Compensation method for 850 fiber-optic gyroscope total temperature scale factor

Abstract

The invention discloses a compensation method for a full-temperature scale factor of an 850 fiber-optic gyroscope, which solves the problem that under the constraint conditions of miniaturization, light weight and low power consumption of the 850 fiber-optic gyroscope, a conventional temperature sensor arrangement method is not adopted, but the existing hardware is utilized to acquire a diode voltage parameter of an 850 light source as a parameter associated with the scale factor, so that the total-temperature scale factor of the 850 fiber-optic gyroscope is compensated. Meanwhile, according to the change rule of the voltage parameters under the full temperature, the full-temperature scale factor change of the fiber-optic gyroscope is compensated, so that the range change of the full-temperature scale factor of the 850 fiber-optic gyroscope is improved, and the scale factor performance of the temperature-control-free 850 fiber-optic gyroscope under the full temperature can be improved.

Description

Technical Field

[0001] The invention relates to a method for compensating a full-temperature scaling factor of an optical fiber gyroscope, and in particular to a method for compensating a full-temperature scaling factor of a miniaturized optical fiber gyroscope which has strict restrictions on volume and power consumption. Background Art

[0002] Gyroscopes are core components of various inertial measurement systems. They are used to sense the angular motion of sensitive carriers relative to inertial space and measure the angular displacement and angular velocity of the carrier. Together with accelerometers and navigation computers, they form an inertial navigation system and are one of the key factors that restrict the performance of guided weapon systems.

[0003] At present, due to the factors of fiber bending limit and fiber volume, the volume of fiber optic gyroscope optical path accounts for a large proportion, which is the main bottleneck for the development of ultra-miniaturization of fiber optic gyroscope. Especially for fiber optic gyroscope, the length and diameter of fiber directly affect the scale factor of fiber optic gyroscope. When the scale factor increases, for the same phase difference The smaller the error of the angular rate Ω obtained after demodulation, the higher the accuracy of the fiber optic gyroscope. Therefore, for the fiber optic gyroscope, there is a certain contradiction between accuracy and miniaturization. To reduce the volume of the fiber optic gyroscope, it is usually necessary to first reduce the volume of the optical path part by reducing the length of the fiber optic coil or reducing the average diameter of the fiber optic coil. Therefore, on the basis of reducing the size of the fiber optic ring to a certain extent, it is also necessary to start from the overall structural design, reasonably layout the devices, and integrate the circuit part to reduce the number of circuit boards, so as to achieve the miniaturization and lightness of the fiber optic gyroscope while ensuring accuracy.

[0004] In terms of miniaturization of fiber optic gyroscopes, at present, the main technical approach to reduce the size of fiber optic gyroscopes is to reduce the length of the fiber optic coil by using ultra-fine optical fibers that are smaller than the diameter of existing optical fibers, and reduce the average diameter D of the fiber optic coil; at the same time, all optical components and circuit components use miniaturized devices. Choosing a suitable solution is conducive to improving the performance of the gyroscope as much as possible under the same volume limit. According to the different universal transparent windows of quartz optical fibers, they are usually divided into 850nm wavelength fiber optic gyroscopes, 1310nm wavelength fiber optic gyroscopes, and 1550nm wavelength fiber optic gyroscopes. From the development status of gyroscopes, 850nm wavelength fiber optic gyroscopes are widely used at home and abroad, that is, the central wavelength of the light emitted by the light source is 850nm, and the working wavelength of the miniaturized optical devices used in all gyroscopes is 850nm.

[0005] For the light source, the main parameters are the optical power and center wavelength of the light source. Since the miniaturized and low-power gyroscope requires the full-temperature power consumption to be as low as possible, the selected light source is required not to add a refrigerator. Since the material systems of the active areas of the 850nm light source and the 1310nm light source are different, the 850nm light source is GaALAs / GaAs, while the material of the 1310nm light source is InxGal-xAsypl-y / InP. Comparing the two light sources, without cooling, the center wavelength stability and power stability of the 850nm light source are significantly higher than those of the 1310nm light source. Generally, the center wavelength stability of the 850nm light source is about 1 / 3 of the latter, and the power stability is about 1 / 5 of the latter. In addition, under the same driving current, the fiber output power of the 850nm light source is about 1.5 to 2 times that of the 1310nm light source, which can realize multi-axis multiplexing, further simplify the system's light source driving circuit, and reduce the system size. This is also the main reason why miniaturized gyroscopes mostly use 850nm light sources.

