A spherical IMU dynamic calibration device and a calibration method

Abstract

The application provides a kind of spherical IMU dynamic calibration device and calibration method, device is equipped with motor under a closed type rotating disc, rotating disc is placed with the spherical IMU of the outer surface of which is drawn with Boolean image, motor drives rotating disc synchronous rotation, so that spherical IMU does complex motion on rotating disc;A camera is hung above the central axis of rotating disc, its lens is perpendicular to the surface of rotating disc for collecting the motion image of spherical IMU, and then the optical measurement data of spherical IMU is obtained;After testing, the optical measurement data of spherical IMU obtained by camera and the electronic measurement data output by IMU internal MEMS chip are calibrated with each other, to complete the calibration in the dynamic test process of spherical IMU.The application also provides a corresponding calibration method, solves the problem that the calibration work of IMU under static or quasi-static condition in the prior art cannot meet the error correction requirements of dynamic working condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inertial measurement technology, and in particular to a spherical IMU dynamic calibration device and method. BACKGROUND

[0002] IMU (Inertial Measurement Unit) based on MEMS (Micro-Electro-Mechanical System) is increasingly applied in various fields of inertial measurement, such as navigation control, automatic driving, industrial measurement and control, and geological exploration, due to its small size, light weight, and low cost. However, the test error of the IMU based on MEMS accumulates over time, and the precision easily deteriorates over a long period of use, so external observation values need to be introduced to correct the IMU.

[0003] The calibration method of the IMU is generally divided into two categories: one is a test calibration method excited by the motion parameters of the earth's surface, and the other is a test calibration method by controlling precise instruments to generate motion parameter benchmarks. The first method is to use the natural excitation of the earth's rotation angular velocity and the gravity acceleration to the IMU, compare it with the output parameters of the IMU itself, then transform multiple different positions and compare multiple times, and according to the error model of the IMU, when the number of positions is equal to the number of error coefficients in the error model, the error coefficients can be solved by simultaneous equations. This method usually uses the least square method to process experimental data, and can calibrate each error coefficient, and has high precision in static test calibration, but low precision in dynamic test. This is because the motion parameters of the earth's surface produce certain additional interference to the IMU.

[0004] The second method is to use precise instruments to control the generation of motion parameter benchmarks, which can make the IMU achieve precise circular motion, linear motion, and even sinusoidal motion, to produce a series of standard motion excitations, and compare them with the output parameters of the IMU itself, and according to the error model of the IMU, the error parameters of the IMU can be determined. This method has high precision in static or dynamic test calibration, but the test equipment structure is complex and the cost is high.

[0005] Generally, the actual use of the IMU is a dynamic process. Since the static and dynamic working conditions of the calibration work differ greatly, if the IMU calibrated in static state is used to predict its actual dynamic working condition, the error is large, so the first method cannot well meet the error correction requirements of the IMU in dynamic working condition, and the second method can well meet the error correction requirements of the IMU in dynamic working condition, but the test cost is high. Therefore, the IMU dynamic calibration device in the prior art cannot meet the measurement precision and convenience requirements in actual use. SUMMARY

[0006] The application provides a spherical IMU dynamic calibration device and a calibration method.

[0007] In a first aspect of the application, a spherical IMU dynamic calibration device is provided, comprising:

[0008] A motor is arranged below a closed rotary disc, and a spherical IMU with a Boolean image drawn on the outer surface is placed on the rotary disc, the motor drives the rotary disc to rotate synchronously, so that the spherical IMU performs complex motion on the rotary disc;

[0009] A camera is hung above the central axis of the rotary disc, and the lens of the camera is perpendicular to the surface of the rotary disc to collect the motion image of the spherical IMU, and then the optical measurement data of the spherical IMU is obtained;

[0010] After the test, the optical measurement data of the spherical IMU obtained by the camera and the electronic measurement data output by the MEMS chip inside the IMU are calibrated with each other to complete the calibration in the dynamic test process of the spherical IMU.

