JP2014106086A - Optical fiber gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to satisfactorily and stably restrict a change in angular velocity output due to Faraday effect even if a secular change or temperature change occurs in optical fiber characteristics.SOLUTION: An optical fiber gyro comprises: a magnetic sensor; feedback coils 23, 23, and 23wound around an optical fiber coil 70; and a feedback circuit that causes a feedback current to flow in the feedback coil. The magnetic sensor comprises: a core 10; a pair of coils 21 and 22 wound in places opposite the core 10 and connected in series so as to cause the core 10 to generate a magnetic flux in the same winding direction; an excitation power source that applies an AC current, in which DC currents are superposed, to the coils 21 and 22; and a detection circuit connected to the contact points of the pair of coils 21 and 22. The feedback coils 23, 23, and 23generate a magnetic field that offsets a magnetic field detected by the corresponding magnetic sensors (sensor parts 15, 15, and 15).

Description

  The present invention relates to an optical fiber gyro, and more particularly to an optical fiber gyro capable of suppressing fluctuations in angular velocity output due to the Faraday effect.

  In an optical fiber gyro that detects the angular velocity applied to the optical fiber coil by detecting the phase difference between the clockwise light and the counterclockwise light propagated to the optical fiber coil, the optical fiber coil It is known that the angular velocity output varies due to the Faraday effect.

  Patent Document 1 describes that in order to cope with this problem, the end of an optical fiber is twisted to compensate for magnetic sensitivity and suppress fluctuations in angular velocity output.

JP-A-6-341842

  However, the method of compensating the magnetic sensitivity by twisting the end of the optical fiber as described above has a drawback that the angular velocity output fluctuates because the compensation becomes insufficient due to aging or temperature change of the optical fiber characteristics.

  SUMMARY OF THE INVENTION In view of this problem, an object of the present invention is to provide an optical fiber gyro capable of satisfactorily and stably suppressing fluctuations in angular velocity output due to the Faraday effect even when aging or temperature changes occur in the optical fiber characteristics. There is to do.

  According to the first aspect of the present invention, an optical fiber gyro for detecting a phase difference between right-handed light and left-handed light propagated through an optical fiber coil and detecting an angular velocity applied to the optical fiber coil includes: a magnetic sensor; A magnetic sensor is provided with a feedback coil and a feedback circuit wound around an optical fiber coil, and the magnetic sensor is wound with a core constituting a closed magnetic circuit and with central axes parallel to each other at opposite positions of the core. A pair of coils connected in series so as to generate magnetic flux in the circumferential direction, an excitation power source that applies an alternating current in which a direct current is superimposed on the pair of coils, and a detection circuit connected to a connection point of the pair of coils The feedback circuit includes a reference voltage source that generates a reference voltage, an adder that adds the output of the detection circuit and the reference voltage, and an output of the adder that amplifies the feedback. More becomes amplifier supplying a feedback current to Le, the central axis of the feedback coil is parallel to the center axis of the pair of coils, the feedback coil generates a magnetic field that cancels the magnetic field by the magnetic sensor has detected.

  According to a second aspect of the present invention, in the first aspect of the present invention, the detection circuit includes a synchronous detector for synchronously detecting the voltage at the connection point using the AC excitation voltage of the excitation power supply, and a low-pass filter for smoothing the output of the synchronous detector. It becomes more.

  In the invention of claim 3, in the invention of claim 1, the detection circuit includes a DC circuit breaker that removes the DC component of the voltage at the connection point, a full wave rectifier that performs full wave rectification on the output of the DC circuit breaker, and a full wave rectifier. It consists of a low-pass filter that smoothes the output.

  According to a fourth aspect of the present invention, in the first aspect of the invention, the detection circuit includes a direct current circuit breaker that removes a direct current component of the voltage at the connection point, a half wave rectifier that rectifies the output of the direct current circuit breaker, and a half wave rectifier. It consists of a low-pass filter that smoothes the output.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the core around which the pair of coils is wound is located inside the feedback coil, and is brought into a magnetic equilibrium state by the magnetic field generated by the feedback coil.

  In the invention of claim 6, in the invention of claim 5, the core around which the pair of coils is wound is arranged inside the bobbin around which the optical fiber coil is wound.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, the feedback coil is wound around a housing containing the optical fiber coil.

