Shell-shaped IMU Based on MEMS and Optical Synchronous Measurement and Its Usage Method

Abstract

The present invention provides a shell-shaped IMU based on MEMS and optical synchronous measurement and a method for using the same. The shell-shaped IMU includes a MEMS chip, a battery pack, and an external housing. The MEMS chip and the battery pack are connected and fixed within the external housing. The outer surface of the external housing is dyed with a Boolean image of alternating black and white colors, so that the shell-shaped IMU is suitable for MEMS and optical synchronous measurement, and the obtained optical measurement data and electronic measurement data are calibrated with each other for calibration. The present invention also provides a method for using the shell-shaped IMU based on MEMS and optical synchronous measurement, which can obtain two sets of data of electronic measurement and optical measurement respectively through the MEMS chip and the dyed outer shell, keep the two measurement methods synchronized, can be calibrated with each other, avoid deviation of IMU data, and can be used in test scenarios with large dynamics.

Description

Technical Field

[0001] The present invention belongs to the technical field of inertial measurement, and in particular relates to a shell-shaped IMU based on MEMS and optical synchronous measurement and a method for using the same. Background Art

[0002] MEMS (micro-electromechanical systems)-based IMUs (inertial measurement units) are fully autonomous and resistant to interference, offering high accuracy for short periods of time. However, due to the principle of integration, errors accumulate over time, leading to decreased accuracy over extended periods. To reduce error accumulation, it is necessary to incorporate external observations to correct the IMU.

[0003] An optically based IMU can provide high-speed cameras with spatial images featuring distinct feature points. By matching these feature points in space and tracking them in time, and then converting them through mathematical equations, the IMU's position and attitude can be determined. However, due to the limited acquisition frequency, this method cannot capture even small disturbances. Furthermore, errors in extrapolating the IMU's motion trajectory accumulate over time, leading to stability issues.

[0004] Furthermore, when the image background is monotonous or too similar, or when the IMU itself is highly dynamic, such as during sharp turns, the overlap between adjacent images is too small, causing the optical measurement equation to fail. Therefore, it is necessary to employ other testing methods to enhance the stability of the algorithm. Summary of the Invention

[0005] To solve the above problems, the present invention provides a shell-shaped IMU based on MEMS and optical synchronous measurement and a method of using the same.

[0006] A shell-shaped IMU based on MEMS and optical synchronous measurement, comprising a MEMS chipset, a battery pack, and an external shell, wherein the MEMS chipset and the battery pack are connected and fixed in the external shell;

[0007] The outer surface of the outer shell is dyed with a black and white Boolean image, so that the shell-shaped IMU is suitable for MEMS and optical synchronous measurement, and the obtained optical measurement data and electronic measurement data are calibrated with each other for calibration.

[0008] Furthermore, the MEMS chipset uses a microprocessor and a dynamic solution and Kalman dynamic filtering algorithm to quickly solve the real-time motion posture of the shell-shaped IMU; and uses digital filtering technology to reduce measurement noise;

[0009] The MEMS chipset is internally integrated with a posture solver to cooperate with a dynamic Kalman filter algorithm to accurately output measurement data in a dynamic environment.

[0010] Furthermore, the outer shell is spherical, and the shell-shaped IMU is a spherical IMU.

[0011] In the second aspect of the present invention, a method for using a shell-shaped IMU based on MEMS and optical synchronous measurement is provided. The method includes the following steps:

[0012] S100: Two cameras are arranged orthogonally adjacent to each other, and the imaging ports are respectively facing the solid wall surface of the motion field where the shell-shaped IMU is located to collect the motion images of the shell-shaped IMU.

[0013] S200: Obtain the two-dimensional motion trajectory of the shell-shaped IMU according to the motion images collected by the two cameras, and use the redundant data in the vertical direction in the motion images of the two cameras to compare the motion trajectory in the third dimension, and then generate the three-dimensional motion trajectory of the shell-shaped IMU to obtain the three-axis motion acceleration of the shell-shaped IMU.

[0014] S300: Synthesize the projections of the outer surface of the shell-shaped IMU during the motion into a two-dimensional image, compare it with the Boolean image of the outer surface of the shell-shaped IMU, generate the three-dimensional rotation trajectory of the shell-shaped IMU, and obtain the three-axis motion angular velocity of the shell-shaped IMU.

