Fiber optic gyro device

Abstract

A fiber optic gyro device capable of improving the accuracy of the detection results of the fiber optic gyro device is provided. [Solution] This fiber optic gyro device includes a light source module 1, an optical fiber cable 2, an optical fiber coil 4 into which light passing through the optical fiber cable 2 in one direction is branched and enters from both one end and the other end, an optical phase modulator 3 that changes the phase of the light passing through the optical fiber coil 4 using a signal of a drive frequency DF and a feedback signal FS, a light source drive circuit 10 that drives the light source module 1, a power supply circuit 11 that has a switching circuit 111 that performs DC / DC conversion and supplies power to the light source drive circuit 10, a temperature sensor 13 that measures the temperature of the power supply circuit 11, and a control circuit 12 that controls the switching frequency SF of the switching circuit 111 based on the measurement result of the temperature sensor 13 so that the switching frequency SF is different from an integer multiple of the drive frequency DF.

Description

[Technical Field]

[0001] The present invention relates to a fiber optic gyro device. [Background technology]

[0002] Conventionally, a fiber optic gyro device has been known that includes a light source module, an optical fiber cable, an optical fiber coil, an optical phase modulator, a light source drive circuit, and a power supply circuit. The light source module emits light. One end of the optical fiber cable is connected to the light source module. The light emitted from the light source module enters the optical fiber cable. The light that enters the optical fiber cable from the light source module passes through the optical fiber cable in one direction. An optical phase modulator is provided at the other end of the optical fiber cable.

[0003] Both ends of the optical fiber coil are connected to the optical phase modulator. Light passing through the optical fiber cable in one direction enters one end and the other end of the optical fiber coil via the optical phase modulator. The light that enters one end of the optical fiber coil passes through the optical fiber coil and exits from the other end of the optical fiber coil. The light that enters the other end of the optical fiber coil passes through the optical fiber coil and exits from one end of the optical fiber coil.

[0004] The light emitted from the other end of the optical fiber coil and the light emitted from one end of the optical fiber coil are combined by the optical phase modulator. The combined light enters the optical fiber cable. The light that enters the optical fiber cable from the optical phase modulator passes through the optical fiber cable in the other direction. In the optical fiber cable, the light emitted from the other end of the optical fiber coil and the light emitted from the one end of the optical fiber coil interfere with each other.

[0005] When a rotational force acts on the optical fiber coil, a phase difference occurs between the light exiting from one end of the optical fiber coil and the light exiting from the other end of the optical fiber coil depending on the angular velocity of the optical fiber coil. The optical phase modulator changes the phase of the light entering one end of the optical fiber coil or the phase of the light entering the other end of the optical fiber coil so that the phase difference of the light becomes zero.

[0006] The light source drive circuit drives the light source module. The power supply circuit has a switching circuit that performs DC / DC conversion and supplies power to the light source drive circuit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-147863 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the configuration of the fiber optic gyro device described in Patent Document 1, a fixed switching frequency is preset in the power supply circuit. The switching frequency changes in response to changes in the temperature of the power supply circuit. If the switching frequency changes due to changes in the temperature of the power supply circuit and coincides with an integer multiple of the drive frequency, fluctuations occur in the angular velocity values ​​detected by the fiber optic gyro device. This results in a problem of large errors in the detection results of the fiber optic gyro device.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fiber optic gyro device that can improve the accuracy of the detection results of the fiber optic gyro device. [Means for solving the problem]

[0010] The fiber optic gyro device according to the present invention includes a light source module that emits light, an optical fiber cable through which the light emitted from the light source module passes, an optical fiber coil into which light passing in one direction through the optical fiber cable is branched and into which the branched light enters both one end and the other end, an optical phase modulator that changes the phase of the light passing through the optical fiber coil using a signal of a drive frequency output from an oscillation circuit and a feedback signal output from a feedback signal generating circuit, a light source drive circuit that drives the light source module, a power supply circuit that has a switching circuit that performs DC / DC conversion and supplies power to the light source drive circuit, a temperature sensor that measures the temperature of the power supply circuit, and a control circuit that controls the switching frequency of the switching circuit based on the measurement result of the temperature sensor so that the switching frequency is different from an integer multiple of the drive frequency. In the fiber optic gyro device according to the present invention, the power supply circuit generates a switching frequency using a control signal output from the control circuit, and the control circuit controls the switching frequency via the control signal. In the fiber optic gyro device according to the present invention, the control circuit outputs a control signal so that the switching frequency remains constant regardless of changes in the temperature of the power supply circuit. [Effects of the Invention]

