A strapdown inertial navigation system level calibration method based on temperature-controlled double-axis position turntable

Abstract

The application provides a strapdown inertial navigation system level calibration method based on a temperature control double-shaft position turntable, and solves the problems of large workload, error-prone, high cost, waste of equipment and manpower and the like of the prior calibration method. The application proposes a temperature and position calibration based on a temperature control double-shaft position turntable, overcomes the double-shaft turntable rotation position limitation, and designs a rotation position and rotation scheme in a targeted manner. Meanwhile, the automatic rotation position of the turntable realizes automatic calibration of the positions of the product gyroscopes and accelerometers. The application can also control the temperature of the turntable temperature box, automatically identify the corresponding temperature points of the product and capture the error parameters of the product at the corresponding temperature points, and automatically solve the compensation values of the initial temperature changes of the zero positions of the gyroscopes and accelerometers.

Description

Technical Field

[0001] This invention belongs to the field of inertial navigation calibration technology, specifically relating to a strapdown inertial navigation system calibration method based on a temperature-controlled dual-axis position turntable. Background Technology

[0002] Inertial navigation / attitude and bearing (INS) products can measure and output real-time navigation information of the aircraft, including heading, pitch, roll, longitude, latitude, altitude, eastward speed, northward speed, and azimuth speed. They also output the aircraft's three-axis angular rates and three-axis acceleration signals. INS / INS systems possess high-precision autonomous navigation, multiple information parameter outputs, and the ability to maintain accuracy over long periods. They serve as the information foundation for weapon systems and flight control systems, and are therefore often considered the most important navigation equipment.

[0003] Before use, inertial navigation / attitude products must undergo calibration tests to determine the various error parameters of the gyroscopes and accelerometers, and then compensate for them within the inertial navigation system. Currently, the commonly used position calibration method is three-axis calibration. The calibration process requires manual operation of software to change each position. This method demands highly skilled operators, involves a huge workload, is prone to errors, and requires recalibration to correct any errors. Similarly, current temperature calibration requires operators to manually model and calculate temperature compensation parameters based on a large amount of collected gyroscope and accelerometer data ranging from low to high temperatures. This is labor-intensive, inefficient, and prone to errors, leading to unsatisfactory inertial navigation performance. Errors necessitate recalibration and recalculation, wasting significant equipment and human resources and delaying production cycles.

[0004] Therefore, it is necessary to explore a new method for calibration of strapdown inertial navigation systems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing calibration methods, such as large workload, high error rate, high cost, and waste of equipment and manpower, by providing a strapdown inertial navigation system-level calibration method based on a temperature-controlled dual-axis position turntable.

[0006] The concept of this invention:

[0007] To address the problems of existing calibration methods, this invention conducted a comparative study and found that, compared to three-axis turntables of the same precision, dual-axis turntables not only offer advantages in terms of economy and space requirements, but also can cover the combination of speed and attitude in existing product calibration processes, thus completely replacing three-axis calibration solutions. Therefore, to simplify calibration equipment and reduce calibration costs, this invention proposes to conduct research on automatic temperature and dual-axis turntable calibration technology based on a temperature-controlled dual-axis position turntable, to achieve fully automatic temperature and dual-axis calibration for inertial navigation / attitude and flight.

[0008] Based on the above inventive concept, and to achieve the above objectives, the technical solution provided by this invention is as follows:

[0009] A strapdown inertial navigation system calibration system based on a dual-axis position turntable is characterized by including a temperature-controlled dual-axis position turntable, a mounting bracket, calibration fixtures, cables, testing fixtures, and a main control computer.

[0010] The temperature-controlled dual-axis position turntable has two mutually perpendicular rotation axes, providing a high-precision attitude basis for inertial navigation system calibration and testing; the turntable is the core of the calibration system and is mainly used for inertial navigation system temperature calibration tests and position rotation tests;

[0011] The calibration fixture is installed on the turntable surface of the inner frame of the temperature control dual-axis position turntable temperature chamber, providing an installation positioning reference for the inertial navigation system;

[0012] The mounting bracket is used to fix the inertial navigation system on the calibration fixture;

[0013] The inertial navigation system is connected to the main control computer via cables and test fixtures. The test fixtures are used for signal transmission (specifically, signal switching between the inertial navigation system and the main control computer) and to control the power-on / off and state switching of the inertial navigation system (the state here refers to either the test state or the calibration state).