[0011] Further, the projection of the Boolean image on the outer surface of the spherical IMU on the plane is unique for each direction of the spherical shell of the spherical IMU.

[0012] Further, an inner cylinder and an outer cylinder are arranged around the central axis on the rotary disc, and a rotating groove in the form of a ring is formed between the inner cylinder and the outer cylinder, and the spherical IMU is placed in the rotating groove to perform complex motion.

[0013] Further, a plurality of triangular prisms are symmetrically arranged on the periphery of the rotary disc, so that the camera can obtain the attitude image of the spherical IMU in the same scene from multiple angles.

[0014] Further, all the triangular prisms are fixedly arranged on the periphery of the rotary disc and do not rotate with the rotary disc, and preferably four triangular prisms are arranged.

[0015] The image acquisition range of the lens of the camera covers the range of the whole rotary disc and all the triangular prisms.

[0016] In a second aspect of the application, a calibration method of the spherical IMU dynamic calibration device is also provided, and the calibration method comprises the following steps:

[0017] S100: control the motor and the camera to work synchronously, the motor drives the rotary disc to rotate synchronously, so that the spherical IMU with the Boolean image drawn on the outer surface performs complex motion on the rotary disc;

[0018] S200: outputting actual electronic measurement data of the spherical IMU by a MEMS chip inside the spherical IMU;

[0019] S300: a camera collects a motion image of the spherical IMU and an attitude image of the spherical IMU in the triangular prism, and generates a three-dimensional motion trajectory and a three-dimensional rotation trajectory of the spherical IMU by using an optical measurement method according to image information collected by the camera, and further obtains optical measurement data of the spherical IMU;

[0020] S400: the optical measurement data obtained by the camera and the electronic measurement data output by the MEMS chip inside the IMU are mutually calibrated to determine the pose information of the spherical IMU in the motion process.

[0021] Further, the mutual calibration process in step S400 is as follows:

[0022] S401. The camera and the spherical IMU work synchronously, and in the same scene, according to the image shot by the camera, two adjacent triangular prism collected images are selected to obtain color images I and J of the spherical IMU, and the MEMS chip obtains three-axis motion acceleration [a x ,a y ,a z ] and three-axis motion angular velocity [w x ,w y ,w z ];

[0023] S402. The three-dimensional motion trajectory of the spherical IMU is obtained by using the optical measurement method, that is, the real displacement [S cx ,S cy ,S cz ] and Euler angles [α c ,β c ,γ c ] of the spherical IMU are obtained;

[0024] S403. The three-axis motion acceleration [a x ,a y ,a z ] and the three-axis motion angular velocity [w x ,w y ,w z ] of the spherical IMU are filtered by using a Kalman filtering algorithm to obtain Kalman filtering estimated three-axis motion acceleration and Kalman filtering estimated three-axis motion angular velocity The Kalman filtering estimated three-axis motion acceleration is converted into three-axis displacement [S xk ,S yk ,Szk ] using Euler dynamic equation transformed into Euler angles [alpha k , beta k , gamma k ];

[0025] S404. After every interval of time, the three-axis displacement [S cx , S cy , S cz ] and Euler angles [alpha c , beta c , gamma c ] obtained by optical measurement are used to correct the three-axis displacement [S xk , S yk , S zk ] and Euler angles [alpha k , beta k , gamma k ] obtained by electronic measurement, so as to eliminate the deviation introduced by the integration process;

[0026] S405. The above steps are repeated in sequence until the calibration is completed.

[0027] Further, the specific process of generating the three-dimensional motion trajectory of the spherical IMU is as follows: selecting image information from two adjacent prisms, and cross-correlating the vertical acceleration time series from two adjacent angles; when the cross-correlation coefficient of the two acceleration time series is greater than 98%, the three-dimensional motion trajectory of the spherical IMU is generated.