[0011] According to the fiber optic gyro device of the present invention, the accuracy of the detection results of the fiber optic gyro device can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a fiber optic gyro device according to a first embodiment. [Figure 2] FIG. 10 is a block diagram showing a fiber optic gyro device of a comparative example. [Figure 3] 10 is a graph showing the relationship between the temperature and the switching frequency of a power supply circuit in a fiber optic gyro device. [Figure 4] 10 is a graph showing the switching frequency of the fiber optic gyro device of the comparative example. [Figure 5] 4 is a graph showing the switching frequency of the fiber optic gyro device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiment 1 1 is a block diagram showing a fiber optic gyro device according to embodiment 1. The fiber optic gyro device according to embodiment 1 includes a light source module 1, an optical fiber cable 2, an optical phase modulator 3, an optical fiber coil 4, an oscillation circuit 5, a coupler 6, a detector module 7, a detector circuit 8, and a feedback signal generating circuit 9. The fiber optic gyro device according to embodiment 1 also includes a light source driving circuit 10, a power supply circuit 11, a control circuit 12, and a temperature sensor 13.

[0014] The light source module 1 emits light. One end of the optical fiber cable 2 is connected to the light source module 1. The light emitted from the light source module 1 enters the optical fiber cable 2. The light that enters the optical fiber cable 2 from the light source module 1 passes through the optical fiber cable 2 in one direction.

[0015] An optical phase modulator 3 is provided at the other end of the optical fiber cable 2. Both ends of an optical fiber coil 4 are connected to the optical phase modulator 3. Light that has passed through the optical fiber cable 2 in one direction enters one end 41 and the other end 42 of the optical fiber coil 4 via the optical phase modulator 3. The light that has entered one end 41 of the optical fiber coil 4 passes through the optical fiber coil 4 and exits from the other end 42 of the optical fiber coil 4. The light that has entered the other end 42 of the optical fiber coil 4 passes through the optical fiber coil 4 and exits from the one end 41 of the optical fiber coil 4.

[0016] The light emitted from the other end 42 of the optical fiber coil 4 and the light emitted from one end 41 of the optical fiber coil 4 are combined by the optical phase modulator 3. The combined light enters the optical fiber cable 2. The light that enters the optical fiber cable 2 from the optical phase modulator 3 passes through the optical fiber cable 2 in the other direction. In the optical fiber cable 2, the light emitted from the other end 42 of the optical fiber coil 4 and the light emitted from one end 41 of the optical fiber coil 4 interfere with each other.

[0017] When a rotational force acts on the optical fiber coil 4, a phase difference occurs between the light emitted from the other end 42 of the optical fiber coil 4 and the light emitted from one end 41 of the optical fiber coil 4, depending on the angular velocity of the optical fiber coil 4.

[0018] A signal with a drive frequency DF is input to the optical phase modulator 3 from an oscillation circuit 5. The drive frequency DF is, for example, 100 kHz. In addition, a feedback signal FS is input to the optical phase modulator 3 from a feedback signal generation circuit 9.

[0019] The optical phase modulator 3 is driven by a signal with a drive frequency DF. Based on the feedback signal FS, the optical phase modulator 3 changes the phase of the light entering one end 41 of the optical fiber coil 4 or the phase of the light entering the other end 42 of the optical fiber coil 4 so that the phase difference of the light becomes zero.

[0020] A coupler 6 is provided in the portion of the optical fiber cable 2 between the light source module 1 and the optical phase modulator 3. The coupler 6 branches the light that enters the optical fiber cable 2 from the optical phase modulator 3. The branched light is input to a detector module 7.

[0021] The detector module 7 photoelectrically converts the light input to the detector module 7. The photoelectrically converted optical signal is output from the detector module 7 and input to the detector circuit 8.

[0022] The detector circuit 8 receives a signal of the drive frequency DF from the oscillator circuit 5. The detector circuit 8 uses the photoelectrically converted optical signal and the signal of the drive frequency DF to detect, in the photoelectrically converted optical signal, a signal when the signal of the drive frequency DF is a positive voltage and a signal when the signal of the drive frequency DF is a negative voltage. The detection result of the detector circuit 8 is output from the detector circuit 8 and input to the feedback signal generating circuit 9.