[0014] The main control computer is used for inertial navigation system testing, controlling the entire calibration process, including the rotation of the temperature-controlled dual-axis position turntable, data acquisition, and calculation. In other words, the main control computer has an automatic calibration function, used to control the temperature-controlled dual-axis position turntable to achieve dual-axis rotation of the inertial navigation system, control the temperature of the temperature chamber of the temperature-controlled dual-axis position turntable, automatically calibrate the position of the dual-axis turntable of the inertial navigation system, automatically identify the temperature point of the temperature chamber, and read and calculate the error parameters of the current temperature point to achieve automatic temperature calibration.

[0015] Meanwhile, this invention provides a strapdown inertial navigation system (INS) calibration method based on a dual-axis position turntable. The method achieves automatic dual-axis position calibration, temperature calibration, and system error compensation of the INS through the aforementioned dual-axis position turntable-based INS calibration system. The specific steps are as follows:

[0016] 1) According to the structure of the strapdown inertial navigation system calibration system based on the dual-axis position turntable, first install the calibration fixture on the turntable surface of the temperature control dual-axis position turntable temperature chamber inner frame, and then fix the inertial navigation system to be calibrated on the calibration fixture through the mounting bracket.

[0017] 2) The main control computer controls the temperature-controlled dual-axis position turntable to rotate and perform initial positioning of the inertial navigation system;

[0018] 3) Temperature calibration

[0019] 3.1) After the main control computer controls the inertial navigation system to power on and enter the calibration state, the main control computer controls the temperature-controlled dual-axis position turntable to conduct temperature calibration tests on the inertial navigation system at different temperatures, and collects the raw pulse data of the inertial navigation system gyroscope and accelerometer at each temperature;

[0020] 3.2) Using the data collected in step 3.1), parameter compensation is automatically performed over the entire temperature range based on the piecewise curve fitting model, and the temperature compensation parameters are written into the inertial navigation system.

[0021] Because the output of gyroscopes and accelerometers exhibits nonlinearity with temperature changes, it is necessary to process the raw pulse data of gyroscopes and accelerometers at different temperatures before calibrating them. Then, the relationship between the output pulse values ​​of gyroscopes and accelerometers and the initial power-on temperature and temperature changes should be calculated. This involves calculating the corresponding zero-point deviation compensation and temperature change rate deviation compensation to avoid introducing the influence of temperature on the calibration of accelerometers and gyroscopes.

[0022] 4) Calibration and parameter calculation

[0023] Specifically, this includes accelerometer position calibration and parameter calculation, and gyroscope calibration and parameter calculation;

[0024] The accelerometer position calibration and parameter calculation are specifically as follows:

[0025] ①. The main control computer controls the temperature-controlled dual-axis position turntable to rotate, so that the sensitive axes of the three accelerometers of the inertial navigation system point to nine positions respectively: "sky--west--south", "earth--west--north", "earth--east-south", "east--sky-south", "east--earth--north", "west--earth--south", "west--south-sky", "west--north--earth", and "east--south-earth", and collects the output pulse value of the accelerometer at each position within the same time period;

[0026] ②. Using the average value of 9 samples, calculate the zero point and scale coefficient of the accelerometer according to the calibration principle of the accelerometer;

[0027] The specific steps for gyroscope calibration and parameter calculation are as follows:

[0028] Ⅰ. The main control computer controls the temperature-controlled dual-axis position turntable to rotate one revolution clockwise and one revolution counterclockwise around the X-axis, Y-axis and Z-axis respectively, and records the cumulative output pulse of the three axial gyroscopes of the inertial navigation system during the rotation process;

[0029] II. Using the results of 6 samplings, calculate the zero position and scale coefficient of the gyroscope according to the gyroscope calibration principle;

[0030] 5) Write the zero position and scale coefficient of the accelerometer and the zero position and scale coefficient of the gyroscope obtained in step 4) into the inertial navigation system parameter table to complete the calibration.

[0031] Furthermore, in step 2), the initial positioning refers to the X-axis, Y-axis, and Z-axis of the inertial navigation system pointing to the east, north, and sky, respectively.