[0015] S400: Obtain the optical measurement data through steps S200 and S300. Based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained through the camera, the electronic measurement data and the optical measurement data are calibrated with each other.

[0016] Furthermore, the specific process of generating the three-dimensional rotation trajectory of the shell-shaped IMU is as follows:

[0017] Create a piecewise constant analytical function describing the Boolean image of the outer surface of the shell-shaped IMU. Given any coordinate on the outer surface, the piecewise constant analytical function returns 0 or 1.

[0018] Use the projections of the outer surface of the shell-shaped IMU during the motion to synthesize a two-dimensional image.

[0019] Compare the synthesized two-dimensional image of one frame with the Boolean image of the outer surface of the shell-shaped IMU, and use the minimization function to determine the best match to obtain the three-dimensional rotation trajectory of this frame of image.

[0020] Repeat the above process until the comparison of all frames of two-dimensional images is completed to generate the three-dimensional rotation trajectory of the shell-shaped IMU.

[0021] Furthermore, the Boolean image of the outer surface of the shell-shaped IMU is composed of multiple infinitesimal surface elements. Any coordinate on the outer surface of the shell-shaped IMU corresponds to the color of the infinitesimal surface element, and the color of each infinitesimal surface element is a single color.

[0022] Further, the process of mutual calibration is as follows:

[0023] S401. Control the camera and the shell-shaped IMU to work synchronously. In the same scene, the two cameras respectively obtain the color images I and J of the shell-shaped IMU, and the MEMS chip obtains the three-axis motion acceleration [a x , a y , a z and the three-axis motion angular velocity [w x , w y , w z ;

[0024] S402. Use the method of step S200 to obtain the three-dimensional motion trajectory of the shell-shaped IMU, that is, obtain the true displacement [S cx , S cy , S cz and the Euler angles [α c , β c , γ c ;

[0025] S403. Use the Kalman filter algorithm to filter the three-axis motion acceleration [a x , a y , a z and the three-axis motion angular velocity [w x , w y , w z to obtain the three-axis motion acceleration estimated by the Kalman filter and the three-axis motion angular velocity estimated by the Kalman filter Use the uniformly accelerated motion formula to convert it into three-axis displacement [S xk , S yk , S zk , and use the Euler dynamics equation to convert the three-axis motion angular velocity estimated by the Kalman filter into Euler angles [α k , β k , γ k ;

[0026] S404. After every Δt time, use the true displacement [S cx , S cy , S cz and the Euler angles [α c , β c , γ c obtained by the method of step S200 to correct the three-axis displacement [S xk , S yk , S zk and the Euler angles [α k , β k, γ k Modify to eliminate the deviation introduced by the integration process;

[0027] S405. Repeat the above steps sequentially until the calibration ends.

[0028] Furthermore, the specific process of generating the three-dimensional motion trajectory of the shell-shaped IMU is as follows: Cross-correlate the vertical acceleration time series of the motion images from two cameras. When the cross-correlation coefficient of the two acceleration time series is greater than 98%, generate the three-dimensional motion trajectory of the shell-shaped IMU.

[0029] Furthermore, based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained through the camera, it can be applicable to the calibration of the shell-shaped IMU, or can be applicable to inertial measurement work, or can be applicable to both the calibration of the shell-shaped IMU and inertial measurement work.

[0030] The present invention has the following beneficial effects compared with the prior art:

[0031] 1. The shell-shaped IMU designed by the present invention can be applicable to different-shaped outer shells, is easy to use, and the Boolean image designed on the outer shell solves the problem of too small image overlap caused by a single or overly similar image background. The adoption of the Boolean image is conducive to optical measurement and is beneficial to the mutual calibration and calibration work of MEMS and optical synchronous measurement.

[0032] 2. The usage method of the shell-shaped IMU based on MEMS and optical synchronous measurement provided by the present invention can obtain two sets of data of electronic measurement and optical measurement through the MEMS chip and the dyed outer shell respectively, keep the two measurement methods synchronized, can be mutually calibrated, avoid deviation of IMU data, and can be used in test scenarios with large dynamics. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained based on the provided drawings.

