Method for expanding measurement range of optical fiber gyroscope

Abstract

The invention particularly relates to a method for expanding the measurement range of an optical fiber gyroscope, and solves the technical problems that the starting angular rate of the existing optical fiber gyroscope must be smaller than the theoretical angular rate and the angular acceleration of the optical fiber gyroscope has a theoretical upper limit. The method for expanding the measurement range of the optical fiber gyroscope comprises the following steps: 1) reading an output value of the MEMS sensor; 2) correcting the zero position and polarity of the MEMS sensor; 3) calculating and setting the measurement range [-Omega Pi, + Omega Pi] of the optical fiber gyroscope; 4) measuring the angular rate omega of the external carrier in real time; 5) judging whether the angular rate omega MEMS measured by the MEMS sensor exceeds the measurement range [-omega pi, + omega pi], if so, carrying out iterative calculation to obtain the final angular rate omega MEMS, and simultaneously correcting the values of the feedback register and the integral output register by using the final angular rate omega MEMS to complete the expansion of the measurement range of the optical fiber gyroscope and output the corrected angular rate; otherwise, the angular rate is not corrected, and the optical fiber gyroscope normally outputs the angular rate.

Description

Technical Field

[0001] The invention specifically relates to a method for extending the measurement range of a fiber optic gyroscope. Background Art

[0002] The theoretical measurement range of the fiber optic gyroscope is limited by the fiber ring length and equivalent diameter. When the above two factors remain unchanged, the measurement range of the fiber optic gyroscope should be expanded in practical applications. The current general practice is based on the single-fringe expansion theory. However, this theory has two restrictions in practical applications: the fiber optic gyroscope must be started from the first fringe (theoretical angular velocity) and the angular acceleration of the fiber optic gyroscope has a theoretical upper limit.

[0003] Based on the single fringe expansion theory, it is assumed that the limit measurement range of the fiber optic gyroscope is ±500 (°) / s, the fiber optic gyroscope output digital quantity is 26 bits, if all the bits are fed back, the angular rate represented by each least significant bit is 0.053 (°) / h. Due to the limitation of the number of bits of the D / A converter, the lower 10 bits are discarded, and the angular rate represented by the least significant bit fed back to the D / A converter is 54.9 (°) / h. The fiber optic gyroscope outputs digital quantities: "00...00" to "11...11", representing from 0 to ±500 (°) The digital value fed back to the D / A converter takes the high 16 bits of the digital output of the fiber optic gyroscope, ranging from 0 to 65535 ("1111111111111111"), which also represents 0 to ±500. (°) / s for all angular rate values. When the input angular rate is greater than ±Ω π (±500 (°) / s), the 26-bit register cannot meet the requirement. At this time, the output bit number of the fiber optic gyroscope needs to be expanded. If the measurement range is expanded by 2 times, the output angular rate register of the fiber optic gyroscope needs to reach 27 bits; if the measurement range is expanded by 4 times, the output angular rate register of the fiber optic gyroscope needs to reach 28 bits. By analogy, if the measurement range is expanded by 2n, the number of bits of the fiber optic gyroscope is 26+n bits.

[0004] In order to ensure that the initial phase difference caused by the rotation of the fiber optic gyroscope is within the first-order interference fringes (i.e. the rotation angular rate is from -Ω π ~+Ω π After the closed-loop operation, it can stably work at the bias working point of the first interference fringe, and has an upper limit requirement on the maximum angular acceleration input to the fiber optic gyroscope, that is, the rotational angular acceleration caused by the instantaneous impact on the fiber optic gyroscope cannot exceed a certain limit. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems that the starting angular rate of the existing fiber optic gyroscope must be less than the theoretical angular rate and the angular acceleration of the fiber optic gyroscope has a theoretical upper limit, and to provide a method for extending the measurement range of the fiber optic gyroscope.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for extending the measurement range of a fiber optic gyroscope is characterized in that it comprises the following steps:

[0008] 1] Coaxially set a MEMS sensor on the measurement axis of the fiber optic gyroscope and read the output value of the MEMS sensor;

[0009] 2] According to the output value of the MEMS sensor, the zero position and polarity of the fiber optic gyroscope are used to correct the zero position and polarity of the MEMS sensor respectively;

[0010] 3] Calculate and set the measurement range of the fiber optic gyroscope [-Ω π , +Ω π ];

[0011] 4] After the external carrier is instantly started, the fiber optic gyroscope and MEMS sensor are used to measure the angular velocity of the external carrier in real time;

[0012] 5] Determine the angular rate Ω measured by the MEMS sensor MEMS Is it beyond the measurement range [-Ω π , +Ω π ], if so, perform iterative calculation to obtain the final angular velocity Ω MEMS , and then use the final angular rate Ω MEMS At the same time, the values ​​of the feedback register and the integral output register are corrected to complete the expansion of the measurement range of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is made and the fiber optic gyroscope outputs the angular rate normally.

