Optical fiber gyroscope

Abstract

To obtain an optical fiber gyroscope that can improve the accuracy of the detection results of the optical fiber gyroscope. [Solution] This optical fiber gyro device includes 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 switching circuit 111 that performs DC / DC conversion and a power supply circuit 11 that 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 the switching frequency SF does not interfere with the frequency components of the pulse frequency PF of the PWM control.

Description

Technical Field

[0001] This invention relates to an optical fiber gyroscope device.

Background Art

[0002] Conventionally, an optical fiber gyroscope device including 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 has been known. 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 has entered 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. The light that has passed through the optical fiber cable in one direction enters each of one end and the other end of the optical fiber coil via the optical phase modulator. The light that has entered 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 has entered 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 that has exited from the other end of the optical fiber coil and the light that has exited 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 has entered 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 that has exited from the other end of the optical fiber coil and the light that has exited from one end of the optical fiber coil interfere with each other.

[0005] When a rotational force acts on an optical fiber coil, a phase difference occurs between the light emitted from the other end of the optical fiber coil and the light emitted from the other end of the optical fiber coil, depending on the angular velocity of the optical fiber coil. An 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 Publication No. 2005-147863 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, in the configuration of the optical fiber gyro device described in Patent Document 1, a constant switching frequency is pre-set in the power supply circuit. When 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 optical fiber gyro device. As a result, there was a problem in that the error included in the detection result of the optical fiber gyro device became large.

[0009] This invention was made to solve the problems described above, and its objective is to provide an optical fiber gyroscope that can improve the accuracy of the detection results of the optical fiber gyroscope. [Means for solving the problem]

[0010] The optical fiber gyro device according to this invention comprises 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 DC / DC conversion switching circuit and supplies power to the light source drive circuit, and a frequency adjustment circuit that changes the switching frequency so that the switching frequency of the switching circuit does not interfere with the frequency component of the pulse frequency of the PWM control. In the optical fiber gyro device according to this invention, the frequency adjustment circuit generates a switching frequency that does not interfere with the frequency components of the pulse frequency by dividing the reference frequency. [Effects of the Invention]

[0011] According to the optical fiber gyro device of this invention, the accuracy of the detection results of the optical fiber gyro device can be improved. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing an optical fiber gyro device according to Embodiment 1. [Figure 2] This is a block diagram of a comparative example of an optical fiber gyro device. [Figure 3] This graph shows the pulse frequency signal of PWM control in the light source drive circuit of an optical fiber gyroscope device. [Figure 4] This graph shows the switching frequency and pulse frequency of the optical fiber gyro device in the comparative example. [Figure 5] This graph shows the switching frequency and pulse frequency of the optical fiber gyro device according to Embodiment 1. [Modes for carrying out the invention]

[0013] Embodiment 1. Figure 1 is a block diagram showing an optical fiber gyro device according to Embodiment 1. The optical fiber gyro device according to Embodiment 1 comprises 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 optical fiber gyro device according to Embodiment 1 also comprises a light source drive circuit 10, a power supply circuit 11, and a frequency adjustment circuit 12.

[0014] Light source module 1 emits light. One end of optical fiber cable 2 is connected to light source module 1. The light emitted from light source module 1 enters optical fiber cable 2. The light that enters optical fiber cable 2 from light source module 1 travels through 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 passing 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. Light that enters 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. Light that enters the other end 42 of the optical fiber coil 4 passes through the optical fiber coil 4 and exits from 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 the one end 41 of the optical fiber coil 4 are coupled by the optical phase modulator 3. The coupled light enters the optical fiber cable 2. The light that enters the optical fiber cable 2 from the optical phase modulator 3 travels 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 the 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 emerging from the other end 42 of the optical fiber coil 4 and the light emerging from one end 41 of the optical fiber coil 4 in accordance with the angular velocity of the optical fiber coil 4.

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

[0019] The optical phase modulator 3 is driven by a signal of the drive frequency DF. 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 based on the feedback signal FS.

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

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

[0022] A signal of the drive frequency DF is input to the detector circuit 8 from the oscillation 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, the signal when the signal of the drive frequency DF is at a positive voltage and the signal when the signal of the drive frequency DF is at a negative voltage. The detection result of the detector circuit 8 is output from the detector circuit 8 and input to the feedback signal generation circuit 9.