[0034] Figure 1 It is a schematic structural diagram of the shell-shaped IMU optical measurement device in the embodiment of the present invention;

[0035] Figure 2 It is a schematic structural diagram of the shell-shaped IMU in the embodiment of the present invention (taking a spherical shape as an example in the figure);

[0036] Figure 3Schematic diagram of the shell-shaped IMU's external shell dyed with a Boolean image in an embodiment of the present invention (taking a sphere as an example in the figure);

[0037] Figure 4 Flow schematic diagram of the usage method of the shell-shaped IMU based on MEMS and optical synchronous measurement in an embodiment of the present invention;

[0038] Figure 5 Flow schematic diagram of generating the three-dimensional motion trajectory of the shell-shaped IMU in an embodiment of the present invention;

[0039] Figure 6 Schematic diagram of the deviation between the electronic measurement numerical value and the actual physical value in an embodiment of the present invention;

[0040] Reference numerals in the figure:

[0041] 1 - Shell-shaped IMU, 2 - First wall, 3 - Second wall, 4 - First camera, 5 - Second camera, 6 - Wall bracket, 7 - Upper outer shell, 8 - Lower outer shell, 9 - Inner liner, 10 - MEMS chipset, 11 - Gasket. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] As Figures 1-3 shown, for the shell-shaped IMU based on MEMS and optical synchronous measurement, the shell-shaped IMU 1 includes an MEMS chipset, a battery pack, and an external shell. The MEMS chipset and the battery pack are connected and fixed inside the external shell 1; the outer surface of the external shell is dyed with a Boolean image of black and white colors alternating, so that the shell-shaped IMU 1 is suitable for MEMS and optical synchronous measurement, and the obtained optical measurement data and electronic measurement data are mutually calibrated for calibration.

[0044] The improved shell-shaped IMU provided by the present invention has a Boolean image coated on the outer surface of the external shell, which can solve the problem that when using optical measurement, due to a single or overly similar background and too small overlap degree between adjacent images, the optical calculation equation fails to solve. Moreover, the present invention can adopt electronic and optical synchronous measurement, and the two sets of data are mutually calibrated, with high accuracy and good stability.

[0045] In addition, in the present invention, there is no limitation on the shape of the external shell, which can be a regular or irregular shape. As Figure 2As shown in the figure, the shell-shaped IMU1 includes an upper shell 7 and a lower shell 8, and a MEMS chipset 10 is provided inside. An inner liner 9 and a gasket 11 are provided between the MEMS chipset 10 and the shell to fix the chipset and the battery pack, and fix the MEMS chipset and the battery pack inside the shell, which is beneficial to maintaining the stability of the measurement data of the MEMS chipset.

[0046] Inside the MEMS chipset, there is an attitude angle sensor, and this module integrates high-precision gyroscopes, accelerometers, and geomagnetic sensors. Inside the MEMS chipset, a microprocessor and a dynamic solution and Kalman dynamic filtering algorithm are adopted to quickly solve the real-time motion attitude of the shell-shaped IMU; digital filtering technology is adopted to reduce measurement noise and improve measurement accuracy. The attitude resolver inside the MEMS chipset, in cooperation with the dynamic Kalman filtering algorithm, accurately outputs measurement data in a dynamic environment. The attitude measurement accuracy is 0.05 degrees under static conditions and 0.1 degrees under dynamic conditions.

[0047] In a specific embodiment, it is preferred that the outer shell is spherical, and the shell-shaped IMU is a spherical IMU, as Figure 2 shown. The spherical IMU can approximately simulate spherical soil particles. In the field of geological exploration technology, the MEMS-based IMU can be used to study the complex particle motion characteristics, such as landslides, piping, debris flows, etc. The characteristic point is that the IMU itself represents approximately spherical soil particles and has a large dynamic range. Therefore, the spherical IMU designed in the present invention with high measurement accuracy and good stability has important scientific value and engineering significance for studying the mechanism of geological disasters.

[0048] In this embodiment, in order to obtain accurate optical measurement data as much as possible, it is preferred to dye black and white checkerboard patterns on the outer shell of the spherical IMU, as Figure 3 shown.