[0006] However, without adding a refrigerator to the 850nm light source, the extreme variation of the center wavelength of the 850nm light source at full temperature will inevitably be much greater than the variation of the center wavelength of the light source after temperature control. Generally, the center wavelength of an 850nm light source with temperature control varies by about 150pm to 300ppm in the full temperature range of -45℃ to +70℃, and the center wavelength of an 850nm light source without temperature control varies by about 20,000pm to 30,000ppm in the full temperature range of -45℃ to +70℃. If the scale factor of the fiber optic gyroscope using an 850nm light source without temperature control is not compensated, the full-temperature scale factor of the gyroscope may have an extreme variation of about 2% to 3%, which will seriously affect the gyroscope scale factor performance.

[0007] The accuracy of the scale factor reflects the accuracy of the fiber optic gyroscope in the entire dynamic range. Due to the influence of temperature on the parameters of the fiber optic gyroscope and its components, the scale factor of the fiber optic gyroscope is different at different temperatures. That is, the change in the scale factor caused by temperature leads to the gyroscope output error, so certain measures must be taken to compensate. Summary of the invention

[0008] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, a compensation method for the full temperature scale factor of an 850 fiber optic gyroscope is proposed, and based on the linear relationship between the fiber optic gyroscope temperature and the light source diode voltage, the full temperature scale factor is compensated online by measuring the light source diode voltage.

[0009] The technical solution of the present invention is:

[0010] A method for compensating the full-temperature scale factor of an 850 fiber optic gyroscope is disclosed. The voltage of a light source diode in the 850 fiber optic gyroscope is collected as a reference variable associated with the scale factor, and the full-temperature scale factor change of the fiber optic gyroscope is compensated according to a relationship equation between the scale factor and the diode voltage at full temperature.

[0011] Furthermore, the 850 fiber optic gyroscope includes an optical path, a signal processing circuit and a scale factor compensation module, the optical path mainly includes a light source, a coupler, a Y integrated optical modulator, a Sagnac sensitive fiber ring and a detector, and the signal processing circuit includes a light source driving circuit and a closed-loop control processing circuit;

[0012] The light source driving circuit is used to provide driving current to the light source, collect the light source diode voltage and convert it into a voltage digital signal;

[0013] The closed-loop control processing circuit demodulates the rate signal, collects the voltage digital signal, and outputs the rate signal and the voltage digital signal together in a frame;

[0014] The scale factor compensation module compensates the gyro scale factor online according to the voltage digital signal.

[0015] Furthermore, an 850 fiber optic gyroscope is placed in an incubator, and multiple incubator temperatures with step-by-step increments are set. The fiber optic gyroscope is calibrated after being kept warm for a set time at each temperature point. The fiber optic gyroscope scale factor obtained from the test and the collected light source diode voltage are fitted to obtain the relationship equation between the scale factor and the diode voltage at all temperatures.

[0016] Furthermore, the response value of the fiber optic gyroscope to the rotation speed is processed to realize the compensation of the scale factor. The data processing method is:

[0017] D B =K(V d0 ) / K(V d )×D

[0018] Where D B is the response value of the fiber optic gyro after compensation for the scale factor, D is the response value of the fiber optic gyro before compensation, K(V d0 ) is the reference voltage V of the light source diode voltage during fitting d0 The corresponding fiber optic gyro scale factor, K(V d ) is the current light source diode voltage V d The corresponding fiber optic gyro scale factor.

[0019] Furthermore, the relationship equation between the scale factor and the diode voltage at full temperature is:

[0020]

[0021] In the formula, K(Vd0 ) is the gyro diode voltage V d0 The scale factor of the gyro; a1, b1, c1, d1 are coefficients;

[0022] Select the light source diode voltage V corresponding to one of the temperature boxes d0 As the reference voltage, the scale factor values ​​measured at other temperature points and the voltage of the gyroscope's internal light source diode are substituted into the above formula, and the fitting values ​​of coefficients a1, b1, c1, and d1 are obtained according to the least squares fitting.

[0023] Furthermore, a plurality of step-increasing incubator temperatures are set, the incubator temperature range is -45°C to 70°C, and the gradient is 10°C.

[0024] Furthermore, the closed-loop control processing circuit and the light source driving circuit are connected to form an integrated circuit via a flexible board.