[0023] The feedback signal generating circuit 9 calculates the phase difference between the light emitted from the other end 42 of the optical fiber coil 4 and the light emitted from the one end 41 of the optical fiber coil 4 based on the detection result of the detector circuit 8. Furthermore, based on the calculation result of the phase difference, the feedback signal generating circuit 9 outputs a feedback signal FS so that the phase difference becomes 0. Furthermore, the feedback signal generating circuit 9 outputs a signal corresponding to the feedback signal FS when the phase difference is 0 as the value of the angular velocity of the optical fiber coil 4. The value of the angular velocity output from the feedback signal generating circuit 9 is the value of the angular velocity detected by the fiber optic gyro device.

[0024] The light source drive circuit 10 drives the light source module 1. The light source drive circuit 10 is supplied with power from a power supply circuit 11.

[0025] The power supply circuit 11 has a switching circuit 111 that performs DC / DC conversion. A switching frequency SF is used in the switching circuit 111. The switching circuit 111 performs DC / DC conversion, and the power supply circuit 11 supplies power to the light source drive circuit 10. A control signal CS is input to the power supply circuit 11 from a control circuit 12. The power supply circuit 11 generates the switching frequency SF using the control signal CS output from the control circuit 12.

[0026] The control circuit 12 receives the measurement result of a temperature sensor 13 that measures the temperature of the power supply circuit 11. Based on the measurement result of the temperature sensor 13, the control circuit 12 outputs a control signal CS that is input to the power supply circuit 11.

[0027] Specifically, based on the measurement result of the temperature sensor 13, the control circuit 12 outputs a control signal CS to control the switching frequency SF of the switching circuit 111 so that the switching frequency SF is different from a value that is an integer multiple of the drive frequency DF.

[0028] The control circuit 12 outputs a control signal CS so that the switching frequency SF is constant regardless of changes in the temperature of the power supply circuit 11.

[0029] 2 is a block diagram showing a comparative example of an optical fiber gyro device. Unlike the optical fiber gyro device according to the first embodiment, the optical fiber gyro device according to the comparative example does not include a control circuit 12 and a temperature sensor 13. In the optical fiber gyro device according to the comparative example, a constant switching frequency SF is preset in the power supply circuit 11. Other configurations of the optical fiber gyro device according to the comparative example are similar to those of the optical fiber gyro device according to the first embodiment.

[0030] Fig. 3 is a graph showing the relationship between the temperature of the power supply circuit 11 in the fiber optic gyro device and the switching frequency SF. Fig. 4 is a graph showing the switching frequency SF of the fiber optic gyro device of the comparative example. Fig. 5 is a graph showing the switching frequency SF of the fiber optic gyro device according to the first embodiment. In Fig. 3, the switching frequency SF of the fiber optic gyro device according to the first embodiment is shown by a solid line, and the switching frequency SF of the fiber optic gyro device of the comparative example is shown by a dotted line.

[0031] In the fiber optic gyro device of the comparative example, the switching frequency SF changes in response to changes in the temperature of the power supply circuit 11. Specifically, as the temperature of the power supply circuit 11 rises, the switching frequency SF increases. Therefore, in the fiber optic gyro device of the comparative example, changes in the temperature of the power supply circuit 11 may cause the switching frequency SF to coincide with an integer multiple of the drive frequency DF. FIGS. 3 and 4 show that in the fiber optic gyro device of the comparative example, the switching frequency SF may coincide with four times the drive frequency DF. When the switching frequency SF coincides with an integer multiple of the drive frequency DF, fluctuations occur in the angular velocity values ​​detected by the fiber optic gyro device of the comparative example. As a result, the error contained in the detection result of the fiber optic gyro device of the comparative example increases.

[0032] On the other hand, in the fiber optic gyro device according to the first embodiment, the switching frequency SF is constant regardless of the temperature of the power supply circuit 11. FIGS. 3 and 5 show that in the fiber optic gyro device according to the first embodiment, the switching frequency SF is constant between four and five times the drive frequency DF. Therefore, in the fiber optic gyro device according to the first embodiment, the switching frequency SF does not coincide with an integer multiple of the drive frequency DF. This improves the accuracy of the detection results of the fiber optic gyro device according to the first embodiment.