[0032] Furthermore, in step 3), the different temperatures refer to -55℃, -40℃, -20℃, 0℃, 20℃, 40℃, 60℃, and 70℃, i.e., performing 8-point temperature calibration; of course, 6-point temperature calibration can also be performed according to requirements, such as: -40℃, -20℃, 0℃, 20℃, 40℃, and 65℃.

[0033] Furthermore, in step 4), during the accelerometer position calibration and parameter calculation, the output pulse values ​​of the accelerometers at nine positions are collected for 1 minute each.

[0034] Advantages of this invention:

[0035] 1. This invention proposes a temperature and position calibration method based on a temperature-controlled dual-axis position turntable. It not only overcomes the limitations of dual-axis turntable rotation but also specifically designs a rotation position and rotation scheme. Furthermore, it enables automatic calibration of the product's gyroscope and accelerometer positions through automatic turntable rotation. Simultaneously, this invention can control the turntable chamber temperature, automatically identify the corresponding temperature point of the product and capture the product error parameters at that temperature point, and automatically resolve the compensation values ​​for gyroscope and accelerometer zero-point changes with initial temperature. Compared to the original manual three-axis calibration method, this calibration method has advantages such as high efficiency and high automation. It is suitable for the automatic calibration of inertial navigation products, avoids calibration rework caused by human factors, and significantly improves the efficiency of inertial navigation / attitude calibration.

[0036] 2. This invention establishes a calibration model for a dual-axis gyroscope and accelerometer, automatically controls the temperature-controlled dual-axis turntable to rotate to a specified position, and determines the temperature point to be read during temperature calibration. It also enables the acquisition and calculation of data at different temperature points and rotation positions, automatically completes the parameter calibration and compensation of the inertial navigation system, and achieves temperature and position calibration compensation for inertial navigation products, thereby improving the navigation accuracy of the inertial navigation system. Attached Figure Description

[0037] Figure 1 A schematic diagram of the strapdown inertial navigation system calibration connection on a dual-axis position turntable;

[0038] The attached figures are labeled as follows:

[0039] 1-Temperature-controlled dual-axis position turntable; 2-Inertial navigation system; 3-Mounting bracket; 4-Calibration fixture; 5-Cable; 6-Test fixture; 7-Main control computer; 8-Main control computer switch; 9-Socket; 10-Main power switch; 11-Turntable surface; 12-Turntable power supply switch; 13-28V power converter. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] like Figure 1 As shown, the strapdown inertial navigation system (INS) calibration system based on a dual-axis position turntable includes a temperature-controlled dual-axis position turntable, a mounting bracket, a calibration fixture, cables, a testing fixture, and a main control computer. The temperature-controlled dual-axis position turntable has two mutually perpendicular rotation axes, providing a high-precision attitude foundation for INS calibration and testing. The calibration fixture is mounted on the turntable surface within the temperature chamber frame of the temperature-controlled dual-axis position turntable, providing an installation positioning reference for the INS; in this embodiment, this is called "north-finding." Regardless of the position of the temperature-controlled dual-axis position turntable, the calibration fixture can provide an installation reference for the INS. The mounting bracket is used to fix the INS onto the calibration fixture. The INS is connected to the main control computer sequentially via cables and the testing fixture. The testing fixture is used for signal transmission and to control the power-on / off and state switching of the INS. The main control computer is used for INS testing, controlling the entire calibration process, the rotation of the temperature-controlled dual-axis position turntable, data acquisition, and computation. The assembly of each component switch and the power conversion settings are clear to those skilled in the art and will not be described in detail here.

[0042] The method for calibrating an inertial navigation system using the above calibration system includes the following steps:

[0043] 1) First, install the calibration fixture on the turntable surface of the inner frame of the temperature control dual-axis position turntable chamber, and then fix the inertial navigation system to be calibrated on the calibration fixture through the mounting bracket.

[0044] 2) The main control computer controls the temperature-controlled dual-axis position turntable to rotate and perform initial positioning of the inertial navigation system. Due to the limitations of the turntable structure, the inertial navigation system can only achieve one full rotation clockwise and counterclockwise when the Z gyroscope points to the sky, while the X or Y gyroscope cannot rotate around its sensitive axis when it points to the sky. Therefore, in this embodiment, the initial positioning means that the X-axis, Y-axis and Z-axis of the inertial navigation system point to the east, north and sky respectively.

