JPH11287659A - Optical fiber gyro having failure self-diagnostic function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit failure diagnosis without stopping the operation of an optical fiber gyro and to construct the optical fiber gyro at low cost. SOLUTION: An optical integrated circuit 2 has a light branching/combining part 2a and a phase modulator 2b, and light outputted from an SLD (superluminescent diode) 4 is inputted to a sensing loop 1 coupled to the light branching/combining part 2a. A bias phase modulation signal 17 and a stepped wave modulation signal 16 are imparted from an ASIC 10 (application specific integrated circuit) to the phase modulator 2b to form a closed loop type optical fiber gyro. A spike signal which is generated each time the optical output maximum point of the bias phase modulation signal 17 imparted to the phase modulator 2b is passed is detected by a PD(photodiode) 5, and the failure of each component member is recognized by use of the ASIC 10 and a CPU 12 in accordance with the level of the spike signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical fiber gyro having a self-diagnosis function, and more particularly, to a closed-loop optical fiber gyro.

[0002]

2. Description of the Related Art A closed-loop optical fiber gyro receives a rotational angular velocity, and applies a phase modulation signal for canceling a phase difference generated due to a Sagnac effect between left-handed light and right-handed light. This is a method called a null method in which control is performed so that no change occurs in the output signal. In such a method, the output signal does not change, and no abnormality can be detected from the change in the output signal. Further, since the signal processing is internally closed by the configuration of the closed loop, it is difficult to externally grasp the state of the sensor.

Conventionally, the quality of an optical fiber gyro itself is determined by incorporating the optical fiber gyro into a device or apparatus to which the optical fiber gyro is applied, and then physically giving a rotational angular velocity to the optical fiber gyro and checking the output. For example, when an abnormal output is output, it is determined that the optical fiber gyro has failed. To improve this, a device having a self-diagnosis function has been proposed. For example, in an optical fiber gyro (an optical interference gyro with a self-diagnosis function) having a self-diagnosis function disclosed in Japanese Patent Laid-Open No. 4-52511, a failure detection signal is superimposed on a phase modulation signal, and a phase detection means at that time is used. Or the output of the optical fiber gyro.

[0004]

However, according to the conventional optical fiber gyro having a self-diagnosis function, it is possible to diagnose the failure of the optical fiber gyro body, but it is not possible to detect the failure of the failure diagnosis section itself. . Further, it is impossible to specify the failure location of the optical fiber gyro from the failure diagnosis result. In addition, during execution of the failure diagnosis, the sensor operation must be stopped, so that the rotational angular velocity may not be accurately measured.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical fiber gyro having a self-diagnosis function which enables a failure diagnosis without stopping the operation of the optical fiber gyro and which can be configured at a low cost.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical path that makes at least one round, and an interference unit that causes left-handed light and right-handed light to enter and interfere with the optical path. A phase modulation means coupled to the interference means and providing alternating phase modulation to the left-handed light and the right-handed light;
A bias phase modulation signal generating means for applying a bias phase modulation signal to the phase modulation means; a photoelectric conversion means for converting the light intensity of the interference light from the interference means into an electric signal; and an output from the photoelectric conversion means. Phase difference detecting means for detecting phase difference information between the left-handed light and the right-handed light, and providing a phase difference of opposite sign to a signal from the phase difference detecting means to output a step-like phase modulated wave. And a staircase wave amplitude control means for controlling the maximum amplitude of the staircase wave by the staircase wave generation means to give a phase difference of 2π between the left-handed light and the right-handed light. An optical fiber gyro that negatively feeds back the output of the staircase wave generation means to the phase modulation means so that the phase difference between the counterclockwise light and the clockwise light in the optical path becomes zero. Signal A spike signal generated every time the bias phase modulation signal applied to the means passes through the maximum point of the optical output is acquired through the photoelectric conversion means, and a failure of a component is determined based on the level of the spike signal. An optical fiber gyro having a self-diagnosis function, comprising:

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical fiber gyro having a self-diagnosis function according to the present invention. An optical integrated circuit (optical IC) 2 is connected to a sensing loop 1 in which an optical fiber is formed into a loop with a predetermined loop diameter and a predetermined number of turns. Both ends of the loop 1 are connected. A phase modulator 2b that shifts the phase of light in series at one end or both ends of the sensing loop 1 is disposed downstream of the optical branching / combining unit 2a, and a staircase modulation signal and a bias phase modulation signal are applied. . An optical coupler 3 is provided on the input side of the optical integrated circuit 2.
Are combined. The optical coupler 3 is coupled with an SLD (super luminescent diode) 4 as a light source and a PD (photodiode) 5 as a photoelectric conversion unit.

