A method for extending the measurement range of a fiber-optic gyroscope

Abstract

This invention specifically relates to a method for extending the measurement range of a fiber optic gyroscope, solving the technical problems that the starting angular rate of existing fiber optic gyroscopes must be less than the theoretical angular rate and that there is a theoretical upper limit to the angular acceleration of fiber optic gyroscopes. The method for extending the measurement range of a fiber optic gyroscope includes the following steps: 1) reading the output value of a MEMS sensor; 2) correcting the zero point and polarity of the MEMS sensor; 3) calculating and setting the measurement range of the fiber optic gyroscope [-Ω]. π +Ω π ]; 4) Real-time measurement of the angular velocity Ω of the external carrier; 5) Determination of the angular velocity Ω measured by the MEMS sensor MEMS Is it outside the measurement range? [-Ω] π +Ω π If so, then perform iterative calculations to obtain the final angular velocity Ω. MEMS Then use the final angular velocity Ω MEMS Simultaneously, the values ​​of the feedback register and the integral output register are corrected to complete the measurement range expansion 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.

Description

Technical Field

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

[0002] The theoretical measurement range of a fiber optic gyroscope is limited by the fiber loop length and equivalent diameter. Assuming these two factors remain constant, the common approach to extending the measurement range of a fiber optic gyroscope in practical applications is based on the single-fringe extension theory. However, this theory has two limitations in practical applications: the fiber optic gyroscope must start from the first fringe (theoretical angular rate), and there is a theoretical upper limit to the angular acceleration of the fiber optic gyroscope.

[0003] Based on the single-fringe spread theory, it is assumed that the limiting measurement range of the fiber optic gyroscope is ±500°. (°) The fiber optic gyroscope outputs a 26-bit digital signal per second. If all bits are fed back, each least significant bit represents an angular velocity of 0.053 Å. (°) / h. Due to the limitation of the D / A converter's bit width, the lower 10 bits are discarded, so the least significant bit fed back to the D / A converter represents an angular rate of 54.9. (°) / h. The fiber optic gyroscope outputs digital values: "00……00" to "11……11", representing values ​​from 0 to ±500 respectively. (°) All angular velocity values ​​per second. The digital value fed back to the D / A converter is the high 16 bits of the digital output of the fiber optic gyroscope, ranging from 0 to 65535 ("1111111111111111" also represents 0 to ±500). (°) All angular velocity values ​​per second. When the input angular velocity is greater than ±Ω... π (±500 (°) If the measurement range is increased by 2 times, the 26-bit register is insufficient. In this case, the number of bits of the fiber optic gyroscope output needs to be expanded. If the measurement range is increased by 2 times, the number of bits of the fiber optic gyroscope output angular rate register needs to reach 27 bits; if the measurement range is increased by 4 times, the number of bits of the fiber optic gyroscope output angular rate register needs to reach 28 bits, and so on. If the measurement range is increased by 2n, the number of bits of the fiber optic gyroscope is 26+n bits.

[0004] 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 rotational angular rate starts from -Ω), π ~+Ω π (At the beginning), after it is in closed-loop operation, it can work stably at the bias point of the first interference fringe. There is an upper limit requirement for the maximum angular acceleration of the fiber optic gyroscope input, 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 this invention is to solve the technical problems that the starting angular rate of existing fiber optic gyroscopes must be less than the theoretical angular rate and that there is a theoretical upper limit to the angular acceleration of fiber optic gyroscopes, and to provide a method for extending the measurement range of fiber optic gyroscopes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for extending the measurement range of a fiber optic gyroscope, characterized by the following steps:

[0008] 1. A MEMS sensor is coaxially mounted on the measurement axis of the fiber optic gyroscope, and the output value of the MEMS sensor is read.

[0009] 2】Based on the output value of the MEMS sensor, the zero position and polarity of the MEMS sensor are corrected using the zero position and polarity of the fiber optic gyroscope, respectively.

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

[0011] 4) After the external carrier starts up instantly, the angular rate of the external carrier is measured in real time using both fiber optic gyroscopes and MEMS sensors.