  In the invention of claim 8, in the invention of any one of claims 1 to 7, there are a plurality of sets of cores, a detection circuit, a feedback coil, and a feedback circuit in which a pair of coils are wound. The feedback coils are arranged in directions in which the central axes are orthogonal to each other.

  According to the present invention, the fluctuation of the angular velocity output caused by the Faraday effect of the optical fiber coil due to the influence of the external magnetic field can be suppressed, and the angular velocity output caused by the Faraday effect can be suppressed even if the optical fiber characteristics change over time or temperature. It is possible to obtain an optical fiber gyro in which fluctuations can be satisfactorily and stably suppressed.

The figure which shows the structure outline | summary of the magnetic sensor with which the optical fiber gyroscope by this invention is provided, a feedback coil, and a feedback circuit. The block diagram which shows the function structure of the magnetic sensor shown in FIG. 1, a feedback coil, and a feedback circuit. The graph which shows a BH curve and a relative magnetic permeability. The block diagram which shows the other example of a function structure of the magnetic sensor shown in FIG. 1, a feedback coil, and a feedback circuit. The figure for demonstrating the principal part structure in the 1st Example of the optical fiber gyroscope by this invention. The figure for demonstrating the principal part structure in the 2nd Example of the optical fiber gyroscope by this invention. The figure for demonstrating the principal part structure in the 3rd Example of the optical fiber gyroscope by this invention.

  First, the configuration of a magnetic sensor, a feedback coil, and a feedback circuit included in an optical fiber gyro according to the present invention will be described with reference to FIGS. FIG. 1 shows an outline of the configuration, and FIG. 2 shows a functional configuration in a block diagram.

  The core 10 constituting the closed magnetic path is made of a high magnetic permeability material such as permalloy, and is a toroidal core in this example. Coils 21 and 22 are wound around the core 10 at positions facing each other with the central axes parallel to each other. The coils 21 and 22 are wound in the same direction along the circumferential direction of the core 10 and are connected in series so as to generate a magnetic flux in the same circumferential direction when a current is applied to the coils 21 and 22. .

  An excitation power source 30 is connected to one end of one coil 21. The excitation power source 30 includes a direct current power source 31 and an alternating current power source 32, and can apply an alternating current superimposed with a direct current to the coils 21 and 22. In FIG. 1, 33 indicates a DC circuit breaker (capacitor).

  A direct current is applied to the coils 21 and 22 by the direct current power source 31, thereby generating a direct magnetic flux in the core 10. In FIG. 1, arrows a and b illustrate the directions of magnetic fluxes generated by the coils 21 and 22, respectively. The magnetic fluxes generated by the coils 21 and 22 are in the same direction in the circumferential direction of the core 10.

  FIG. 3 shows the BH curve and relative permeability of the core 10, and the direct current applied to the coils 21 and 22 is set so as to generate a direct current magnetic field of about 8 A / m, for example. The value of this magnetic field: 8 A / m is located approximately at the center of the region where the relative permeability changes linearly with respect to the magnetic field.

The coils 21 and 22 have the same number of turns, and the inductance L1 of the coil 21 and the inductance L2 of the coil 22 are equal. An AC voltage on which a DC voltage is superimposed is generated at the connection point P between the coil 21 and the coil 22 by an excitation power source 30 including a DC power source 31 and an AC power source 32. The AC voltage Vd at the connection point P is defined as Vac as the AC excitation voltage of the excitation power source 30.
Vd = (L2 / (L1 + L2)). Vac (1)
When the external magnetic field is 0, since the inductances L1 and L2 of the coil 21 and the coil 22 are equal, the AC voltage Vd at the connection point P is ½ of the AC excitation voltage Vac.

  On the other hand, as shown in FIG. 1, when the external magnetic field M passes through the core 10, a magnetic flux proportional to the external magnetic field M is generated in a portion of the core 10 where the coils 21 and 22 are located. As a result, the DC magnetic flux is strengthened in the portion where the coil 22 is located, and the DC magnetic flux cancels out in the portion where the coil 21 is located. Therefore, the magnetic flux density inside the core 10 changes in the portion where the coil 21 is located and the portion where the coil 22 is located.