[0025] The advantages of the present invention compared with the prior art are:

[0026] (1) The present invention adds one A / D as a reference variable for the scale factor compensation of the fiber optic gyroscope, and no electronic components such as temperature sensors or platinum resistors are required, which saves the internal space of the fiber optic gyroscope and reduces the difficulty of miniaturized 850 fiber optic gyroscope structure design.

[0027] (2) In the present invention, only one A / D needs to be added to the light source driving circuit. Compared with adding one temperature sensor or platinum resistor and other electronic components, the circuit power consumption is lower and the overall system complexity is smaller. There is no need to add a corresponding temperature sampling circuit for the platinum resistor or thermistor, which further reduces the power consumption and complexity of the overall system.

[0028] (3) The FPGA in the closed-loop control processing circuit of the present invention can realize the output of the reference variable required for the scale factor compensation by collecting the signal of the newly added A / D. No other hardware is needed, and only software functions are required to achieve it, which also reduces the complexity of the overall system and has lower costs.

[0029] (4) The present invention collects the signal of the 850 light source diode voltage as the reference variable required for scale factor compensation, which has a better linear relationship with the wavelength of the light source. Compared with the traditional temperature sensor collection method, it avoids the lag of temperature collection and the influence of temperature errors caused by heat conduction and heat radiation. The diode voltage can directly reflect the real-time change of the average wavelength of the light source, and the average wavelength of the light source and the gyro scale factor are in a direct linear relationship, which has a better effect on scale factor compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0031] Figure 1 This is a schematic diagram of the internal structure of a fiber optic gyroscope according to an embodiment of the present invention;

[0032] Figure 2 This is the relationship between the wavelength of the light source and the diode voltage when the light source has a constant light power of 850 at full temperature;

[0033] Figure 3 This is the relationship between the wavelength of the light source and the diode voltage when the light source is driven at a constant current of 850° at full temperature;

[0034] Figure 4 This is a flow chart of the improved data processing method of the fiber optic gyroscope according to an embodiment of the present invention;

[0035] Figure 5 This is a graph showing the compensation effect of modeling the full temperature scaling factor of the fiber optic gyroscope according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0037] The change of scale factor caused by temperature will lead to the output error of fiber optic gyroscope, so certain measures must be taken to compensate. The conventional method is to use the polynomial (Ω, T) model to model and compensate the scale factor performance of fiber optic gyroscope. This method can suppress the repeatability of full temperature scale factor to about 10 times smaller.

[0038] Under temperature environment, for the fiber optic gyroscope with feedback gain control, the scale factor can be expressed as

[0039]

[0040] Where K(T), L(T), D(T), and λ(T) represent the scale factor of the fiber optic gyroscope, the length of the optical fiber in the optical fiber ring, the average diameter of the optical fiber ring, and the average wavelength, respectively, when the internal temperature of the gyroscope is T.

[0041] Since functions such as L(T), D(T), and λ(T) cannot be accurately obtained, the function K(T) is generally obtained through experimental modeling. Assuming that the scale factor K(T) measured in the experiment of the fiber optic gyroscope increases monotonically with the internal temperature T, K(T) can be expressed by a third-order (or fifth-order) polynomial in engineering applications, that is,

[0042] K(T)=K(T0)·(a·T 3 +b·T 2 +c·T+d) (2)

[0043] Where K(T0) is the scale factor of the gyroscope when the internal temperature of the gyroscope is T0; a, b, c, d are polynomial coefficients, and their values ​​can be obtained through error test methods.

[0044] The present invention obtains the law by collecting the full temperature wavelength change of the 850 light source and its diode voltage change. Figure 2 As shown in Figure 2, as the temperature increases, the wavelength λ of the light source increases linearly, while the light source diode voltage V decreases linearly.

[0045] If the driving current of the 850 light source is constant and the wavelength of the light source and the diode voltage are monitored as the temperature changes, the law is as follows: Figure 3 As shown, as the temperature increases, the wavelength of the light source increases linearly, while the voltage of the light source diode decreases linearly.

[0046] It can be seen that the 850 light source diode voltage is basically linearly related to the 850 light source wavelength, and the gyro scale factor is also linearly related to the light source wavelength. Therefore, the online compensation of the gyro scale factor can be achieved by collecting the light source diode voltage.