[0013] Further, step 2] is specifically as follows:

[0014] 2.1. Place the fiber optic gyroscope at the "up, east, and north" positions respectively, and measure the zero position of the fiber optic gyroscope's X-axis, Y-axis, and Z-axis to be Ω X0 ,Ω Y0 ,Ω Z0 ;

[0015] 2.2. Using the zero position Ω of the fiber optic gyroscope X0 ,Ω Y0 ,Ω Z0 Correct the zero position of the X-axis, Y-axis, and Z-axis of the MEMS sensor respectively;

[0016] 2.3. Correct the polarity of the MEMS sensor according to the output polarity of the fiber optic gyroscope.

[0017] Further, step 5] is specifically as follows:

[0018] Determine the angular rate Ω measured by the MEMS sensor MEMS Is it beyond the measurement range [-Ω π , +Ω π ], when the angular rate Ω measured by the MEMS sensor MEMS >Ω π When, according to Ω MEMS =nΩ π +Ω 反馈 Perform iterative calculations, or when the angular rate -Ω measured by the MEMS sensor MEMS <-Ω π When, according to -Ω MEMS =-nΩ π -Ω 反馈 Perform iterative calculation to obtain the final angular rate Ω 反馈 and angular rate nΩ π ; The final angular rate Ω 反馈 Assigned to the feedback register, angular rate nΩ π Assign a value to the integral output register in the FPGA to complete the expansion of the measurement range of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is made and the fiber optic gyroscope outputs the angular rate normally; the n is an integer greater than or equal to 1.

[0019] Furthermore, in step 1], the MEMS sensor is arranged on the digital demodulation circuit of the fiber optic gyroscope and is coaxially arranged with the fiber optic ring module of the fiber optic gyroscope.

[0020] Beneficial effects of the present invention:

[0021] 1) The present invention provides a method for extending the measurement range of a fiber optic gyroscope. First, a MEMS sensor is used to correct the zero position and polarity of the fiber optic gyroscope to obtain an angular velocity output with high accuracy, thereby avoiding misjudgment and improving the measurement accuracy of the fiber optic gyroscope.

[0022] 2) The present invention provides a method for extending the measurement range of a fiber optic gyroscope. When an external carrier is started at high speed, a MEMS sensor is used to perform a correction algorithm beyond the theoretical measurement range, so that the closed-loop feedback loop of the fiber optic gyroscope is always controlled within the measurement range [-Ω π , +Ω π ], ensuring the normal closed loop of the fiber optic gyroscope after high-speed startup.

[0023] 3) The present invention provides a method for extending the measurement range of a fiber optic gyroscope, which overcomes the two major limiting conditions for extending the measurement range of a fiber optic gyroscope at present: a) the starting angular velocity of the fiber optic gyroscope must be less than the theoretical angular velocity; b) there is a theoretical upper limit to the angular acceleration of the fiber optic gyroscope.

[0024] 4) The present invention provides a method for extending the measurement range of a fiber optic gyroscope, which adds a MEMS sensor to the layout and wiring of the digital demodulation circuit of the fiber optic gyroscope without changing the structure and accuracy of the original fiber optic gyroscope. The method is convenient to implement and enhances the environmental adaptability of the fiber optic gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a fiber optic gyroscope in an embodiment of a method for extending the measurement range of a fiber optic gyroscope of the present invention;

[0026] Figure 2 It is a flow chart of an embodiment of a method for extending the measurement range of a fiber optic gyroscope according to the present invention;

[0027] Figure 3 It is a schematic diagram of the requirements for the shock response spectrum test in an embodiment of a method for extending the measurement range of a fiber optic gyroscope of the present invention, wherein the horizontal axis represents the test spectrum frequency and the vertical axis represents the shock magnitude (acceleration);

[0028] Figure 4 This is a schematic diagram of the fiber optic gyroscope shock response test without MEMS sensor correction. The horizontal axis represents time in 0.1 seconds, and the vertical axis represents the bias value of the fiber optic gyroscope in units of (°) / h, green is X-axis, blue is Y-axis, red is Z-axis;