  When the magnetic flux density changes, as can be seen from FIG. 3, the relative permeability of the core 10 changes. Since the magnetic flux density is increased in the portion where the coil 22 is located, the relative permeability is reduced, and in the portion where the coil 21 is located, the magnetic flux density is reduced, so that the relative permeability is increased. Due to this change in the relative permeability, the inductance L2 of the coil 22 decreases and the inductance L1 of the coil 21 increases. Therefore, from the equation (1), the AC voltage Vd at the connection point P is smaller than the value when the external magnetic field is 0, that is, smaller than ½ of the AC excitation voltage Vac.

  A detection circuit 40 is connected to a connection point P between the coils 21 and 22. In this example, the detection circuit 40 includes a synchronous detector 41 and a low-pass filter 42 as shown in FIG. The synchronous detector 41 synchronously detects the voltage at the connection point P using the AC excitation voltage Vac of the excitation power supply 30. The low-pass filter 42 smoothes the output of the synchronous detector 41. The synchronously detected voltage passes through the low-pass filter 42 and becomes an output Vo. The magnetic sensor obtains the output Vo in this way, and this output Vo is proportional to the magnitude of the external magnetic field M.

  The feedback circuit 50 is connected to the subsequent stage of the detection circuit 40 of the magnetic sensor having the above configuration. The feedback circuit 50 includes a reference voltage source 51 that generates a reference voltage, an output (output of the low-pass filter 42) Vo of the detection circuit 40 and an adder 52 that adds the reference voltage, and an output of the adder 52 that amplifies the feedback coil. 23, and an amplifier 53 that feeds a feedback current.

  The feedback coil 23 is wound around the core 10 so as to magnetically balance the core 10. The feedback coil 23 is arranged such that the central axis thereof is parallel to the central axes of the coils 21 and 22 and the magnetic field generated by the feedback coil 23 is parallel to the external magnetic field M. In FIG. 1, an arrow c indicates the direction of magnetic flux generated by the feedback coil 23.

  The reference voltage generated by the reference voltage source 51 is set so that the output (output voltage) Vo output from the low-pass filter 42 when the external magnetic field M is 0 is set to 0V. Therefore, when the external magnetic field M is 0, the feedback current is 0 and no current flows through the feedback coil 23.

  On the other hand, when the external magnetic field M is input as shown in FIG. 1, the output of the low-pass filter 42 is smaller than when the external magnetic field M is zero. Therefore, the output of the adder 52 is a negative voltage. As a result, a negative feedback current flows through the feedback coil 23, and the feedback coil 23 generates a magnetic field that cancels the external magnetic field M detected by the magnetic sensor. The core 10 is in a magnetic equilibrium state with respect to the external magnetic field M.

  The feedback current is converted into a voltage by the reading resistor 60 and output. Therefore, the input external magnetic field M can be measured by the output of the reading resistor 60.

  FIG. 4 shows an example in which the configuration of the detection circuit is changed with respect to FIG. 2. In this example, the detection circuit 40 ′ is a DC circuit breaker that removes a DC component from the voltage at the connection point P of the coils 21 and 22. 43, a full-wave rectifier 44 that full-wave rectifies the output of the DC circuit breaker 43, and a low-pass filter 42 that smoothes the output of the full-wave rectifier 44. Such a detection circuit 40 'may be employed instead of the detection circuit 40 shown in FIG. Note that a half-wave rectifier may be used instead of the full-wave rectifier 44.

  Next, an embodiment of an optical fiber gyro according to the present invention will be described.

  The optical fiber gyroscope includes the magnetic sensor, the feedback coil 23, and the feedback circuit 50 as described above. FIG. 5 shows the structure of the optical fiber coil part as a main part structure of the first embodiment of the optical fiber gyro according to the present invention together with the parts disassembled into parts. In FIG. 80 indicates a bobbin. The optical fiber coil 70 is wound around a bobbin 80 having a cylindrical shape.

In this example, three sensor parts of a magnetic sensor in which a pair of coils 21 and 22 are wound around a core 10 are installed on a bobbin 80, and input to the optical fiber coil 70 by the _three sensor parts 15 ₁ , 15 ₂ , and 15 ₃ . Thus, it is possible to detect external magnetic fields in all directions (external magnetic fields in the X, Y, and Z3 axis directions).

