Small optical fiber gyroscope

Abstract

The invention provides a small-sized fiber-optic gyroscope which comprises a light path part and a photoelectric information processing circuit part, and an integrated module is formed by selecting a mixed component U4 which integrates an FPGA (Field Programmable Gate Array), a D / A (Digital / Analog) conversion function and an A / D (Analog / Digital) conversion function; the optical path part is compactly distributed in the metal shell, and the polarization maintaining optical fiber ring is independently installed in the semi-cylindrical shielding cover adjacent to the metal shell and is isolated from other devices of the optical path part. According to the invention, a hybrid component integrating FPGA, D / A and A / D conversion functions is used for the first time, so that the size of a closed-loop control circuit is greatly reduced. According to the special-shaped small optical path structure designed by the invention, the optical path devices are compactly distributed in the metal shell, and the optical fiber ring is independently mounted in the semi-cylindrical shielding cover and is isolated from other optical devices, so that the magnetic interference of the optical fiber ring to other optical devices is reduced; meanwhile, noise caused by external environment fluctuation is effectively reduced, and the environmental adaptability of the fiber-optic gyroscope is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber optic gyroscopes, and in particular relates to a small fiber optic gyroscope. Technical Background

[0002] Various types of dual-use autonomous unmanned systems, such as guidance systems, torpedoes, general aviation and aerospace vehicles, military and civilian drones, special vehicles, autonomous robots, unmanned intelligent ships and underwater unmanned submersibles, are becoming an emerging industry direction. Autonomous unmanned systems have huge application demands in both military and civilian fields and contain huge commercial value. Fiber optic gyroscopes are an indispensable key component.

[0003] Domestic fiber optic gyroscope technology has reached a relatively high level, but its large size is still a technical bottleneck that restricts the technical performance and adaptability of my country's military and civilian products. At present, the fiber optic gyroscope is too large to meet the demand for ultra-miniaturization of weapons and equipment such as flight guidance systems, drones, unmanned submarines, torpedoes, guided artillery shells and unmanned vehicles. It is an inevitable trend to study a tactical-level small fiber optic gyroscope. Summary of the invention

[0004] In view of this, the present invention proposes a small fiber optic gyroscope, which is used to reduce the volume of the fiber optic gyroscope, so as to meet the urgent demand for ultra-miniaturization of weapon equipment systems. The specific technical solution is as follows:

[0005] A small fiber optic gyroscope comprises an optical path part and an optoelectronic information processing circuit part, wherein the optical path part comprises a light source driving circuit, an SLD light source, a photodetector, an optical fiber coupler, a Y waveguide, and a polarization-maintaining optical fiber ring; the optoelectronic information processing circuit is an integrated module, and the integrated module is composed of a hybrid component U4 that integrates FPGA with D / A and A / D conversion functions; the optical path part is compactly distributed inside a metal shell, and the polarization-maintaining optical fiber ring is separately installed in a semi-cylindrical shielding cover adjacent to the metal shell, and is isolated from other components of the optical path part.

[0006] Furthermore, the light source driving circuit drives the SLD light source to emit light, and the light enters the Y waveguide through the optical fiber coupler. The Y waveguide performs phase modulation on the received optical signal. The phase modulation voltage of the Y waveguide is provided by the optical path information processing circuit. The two optical signals after phase modulation enter the polarization-maintaining optical fiber ring and interfere with each other before entering the Y waveguide again. Then, they enter the photodetector through the optical fiber coupler, convert the optical signal into an electrical signal, and then enter the optical path information processing circuit. The optical path information processing circuit outputs the gyroscope angular velocity.

[0007] Furthermore, the Y waveguide is modulated by modulating the phase point and compensating the phase difference.

[0008] Furthermore, a random modulation method is used to modulate the phase point to form a bias modulation signal.

[0009] Furthermore, phase difference compensation means that the photodetector signal reaches the photoelectric information processing circuit, is converted into a digital quantity by A / D in the photoelectric information processing circuit and sent to the FPGA for digital differential modulation processing, and is integrated and accumulated after processing to form a step wave.

[0010] Furthermore, the step wave signal is superimposed on the bias modulation signal to form a control signal of the Y-waveguide, which is sent to the D / A converter; then it is added to the Y-waveguide control end through an operational amplifier for phase difference feedback to compensate for the Sagnac phase shift and realize closed-loop control of the fiber optic gyroscope.

[0011] Furthermore, the step wave is filtered to form digital angular velocity information.

[0012] Furthermore, the hybrid component U4 adopts BAF1000.

[0013] Beneficial Effects

[0014] 1) The present invention uses a hybrid component that integrates FPGA with D / A and A / D conversion functions for the first time. The hybrid component realizes closed-loop control functions such as A / D conversion of fiber optic gyroscope signals, D / A conversion, and fiber optic gyroscope optical path information calculation and modulation, greatly reducing the volume of the closed-loop control circuit. The present invention can form a miniaturized fiber optic gyroscope with a volume reduced by about 40% compared to a 50 fiber optic gyroscope.