[0028] Further, the specific process of generating the three-dimensional rotation trajectory of the spherical IMU is as follows:

[0029] A piecewise constant analytic function describing the Boolean image of the outer surface of the spherical IMU is created, which returns 0 or 1 for any coordinate on the outer surface;

[0030] The projection synthesis of the outer surface of the spherical IMU during the motion process is used to generate a two-dimensional image;

[0031] The synthesized two-dimensional image of the above is compared with the Boolean image of the outer surface of the spherical IMU, and the best match is determined by using a minimization function to obtain the three-dimensional rotation trajectory of the image;

[0032] The above process is repeated until the comparison of all frames of two-dimensional images is completed, and the three-dimensional rotation trajectory of the spherical IMU is generated.

[0033] Further, the Boolean image of the outer surface of the spherical IMU contains the minimum number of edges and corners.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] 1.The application provides a kind of spherical IMU dynamic calibration device, can obtain two sets of data of IMU electronic measurement and optical measurement by MEMS chip and dyed shell respectively, keep two kinds of measurement synchronous, each other calibration, can avoid IMU data deviation, can improve measurement accuracy.

[0036] 2.The rotating disc and the rotating groove located thereon designed in the application can promote the complex motion state of the spherical IMU, so that the applicable working state of the IMU calibration is wider, and the performance parameters of the spherical IMU in the dynamic motion process can be calibrated by the device.

[0037] 3.The application gives a dynamic calibration method of the spherical IMU, and the following two kinds of test data can be synchronously acquired: electronic measurement data output by the MEMS chip and optical measurement data output by the camera. The two kinds of test data are mutually calibrated, high in accuracy and good in stability, and the performance parameters of the spherical IMU in the dynamic motion process can be calibrated, and the pose information of the small ball in the complex motion process is determined. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only exemplary, and other drawings can be derived from the provided drawings without creative labor for those skilled in the art.

[0039] Figure 1 Fig. 1 is a structural schematic view of the spherical IMU dynamic calibration device in the embodiment of the application;

[0040] Figure 2 Fig. 2 is a schematic view of the shell dyed Boolean image of the spherical IMU in the embodiment of the application;

[0041] Figure 3 Fig. 3 is a flow schematic view of the dynamic calibration method of the spherical IMU in the embodiment of the application;

[0042] Markings in the figure:

[0043] 1-camera, 2-transparent top cover, 3-prism, 4-spherical IMU, 5-workbench, 6-base, 7-motor, 8-motor holder, 9-rotating disc, 10-outer cylinder, 11-inner cylinder. DETAILED DESCRIPTION

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figure 1 As shown, a spherical IMU dynamic calibration device includes: a motor 7 installed under a closed rotating disk 9; a spherical IMU 4 with a Boolean image drawn on its outer surface placed on the rotating disk 9; the motor 7 drives the rotating disk 9 to rotate synchronously, causing the spherical IMU 4 to perform complex movements on the rotating disk 9; a camera 1 is suspended above the central axis of the rotating disk 9, with its lens perpendicular to the surface of the rotating disk 9 to acquire motion images of the spherical IMU 4, thereby obtaining optical measurement data of the spherical IMU 4; after testing, the optical measurement data of the spherical IMU 4 acquired by the camera 1 and the electronic measurement data output by the MEMS chip inside the IMU are mutually calibrated to complete the calibration during the dynamic testing process of the spherical IMU.

[0046] The spherical IMU dynamic calibration device provided by this invention features a spherical IMU that is dynamic on a rotating disk. It can acquire two sets of data—electronic and optical—through a MEMS chip and a stained shell, respectively, maintaining synchronization and mutual calibration between the two measurement methods. This avoids IMU data deviation and improves measurement accuracy. Furthermore, this invention differs from conventional calibration methods that use Earth surface motion parameters as excitation or generate motion parameter benchmarks through precision instruments. The latter two methods calibrate the IMU's output parameters against the excitation parameters, while this invention calibrates the IMU's output parameters against optical measurement parameters, resulting in higher accuracy.