[0047] Based on the above rules, the present invention proposes a new compensation method for the full-temperature scale factor of an 850 fiber optic gyroscope, which solves the problem that the 850 fiber optic gyroscope does not adopt the conventional method of arranging temperature sensors under the constraints of miniaturization, light weight and low power consumption, but uses existing hardware to collect the diode voltage parameters of the 850 light source as parameters associated with the scale factor. At the same time, according to the change rule of the voltage parameter under full temperature, the full-temperature scale factor change of the fiber optic gyroscope is compensated, thereby improving the extreme change of the full-temperature scale factor of the 850 fiber optic gyroscope, which is beneficial to improving the scale factor performance of the 850 fiber optic gyroscope without temperature control under full temperature.

[0048] The method includes:

[0049] 1) Optimize the internal structure of the fiber optic gyroscope

[0050] The fiber optic gyroscope is composed of an optical path and a signal processing circuit. The optical path includes a light source 1, a coupler 2, a Y integrated optical modulator 3, a Sagnac sensitive fiber ring 4, and a detector 5. The signal processing circuit includes a light source driving circuit 11, a closed-loop control processing circuit 6 (including an A / D conversion circuit 8, a D / A conversion circuit 10 and an FPGA 9).

[0051] The light source driving circuit 11 is used to provide driving current to the 850 light source 1. The difference from the usual design is that the light source driving circuit has an additional A / D 7 for collecting the diode voltage of the 850 light source 1 and converting it into a digital quantity. Its function of providing driving current is the same as that of an ordinary light source driving circuit; the injection current is usually 60mA to 100mA.

[0052] The light source driving circuit 11 used in the 850 fiber optic gyroscope does not provide temperature control current to the light source 1, because the fiber optic gyroscope using the 850 solution has very strict requirements on volume and power consumption. The volume is generally not larger than Ф24mm×50mm, and the full-temperature power consumption is generally not larger than 1.2W. Therefore, canceling the temperature control function can reduce power consumption to the greatest extent.

[0053] The closed-loop control processing circuit collects the signal of the newly added A / D7 through FPGA9, and frames it together with the rate signal demodulated by the fiber optic gyroscope for output. Due to the small internal volume and very tight space of the 850 fiber optic gyroscope, no additional temperature sensor is installed, and the reference signal for scale factor compensation no longer uses the temperature signal of the temperature sensor, but uses the light source diode voltage signal of A / D7 output by FPGA9.

[0054] The closed-loop control processing circuit 6 can be connected to the light source driving circuit 11 via the flexible board 12 to form an integrated circuit.

[0055] 2) Scale factor full temperature variation law:

[0056]

[0057] Where K(V d0 ) is the gyro diode voltage V d0 The scale factor of the gyro; a1, b1, c1, d1 are coefficients, and their values ​​can be obtained through error testing. Select the light source diode voltage V corresponding to one of the temperature boxes d0 As the reference voltage, the scale factor values ​​measured at other temperature points and the voltage of the gyroscope's internal light source diode are substituted into the above formula, and the fitting values ​​of coefficients a1, b1, c1, and d1 are obtained according to the least squares fitting.

[0058] The method of scale factor test modeling is as follows: ① According to the working environment requirements of the fiber optic gyroscope, select the temperature points for modeling, such as -45℃, -40℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, and 70℃; ② Put the fiber optic gyroscope into an incubator with a turntable, keep it warm for a certain period of time (such as 2h), and then calibrate it to obtain the scale factor values ​​{K1, K2, K3, K4, K5, K6, K7, K8, K9, K10, K11, K12} of the fiber optic gyroscope at different temperature points and the corresponding gyroscope light source diode voltage; ③ Take the corresponding gyroscope light source diode voltage V when T0 = 20℃ d0 , then K(V d0 )=K7, substituting the scale factor value measured at each temperature point and the internal temperature value of the gyroscope into the above formula, and using the least squares fitting method, the fitting values ​​of the polynomial coefficients a1, b1, c1, and d1 can be obtained.

