CN-121977607-A - IMU coordinate system extraction method based on accelerometer and cube mirror

CN121977607ACN 121977607 ACN121977607 ACN 121977607ACN-121977607-A

Abstract

The invention provides an IMU coordinate system extraction method based on an accelerometer and a cube mirror, and belongs to a test calibration method in the field of navigation. The invention comprises the following steps: the IMU is respectively arranged at three positions (X-axis indicates heaven Y-axis refers to the heaven and Z-axis refers to the heaven), the cube elevation was measured using an auto-collimation theodolite with the IMU in each position, and the output of the IMU triaxial add-up and theodolite measurements were recorded. The recorded readings are processed by using a matched calibration algorithm, so that an accurate installation offset angle (the accuracy is better than 30 ") between the IMU coordinate system and the cube mirror coordinate system can be obtained, and the IMU coordinate system is imaged and led out to a measurable entity of the cube mirror. The method has the advantages of convenience in operation, accuracy, small error and strong practicability.

Inventors

LIU ZHAO
YANG GUOLIANG
LIU TONG
WEI XUEDONG
ZHANG GE
WEI SHUAI
ZHANG CHAOJUN
XIA JIAHE

Assignees

中国航空工业集团公司西安飞行自动控制研究所

Dates

Publication Date: 20260505
Application Date: 20251227

Claims (8)

1. An IMU coordinate system extraction method based on an accelerometer and a cube mirror is characterized by comprising the following steps: Step 1, fixedly connecting a cube mirror with an IMU; step 2, under a geographic coordinate system, enabling an X-axis of the IMU to refer to the sky/earth, recording an IMU triaxial addition output result, and recording a zenith angle or an elevation angle obtained by a theodolite measurement cube mirror; Step 3, under a geographic coordinate system, enabling a Y-axis of the IMU to refer to the sky/earth, recording an IMU triaxial addition output result, and recording a zenith angle or an elevation angle obtained by a theodolite measurement cube mirror; step 4, under a geographic coordinate system, enabling the Z axis of the IMU to point to the sky/earth, recording the three-axis addition output result of the IMU, and recording the zenith angle or elevation angle obtained by the theodolite measurement cube mirror; Step 5, processing and calibrating calculation are carried out according to the addition output result recorded by the IMU X and Y, Z axis indicating days obtained in the steps 2,3 and 4 and the zenith angle or elevation angle obtained by the theodolite measuring the cube mirror, so as to obtain the offset angle between the IMU coordinate system and the cube mirror coordinate system; And 6, converting parameters under the IMU coordinate system into a cube mirror coordinate system according to the deflection angle.
2. The method for extracting the IMU coordinate system based on the accelerometer and the cube mirror according to claim 1, wherein the cube mirror is a regular cube made of metal or glass material and has 3-5 high reflection surfaces, which are called cube reference mirrors.
3. The method for extracting the IMU coordinate system based on the accelerometer and the cube mirror according to claim 1, wherein the theodolites in the steps 2, 3 and 4 are required to have an auto-collimation function.
4. The method for extracting the IMU coordinate system based on the accelerometer and the cube according to claim 1, wherein the specific process of measuring the cube by the theodolite in the step 2 comprises the following steps: step 2.1, erecting a theodolite and an IMU by using devices such as a bracket, a cushion block and the like, so that the measuring center line of the theodolite and the cube mirror are basically at the same height; step 2.2, adjusting the theodolite foot spiral to center the round level bubble and center the theodolite horizontal tube bubble at any position; step 2.3, adjusting an eyepiece to enable a cross hair to be clear, and adjusting an objective lens to infinity; And 2.4, opening the autocollimation illumination of the theodolite, and adjusting the orientation of the theodolite to enable the autocollimation reflected light to coincide with the cross hair.
5. The method for extracting the IMU coordinate system based on the accelerometer and the cube according to claim 1, wherein the specific process of measuring the cube by the theodolite in the step 3 comprises the following steps: Step 3.1, erecting a theodolite and an IMU by using devices such as a bracket, a cushion block and the like, so that the measuring center line of the theodolite and the cube mirror are basically at the same height; Step 3.2, adjusting the theodolite foot spiral to center the round level bubble and center the theodolite horizontal tube bubble at any position; 3.3, adjusting an eyepiece to enable the cross hair to be clear, and adjusting an objective lens to infinity; And 3.4, opening the autocollimation illumination of the theodolite, and adjusting the orientation of the theodolite to enable the autocollimation reflected light to coincide with the cross hair.
6. The method for extracting the IMU coordinate system based on the accelerometer and the cube according to claim 1, wherein the specific process of measuring the cube by the theodolite in the step 4 comprises the following steps: step 4.1, erecting a theodolite and an IMU by using devices such as a bracket, a cushion block and the like, so that the measuring center line of the theodolite and the cube mirror are basically at the same height; step 4.2, adjusting the theodolite foot spiral to center the round level bubble and center the theodolite horizontal tube bubble at any position; step 4.3, adjusting an eyepiece to enable the cross hair to be clear, and adjusting an objective lens to infinity; and 4.4, opening the autocollimation illumination of the theodolite, and adjusting the orientation of the theodolite to enable the autocollimation reflected light to coincide with the cross hair.
7. The IMU coordinate system extraction method based on the accelerometer and the cube mirror according to claim 1, wherein in the step 5, the method specifically comprises the following steps: step 5.1, respectively carrying out normalization processing on the added output results recorded by the IMU X and Y, Z axis finger days obtained in the steps 2, 3 and 4 to obtain normalized vectors; Step 5.2, preprocessing the zenith angle or the horizontal angle of the theodolite obtained in the steps 2, 3 and 4, and constructing a unit vector by using the outputs of the theodolites in two directions in the same step; Step 5.3, selecting the addition normalized vector and the theodolite construction vector processed in the step 2-3 according to the steps 5.1 and 5.2, calculating a direction cosine matrix 1 according to a double-vector attitude determination principle, calculating a direction cosine matrix 2 after exchanging a main vector, averaging after adding the two matrices, and calculating a group of deflection angle values containing 3 elements according to the result; And 5.4, carrying out the same treatment on the steps 2-4 and 3-4 according to the step 5.3. At this time, 3 sets of deflection angle values are obtained, 1 element is extracted from the same position of the 3 sets of deflection angles according to rules, and the extracted 3 elements form a final deflection angle value.
8. The IMU coordinate system extraction method based on the accelerometer and the cube mirror according to claim 1, wherein in the step 6, the method specifically comprises the following steps: Step 6.1, converting the deflection angle value obtained in the step 5 into a direction cosine matrix, and converting the deflection angle value into coordinate system conversion parameters such as quaternion, rodrign parameters and the like; And 6.2, converting the parameters to be converted according to mathematical rules by using the coordinate system conversion parameters obtained in the step 6.1.

