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 optical fiber gyro device comprises a light source module 1 that emits light, a light source drive circuit 10 that drives the light source module 1 by PWM control, 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, and a frequency adjustment circuit 12 that changes the switching frequency SF of the switching circuit 111 so that it does not interfere with the frequency component of the pulse frequency PF of the PWM control.

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 by PWM (Pulse Width Modulation) control. 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. If the switching frequency interferes with the frequency component of the pulse frequency of the PWM control, fluctuations occur in the angular velocity value detected by the fiber optic gyro device. As a result, there is a problem in that the error included in the detection result of the fiber optic gyro device becomes large.

[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 of the present invention includes a light source module that emits light, a light source drive circuit that drives the light source module by PWM control, a power supply circuit that has a switching circuit that performs DC / DC conversion and supplies power to the light source drive circuit, and a frequency adjustment circuit that changes the switching frequency of the switching circuit so that it does not interfere with the frequency component of the pulse frequency of the PWM control. In the fiber optic gyro device according to the present invention, the frequency adjustment circuit divides the reference frequency to generate a switching frequency that does not interfere with the frequency component of the pulse frequency. [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] 4 is a graph showing a pulse frequency signal of PWM control in a light source drive circuit of the fiber optic gyro device. [Figure 4] 10 is a graph showing the switching frequency and pulse frequency of the fiber optic gyro device of the comparative example. [Figure 5] 4 is a graph showing the switching frequency and pulse 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 generation circuit 9. The fiber optic gyro device according to embodiment 1 also includes a light source drive circuit 10, a power supply circuit 11, and a frequency adjustment circuit 12.

[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 of a drive frequency DF. Based on a 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 by PWM control at a preset pulse frequency PF. 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. The switching frequency SF is input to the power supply circuit 11 from a frequency adjustment circuit 12. The power supply circuit 11 performs DC / DC conversion using the switching frequency SF output from the frequency adjustment circuit 12.

[0026] The frequency adjustment circuit 12 changes the switching frequency SF so that it does not interfere with the frequency component of the pulse frequency PF, and inputs the changed frequency to the power supply circuit 11. Specifically, the frequency adjustment circuit 12 has a frequency divider circuit that divides a reference frequency, and by dividing the reference frequency, generates a switching frequency SF that does not interfere with the frequency component of the pulse frequency PF. An example of the frequency divider circuit is an FPGA (Field Programmable Gate Array).

[0027] The frequency adjustment circuit 12 changes the switching frequency SF when an operator operates the frequency adjustment circuit 12. Note that the frequency adjustment circuit 12 may automatically change the switching frequency SF by inputting the pulse frequency PF to the frequency adjustment circuit 12.

[0028] 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 frequency adjustment circuit 12. 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.

[0029] 3 is a graph showing the pulse frequency PF signal of PWM control in the light source driving circuit 10 of the fiber optic gyro device. In PWM control, a fixed pulse frequency PF is set in advance. The pulse frequency PF has a rectangular wave shape. Therefore, the pulse frequency PF contains multiple frequency components.

[0030] Fig. 4 is a graph showing the frequency components of the switching frequency SF and pulse frequency PF of the fiber optic gyro device of the comparative example. Fig. 5 is a graph showing the frequency components of the switching frequency SF and pulse frequency PF of the fiber optic gyro device according to embodiment 1. Of the multiple frequency components included in the pulse frequency PF, Figs. 4 and 5 show three adjacent frequency components PFn-1, PFn, and PFn+1.

[0031] In the optical fiber gyro device of the comparative example, a fixed value of switching frequency SF is preset. FIG. 4 shows that the switching frequency SF may interfere with the frequency component PFn of the pulse frequency PF. When the switching frequency SF interferes with the frequency component of the pulse frequency PF, fluctuations occur in the value of the angular velocity detected by the optical fiber gyro device. As a result, the error contained in the detection result of the optical fiber gyro device increases.

[0032] On the other hand, in the fiber optic gyro device according to the first embodiment, the frequency adjustment circuit 12 changes the switching frequency SF and inputs it to the power supply circuit 11 so that the switching frequency SF does not interfere with the frequency component of the pulse frequency PF. FIG. 5 shows that the switching frequency SF changes so that the switching frequency SF is in the intermediate portion between the frequency component PFn-1 and the frequency component PFn of the pulse frequency PF, or in the intermediate portion between the frequency component PFn and the frequency component PFn+1 of the pulse frequency PF. By changing the switching frequency SF, the switching frequency SF does not interfere with the frequency component of the pulse frequency PF. This improves the accuracy of the detection results of the fiber optic gyro device.

[0033] As described above, the fiber optic gyro device according to the first embodiment includes the light source module 1, the light source drive circuit 10, the power supply circuit 11, and the frequency adjustment circuit 12. The light source module 1 emits light. The light source drive circuit 10 drives the light source module 1 using PWM control. The power supply circuit 11 has a switching circuit 111 that performs DC / DC conversion and supplies power to the light source drive circuit 10. The frequency adjustment circuit 12 changes the switching frequency SF of the switching circuit 111 so that it does not interfere with the frequency component of the pulse frequency PF of the PWM control. With this configuration, the switching frequency SF does not interfere with the frequency component of the pulse frequency PF. This can improve the accuracy of the detection results of the fiber optic gyro device.

[0034] Furthermore, in the fiber optic gyro device according to the first embodiment, the frequency adjustment circuit 12 divides the reference frequency to generate a switching frequency SF that does not interfere with the frequency component of the pulse frequency PF. With this configuration, the frequency adjustment circuit 12 can generate a switching frequency SF that does not interfere with the frequency component of the pulse frequency PF with a simple configuration.

[0035] 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]

[0036] 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 frequency adjustment circuit, 41 one end, 42 other end, 111 switching circuit.

Claims

1. a light source module (1) that emits light; a light source driving circuit (10) that drives the light source module (1) by PWM control; 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 frequency adjusting circuit (12) that changes the switching frequency (SF) of the switching circuit (111) so that the frequency component of the switching frequency (SF) does not interfere with the frequency component of the pulse frequency (PF) of the PWM control; an optical fiber coil (4) into which light emitted from the light source module (1) enters; a feedback signal generating circuit (9) that detects the value of the angular velocity based on a phase difference generated between the light emitted from the other end of the optical fiber coil (4) and the light emitted from one end of the optical fiber coil (4); A fiber optic gyro device comprising:

2. 2. The fiber optic gyro device according to claim 1, wherein the frequency adjusting circuit (12) generates the switching frequency (SF) that does not interfere with the frequency component of the pulse frequency (PF) by dividing a reference frequency.

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