The SLD 4 has a PD 6 as a photoelectric conversion means.
The output terminal of the PD 6 is connected to an APC (Automatic Power Control) circuit 7 for controlling the optical output of the SLD 4. APC circuit 7
Comprises an output transistor 8a, resistors 8b and 8c, and an amplifier 10a to be described later. A preamplifier 9 is connected to PD5, and the amplified output is an ASIC.
(Application Specific Integrated Circuit) is applied to 10.

The ASIC 10 includes an amplifier 10a, an A / D converter 10b, a gate array 10c, a D / A converter 10
d, 10e, an oscillation circuit 10f, and the like. The crystal oscillator 11 is connected to the oscillation circuit 10f. The ASIC 10 has a C for executing a failure diagnosis process.
A PU 12 is connected, and an EEPROM 13 in which a failure diagnosis program is stored is connected to the CPU 12. Further, a reset / power supply circuit 14 for supplying power to the CPU 12 and the ASIC 10 and for resetting the CPU 12 and the ASIC 10 is provided. In addition, in order to combine the staircase modulation signal 16 output from the D / A converter 10e and the bias phase modulation signal 17 output from the gate array 10c and output the combined signal to the phase modulator 2b, the synthesis circuit 15 Is provided. A / D converter 10b, gate array 10c, CPU
12 forms a failure diagnosis means.

FIG. 2 shows the waveforms of the staircase modulation signal 16 and the bias phase modulation signal 17 output from the ASIC 10. The bias phase modulation signal 17 output from the gate array 10c of the ASIC 10 has a (π / 4) radian phase shift with respect to clockwise light and counterclockwise light passing through the phase modulator 2b in the optical integrated circuit 2, and (− (π / 4) radian phase shift is applied alternately for each light propagation time τ of the sensing coil 1, and is supplied to the phase modulator 2 b via the synthesizing circuit 15. In this case, the modulation frequency is f _m
= 1 / 2τ.

In the above configuration, the output light of the SLD 4 is incident on both ends of the sensing coil 1 through the optical coupler 3 via the optical splitter / combiner 2a in the optical integrated circuit 2 as clockwise light and counterclockwise light. The left-handed light and right-handed light after propagating in the sensing coil 1 are separated by the light branching / combining unit 2a.
Are combined into interference light. The interference light enters the PD 5 as a photoelectric conversion unit through the optical coupler 3, is converted into an electric signal corresponding to the light intensity, is amplified by the preamplifier 9, and is input to the A / D converter 10 b of the ASIC 10.
The PD 6 constantly monitors the output light of the SLD 4, photoelectrically converts the received light, and outputs the light to the APC circuit 7. The APC circuit 7 controls the light intensity of the output light of the SLD 4 based on the output of the PD 6 so as to maintain a constant value.

When the rotational angular velocity Ω is not input to the sensing coil 1, the phase difference between the clockwise light and the counterclockwise light transmitted through the sensing coil 1 is zero. However, when the rotational angular velocity Ω is input to the sensing coil 1, a phase difference Φ _S is generated due to the Sagnac effect. The phase difference Φ _S is represented by the following equation. Φ _S = (4πRL / λc) · Ω (where R: radius of sensing coil, λ: wavelength of light source, L: length of optical fiber, c: speed of light).

FIG. 3 shows an optical output waveform of the preamplifier 9 in an open loop (when negative feedback control is not performed).
When the rotational angular velocity Ω is zero, the output waveform of the preamplifier 9 becomes a waveform shown in “at rest” in FIG. The spike signal 18 in FIG. 3 is generated when the bias phase modulation signal 17 passes through the optical output maximum point, and its magnitude is
Is proportional to the light receiving level of the optical signal. When the rotational angular velocity Ω occurs, a signal step 31 occurs due to the τ output interval corresponding to the rotational angular velocity Ω (the waveform at the time of “rotation” in FIG. 3).