[0012] 5】Determine the angular velocity Ω measured by the MEMS sensor MEMS Is it outside the measurement range [-Ω]? π +Ω π If so, then perform iterative calculations to obtain the final angular velocity Ω. MEMS Then use the final angular velocity Ω MEMS Simultaneously, the values ​​of the feedback register and the integral output register are corrected to complete the measurement range expansion 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] Furthermore, step 2 specifically involves:

[0014] 2.1 Place the fiber optic gyroscope at the "up," "east," and "north" positions respectively, and measure the zero points of the X, Y, and Z axes of the fiber optic gyroscope as Ω. X0 Ω Y0 Ω Z0 ;

[0015] 2.2 Utilizing the zero-position Ω of a fiber optic gyroscope X0 Ω Y0 Ω Z0 These correspond to correcting the zero position of the X, Y, and Z axes 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] Furthermore, step 5 specifically involves:

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

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

[0020] The beneficial effects of this invention are:

[0021] 1) The present invention provides a method for extending the measurement range of a fiber optic gyroscope. First, the fiber optic gyroscope is corrected for zero position and polarity using a MEMS sensor to obtain a high-accuracy angular rate output, avoid misjudgment, and improve the measurement accuracy of the fiber optic gyroscope.

[0022] 2) This invention provides a method for extending the measurement range of a fiber optic gyroscope. Under high-speed startup of an external carrier, an algorithm using a MEMS sensor for post-correction beyond the theoretical measurement range is employed to consistently control the closed-loop feedback circuit of the fiber optic gyroscope within the measurement range [-Ω]. π +Ω π This ensures the normal closed-loop operation 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 limitations of the current method for extending the measurement range of a fiber optic gyroscope: a) the starting angular rate of the fiber optic gyroscope must be less than the theoretical angular rate; 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 by adding a MEMS sensor to the digital demodulation circuit layout and wiring of the fiber optic gyroscope without changing the original structure and accuracy of the fiber optic gyroscope. This method is convenient to implement and enhances the environmental adaptability of the fiber optic gyroscope. Attached Figure Description

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

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

[0027] Figure 3 This is a schematic diagram of the impact response spectrum test requirements in an embodiment of a method for extending the measurement range of a fiber optic gyroscope according to the present invention. The horizontal axis represents the frequency of the test spectrum, and the vertical axis represents the magnitude of the impact (acceleration).

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

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

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

[0031] Figure 7 This is a schematic diagram of a high-speed startup test of the fiber optic gyroscope with MEMS sensor correction according to 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 represent the X-axis starting angular rate of 200. (°) / s、400 (°) / s、800 (°) / s、1000 (°) / s, and its output is 200. (°) / s、400 (°) / s、800 (°) / s、1000 (°) / s. Detailed Implementation

[0032] like Figure 1 As shown, the fiber optic gyroscope includes an optical section and an electrical section (i.e., a digital demodulation circuit). The optical section includes a fiber optic loop, an optical phase modulator, and a photodetector arranged sequentially along the optical path. The electrical section 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 before sending it 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 includes the following steps:

[0034] 1. A MEMS sensor is coaxially mounted on the measurement axis of the fiber optic gyroscope, and the MEMS sensor communicates with the FPGA in the fiber optic gyroscope to read the output value of the MEMS sensor.

[0035] The MEMS sensor is designed and laid out on the digital demodulation circuit of the fiber optic gyroscope. At the same time, in the structural design of the gyroscope, the MEMS sensor laid out on the digital demodulation circuit is coaxially set with the fiber optic ring module of the fiber optic gyroscope.

[0036] 2】Based on the output value of the MEMS sensor, the zero position and polarity of the MEMS sensor are corrected using the zero position and polarity of the fiber optic gyroscope, respectively.

[0037] 2.1 Place the fiber optic gyroscope at the "up," "east," and "north" positions respectively, and measure the zero points of the X, Y, and Z axes of the fiber optic gyroscope as Ω. X0 Ω Y0 Ω Z0 ;

[0038] 2.2 Utilizing the zero-position Ω of a fiber optic gyroscope X0 Ω Y0 Ω Z0 These correspond to correcting the zero position of the X, Y, and Z axes 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 its measurement range Ω. π Ω π ∈[-Ω π +Ω π The measurement range Ω of the fiber optic gyroscope is set in the FPGA. π ;

[0041] 4】After the external carrier starts up instantly, the angular rate Ω of the external carrier is measured in real time using both fiber optic gyroscope and MEMS sensor;