[0047] In one specific embodiment, such as Figure 1 As shown, the motor 7 and its mounting bracket 8 are embedded in a cylindrical base 6. The base 6 is fixed to a horizontal workbench 5 by bolts. A rotating disk 9 is embedded in the workbench 5. The motor 7 is fixed below the rotating disk 9 and can drive the rotating disk 9 to rotate synchronously. A transparent top cover 2 is provided on the rotating disk 9 to form a closed space. An inner cylinder 11 and an outer cylinder 10 are provided on the rotating disk 9 around a central axis. An annular rotating groove is formed between the inner cylinder 11 and the outer cylinder 10. A spherical IMU 4 is placed in the rotating groove and performs complex movements. The rotating groove rotates under the action of the motor, which can excite the spherical IMU in the groove to perform complex movements.

[0048] Generally, the rotating disc can be selected to make the spherical IMU move thereon for dynamic calibration. If the rotating disc is used to make the spherical IMU do complex motion on the rotating disc, the rotating speed needs to be changed to easily generate complex motion, and in a certain rotating speed range, the spherical IMU can be more stable to follow the rotating disc to rotate.

[0049] Preferably, the spherical IMU does complex motion in the annular rotating groove. If the rotating groove is used, even if the rotating speed is not changed, the small ball can also generate complex motion when colliding with the inner wall surface. The rotating groove is more likely to make the small ball do complex motion than the rotating disc.

[0050] The rotating speed of the motor 7 is controlled by the computer terminal operation, and the rotating groove can be driven to rotate according to the input instruction. A spherical IMU is placed in the rotating groove, and black and white stripes are dyed on the shell of the spherical IMU, as shown in Figure 2 The transparent top cover 2 on the rotating disc 9 can prevent the small ball from escaping and flying out of the rotating groove. The top cover 2 is composed of two symmetrical parts, and the workbench 5 and the base 6 are integrally installed to complete the symmetrical structure, so as to reduce the influence of the vibration of the workbench related structure on the measurement accuracy. A camera 1 is hung 0.5 meters above the rotating disc 9, and the lens of the camera 1 is vertically downward.

[0051] In order to facilitate observation and collection of the posture of the small ball at each direction on the rotating disc, a plurality of triangular prisms 3 are symmetrically arranged on the periphery of the rotating disc 9, which are used for the camera 1 to obtain the posture image of the spherical IMU 4 from multiple angles in the same scene, that is, one camera can record the posture image of the small ball from multiple angles, which can save the number of cameras.

[0052] In the embodiment, the image acquisition range of the lens of the camera 1 covers the whole rotating disc 9 and the range of all the triangular prisms 3. Among them, all the triangular prisms 3 do not rotate with the rotating groove, and the number of the triangular prisms is generally determined according to the shape of the workbench 5, as shown in Figure 1 The workbench is a square, so four triangular prisms 3 are preferred.

[0053] In order to further facilitate optical measurement of the motion posture of the spherical IMU and improve the measurement accuracy, a black and white image is dyed on the outer surface of the spherical IMU in the present application, and the color difference is large, which is beneficial to camera acquisition and information analysis. In addition, the projection of the black and white image on the outer surface of the spherical IMU on the plane is unique for each direction of the spherical shell of the spherical IMU, so that it is easier to use the optical measurement method to position and analyze the posture of the spherical IMU.

[0054] In the second aspect of the present application, a calibration method of a spherical IMU dynamic calibration device is provided, as shown in Figure 3 The calibration method comprises the following steps:

[0055] S100: control the motor and the camera to work synchronously, the motor drives the rotating disc to rotate synchronously, so that the spherical IMU with the Boolean image on the outer surface does complex motion on the rotating disc.