[0049] In the second aspect of the present invention, based on the above shell-shaped IMU, the present invention also provides a method for using a shell-shaped IMU based on MEMS and optical synchronous measurement, as Figure 4 shown, and the method includes the following steps:

[0050] S100: Two cameras are arranged orthogonally adjacent to each other, and the imaging ports are respectively facing the solid wall surface of the motion place where the shell-shaped IMU is located, and the motion images of the shell-shaped IMU are collected.

[0051] Optical measurement can be completed with the help of a camera. The schematic diagram of the optical measurement device is as Figure 1As shown in the figure, the field of view and magnification of the first camera 4 and the second camera 5 are the same. The field of view of the cameras covers the entire width of the movement range of the shell-shaped IMU. The image acquisition ports of the two cameras face the adjacent first wall 2 and second wall 3 of the IMU movement site respectively. The walls 2 and 3 are supported and fixed by the wall brackets 6. In this embodiment, a gray wall is selected for image acquisition. The lines of sight of the two cameras are orthogonal, and images of the same scene during the movement of the shell-shaped IMU can be acquired from two angles.

[0052] S200: Obtain the two-dimensional movement trajectory of the shell-shaped IMU based on the movement images collected by the two cameras. Use the redundant data in the vertical direction of the movement images of the two cameras to compare the movement trajectories in the third dimension, and then generate the three-dimensional movement trajectory of the shell-shaped IMU to obtain the three-axis movement acceleration of the shell-shaped IMU.

[0053] In this embodiment, the specific process of generating the three-dimensional movement trajectory is as follows: Cross-correlate the vertical acceleration time series from the movement images of the two cameras. When the cross-correlation coefficient of the two acceleration time series is greater than 98%, the three-dimensional movement trajectory of the shell-shaped IMU is generated, and no complex spatial reconstruction algorithm is required.

[0054] S300: Synthesize the projections of the outer surface of the shell-shaped IMU during movement into a two-dimensional image, compare it with the Boolean image of the outer surface of the shell-shaped IMU, generate the three-dimensional rotation trajectory of the shell-shaped IMU, and obtain the three-axis movement angular velocity of the shell-shaped IMU.

[0055] The specific process of generating the three-dimensional rotation trajectory of the shell-shaped IMU is as Figure 5 shown.

[0056] S301. Select the Boolean image and establish an analytical function.

[0057] Create a piecewise constant analytical function that describes the Boolean image of the outer surface of the shell-shaped IMU Given any coordinate on the outer surface, the piecewise constant analytical function returns 0 or 1. Where θ and are the azimuth angle and the polar angle respectively, and is independent of the radius of the outer shell.

[0058] The Boolean image of the outer surface of the shell-shaped IMU consists of several infinitesimal surface elements. Any coordinate on the outer surface of the shell-shaped IMU corresponds to the color of the infinitesimal surface element. The color of each infinitesimal surface element is a single color. The function corresponding to one color returns 0, and the other returns 1, that is, the coordinates of each point F on the Boolean image are determined.

[0059] S302. Create a drawing template and draw on the outer shell.

[0060] Using a 3D printed painting template and a spray gun system, the color represented by the function is painted onto the outer shell. To reduce the errors introduced in this step, the painting must be as precise as possible.

[0061] S303. Obtain the observation image and preprocess it.

[0062] Under the optical measurement device, when the camera and the shell-shaped IMU are working synchronously, the projection of the outer surface of the shell-shaped IMU on the plane is obtained, and the projection image information is preprocessed. The projections of the outer surface of the shell-shaped IMU during movement are synthesized into a two-dimensional image. The synthesized image in any given direction is analytically known and does not need to be determined from a static image. The projection is a function of the rotation angle of the sphere and can also be conceptually understood as the projection of the physical shell recorded by the camera.

[0063] S304. Initial matching and projection on the two-dimensional synthesized image.

[0064] Compare the synthesized two-dimensional image frame with the Boolean image of the outer surface of the shell-shaped IMU until the best match is determined using the minimization function to obtain the three-dimensional rotation trajectory of this frame of image.

[0065] In this embodiment, data matching needs to be performed frame by frame. First, compare a synthesized two-dimensional image frame with the Boolean image of the outer surface of the shell-shaped IMU for initial matching and projection on the two-dimensional synthesized image. Use the cost function for discrimination. If the minimum value is reached, the best match is generated; otherwise, change the match, synthesize a new image using the projection of the IMU on the plane again, and then determine whether the new cost function reaches the minimum value.

