signal supplied to the synchronous detecting means is switched by a diagnostic command to synchronously detect an even multiple of the phase modulation frequency. , The stable point of the closed loop is shifted to a position where the phase difference between the clockwise light and the counterclockwise light is 90 ° or an odd multiple thereof, and the output of the optical interference angular velocity meter obtained by the feedback signal generating means at that time is used as a diagnostic signal. An optical interference angular velocity meter characterized by being sent to a diagnostic circuit to monitor the frequency of the feedback signal. 3. An optical path that makes at least one round, branching means for passing clockwise light and counterclockwise light to the optical path, and interference means for interfering the clockwise light and counterclockwise light propagating through the optical path. And a phase modulation unit arranged between the branching unit and one end of the optical path to apply phase modulation to the clockwise light and the counterclockwise light, and arranged between the branching unit and the other end of the optical path. Feedback phase difference generating means for generating a phase difference between the clockwise light and the counterclockwise light, a light receiver for detecting the light intensity of the interference light obtained by the interference means as an electric signal, and an output from the light receiver Among these, a synchronous detection means for synchronously detecting the modulation frequency of the phase modulation means or a component of an odd multiple thereof, and a feedback signal generated by the output of the synchronous detection means and supplied to the feedback phase difference generation means. In a closed loop type optical interference gyro including a feedback signal generating means, the order of the frequency of a reference signal supplied to the synchronous detecting means is switched by a first diagnostic command to synchronize an even multiple component of the phase modulation frequency. The detection is performed, the stable point of the closed loop is shifted to the position where the phase difference between the clockwise light and the counterclockwise light is 90 ° or an odd multiple thereof, and the output of the optical interference angular velocity meter at that time is sent to the diagnostic circuit, and the second The reference signal and the phase of which the order of the frequency is switched by the diagnostic command of
The phase difference between the clockwise light and the counterclockwise light is further shifted by 180 ° from the stable point of the closed loop by further detecting the component of the even multiple of the phase modulation frequency by synchronously detecting the reference signal shifted by 0 °. The position of the optical interference angular velocity meter is set to a different position, and the output of the optical interference angular velocity meter obtained from the feedback signal generating means at that time is sent to a diagnostic circuit to monitor the frequency of the feedback signal.