Description

IMU coordinate system extraction method based on accelerometer and cube mirror Technical Field The invention relates to the technical field of calibration of aviation tests, in particular to an IMU coordinate system extraction method based on an accelerometer and a cube mirror. Background When the pose reference system is used in the airborne photoelectric aiming system, the optical system coordinate system of the photoelectric aiming system is always required to be unified with the IMU component coordinate system in the pose reference system, and the essence is that high-precision deflection angle information (better than 30 angular seconds) between the optical system coordinate system and the IMU coordinate system is required to be obtained. The extraction of the coordinate system of the optical system is relatively simple, and can be realized by using an auto-collimation theodolite and an auto-collimation laser, while the extraction of the coordinate system of the IMU is relatively complex. The IMU is generally composed of a three-axis gyroscope and a three-axis addition, the coordinate system of the IMU is determined by the addition output after calibration, and no method is available outside the IMU for direct measurement, so that the offset angle between the IMU and the optical system cannot be calibrated. Disclosure of Invention The invention aims to provide an IMU coordinate system extraction method based on an accelerometer and a cube mirror, which comprises the steps of additionally arranging the cube mirror on an IMU, determining an installation deflection angle between the IMU coordinate system and the cube mirror coordinate system, and extracting the IMU coordinate system to the cube mirror through coordinate system conversion. The technical scheme of the invention is as follows: The invention provides an IMU coordinate system extraction method based on an accelerometer and a cube mirror, which can be applied to any scene requiring accurate acquisition of an IMU coordinate system and comprises the following steps: Step 1, fixedly connecting a cube mirror with an IMU; step 2, under a geographic coordinate system, enabling an X-axis of the IMU to refer to the sky/earth, recording an IMU triaxial addition output result, and recording a zenith angle or an elevation angle obtained by a theodolite measurement cube mirror; Step 3, under a geographic coordinate system, enabling a Y-axis of the IMU to refer to the sky/earth, recording an IMU triaxial addition output result, and recording a zenith angle or an elevation angle obtained by a theodolite measurement cube mirror; step 4, under a geographic coordinate system, enabling the Z axis of the IMU to point to the sky/earth, recording the three-axis addition output result of the IMU, and recording the zenith angle or elevation angle obtained by the theodolite measurement cube mirror; Step 5, processing and calibrating calculation are carried out according to the addition output result recorded by the IMU X and Y, Z axis indicating days obtained in the steps 2,3 and 4 and the zenith angle or elevation angle obtained by the theodolite measuring the cube mirror, so as to obtain the offset angle between the IMU coordinate system and the cube mirror coordinate system; And 6, converting parameters under the IMU coordinate system into a cube mirror coordinate system according to the deflection angle. In one possible embodiment, the cube is a cube made of metal or glass, and typically has 3 to 5 highly reflective surfaces, which may also be referred to as a cube reference mirror. In one possible embodiment, the theodolites in steps 2,3 and 4 need to have auto-collimation function. In one possible embodiment, the specific process of measuring the cube by the theodolite in the step 2 includes: step 2.1, erecting a theodolite and an IMU by using devices such as a bracket, a cushion block and the like, so that the measuring center line of the theodolite and the cube mirror are basically at the same height; step 2.2, adjusting the theodolite foot spiral to center the round level bubble and center the theodolite horizontal tube bubble at any position; step 2.3, adjusting an eyepiece to enable a cross hair to be clear, and adjusting an objective lens to infinity; And 2.4, opening the autocollimation illumination of the theodolite, and adjusting the orientation of the theodolite to enable the autocollimation reflected light to coincide with the cross hair. In one possible embodiment, the specific process of measuring the cube by the theodolite in the step 3 includes: Step 3.1, erecting a theodolite and an IMU by using devices such as a bracket, a cushion block and the like, so that the measuring center line of the theodolite and the cube mirror are basically at the same height; Step 3.2, adjusting the theodolite foot spiral to center the round level bubble and center the theodolite horizontal tube bubble at any position; 3.3, adjusting an eyepiece to enable the cross h