The sensor units 15 ₁ and 15 ₂ are installed on the upper and lower flanges 81 and 82 of the bobbin 80, respectively, and a horizontal external magnetic field is detected by the sensor units 15 ₁ and 15 ₂ . The sensor unit 15 ₃ detects an external magnetic field in the vertical direction is installed as shown in FIG. 5 on the inside of the bobbin 80 (the cylinder).

These three sensors _{15 1,} 15 2, 15 feedback coil ₂₃ respectively to ₃ corresponding _1, 23 2, 23 ₃ are provided as shown in FIG. The feedback coils 23 ₁ and 23 ₂ corresponding to the sensor units 15 ₁ and 15 ₂ surround the optical fiber coil 70 and the sensor units 15 ₁ and 15 ₂ and are wound around them, and the feedback coils 23 ₁ and 15 ₂ correspond to the sensor unit 15 _3. coil 23 ₃ is wound around the optical fiber coil 70. The central axes of the feedback coils 23 ₁ , 23 ₂ , and 23 ₃ are parallel to the central axes of the coils 21 and 22 of the corresponding sensor portions 15 ₁ , 15 ₂ , and 15 ₃ .

The above-described structure in this embodiment, the sensor unit _{15 1,} 15 2, 15 ₃ feedback coil ₂₃ 1 a magnetic field to cancel the external magnetic field detection _{respectively,} 23 2, 23 ₃ has become what occurs respectively . Thus, the influence of the external magnetic field on the optical fiber coil 70 can be eliminated and the magnetic sensitivity can be compensated, and the external magnetic field is detected and canceled. Even if it occurs, it is not affected by this, and in this example, the angular velocity output does not fluctuate due to aging or temperature change of the optical fiber characteristics.

  In this example, the optical fiber gyro has three sets of a core 10 around which a pair of coils 21 and 22 are wound, a detection circuit, a feedback coil 23, and a feedback circuit 50. The excitation power supply 30 does not need to be individually provided and can be shared.

FIG. 6 shows the configuration of the main part of a second embodiment of the optical fiber gyro according to the present invention in the same manner as in FIG. 5. In this example, a sensor unit 15 for detecting an external magnetic field in the vertical direction with respect to FIG. ₃ and it has become that deletes the corresponding feedback 23 _3.

  Since the optical fiber coil 70 has a very low sensitivity to a magnetic field in the vertical direction, the configuration as shown in FIG. 6 can be adopted. Even if this configuration is used when the external magnetic field is small, the magnetic sensitivity This compensation is sufficient.

Next, a third embodiment of the optical fiber gyro according to the present invention will be described with reference to FIG. 7 is shows a main configuration of a three-axis fiber optic gyro is configured using three optical fiber coil 70 'to the sensor unit 15 ₃ is installed in the bobbin 80, as shown in FIG. 7A The

The three optical fiber coils 70 ′ are housed and fixed in the housing 90 as shown in FIG. 7B with the central axes (angular velocity detection axes) orthogonal to each other (the X, Y, and Z 3 axes). . Then, winding the three feedback coil ₂₃ 1, as shown in FIG. 7C around the housing _90, 23 2, 23 _3. The three feedback coils 23 ₁ , 23 ₂ , and 23 ₃ generate magnetic fields that cancel out the X, Y, and Z3 axis external magnetic fields detected by the _three sensor units 15 ₃ , respectively.

According to the configuration shown in FIG. 7, the magnetic sensitivity of the triaxial optical fiber gyro can be compensated by eliminating the influence of the external magnetic field. In addition, since the sensor includes _three sensor units 153 whose detection axes are X, Y, and Z3 axes, that is, a three-axis magnetic sensor, the orientation can be detected by the three-axis magnetic sensor. Therefore, a sensor in which the three-axis optical fiber gyro and the direction sensor are integrated can be obtained.

  Although the embodiments of the present invention have been described above, the magnetic sensor provided in the optical fiber gyro according to the present invention needs to be excited until the core 10 is magnetically saturated, unlike a conventional general fluxgate type magnetic sensor, for example. In other words, the core 10 is not magnetically saturated. Therefore, there is no leakage of the excitation magnetic flux, and the optical fiber coil 70 is not affected by the excitation magnetic flux. Further, since the core 10 is not magnetically saturated, the excitation current may be small, and power consumption may be small.