FIG. 4 shows an optical output waveform of the preamplifier 9 in a closed loop (when negative feedback control is performed). When the rotational angular velocity Ω occurs, negative feedback control is executed by the staircase wave modulation signal 16 applied to the phase modulator 2b. That is, the right-handed light and the left-handed light propagated through the sensing coil 1 make the staircase wave modulated signal 1 so that the phase difference Φ _S is canceled.
By performing the negative feedback modulation by 6, the pre-amplifier output state is returned to when the rotational angular velocity Ω is zero (the state of “at rest” in FIG. 3). In this closed loop system, the rotational angular velocity Ω and the angle are obtained from the negative feedback control signal (signal obtained on the path from PD5 → Preamplifier 9 → ASIC 10).

FIG. 5 shows a detailed configuration of a main part of the gate array 10c. The gate array 10c includes an A / D converter 10
a code converter 21 for code-converting the A / D converted value by b;
Rate register 22 for storing angular velocity information, 2π control register 2 for controlling maximum amplitude _Vref of staircase wave
3. It comprises a ramp register 24 for integrating the rate register value of the rate register 22, and a data register 25 for storing output data of the ramp register 24.

In the configuration of FIG. 5, the A / D converter 10b
The A / D conversion value is converted in code by the code converter 21.
The angular velocity information is input to the rate register 22 and the 2π control register 23. The value of the rate register of the rate register 22 is integrated by the ramp register 24 and converted into angle information. The converted value is stored in the CPU 12
And output as staircase wave signal output data
The signal is input to the / A converter 10e and converted into an analog sawtooth signal. The A / D converter 10b samples data necessary for closed loop control, detects the level of the spike signal 18, and sends it to the CPU 12.
The CPU 12 can determine the deterioration of the light source, the increase of the loss of the optical components, the decrease of the gain of the preamplifier 9, the abnormality of the APC circuit 7, and the like from the decrease in the level of the spike signal 18.

The gate array 10c has a function of outputting an error flag when the same value continues for a certain period of time, that is, when there is no change in the register value of the rate register 22. By detecting the presence or absence of this error flag by the CPU 12, the CPU 12 can determine whether the A / D converter 10b and the PD 5 serving as a photoelectric conversion unit have failed. An error flag is also output when the phase difference between left-handed light and right-handed light is 2π or more, that is, when a value corresponding to the maximum amplitude of the staircase wave is stored in the rate register 22. When a phase difference of 2π or more occurs, the rotational angular velocity Ω
Error occurs. Further, a phase difference of 2π or more occurs,
In addition, when such a fast change that the closed-loop control cannot respond (abnormality of the logical operation unit, excessive impact, or the like) is applied, the peak of the next interference fringe shifted by 2π phase is stabilized, leading to malfunction. Therefore, in this case as well, an error flag is output, and when the error flag CPU 12 detects the error, a failure is determined.

The 2π control register 23 has a function of outputting an error flag when the register value reaches the upper limit value and the lower limit value.
By detecting at U12, it is possible to determine the damage of the optical component or the failure of the component related to the phase modulation. Since the decrease in the optical output increases the noise of the optical gyro, the state is confirmed in advance by a test, and an abnormal value of the spike level is determined.

As described above, when there is no change in the value of the rate register 22, it is possible to detect the failure of the A / D converter 10b and the PD 5 at the preceding stage. The value of the rate register 22 is the phase difference 2π between the left-handed light and the right-handed light.
By detecting the above, it is possible to determine the divergence of the closed loop control due to the abnormality of the logical operation unit and the excessive impact. Further, by detecting the arrival of the upper and lower limit values of the 2π control register 23 in accordance with the staircase wave amplitude control, it is possible to diagnose the damage of the optical components and the failure of the phase modulator 2b.

FIG. 6 shows the occurrence of a malfunction when phase difference information of 2π or more is stored in the rate register 22.
As shown in (a), when a phase difference Φ _{S of} 2π or more occurs and a rapid change in which closed-loop control cannot respond occurs, the peak of the next interference fringe whose phase is shifted by 2π is (b).
And an error occurs in the rotational angular velocity Ω. It is desirable that the diagnosis data for failure determination is always added to the angular velocity data and angle data of the optical gyro, and is in a communication format that can be constantly monitored on the system side.

The present invention is not limited to the above-described embodiment, and the following changes and modifications are possible. (1) A / D conversion by the A / D converter 10b is not performed at the peak of the spike signal, and the spike signal 18 is analog-integrated by a newly provided low-pass filter, and then A / D converted by the A / D converter 10b. May be performed. (2) The rate register 22 may not output an error flag even if the register value is 2π or more, and may output the error flag at full scale guaranteed as an optical gyro specification. (3) Instead of outputting an error at the upper / lower limit value of the 2π control register 23, D / A corresponding to the upper / lower limit value
The determination may be made based on the value of the output (V _ref ) of the converter 10e.