[0056] It is generally preferred that the spherical IMU does complex motion, i.e. arbitrary motion, in the rotating groove on the rotating disc.

[0057] S200: output the actual electronic measurement data of the spherical IMU through the MEMS chip inside the spherical IMU.

[0058] S300: the camera collects the motion image of the spherical IMU and the posture image of the spherical IMU in the triangular prism, generates the three-dimensional motion trajectory and the three-dimensional rotation trajectory of the spherical IMU according to the image information collected by the camera, and further obtains the optical measurement data of the spherical IMU.

[0059] The specific process of generating the three-dimensional motion trajectory of the spherical IMU is as follows: in this embodiment, the entire workbench, including the four prisms, is within the camera range of the camera, the camera can record the 2D motion trajectory of the small ball from four angles through the four prisms, and then the redundant data in the vertical direction of the images taken from two adjacent angles are selected to compare the motion trajectory in the vertical dimension.

[0060] That is, the image information from the two adjacent triangular prisms is selected, and the vertical acceleration time series from the two adjacent angles are cross-correlated; when the cross-correlation coefficient of the two acceleration time series is greater than 98%, the three-dimensional motion trajectory of the spherical IMU is generated, and the three-axis motion acceleration of the spherical IMU is obtained without complex spatial reconstruction algorithm.

[0061] The specific process of generating the three-dimensional rotation trajectory of the spherical IMU is as follows:

[0062] S301. Create a piecewise constant analytic function describing the Boolean image on the outer surface of the spherical IMU Given any coordinate on the outer surface, the piecewise constant analytic function returns 0 or 1.

[0063] The Boolean image on the outer surface of the spherical IMU is composed of a plurality of infinitesimal surface units, any coordinate on the outer surface of the spherical IMU corresponds to the color of the infinitesimal surface unit, the color of each infinitesimal surface unit is a single color, and a function corresponding to one color returns 0 and a function corresponding to another color returns 1, that is, the coordinates of each point F on the Boolean image are determined.

[0064] In addition, the piecewise constant analytic function of the Boolean image The projection on the plane must be unique for each direction of the sphere, while the Boolean image of the outer surface of the spherical IMU contains the minimum number of edges and corners. Accordingly, when analyzing the optical measurement data of the spherical IMU using the optical measurement method, the algorithm can quickly converge to the global minimum value, and a smooth and continuous rotation trajectory can be described from any direction, including around the Euler angle singularity, without encountering the problem of gimbal lock.

[0065] S302. The projection synthesis of the outer surface of the spherical IMU during the movement is used to form a two-dimensional image.

[0066] The synthesized image of any given direction can be obtained by analysis, without the need to determine it from a static image. The projection is a function of the rotation angle of the sphere, which can be understood as the projection of the physical sphere recorded on the camera.

[0067] S303. The synthesized two-dimensional image of the above-mentioned frame is compared with the Boolean image of the outer surface of the shell-shaped IMU, and the best match is determined using a minimization function to obtain the three-dimensional rotation trajectory of the frame image.

[0068] Among them, different forms of minimization functions can be used to determine the best match. For example, the cross-correlation function of the synthesized pattern and the image captured by the camera can be used to find the best match. A cost function can also be used to search for a matching item.

[0069] In this embodiment, a cost function is preferably used, which is defined as the sum of the absolute differences between the binary image pixels and the corresponding pixels in the synthesized image, and then the Nelder-Mead minimization algorithm is used to determine the best match.

[0070] S304. Repeat the above process until the comparison of all two-dimensional images is completed, generate the three-dimensional rotation trajectory of the shell-shaped IMU, and obtain the three-axis angular velocity of the spherical IMU.

[0071] S400: The optical measurement data obtained by the camera and the electronic measurement data output by the MEMS chip inside the IMU are mutually calibrated to determine the pose information of the spherical IMU during the movement.