[0015] 2) The use of U4 will increase the nonlinear error of DA conversion, and the traditional square wave modulation and demodulation method cannot meet the requirements of fiber optic gyroscope indicators. The present invention adopts a random phase jump modulation method, introduces an 8-state Markov chain into the modulation signal, randomly selects the modulation phase through state rotation, reduces the interference of the modulation signal on the analog signal, and suppresses the nonlinear error.

[0016] 3) With the traditional cylindrical structure, the small optical path system is easily affected by internal heat sources, magnetic fields, stress, etc., resulting in a serious reduction in the accuracy of the gyroscope. The special-shaped small optical path structure designed by the present invention distributes the optical path components compactly inside the metal shell, and installs the optical fiber ring separately in the semi-cylindrical shielding cover to isolate it from other optical components, which not only reduces the magnetic interference of the optical fiber ring on other optical components, but also effectively reduces the noise introduced by external environmental fluctuations and improves the environmental adaptability of the fiber optic gyroscope.

[0017] 4) The method of the present invention can reduce the volume of the fiber optic gyroscope while ensuring accuracy, meeting the demand for ultra-miniaturization of weapon equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The system block diagram of the present invention is

[0019] Figure 2 AD conversion circuit for fiber optic gyroscope

[0020] Figure 3 DA conversion circuit for fiber optic gyroscope

[0021] Figure 4 Schematic diagram of the results of the present invention

[0022] Figure 5 The signal returned by the detector of the present invention

[0023] Figure 6 Schematic diagram of bias modulation for square wave signal

[0024] Figure 7 The voltage waveform at the detector end when the square wave is modulated DETAILED DESCRIPTION

[0025] To achieve the above object, the present invention adopts the following technical solutions:

[0026] A small fiber optic gyroscope includes an optical path part and an optoelectronic information processing circuit part, wherein the optical path part includes a light source driving circuit, an SLD light source, a photodetector, an optical fiber coupler, a Y waveguide, and a polarization-maintaining optical fiber ring. The optoelectronic information processing circuit is an integrated module, and the integrated module is composed of a hybrid component U4 that integrates FPGA with D / A and A / D conversion functions. The optical path part is compactly distributed inside a metal shell, and the polarization-maintaining optical fiber ring is separately installed in a semi-cylindrical shielding cover adjacent to the metal shell, and is isolated from other components of the optical path part. The model of the hybrid component U4 is BAF1000.

[0027] The detector signal reaches U4, where it is converted into digital quantity by A / D and sent to FPGA for digital differential demodulation. The processed data is used as the closed-loop feedback input signal, and a step wave is generated through digital accumulation. The step wave signal is then superimposed with the bias modulation signal to form the control signal of the Y waveguide, which is sent to the D / A converter; then it is added to the Y waveguide control end through the operational amplifier for phase difference feedback, compensating for the Sagnac phase shift, and realizing closed-loop control of the fiber optic gyroscope; the step wave is filtered to form digital angular velocity information and output.

[0028] The use of U4 will increase the nonlinear error of DA conversion, and the traditional square wave modulation and demodulation method cannot meet the requirements of fiber optic gyroscope indicators. This embodiment adopts a random phase jump modulation method, introduces an 8-state Markov chain into the modulation signal, randomly selects the modulation phase through state rotation, reduces the interference of the modulation signal on the analog signal, and suppresses the nonlinear error.

[0029] In this embodiment, a special-shaped small optical path structure is designed. The optical path components are compactly distributed inside the metal shell, and the optical fiber ring is installed separately in a semi-cylindrical shielding cover to be isolated from other optical components, which not only reduces the magnetic interference of the optical fiber ring to other optical components, but also effectively reduces the noise introduced by external environmental fluctuations, thereby improving the environmental adaptability of the fiber optic gyroscope.

[0030] The following is further described in conjunction with the principles of the present invention:

[0031] 1) After the optical signal enters the fiber ring, interference occurs, and the signal returned by the detector is as follows Figure 5 As shown, it can be seen that if the light ring does not detect the rotation angular velocity, the intensity of the detection signal is 2I0. When there is rotation:

[0032]

[0033] in, is the phase caused by rotation. We can see that because the cosine wave is an even function, we have no way to detect which direction it is rotating. Therefore, there is the following modulation scheme (classical principle, which can be found in textbooks).

[0034] 2) The Y-waveguide modulates the optical signal from the coupler so that the two beams of light split by the Y-waveguide receive different phase modulations at different times. The purpose of this is that the fiber optic gyroscope alternately works at ±π / 2 points in two adjacent half-cycles of the square wave modulation cycle. When stationary, the gyroscope output waveform is a straight line, and the same signal is given in two adjacent half-cycles of the square wave. This is reflected in the detector as the voltage values ​​sampled in two adjacent cycles are the same.