In the embodiment described above, the sensor portions 15 ₁ , 15 ₂ , and 15 ₃ of the magnetic sensor are installed on the bobbin 80 and integrated with the optical fiber coil 70, but it is not necessarily integrated with the optical fiber coil 70, for example, It is good also as a structure arrange | positioned in the immediate vicinity of the optical fiber coil 70. FIG. Further, the size of the core 10 is not particularly limited.

  As in the third embodiment, since the first embodiment also includes a three-axis magnetic sensor, the orientation can be detected by the three-axis magnetic sensor. As described above, when the detection output of the magnetic sensor is used for azimuth detection or the like, the reading resistor 60 for reading the feedback current flowing in the feedback coil 23 shown in FIG. 2 or FIG. 3 is required. In order to realize the compensated optical fiber gyro, the reading resistor 60 becomes unnecessary.

10 cores 15 ₁ , 15 ₂ , 15 ₃ sensor units 21, 22 coils 23, 23 ₁ , 23 ₂ , 23 ₃ feedback coil 30 excitation power supply 31 DC power supply 32 AC power supply 33 DC breaker 40, 40 ′ detection circuit 41 synchronous detection 42 Low-pass filter 43 DC circuit breaker 44 Full wave rectifier 50 Feedback circuit 51 Reference voltage source 52 Adder 53 Amplifier 60 Read resistor 70, 70 'Feedback coil
80 Bobbins 81, 82 Flange 90 Case

Claims (8)

An optical fiber gyro that detects a phase difference between clockwise and counterclockwise light propagated to an optical fiber coil and detects an angular velocity applied to the optical fiber coil,
A magnetic sensor, a feedback coil wound around the optical fiber coil, and a feedback circuit;
The magnetic sensor is
A core constituting a closed magnetic circuit;
A pair of coils wound in parallel with each other at positions opposite to each other on the core and connected in series so as to generate magnetic flux in the same circumferential direction in the core;
An excitation power source for applying an alternating current in which a direct current is superimposed on the pair of coils;
A detection circuit connected to a connection point of the pair of coils,
The feedback circuit includes:
A reference voltage source for generating a reference voltage;
An adder for adding the output of the detection circuit and the reference voltage;
An amplifier that amplifies the output of the adder and sends a feedback current to the feedback coil;
The central axis of the feedback coil is parallel to the central axis of the pair of coils,
The optical fiber gyro characterized in that the feedback coil generates a magnetic field that cancels the magnetic field detected by the magnetic sensor. The optical fiber gyro according to claim 1, wherein
The detection circuit includes a synchronous detector that synchronously detects the voltage at the connection point using an AC excitation voltage of the excitation power source, and a low-pass filter that smoothes the output of the synchronous detector. Fiber gyro. The optical fiber gyro according to claim 1, wherein
The detection circuit includes a DC breaker that removes a DC component of the voltage at the connection point, a full-wave rectifier that full-wave rectifies the output of the DC breaker, and a low-pass filter that smoothes the output of the full-wave rectifier; An optical fiber gyro characterized by comprising: The optical fiber gyro according to claim 1, wherein
The detection circuit includes a DC breaker that removes a DC component of the voltage at the connection point, a half-wave rectifier that half-wave rectifies the output of the DC breaker, and a low-pass filter that smoothes the output of the half-wave rectifier. An optical fiber gyro characterized by comprising: The optical fiber gyro according to any one of claims 1 to 4,
The optical fiber gyro, wherein the core around which the pair of coils are wound is located inside the feedback coil and is in a magnetic equilibrium state by a magnetic field generated by the feedback coil. The optical fiber gyro according to claim 5, wherein
An optical fiber gyro, wherein the core around which the pair of coils are wound is disposed inside a bobbin around which the optical fiber coil is wound. The optical fiber gyro according to any one of claims 1 to 6,
An optical fiber gyro, wherein the feedback coil is wound around a casing containing the optical fiber coil. The optical fiber gyro according to any one of claims 1 to 7,
The core having the pair of coils wound thereon, the detection circuit, the feedback coil, and the feedback circuit have a plurality of sets, and the plurality of sets of feedback coils are arranged in directions in which the central axes are orthogonal to each other. An optical fiber gyro characterized by

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