[0045] 3) Temperature calibration

[0046] 3.1) After the main control computer controls the inertial navigation system to power on and enter the calibration state, the main control computer controls the temperature-controlled dual-axis position turntable to conduct temperature calibration tests on the inertial navigation system at different temperatures (eight temperature points: -55℃, -40℃, -20℃, 0℃, 20℃, 40℃, 60℃ and 70℃), and collects the raw pulse data of the inertial navigation system gyroscope and accelerometer at each temperature;

[0047] 3.2) Using the data collected in step 3.1), parameter compensation is automatically performed over the entire temperature range based on the piecewise curve fitting model, and the temperature compensation parameters are written into the inertial navigation system.

[0048] 4) Calibration and parameter calculation

[0049] Specifically, this includes accelerometer position calibration and parameter calculation, and gyroscope calibration and parameter calculation;

[0050] The accelerometer position calibration and parameter calculation are specifically as follows:

[0051] ①. The main control computer controls the temperature-controlled dual-axis position turntable to rotate, so that the sensitive axes of the three accelerometers of the inertial navigation system point to nine positions respectively: "sky--west--south", "earth--west--north", "earth--east-south", "east--sky-south", "east--earth--north", "west--earth--south", "west--south--sky", "west--north--earth", and "east--south--earth" (that is, through a specific arrangement, the sensitive axis of each accelerometer in the inertial navigation system can be calibrated), and the output pulse value of the accelerometer at each position is collected for 1 minute.

[0052] Due to the unique characteristics of the dual-axis position turntable, the accelerometer position calibration is achieved by combining the control of the X and Z axes of the dual-axis turntable to point the inertial navigation system to the above nine positions. The initial positions of the dual-axis turntable at each position are shown in Table 1.

[0053] Table 1. Initial Position of Dual-Axis Turntable under Nine-Position Calibration

[0054]

[0055] ②. Using the average value of 9 samples, calculate the zero point and scale coefficient of the accelerometer according to the calibration principle of the accelerometer;

[0056] The specific steps for gyroscope calibration and parameter calculation are as follows:

[0057] Ⅰ. The main control computer controls the temperature-controlled dual-axis position turntable to rotate one revolution clockwise and one revolution counterclockwise around the X-axis, Y-axis and Z-axis respectively, and records the cumulative output pulse of the three axial gyroscopes of the inertial navigation system during the rotation process;

[0058] Due to the limitations of the turntable structure, the inertial navigation system can only achieve one full clockwise and counterclockwise rotation of the Z gyroscope when it points upwards, while the X or Y gyroscope cannot rotate around its sensitive axis when it points upwards. Therefore, the initial position of the turntable and the rotation axis of the turntable need to be adjusted as follows:

[0059] When rotating along the X-axis, the initial position is adjusted from "X points to the top clockwise" and "X points to the top counterclockwise" rotating around the outer frame of the three-axis turntable once to "X points to the north clockwise" and "X points to the north counterclockwise" rotating around the X-axis of the dual-axis turntable once; when rotating along the Y-axis, the initial position is adjusted from "Y points to the top clockwise" and "Y points to the top counterclockwise" rotating around the outer frame of the three-axis turntable once to "Y points to the north clockwise" and "Y points to the north counterclockwise" rotating around the X-axis of the dual-axis turntable once.

[0060] The initial indexing and rotation axes of the dual-axis turntable during gyroscope calibration are detailed in Table 2.

[0061] Table 2 Initial position and rotation axis of the dual-axis turntable for gyroscope calibration.

[0062]

[0063] II. Using the results of 6 samplings, calculate the zero position and scale coefficient of the gyroscope according to the gyroscope calibration principle;

[0064] 5) Write the zero position and scale coefficient of the accelerometer and the zero position and scale coefficient of the gyroscope obtained in step 4) into the inertial navigation system parameter table to complete the calibration.

[0065] After verification, this method can realize the calculation and automatic writing of calibration parameters for the position and temperature of the inertial navigation system gyroscope and accelerometer. The calibration results are detailed in Table 3.