[0042] 5】Determine the angular velocity Ω measured by the MEMS sensor MEMS Is it outside the measurement range [-Ω]? π +Ω π When the angular velocity Ω measured by the MEMS sensor MEMS >Ω π At that time, the FPGA in the fiber optic gyroscope follows the Ω... MEMS =nΩ π +Ω 反馈 Perform iterative calculations, or when the angular velocity -Ω measured by the MEMS sensor MEMS <-Ω π At that time, the FPGA in the fiber optic gyroscope follows the -Ω MEMS =-nΩ π -Ω 反馈 Perform iterative calculations to obtain the final angular velocity Ω. 反馈 and angular velocity nΩ π The final angular velocity Ω 反馈 The value is assigned to the feedback register in the FPGA, angular rate nΩ π The value is assigned to the integral output register in the FPGA to complete the measurement range extension of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is performed, 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 To perform iterative calculations, first, n is assigned a value, and then based on Ω... MEMS =nΩ π +Ω 反馈 Calculate Ω 反馈 .

[0043] The angular velocity ±Ω measured by MEMS sensors when the external carrier starts at high speed instantaneously. MEMSThe feedback register and integral output register in the fiber optic gyroscope are modified (i.e., the number of bits in the feedback register and integral output register are expanded to utilize the final angular rate Ω). 反馈 The value is assigned to the feedback register in the FPGA, angular rate nΩ π (Assigned to the integral output register in the FPGA), the closed-loop control of the fiber optic gyroscope was re-established, ensuring that the angular rate measured by the fiber optic gyroscope is within Ω. 瞬间 >Ω π or -Ω 瞬间 <-Ω π At that time, the fiber optic gyroscope closed-loop does not fail. Specifically, when Ω 瞬间 ≤Ω π or -Ω 瞬间 ≥-Ω π When Ω is at its maximum, only the integral output register needs to be expanded; no correction is required. 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 This is used to correct the integral output register, where n is a positive integer greater than or equal to 1. The MEMS sensor and 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 When [the condition is met], MEMS sensor correction is initiated.

[0044] In this embodiment, the MEMS sensor is model IAM-20380, and it uses I... 2 After successful communication between the C interface and the FPGA on the digital demodulation circuit of the fiber optic gyroscope, the FPGA reads the measured angular rate data from the MEMS sensor. To compare the effect of MEMS sensor correction on the fiber optic gyroscope under conditions of large impact or high-speed startup after extending the measurement range based on a single stripe, a fiber optic gyroscope with an outer diameter of 70mm using a fiber optic ring module was used. The theoretical measurement range was calculated to be ±140°. (°) / s, impact response tests and high angular rate start-up tests were conducted under two conditions: with and without correction.

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

[0046] Impact conditions: 6000g; impact direction: X-axis, Y-axis, Z-axis of the fiber optic gyroscope; impact response spectrum requirements as follows: Figure 3 As shown, an impact test was designed according to the test requirements of a magnitude range of 0 to 6000 g, a frequency range of 0 to 6000 Hz, a chamfer point of 1000 Hz, and a magnitude tolerance of ±6 dB; the impact results are as follows. Figure 4 , Figure 5 As shown, Figure 4 The image shows the impact data curve of a fiber optic gyroscope without MEMS sensor correction. Figure 5 The image shows the impact data curve of a fiber optic gyroscope with MEMS sensor correction. Figure 4 As can be seen, when a fiber optic gyroscope is subjected to a large-scale impact, the bias values ​​of the X, Y, and Z axes of the fiber optic gyroscope undergo huge jumps and stabilize at a fixed high value, unable to return to the normal values ​​before the impact. From Figure 5 As can be seen, the bias values ​​of the fiber optic gyroscopes on the X, Y, and Z axes remained unchanged before and after the impact, indicating that the MEMS sensor correction was effective. Therefore, the experiment proves that under the condition of single-fringe extended measurement range, the impact test results in a large number of fixed data output values ​​from the fiber optic gyroscope. Using the fiber optic gyroscope corrected by this invention, the impact test results in normal output from the fiber optic gyroscope.