[0029] Figure 5 This is a schematic diagram of the impact response test of the fiber optic gyroscope with MEMS sensor correction in the present invention. The horizontal axis represents time in units of 0.1 seconds, and the vertical axis represents the bias value of the fiber optic gyroscope in units of (°) / h, green is X-axis, blue is Y-axis, red is Z-axis;

[0030] Figure 6 This is a schematic diagram of the high-rate start-up test of the fiber optic gyroscope without MEMS sensor correction. The horizontal axis represents time in 1 second, and the vertical axis represents angular rate in (°) / s, the starting angular rate is 200 (°) / s, blue is the X-axis output fixed value 30000 (°) / s;

[0031] Figure 7 This is a schematic diagram of the high-speed start-up test of the fiber optic gyroscope with MEMS sensor correction in the present invention. The horizontal axis represents time in 1 second, and the vertical axis represents angular rate in 1 second. (°) / s, purple, green, red, and blue are respectively the X-axis starting angular rate 200 (°) / s, 400 (°) / s, 800 (°) / s, 1000 (°) / s, and its output is 200 (°) / s, 400 (°) / s, 800 (°) / s, 1000 (°) / s. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, the fiber optic gyroscope includes an optical part and an electrical part (i.e., a digital demodulation circuit); the optical part includes an optical fiber ring, an optical phase modulator, and a photodetector arranged in sequence along the optical path; the electrical part includes a preamplifier, an A / D converter, an FPGA, a D / A converter, a postamplifier, and a MEMS (Micro ElectroMechanical Systems) sensor connected in sequence; the photodetector converts the optical signal into an electrical signal and sends it to the preamplifier; the preamplifier amplifies the electrical signal and sends it to the A / D converter for analog-to-digital conversion and then to the FPGA for signal processing and correction.

[0033] like Figure 2 As shown, a method for extending the measurement range of a fiber optic gyroscope comprises the following steps:

[0034] 1] Coaxially set a MEMS sensor on the measurement axis of the fiber optic gyroscope, communicate the MEMS sensor with the FPGA in the fiber optic gyroscope, and read the output value of the MEMS sensor;

[0035] The MEMS sensor is designed and arranged on the digital demodulation circuit of the fiber optic gyroscope, and when the gyroscope is structurally designed, the MEMS sensor arranged on the digital demodulation circuit is coaxially arranged with the fiber optic ring module of the fiber optic gyroscope;

[0036] 2] According to the output value of the MEMS sensor, the zero position and polarity of the fiber optic gyroscope are used to correct the zero position and polarity of the MEMS sensor respectively;

[0037] 2.1. Place the fiber optic gyroscope at the "up, east, and north" positions respectively, and measure the zero position of the fiber optic gyroscope's X-axis, Y-axis, and Z-axis to be Ω X0 ,Ω Y0 ,Ω Z0 ;

[0038] 2.2. Using the zero position Ω of the fiber optic gyroscope X0 ,Ω Y0 ,Ω Z0 Correct the zero position of the X-axis, Y-axis, and Z-axis of the MEMS sensor respectively;

[0039] 2.3. Correct the polarity of the MEMS sensor according to the output polarity of the fiber optic gyroscope.

[0040] 3] Perform theoretical calculations on the fiber optic gyroscope to determine the measurement range of the fiber optic gyroscope Ω π ,Ω π ∈[-Ω π , +Ω π ], and set the measurement range of the fiber optic gyroscope in FPGA π ;

[0041] 4] After the external carrier is instantly started, the fiber optic gyroscope and MEMS sensor are used to measure the angular velocity Ω of the external carrier in real time;

[0042] 5] Determine the angular rate Ω measured by the MEMS sensor MEMS Is it beyond the measurement range [-Ω π , +Ω π ], when the angular rate Ω measured by the MEMS sensor MEMS >Ω π When the FPGA in the fiber optic gyroscope is MEMS =nΩ π +Ω 反馈 Perform iterative calculations, or when the angular rate -Ω measured by the MEMS sensor MEMS <-Ω π When the FPGA in the fiber optic gyroscope is MEMS =-nΩ π -Ω 反馈 Perform iterative calculation to obtain the final angular rate Ω 反馈 and angular rate nΩ π ; The final angular rate Ω 反馈 Assigned to the feedback register in the FPGA, angular rate nΩ π Assign to the integral output register in the FPGA to complete the expansion of the fiber optic gyroscope measurement range and output the corrected angular rate; otherwise, no correction is made and the fiber optic gyroscope outputs the angular rate normally; n is an integer greater than or equal to 1. In this embodiment, if the angular rate Ω measured by the MEMS sensor MEMS Out of measurement range [-Ω π , +Ω π ], then according to Ω MEMS =nΩ π +Ω 反馈 Perform iterative calculations, first take a value for n, and then calculate the value based on Ω MEMS =nΩ π +Ω 反馈 Calculate Ω 反馈 .