[0022]

As is apparent from the above description, in the closed-loop type optical fiber gyro, a spike signal generated each time the bias modulation signal applied to the phase modulation means passes through the maximum point of the optical output is detected, and the level is detected based on the level. And a failure diagnosis means for judging a failure of a component member is provided, so that all failures of the components of the optical gyro can be detected, a reliable failure diagnosis can be performed, and a failure location can be specified. Further, since special parts or circuits for failure diagnosis are not required, the configuration can be made at low cost. In addition, since the diagnosis can be performed without stopping the operation of the optical gyro, there is no restriction on use, and the rotational angular velocity can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical fiber gyro having a self-diagnosis function according to the present invention.

FIG. 2 shows waveforms of a staircase wave modulation signal and a bias phase modulation signal output from the ASIC of FIG.

FIG. 3 is a waveform diagram showing an optical output waveform of a preamplifier during an open loop.

FIG. 4 is a waveform diagram showing an optical output waveform of a preamplifier in a closed loop.

FIG. 5 is a block diagram showing a detailed configuration of the ASIC of FIG. 1;

FIG. 6 is an explanatory diagram illustrating a malfunction when phase difference information of 2π or more is accumulated in a rate register.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensing loop 2 Optical integrated circuit 2a Optical branching / combining part 2b Phase modulator 3 Optical coupler 4 SLD (super luminescent diode) 5, 6 PD (photodiode) 7 APC (automatic light output control) circuit 8a Transistor 8b, 8c Resistor 9 Preamplifier 10 ASIC 10a Amplifier 10b A / D converter 10c Gate array 10d, 10e D / A converter 10f Oscillation circuit 11 Crystal oscillator 12 CPU 13 EEPROM 14 Reset / power supply circuit 15 Modulation output circuit 16 Step wave modulation signal 17 Bias phase modulation signal 18 Spike signal 21 Code converter 22 Rate register 23 2π control register 24 Lamp register 25 Data register

Claims (4)

[Claims] 1. An optical path that makes at least one round, an interference unit that causes left-handed light and right-handed light to enter and interfere with the optical path, and is coupled to the interference unit, and is coupled to the left-handed light and the right-handed light. Phase modulation means for applying alternating phase modulation to the surrounding light;
A bias phase modulation signal generating means for applying a bias phase modulation signal to the phase modulation means; a photoelectric conversion means for converting the light intensity of the interference light from the interference means into an electric signal; and an output from the photoelectric conversion means. Phase difference detecting means for detecting phase difference information between the left-handed light and the right-handed light, and providing a phase difference of opposite sign to a signal from the phase difference detecting means to output a step-like phase modulated wave. And a staircase wave amplitude control means for controlling the maximum amplitude of the staircase wave by the staircase wave generation means to give a phase difference of 2π between the left-handed light and the right-handed light. An optical fiber gyro that negatively feeds back the output of the staircase wave generation means to the phase modulation means so that the phase difference between the counterclockwise light and the clockwise light in the optical path becomes zero. Signal A spike signal generated every time the bias phase modulation signal applied to the means passes through the maximum point of the optical output is acquired through the photoelectric conversion means, and a failure of a component is determined based on the level of the spike signal. An optical fiber gyro having a self-diagnosis function, comprising: 2. An A / D converter for converting a phase difference between the left-handed light and the right-handed light into an electric signal, and a rate for accumulating angular velocity information by the A / D converter. 2. The optical fiber gyro according to claim 1, further comprising a register, wherein the failure of the optical fiber gyro is determined based on the fact that the value of the rate register does not change for a predetermined time. 3. The failure diagnosis unit according to claim 2, wherein the failure diagnosis unit determines the failure based on the fact that the value of the rate register has accumulated a phase difference of 2π or more between the left-handed light and the right-handed light. An optical fiber gyro having a self-diagnosis function. 4. The failure diagnosis means according to claim 1, wherein the phase difference between the left-handed light and the right-handed light is accumulated by 2π or more, and the error of the phase difference between the left-right-handed light corresponding to the maximum amplitude of the staircase wave with respect to 2π is obtained. 2. An optical fiber gyro having a self-diagnosis function according to claim 1, further comprising a register for obtaining and adding, and determining a failure when the value of the register is maximum or minimum.