[0047] 2. The high-speed start-up test after expanding the measurement range of the fiber optic gyroscope is specifically as follows:

[0048] Test conditions: The fiber optic gyroscope's startup angular rate was 200°. (°) / s、400 (°) / s、800 (°) / s、1000 (°) / s. Test results are as follows Figure 6 , Figure 7 As shown. Figure 6 This is the high-speed startup data curve of a fiber optic gyroscope without MEMS sensor correction. From Figure 6 As can be seen from this, when there is no MEMS sensor correction, the fiber optic gyroscope at 200 (°) When starting at a rate of / s, the fiber optic gyroscope data is abnormal, and the output is a large fixed value. Figure 7 This is the high-speed startup data curve of a fiber optic gyroscope with MEMS sensor correction. From Figure 7 As can be seen from the data, when corrected with a MEMS sensor, the fiber optic gyroscope performs at 200... (°) / s、400 (°) / s、800 (°) / s、1000 (°)When starting at four rate points per second, the fiber optic gyroscope outputs normally in all cases. Therefore, the experiment proves that when performing a high-rate start-up test based on a single-stripe extended measurement range, the fiber optic gyroscope outputs a large fixed value. When performing a high-angular-rate start-up test using the fiber optic gyroscope modified according to this invention, the fiber optic gyroscope outputs normally.

[0049] 3. The specific steps for conducting rate and stability tests using the modified fiber optic gyroscope of this invention are as follows:

[0050] Rate tests were performed using a fiber optic gyroscope, with six repeated tests. The rate points selected for each test were ±220. (°) / s, ±200 (°) / s, ±150 (°) / s, ±140 (°) / s, ±100 (°) / s, ±50 (°) / s, ±10 (°) / s, ±1 (°) / s. The performance requirements and test results are shown in Table 1:

[0051] Table 1

[0052]

[0053] Zero-position stability tests were performed using a fiber optic gyroscope, with six repeated tests, each lasting one hour. The performance requirements and test results are shown in Table 2.

[0054] Table 2

[0055]

[0056] In summary, as can be seen from Tables 1 and 2, the fiber optic gyroscope with the MEMS sensor correction of this invention performs normally and meets the requirements. Therefore, the fiber optic gyroscope measurement range extension method of this 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, Includes the following steps:

1. A MEMS sensor is coaxially mounted on the measurement axis of the fiber optic gyroscope, and the output value of the MEMS sensor is read. 2】Based on the output value of the MEMS sensor, the zero position and polarity of the MEMS sensor are corrected using the zero position and polarity of the fiber optic gyroscope, respectively.

3. Calculate and set the measurement range of the fiber optic gyroscope [-Ω]. π +Ω π ]; 4) After the external carrier starts up instantly, the angular rate of the external carrier is measured in real time using both fiber optic gyroscopes and MEMS sensors. 5】Determine the angular rate Ω measured by the MEMS sensor MEMS Is it outside the measurement range [-Ω]? π +Ω π If so, then perform iterative calculations to obtain the final angular velocity Ω. MEMS Then use the final angular velocity Ω MEMS Simultaneously correct the values ​​of the feedback register and the integral output register to complete the measurement range extension of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is performed, and the fiber optic gyroscope outputs the angular rate normally. Determine the angular velocity Ω measured by the MEMS sensor MEMS Is it outside the measurement range [-Ω]? π +Ω π When the angular velocity Ω measured by the MEMS sensor MEMS >Ω π At that time, according to Ω MEMS =nΩ π +Ω 反馈 Perform iterative calculations, or when the angular velocity -Ω measured by the MEMS sensor MEMS <-Ω π At that time, according to -Ω MEMS =-nΩ π -Ω 反馈 Perform iterative calculations to obtain the final angular velocity Ω. 反馈 and angular velocity nΩ π The final angular velocity Ω 反馈 The value is assigned to the feedback register, angular rate nΩ π The value is assigned to the integral output register in the FPGA to complete the measurement range expansion of the fiber optic gyroscope and output the corrected angular rate; otherwise, no correction is performed and the fiber optic gyroscope outputs the angular rate normally; where n is an integer greater than or equal to 1.

2. The method for extending the measurement range of a fiber optic gyroscope according to claim 1, characterized in that, Step 2 is as follows: 2.1 Place the fiber optic gyroscope at the "up," "east," and "north" positions respectively, and measure the zero position of the X, Y, and Z axes of the fiber optic gyroscope as Ω. X0 Ω Y0 Ω Z0 ; 2.2 Utilizing the zero-position Ω of a fiber optic gyroscope X0 Ω Y0 Ω Z0 These correspond to correcting the zero position of the X, Y, and Z axes 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. The method for extending the measurement range of a fiber optic gyroscope according to claim 2, characterized in that: In step 1, the MEMS sensor is mounted on the digital demodulation circuit of the fiber optic gyroscope and is coaxially mounted with the fiber optic ring module of the fiber optic gyroscope.

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