[0023] The feedback signal generation 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. The feedback signal generation circuit 9 also outputs a feedback signal FS so that the phase difference becomes 0, based on the calculated phase difference. The feedback signal generation circuit 9 also outputs a signal corresponding to the feedback signal FS when the phase difference is 0 as the angular velocity value of the optical fiber coil 4. The angular velocity value output from the feedback signal generation circuit 9 is the angular velocity value detected by the optical fiber gyro device.

[0024] The light source drive circuit 10 drives the light source module 1 by PWM control of a preset pulse frequency PF. Power is supplied to the light source drive circuit 10 from the power supply circuit 11.

[0025] The power supply circuit 11 has a switching circuit 111 that performs DC / DC conversion. The switching frequency SF is used in the switching circuit 111. By performing DC / DC conversion in the switching circuit 111, 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 the 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 components of the pulse frequency PF, and then inputs it to the power supply circuit 11. Specifically, the frequency adjustment circuit 12 has a frequency divider circuit that divides the reference frequency, and by dividing the reference frequency, it generates a switching frequency SF that does not interfere with the frequency components of the pulse frequency PF. An FPGA (Field Programmable Gate Array) can be used as an example of a frequency divider circuit.

[0027] The change in the switching frequency SF by the frequency adjustment circuit 12 is performed by an operator operating the frequency adjustment circuit 12. Alternatively, the change in the switching frequency SF by the frequency adjustment circuit 12 may be performed automatically by the frequency adjustment circuit 12 when a pulse frequency PF is input to the frequency adjustment circuit 12.

[0028] Figure 2 is a block diagram showing a comparative example optical fiber gyro device. Compared to the optical fiber gyro device according to Embodiment 1, the comparative example optical fiber gyro device does not have a frequency adjustment circuit 12. In the comparative example optical fiber gyro device, a constant switching frequency SF is pre-set in the power supply circuit 11. Other configurations in the comparative example optical fiber gyro device are the same as those in the optical fiber gyro device according to Embodiment 1.

[0029] Figure 3 is a graph showing the pulse frequency PF signal for PWM control in the light source drive circuit 10 of the optical fiber gyro device. In PWM control, a constant pulse frequency PF is preset. The shape of the pulse frequency PF is a rectangular wave. Therefore, the pulse frequency PF contains multiple frequency components.

[0030] Figure 4 is a graph showing the frequency components of the switching frequency SF and pulse frequency PF of the comparative example optical fiber gyro device. Figure 5 is a graph showing the frequency components of the switching frequency SF and pulse frequency PF of the optical fiber gyro device according to Embodiment 1. In Figures 4 and 5, among the multiple frequency components included in the pulse frequency PF, three consecutive frequency components PFn-1, PFn, and PFn+1 are shown.

[0031] In the comparative example optical fiber gyro device, a constant switching frequency SF is pre-set. Figure 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 angular velocity value detected by the optical fiber gyro device. As a result, the error included in the detection results of the optical fiber gyro device becomes larger.

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

[0033] As described above, the optical fiber gyro device according to Embodiment 1 comprises a light source module 1, a light source drive circuit 10, a power supply circuit 11, and a frequency adjustment circuit 12. The light source module 1 emits light. The light source drive circuit 10 drives the light source module 1 by 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 the switching frequency SF 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 makes it possible to improve the accuracy of the detection results of the optical fiber gyro device.

[0034] Furthermore, in the optical fiber gyro device according to Embodiment 1, the frequency adjustment circuit 12 generates a switching frequency SF that does not interfere with the frequency components of the pulse frequency PF by dividing the reference frequency. With this configuration, the frequency adjustment circuit 12 can generate a switching frequency SF that does not interfere with the frequency components of the pulse frequency PF with a simple configuration.

[0035] Although a preferred embodiment 1 of the optical fiber gyro device has been described above, the optical fiber gyro device is not limited to the embodiment 1 described above. Various modifications and transformations can be made to the optical fiber gyro device according to embodiment 1 described above 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 Oscillator circuit, 6 Coupler, 7 Detector module, 8 Detector circuit, 9 Feedback signal generation circuit, 10 Light source drive 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 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), A frequency adjustment circuit (12) that changes the switching frequency (SF) of the switching circuit (111) so that the switching frequency (SF) does not interfere with the frequency components of the pulse frequency (PF) of the PWM control, A fiber optic gyroscope device equipped with this device.

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

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