[0072] Among them, the mutual calibration process is:

[0073] S401. The camera and the spherical IMU work synchronously, and in the same scene, through the camera and the three prisms, two adjacent three-prism captured images are selected to obtain color images I and J of the spherical IMU, and the MEMS chip obtains the three-axis motion acceleration [a x ,a y ,a z ] and three-axis angular velocity [w x ,w y ,wz ];

[0074] S402.Obtain the three-dimensional motion trajectory of the spherical IMU by optical measurement method, that is, obtain the real displacement of the spherical IMU [S cx ,S cy ,S cz ] and Euler angles [α c ,β c ,γ c ];

[0075] S403.Use Kalman filtering algorithm to filter the three-axis motion acceleration [a x ,a y ,a z ] and three-axis motion angular velocity [w x ,w y ,w z ] of the spherical IMU, and obtain the Kalman filtering estimated three-axis motion acceleration and the Kalman filtering estimated three-axis motion angular velocity Convert the Kalman filtering estimated three-axis motion acceleration into three-axis displacement [S xk ,S yk ,S zk ] using the uniform acceleration motion formula, and convert the Kalman filtering estimated three-axis motion angular velocity into Euler angles [α k ,β k ,γ k ] using the Euler dynamics equation;

[0076] S404.Obtain the three-axis displacement [S cx ,S cy ,S cz ] and Euler angles [α c ,β c ,γ c ] by optical measurement method every Δt time, and correct the three-axis displacement [S xk ,S yk ,S zk ] and Euler angles [α k ,β k ,γ k ] obtained by electronic measurement, so as to eliminate the deviation introduced by the integral process;

[0077] S405.Repeat the above steps in turn until the calibration is completed.

[0078] According to the calibration method provided by the application, the following two kinds of test data can be synchronously acquired: 1. electronic measurement data output by the MEMS chip; and 2. optical measurement data output by the camera. The two kinds of test data are mutually calibrated, high in precision, good in stability, and can calibrate performance parameters of the spherical IMU in a dynamic motion process and determine the pose information of the small ball in a complex motion process.

[0079] The above examples are only exemplary embodiments of the application and are not intended to limit the application, and the protection scope of the application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the application within the spirit and protection scope of the application, and the modification or equivalent replacement is also regarded as falling within the protection scope of the application.

Claims

1. A spherical IMU dynamic calibration device, characterized in that, include: A motor is installed under a closed rotating disk, and a spherical IMU with Boolean images drawn on its outer surface is placed on the rotating disk. The motor drives the rotating disk to rotate synchronously, so that the spherical IMU performs complex movements on the rotating disk. A camera is suspended above the central axis of the rotating disk, with its lens perpendicular to the surface of the rotating disk to acquire motion images of the spherical IMU, thereby obtaining optical measurement data of the spherical IMU; After the test, the optical measurement data of the spherical IMU acquired by the camera and the electronic measurement data output by the MEMS chip inside the IMU are calibrated with each other to complete the calibration during the dynamic test of the spherical IMU. The projection of the Boolean image on the outer surface of the spherical IMU onto the plane is unique for each direction of the spherical shell of the spherical IMU.

2. The spherical IMU dynamic calibration device according to claim 1, characterized in that, The rotating disk has an inner cylinder and an outer cylinder around a central axis, and an annular rotating groove is formed between the inner cylinder and the outer cylinder. The spherical IMU is placed in the rotating groove and performs complex movements.

3. The spherical IMU dynamic calibration device according to claim 1, characterized in that, Multiple prisms are symmetrically arranged around the rotating disk, enabling the camera to obtain attitude images of the same scene from multiple angles using the spherical IMU.

4. The spherical IMU dynamic calibration device according to claim 3, characterized in that, All prisms are fixedly mounted around the rotating disk and do not rotate with the rotating disk; The camera lens's image acquisition range covers the entire rotating disk and all the prisms.