[0059] For a fiber optic gyroscope without scale factor compensation, when the rotation speed is Ω and the temperature is T, the response value of the fiber optic gyroscope to the rotation speed is

[0060] D=K(V d )·Ω (4)

[0061] As can be seen from the above formula, the response of the fiber optic gyroscope to the same rotation speed will change with the change of temperature. Therefore, after the fiber optic gyroscope scale factor model K(V d ), the gyro output value D can be processed to realize hardware compensation of the scale factor, and the stability of the fiber optic gyro scale factor under temperature environment can be improved. After the scale factor compensation, when the speed is Ω and the temperature is T, the response value of the fiber optic gyro to the speed is

[0062] D B =K(V d0 )·Ω (5)

[0063] according to Figure 4 The data processing method is shown:

[0064]

[0065] Where D B is the response value of the fiber optic gyro after compensation for the scale factor, D is the response value of the fiber optic gyro before compensation, K(V d0 ) is the reference voltage V of the light source diode voltage during fitting d0 The corresponding fiber optic gyro scale factor, K(V d ) is the current light source diode voltage V d The corresponding fiber optic gyro scale factor finally achieves full temperature compensation of 850 gyro scale factor.

[0066] This method is used to model and compensate the scale factor performance of the 850 fiber optic gyroscope. The full temperature scale factor change is 1.934% before compensation and 0.266% after compensation. The full temperature scale factor compensation is performed on 5 850 micro fiber optic gyroscopes. The full temperature extreme difference of K before and after compensation is shown in Table 1. Figure 5 As shown:

[0067] Table 1 Comparison of the range of 850 fiber optic gyroscope before and after full temperature scale factor compensation

[0068] serial number Range of scale factor before compensation % Range of scale factor after compensation % 01# 1.934 0.266 02# 2.041 0.381 04# 1.838 0.341 06# 2.097 0.202

[0069] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope, characterized in that: The voltage of the light source diode in the 850 fiber optic gyroscope is collected as a reference variable associated with the scale factor. According to the relationship equation between the scale factor and the diode voltage at full temperature, the full-temperature scale factor change of the fiber optic gyroscope is compensated.

2. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 1, characterized in that: The 850 fiber optic gyroscope includes an optical path, a signal processing circuit and a scale factor compensation module. The optical path mainly includes a light source, a coupler, a Y integrated optical modulator, a Sagnac sensitive fiber ring and a detector. The signal processing circuit includes a light source driving circuit and a closed-loop control processing circuit. The light source driving circuit is used to provide driving current to the light source, collect the light source diode voltage and convert it into a voltage digital signal; The closed-loop control processing circuit demodulates the rate signal, collects the voltage digital signal, and outputs the rate signal and the voltage digital signal together in a frame; The scale factor compensation module compensates the gyro scale factor online according to the voltage digital signal.

3. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 1 or 2, characterized in that: The 850 fiber optic gyroscope was placed in a temperature box, and multiple temperature boxes were set with step-by-step increments. The fiber optic gyroscope was calibrated after being kept warm for a set time at each temperature point. The fiber optic gyroscope scale factor obtained from the test and the collected light source diode voltage were fitted to obtain the relationship equation between the scale factor and the diode voltage at all temperatures.

4. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 3, characterized in that: The response value of the fiber optic gyroscope to the rotation speed is processed to realize the compensation of the scale factor. The data processing method is: D B =K(V d0 ) / K(V d )×D Where D B is the response value of the fiber optic gyro after compensation for the scale factor, D is the response value of the fiber optic gyro before compensation, K(V d0 ) is the reference voltage V of the light source diode voltage during fitting d0 The corresponding fiber optic gyro scale factor, K(V d ) is the current light source diode voltage V d The corresponding fiber optic gyro scale factor.

5. The method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 3, characterized in that: The relationship between the scale factor and the diode voltage at full temperature is: In the formula, K(V d0 ) is the gyro diode voltage V d0 The scale factor of the gyro; a1, b1, c1, d1 are coefficients; Select the light source diode voltage V corresponding to one of the temperature boxes d0 As the reference voltage, the scale factor values ​​measured at other temperature points and the voltage of the gyroscope's internal light source diode are substituted into the above formula, and the fitting values ​​of coefficients a1, b1, c1, and d1 are obtained according to the least squares fitting.

6. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 3, characterized in that: Set multiple step-by-step incubator temperatures, with the incubator temperature range being -45°C to 70°C and the gradient being 10°C.

7. A method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 3, characterized in that: Set multiple temperature chambers with step-by-step increments, and perform FOG calibration after the set insulation time at each temperature point. The insulation time should be at least 2 hours.

8. The method for compensating the full temperature scaling factor of an 850 fiber optic gyroscope according to claim 2, characterized in that: The closed-loop control processing circuit and the light source driving circuit are connected to form an integrated circuit through a flexible board.

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