[0035] 3) In a closed-loop fiber optic gyroscope, a square wave signal is usually used for bias modulation. The specific operation is that the FPGA controls the DA output, and the output end of the DA is connected to the Y waveguide, thereby controlling the Y waveguide input voltage. The Y waveguide will modulate the phase of the input optical signal under different voltages, and the voltage difference of adjacent transit time modulations constitutes the modulation point of the optical signal.

[0036] When the input is zero (the gyro is stationary), in the detector signal, the magnitudes of the two periodic signals are the same and the difference is zero.

[0037] When there is a positive angular velocity, the voltage value of the positive half cycle in the detector signal is greater than the voltage value of the negative half cycle.

[0038] When there is a reverse angular velocity, the voltage value of the positive half cycle in the detector signal is smaller than the voltage value of the negative half cycle.

[0039] The voltage waveform at the detector end is as follows: Figure 7 as shown.

[0040] t1→t10 The moment is a transit time, t 10 →t 20 are adjacent transit times. We can see that when there is angular velocity input, the voltage values ​​of adjacent transit times at the detector end are obviously different.

[0041] 4) According to the voltage difference between the positive half cycle and the negative half cycle at the detector end, the subsequent integration and accumulation are performed to form a step wave, the purpose of which is to compensate for the phase difference caused by the external angular velocity. In the optical path, it is reflected in the phase compensation of the cosine wave, so that the cosine wave phase is 0, which is the same as the waveform at rest. In summary, we can make the fiber optic gyroscope always work at the phase modulation point through the modulation of the phase point and the compensation of the phase difference, which can improve the nonlinearity of the fiber optic gyroscope and the angular velocity measurement range of the gyroscope. The specific operation is modulation wave + step wave, which works under the joint action of these two waveforms.

[0042] 5) Gyro output: Previously, a step wave was used for phase compensation. Since the magnitude of the compensation phase is different at different angular velocities, the magnitude of the step wave is processed by digital filtering and used as the output of the fiber optic gyroscope.

[0043] 6) Random modulation: According to the periodicity of the cosine function, modulation is performed at the modulation points A-2π, -A, A, 2π-A, so that the fiber optic gyroscope works randomly at the above four modulation points at each transit time. The so-called N-state modulation is based on the different modulation points A, forming N*A=K*2π, where K is the smallest positive integer that makes the equation valid.

[0044] Note: The transit time mentioned above refers to the time it takes for a light signal to travel around the optical fiber ring.

Claims

1. A small fiber optic gyroscope, comprising an optical path part and an optoelectronic information processing circuit part, wherein the optical path part comprises a light source driving circuit, an SLD light source, a photodetector, an optical fiber coupler, a Y waveguide, and a polarization-maintaining optical fiber ring, and the optoelectronic information processing circuit is an integrated module, characterized in that: The integrated module is composed of a hybrid component U4 that integrates FPGA with D / A and A / D conversion functions; the optical path part is compactly distributed inside the metal shell, and the polarization-maintaining fiber ring is separately installed in a semi-cylindrical shielding cover adjacent to the metal shell, isolated from other devices in the optical path part.

2. A small fiber optic gyroscope according to claim 1, characterized in that: The light source driving circuit drives the SLD light source to emit light, and the light enters the Y waveguide through the optical fiber coupler. The Y waveguide performs phase modulation on the received optical signal. The phase modulation voltage of the Y waveguide is provided by the optical path information processing circuit. The two optical signals after phase modulation enter the polarization-maintaining optical fiber ring and interfere with each other before entering the Y waveguide again. Then, they enter the photodetector through the optical fiber coupler, convert the optical signal into an electrical signal and enter the optical path information processing circuit. The optical path information processing circuit outputs the gyroscope angular velocity.

3. A small fiber optic gyroscope according to claim 1, characterized in that: The Y-waveguide is modulated by modulation of the phase point and compensation of the phase difference.

4. A small fiber optic gyroscope according to claim 1, characterized in that: The phase point is modulated by random modulation to form a bias modulation signal.

5. A small fiber optic gyroscope according to claim 1, characterized in that: Phase difference compensation means that the photodetector signal reaches the photoelectric information processing circuit, is converted into a digital quantity by A / D in the photoelectric information processing circuit and sent to the FPGA for digital differential modulation processing. After processing, it is integrated and accumulated to form a step wave.

6. A small fiber optic gyroscope according to claim 1, characterized in that: The step wave signal is superimposed on the bias modulation signal to form the control signal of the Y-waveguide, which is sent to the D / A converter; then it is added to the control end of the Y-waveguide through the operational amplifier for phase difference feedback, compensating for the Sagnac phase shift, and realizing closed-loop control of the fiber optic gyroscope.

7. A small fiber optic gyroscope according to claim 1, characterized in that: The step wave is filtered to form digital angular velocity information.

8. A small fiber optic gyroscope according to any one of claims 1 to 7, characterized in that: The hybrid component U4 adopts BAF1000.

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