5. A calibration method of the spherical IMU dynamic calibration device according to any one of claims 1-4, characterized in that, The calibration method includes the following steps: S100: Controls the motor and camera to work synchronously. The motor drives the rotating disk to rotate synchronously, so that the spherical IMU with Boolean images on its outer surface can perform complex movements on the rotating disk. S200: Outputs the actual electronic measurement data of the spherical IMU through the MEMS chip inside the spherical IMU; S300: The camera acquires motion images of the spherical IMU and attitude images of the spherical IMU in the prism. Based on the image information acquired by the camera, the three-dimensional motion trajectory and three-dimensional rotation trajectory of the spherical IMU are generated using optical measurement methods, thereby obtaining the optical measurement data of the spherical IMU. S400: Optical measurement data acquired by a camera and electronic measurement data output by the MEMS chip inside the IMU are calibrated together to determine the pose information of the spherical IMU during movement.

6. The calibration method according to claim 5, characterized in that, The mutual calibration process in step S400 is as follows: S401. The camera and the spherical IMU work synchronously, in the same scene, according to the image shot by the camera, the acquisition images of two adjacent prisms are selected, the color images I and J of the spherical IMU are obtained respectively, the MEMS chip obtains the three-axis motion acceleration [a x ,a y ,a z ] and three-axis motion angular velocity [w x ,w y ,w z ] of the spherical IMU; S402. Obtain the three-dimensional motion trajectory of the spherical IMU by optical measurement method, that is, obtain the real displacement [S cx , cy , cz ] and Euler angles [α c ,β c ,γ c ] of the spherical IMU; S403. Filter the three-axis motion accelerations [a x ,a y ,a z ] and the three-axis motion angular velocities [w x ,w y ,w z ] of the spherical IMU using a Kalman filter algorithm to obtain Kalman filter estimated three-axis motion accelerations [ , , ] and Kalman filter estimated three-axis motion angular velocities [ , , ]. The Kalman filter estimated three-axis motion accelerations [a , , ] are converted to three-axis displacements [s xk , yk , zk ] using the uniform acceleration motion formula, and the Kalman filter estimated three-axis angular velocities [ω , , ] are converted to Euler angles [α k , β k , γ k ] using the Euler dynamics equation. S404. The true displacement [S] obtained by optical measurement after each Δt time interval. cx ,S cy ,S cz ] and Euler angles [α c ,β c ,γ c The triaxial displacement [S] obtained by electronic measurement xk ,S yk ,S zk ] and Euler angles [α k ,β k ,γ k Corrections are made to eliminate the bias introduced during the integration process; S405. Repeat the above steps in sequence until the calibration is complete.

7. The calibration method according to claim 5, characterized in that, The specific process of generating the three-dimensional motion trajectory of the spherical IMU is: selecting image information from two adjacent prisms, and cross-correlating vertical acceleration time sequences from two adjacent angles; when the cross-correlation coefficient of the two acceleration time sequences is greater than 98%, the three-dimensional motion trajectory of the spherical IMU is generated.

8. The calibration method of claim 5, wherein, The specific process of generating the three-dimensional rotation trajectory of the spherical IMU is: Step a, creating a piecewise constant analytic function describing the Boolean image of the outer surface of the spherical IMU, which returns 0 or 1 for any coordinate on the outer surface; Step b, synthesizing a two-dimensional image by projecting the outer surface of the spherical IMU during the motion process; Step c, comparing the two-dimensional image synthesized by projecting the outer surface of the spherical IMU during the motion process with the Boolean image of the outer surface of the spherical IMU, and determining the best match by using a minimization function to obtain the three-dimensional rotation trajectory of the synthesized two-dimensional image; Steps b and c are repeated until the comparison of all frames of two-dimensional images is completed, and the three-dimensional rotation trajectory of the spherical IMU is generated.

9. The calibration method of claim 5, wherein, The Boolean image of the outer surface of the spherical IMU contains a minimum number of edges and corners.

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