[0043] When the external carrier starts at high speed instantly, the angular rate ±Ω measured by the MEMS sensor MEMSCorrect the feedback register and integral output register in the fiber optic gyroscope (i.e., expand the number of bits of the feedback register and integral output register, and use the final angular rate Ω 反馈 Assigned to the feedback register in the FPGA, angular rate nΩ π Assigned to the integral output register in FPGA), the closed-loop control of the fiber optic gyroscope is reestablished, so that the angular rate measured by the fiber optic gyroscope is within Ω 瞬间 >Ω π or -Ω 瞬间 <-Ω π When Ω 瞬间 ≤Ω π or -Ω 瞬间 ≥-Ω π When Ω 瞬间 >Ω π or -Ω 瞬间 <-Ω π When,Ω MEMS =nΩ π +Ω 反馈 or -Ω MEMS =-nΩ π -Ω 反馈 , feedback angular rate Ω 反馈 Used to correct the feedback register, nΩ π or -nΩ π It is used to correct the integral output register, where n is a positive integer greater than or equal to 1. The MEMS sensor and the fiber optic gyroscope simultaneously measure the input angular rate Ω signal of the external carrier. When the external carrier suddenly rotates at high speed, the closed-loop feedback angular rate in the fiber optic gyroscope exceeds the measurement range [-Ω π , +Ω π ], start MEMS sensor correction.

[0044] In this embodiment, the model of the MEMS sensor is IAM-20380, using I 2 After the C interface successfully communicates with the FPGA on the digital demodulation circuit in the fiber optic gyroscope, the FPGA reads the measured angular rate data in the MEMS sensor; in order to compare the effect of the MEMS sensor correcting the fiber optic gyroscope under large impact or high-speed startup after the fiber optic gyroscope has expanded its measurement range based on a single stripe, a fiber optic gyroscope with an outer diameter of 70mm is used, and its theoretical measurement range is calculated to be ±140 (°) / s, and carried out impact response tests and high angular rate start-up tests with and without correction.

[0045] 1. The large angular rate (impact response spectrum) test after the fiber optic gyroscope expands its measurement range is as follows:

[0046] Shock condition: 6000g, shock direction: X-axis, Y-axis, Z-axis of the fiber optic gyroscope, shock response spectrum requirements are as follows Figure 3 As shown in the figure, the shock test is designed according to the test requirements of magnitude 0 to 6000g, frequency 0 to 6000hz, inflection point 1000hz, and magnitude tolerance of ±6dB; the shock results are shown in Figure 4 , Figure 5 As shown, Figure 4 This is the shock data curve of the fiber optic gyroscope without MEMS sensor correction. Figure 5 This is the shock data curve of the fiber optic gyroscope with MEMS sensor correction. Figure 4 It can be seen from the figure that when the fiber optic gyroscope is subjected to a large magnitude shock, the bias values ​​of the fiber optic gyroscopes on the X, Y, and Z axes undergo a huge jump and stabilize to a large fixed value, and cannot return to the normal value before the shock. Figure 5 It can be seen that the bias values ​​of the fiber optic gyroscopes on the three axes of X, Y, and Z remain unchanged before and after the impact, so the MEMS sensor correction has taken effect. Therefore, the experiment proves that the fiber optic gyroscope outputs a large constant value when performing an impact test based on the single-fringe extended measurement range. The fiber optic gyroscope outputs a normal value when using the fiber optic gyroscope corrected by the present invention to perform an impact test.

[0047] 2. The high-rate start-up test after the fiber optic gyroscope extends its measurement range is as follows:

[0048] Test conditions: The starting angular rates of the fiber optic gyroscope are 200 (°) / s, 400 (°) / s, 800 (°) / s, 1000 (°) / s. The test results are as follows Figure 6 , Figure 7 shown. Figure 6 This is the high-speed startup data curve of the fiber optic gyroscope without MEMS sensor correction. Figure 6 It can be seen that when there is no MEMS sensor correction, the fiber optic gyroscope is (°) When started at a rate of / s, the fiber optic gyroscope data is abnormal and the output constant is large; Figure 7 This is the high-speed startup data curve of the fiber optic gyroscope with MEMS sensor correction. Figure 7 It can be seen that when the MEMS sensor is used for correction, the fiber optic gyroscope is 200 (°) / s, 400 (°) / s, 800 (°) / s, 1000 (°) / s four rate points start, the fiber optic gyroscope output is normal. Therefore, the test proves that based on the single fringe expansion measurement range, the fiber optic gyroscope data outputs a large constant value when the large rate start test is carried out, and the fiber optic gyroscope output is normal when the fiber optic gyroscope corrected by the present invention is used to carry out the large angular rate start test.