[0066] Table 3 Calibration Parameters

[0067]

[0068]

[0069]

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for calibrating a strapdown inertial navigation system based on a dual-axis position turntable, characterized in that: The method uses a strapdown inertial navigation system-level calibration system based on a dual-axis position turntable, which includes a temperature-controlled dual-axis position turntable, mounting bracket, calibration fixture, cables, test fixtures, and a main control computer. The temperature-controlled dual-axis position turntable has two mutually perpendicular rotation axes, providing a high-precision attitude basis for inertial navigation system calibration and testing; The calibration fixture is installed on the turntable surface of the inner frame of the temperature control dual-axis position turntable temperature chamber, providing an installation positioning reference for the inertial navigation system; The mounting bracket is used to fix the inertial navigation system on the calibration fixture; The inertial navigation system is connected to the main control computer via cables and test fixtures in sequence. The test fixtures are used for signal transmission and to control the power-on and power-off of the inertial navigation system and state switching. The main control computer is used for inertial navigation system testing, controlling the entire calibration process, temperature-controlled dual-axis position turntable rotation, data acquisition, and calculation. The steps of this method are as follows: 1) According to the structure of the strapdown inertial navigation system calibration system based on the dual-axis position turntable, first install the calibration fixture on the turntable surface of the temperature control dual-axis position turntable temperature chamber inner frame, and then fix the inertial navigation system to be calibrated on the calibration fixture through the mounting bracket. 2) The main control computer controls the temperature-controlled dual-axis position turntable to rotate and perform initial positioning of the inertial navigation system; 3) Temperature calibration 3.1) After the main control computer controls the inertial navigation system to power on and enter the calibration state, the main control computer controls the temperature-controlled dual-axis position turntable to conduct temperature calibration tests on the inertial navigation system at different temperatures, and collects the raw pulse data of the inertial navigation system gyroscope and accelerometer at each temperature; 3.2) Using the data collected in step 3.1), parameter compensation is automatically performed over the entire temperature range based on the piecewise curve fitting model, and the temperature compensation parameters are written into the inertial navigation system; 4) Calibration and parameter calculation Specifically, this includes accelerometer position calibration and parameter calculation, and gyroscope calibration and parameter calculation; The accelerometer position calibration and parameter calculation are specifically as follows: ①. The main control computer controls the temperature-controlled dual-axis position turntable to rotate, so that the sensitive axes of the three accelerometers of the inertial navigation system point to nine positions respectively: "sky--west--south", "ground--west--north", "ground--east--south", "east--sky--south", "east--ground--north", "west--ground--south", "west--south--sky", "west--north--ground", and "east--south--ground", and collects the output pulse value of the accelerometer at each position within the same time period; ②. Using the average value of 9 samples, calculate the zero point and scale coefficient of the accelerometer according to the calibration principle of the accelerometer; The specific steps for gyroscope calibration and parameter calculation are as follows: Ⅰ. The main control computer controls the temperature-controlled dual-axis position turntable to rotate one revolution clockwise and one revolution counterclockwise around the X-axis, Y-axis and Z-axis respectively, and records the cumulative output pulse of the three axial gyroscopes of the inertial navigation system during the rotation process; II. Using the results of 6 samplings, calculate the zero position and scale coefficient of the gyroscope according to the gyroscope calibration principle; 5) Write the zero position and scale coefficient of the accelerometer and the zero position and scale coefficient of the gyroscope obtained in step 4) into the inertial navigation system parameter table to complete the calibration.

2. The method for calibration of a strapdown inertial navigation system based on a dual-axis position turntable according to claim 1, characterized in that: In step 2), the initial positioning means that the X-axis, Y-axis, and Z-axis of the inertial navigation system point to the east, north, and sky, respectively.

3. The strapdown inertial navigation system calibration method based on a dual-axis position turntable according to claim 2, characterized in that: In step 3), different temperatures refer to -55℃, -40℃, -20℃, 0℃, 20℃, 40℃, 60℃, and 70℃.

4. The strapdown inertial navigation system calibration method based on a dual-axis position turntable according to claim 3, characterized in that: In step 4), during the accelerometer position calibration and parameter calculation, the output pulse values ​​of the accelerometers at nine positions are collected for 1 minute each.

Images