[0033] As described above, the fiber optic gyro device according to the first embodiment includes the light source module 1, the optical fiber cable 2, the optical fiber coil 4, the optical phase modulator 3, the light source driving circuit 10, the power supply circuit 11, the temperature sensor 13, and the control circuit 12. The light source module 1 emits light. The light emitted from the light source module 1 passes through the optical fiber cable 2. The light passing through the optical fiber cable 2 in one direction is branched, and the branched light enters the optical fiber coil 4 from both one end and the other end. The optical phase modulator 3 changes the phase of the light passing through the optical fiber coil 4 using a signal with a driving frequency DF output from the oscillation circuit 5 and a feedback signal FS output from the feedback signal generating circuit 9. The light source driving circuit 10 drives the light source module 1. The power supply circuit 11 has a switching circuit 111 that performs DC / DC conversion and supplies power to the light source driving circuit 10. The temperature sensor 13 measures the temperature of the power supply circuit 11. The control circuit 12 controls the switching frequency SF of the switching circuit 111 based on the measurement result of the temperature sensor 13 so that the switching frequency SF is different from an integer multiple of the drive frequency DF. With this configuration, the switching frequency SF does not match the integer multiple of the drive frequency DF. This improves the accuracy of the detection result of the fiber optic gyro device.

[0034] Furthermore, in the fiber optic gyro device according to the first embodiment, the power supply circuit 11 generates the switching frequency SF using the control signal CS output from the control circuit 12. The control circuit 12 controls the switching frequency SF via the control signal CS. With this configuration, the control circuit 12 can control the switching frequency SF by inputting the control signal CS to the power supply circuit 11.

[0035] Furthermore, in the fiber optic gyro device according to the first embodiment, the control circuit 12 outputs the control signal CS so that the switching frequency SF remains constant regardless of changes in the temperature of the power supply circuit 11. This configuration makes it possible to prevent the switching frequency SF from approaching a value that is an integer multiple of the drive frequency DF due to changes in the temperature of the power supply circuit 11.

[0036] In the fiber optic gyro device according to the first embodiment, the control circuit 12 controls the switching frequency SF so that the switching frequency SF is constant regardless of changes in the temperature of the power supply circuit 11. However, the present invention is not limited to this configuration. Any configuration may be used in which the control circuit 12 controls the switching frequency SF so that the switching frequency SF is different from a value that is an integer multiple of the drive frequency DF.

[0037] Although the optical fiber gyro device according to the preferred embodiment 1 has been described above, it is not limited to the optical fiber gyro device according to the above-described embodiment 1. Various modifications and conversions can be made to the optical fiber gyro device according to the above-described embodiment 1 without departing from the scope of the claims. [Explanation of symbols]

[0038] 1 light source module, 2 optical fiber cable, 3 optical phase modulator, 4 optical fiber coil, 5 oscillation circuit, 6 coupler, 7 detector module, 8 detector circuit, 9 feedback signal generating circuit, 10 light source driving circuit, 11 power supply circuit, 12 control circuit, 13 temperature sensor, 41 one end, 42 other end, 111 switching circuit.

Claims

1. a light source module (1) that emits light; an optical fiber cable (2) through which the light emitted from the light source module (1) passes; an optical fiber coil (4) into which the light passing through the optical fiber cable (2) in one direction is branched and into which the branched light enters from both one end and the other end; an optical phase modulator (3) that changes the phase of the light passing through the optical fiber coil (4) using a signal of a drive frequency (DF) output from an oscillation circuit (5) and a feedback signal (FS) output from a feedback signal generating circuit (9); a light source driving circuit (10) for driving the light source module (1); a power supply circuit (11) having a switching circuit (111) for performing DC / DC conversion and supplying power to the light source drive circuit (10); a temperature sensor (13) for measuring the temperature of the power supply circuit (11); a control circuit (12) that controls the switching frequency (SF) of the switching circuit (111) based on the measurement result of the temperature sensor (13) so that the switching frequency (SF) is different from a value that is an integer multiple of the drive frequency (DF); A fiber optic gyro device comprising:

2. The power supply circuit (11) generates the switching frequency (SF) using a control signal (CS) output from the control circuit (12), 2. The fiber optic gyro device according to claim 1, wherein said control circuit (12) controls said switching frequency (SF) via said control signal (CS).

3. 3. The fiber optic gyro device according to claim 2, wherein the control circuit (12) controls the switching frequency (SF) via the control signal (CS) so that the switching frequency (SF) is constant regardless of changes in the temperature of the power supply circuit (11).

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