[0049] 3. The speed and stability tests of the modified fiber optic gyroscope according to the present invention are as follows:

[0050] Use fiber optic gyroscope to do rate test, repeat the test for 6 groups, the rate point selected for each group is: ±220 (°) / s, ±200 (°) / s, ±150 (°) / s, ±140 (°) / s, ±100 (°) / s, ±50 (°) / s, ±10 (°) / s, ±1 (°) / s. The index requirements and test results are shown in Table 1:

[0051] Table 1

[0052]

[0053] Use fiber optic gyroscope to do zero stability test, repeat the test for 6 groups, each test lasts for 1 hour. The index requirements and test results are shown in Table 2:

[0054] Table 2

[0055]

[0056] In summary, it can be seen from Table 1 and Table 2 that the function test of the fiber optic gyroscope corrected by the MEMS sensor of the present invention is normal and meets the requirements. Therefore, the method for expanding the measurement range of the fiber optic gyroscope of the present invention is feasible and reliable, and can be applied in the development of other types of fiber optic gyroscopes.

Claims

1. A method for extending the measurement range of a fiber optic gyroscope, characterized in that: The following steps are involved: 1] Coaxially set a MEMS sensor on the measurement axis of the fiber optic gyroscope and read the output value of the MEMS sensor; 2] According to the output value of the MEMS sensor, the zero position and polarity of the fiber optic gyroscope are used to correct the zero position and polarity of the MEMS sensor respectively; 3] Calculate and set the measurement range of the fiber optic gyroscope [-Ω π , +Ω π ]; 4] After the external carrier is instantly started, the fiber optic gyroscope and MEMS sensor are used to measure the angular velocity of the external carrier in real time; 5] Determine the angular rate Ω measured by the MEMS sensor MEMS Is it beyond the measurement range [-Ω π , +Ω π ], if so, perform iterative calculation to obtain the final angular velocity Ω MEMS , and then use the final angular rate Ω MEMS At the same time, the values ​​of the feedback register and the integral output register are corrected to complete the expansion of the measurement range of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is made and the fiber optic gyroscope outputs the angular rate normally.

2. The method for extending the measurement range of a fiber optic gyroscope according to claim 1, characterized in that: Step 2] Specifically: 2.

1. Place the fiber optic gyroscope at the "up, east, and north" positions respectively, and measure the zero position of the fiber optic gyroscope's X-axis, Y-axis, and Z-axis to be Ω X0 ,Ω Y0 ,Ω Z0 ; 2.

2. Using the zero position Ω of the fiber optic gyroscope X0 ,Ω Y0 ,Ω Z0 Correct the zero position of the X-axis, Y-axis, and Z-axis of the MEMS sensor respectively; 2.

3. Correct the polarity of the MEMS sensor according to the output polarity of the fiber optic gyroscope.

3. A method for extending the measurement range of a fiber optic gyroscope according to claim 2, characterized in that: Step 5] Specifically: Determine the angular rate Ω measured by the MEMS sensor MEMS Is it beyond the measurement range [-Ω π , +Ω π ], when the angular rate Ω measured by the MEMS sensor MEMS >Ω π When, according to Ω MEMS =nΩ π +Ω 反馈 Perform iterative calculations, or when the angular rate -Ω measured by the MEMS sensor MEMS <-Ω π When, according to -Ω MEMS =-nΩ π -Ω 反馈 Perform iterative calculation to obtain the final angular rate Ω 反馈 and angular rate nΩ π ; The final angular rate Ω 反馈 Assigned to the feedback register, angular rate nΩ π Assign a value to the integral output register in the FPGA to complete the expansion of the measurement range of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is made and the fiber optic gyroscope outputs the angular rate normally; the n is an integer greater than or equal to 1.

4. A method for extending the measurement range of a fiber optic gyroscope according to claim 3, characterized in that: In step 1], the MEMS sensor is arranged on the digital demodulation circuit of the fiber optic gyroscope and is coaxially arranged with the fiber optic ring module of the fiber optic gyroscope.

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