[0066] Among them, the minimization function can take different forms. For example, the cross-correlation function between the synthesized pattern and the camera image can be used to find the best match. Or, a suitable cost function can also be used to search for the match. In this embodiment, the cost function is used, which is defined as the sum of the absolute differences between the pixels of the binarized image and the corresponding pixels in the synthesized image. Then the Nelder-Mead minimization algorithm is used to determine the direction in which the comparison generates the best match.

[0067] S305. Obtain the next frame of image and return to step S303.

[0068] After completing one frame of two-dimensional image, obtain the next frame of image, return to step S303, and repeat the above process until all frames of two-dimensional images are compared to generate the three-dimensional rotation trajectory of the shell-shaped IMU.

[0069] S400: Obtain the optical measurement data through steps S200 and S300. Based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained by the camera, the two measurement methods are carried out synchronously, and the electronic measurement data and the optical measurement data are calibrated with each other.

[0070] The shell-shaped IMU provided by the present invention, based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained by the camera, can be applicable to the calibration of the shell-shaped IMU, or can be applicable to inertial measurement work, or can be applicable to both the calibration of the shell-shaped IMU and inertial measurement work.

[0071] The IMU needs to be calibrated before use. Therefore, the shell-shaped IMU provided by the present invention can be used to adopt synchronous electronic and optical measurements and calibrate each other during the calibration process. During the formal use process, the optical measurement data is an optional item, and whether to collect the optical data can be selected according to the test conditions.

[0072] The principle of mutual calibration between electronic measurement and optical measurement in the present invention is:

[0073] The physical quantities of inertial measurement are displacement S, velocity V, and acceleration a. The physical quantity directly obtained by electronic measurement is acceleration a, which is a function of time t, and the acquisition frequency is on the order of 1000 hz. The physical quantity directly obtained by optical measurement is displacement S, and the acquisition frequency is on the order of 10 hz.

[0074] For the high-frequency acquisition requirements of particle flow, electronic measurement is more suitable than optical measurement. However, the error of the electronic measurement method will gradually increase with the increase of the acquisition time. As Figure 6 shown, this is because when integrating the acceleration a directly obtained by electronic measurement, a new error term Vconst·T will be introduced.

[0075] According to the uniform acceleration motion formula, it can be obtained that:

[0076]

[0077]

[0078] In the formula, S k represents the three-axis displacement S xk , S yk , S zk is the displacement in any one coordinate axis direction among them, T is the IMU sampling period, a k-1 is the acceleration in the corresponding coordinate axis direction at the k-1 moment, V k-1 and V kx are the initial velocities at the k-1 and k moments respectively, and the initial velocity at the initial moment of the given system is 0.

[0079] To reduce the influence of the error term Vconst·T, the displacement S directly obtained by optical measurement is adopted every period of time Δt. c The displacement S obtained by the above integration k is corrected.

[0080] The correction principles of angular acceleration and angular displacement are similar to the above method.

[0081] According to Euler's dynamics equation, it can be obtained that:

[0082]

[0083] In the formula are the first-order derivatives of Euler angles α k , β k , γ k . The parameters α k-1 , β k-1 , γ k-1 obtained at the (k - 1)th moment are used as the initial values of the above formula.

[0084] Therefore, in the present invention, the process of mutual calibration is as follows:

[0085] S401. Control the camera and the shell-shaped IMU to work synchronously. In the same scene, the two cameras respectively obtain the color images I and J of the shell-shaped IMU, and the MEMS chip obtains 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 shell-shaped IMU;

[0086] S402. Use the method of step S200 to obtain the three-dimensional motion trajectory of the shell-shaped IMU, that is, obtain the true displacement [S cx , S cy , S cz and the Euler angles [α c , β c , γ c of the shell-shaped IMU;

[0087] S403. Use the Kalman filtering algorithm to perform filtering processing on 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 shell-shaped IMU, and obtain the three-axis motion acceleration estimated by the Kalman filter and the three-axis motion angular velocity estimated by the Kalman filter Convert to three-axis displacement [S using the uniformly accelerated motion formula xk , S yk , S zk , and convert the three-axis motion angular velocity estimated by the Kalman filter into Euler angles [α , β k , β k , γ k using Euler's dynamics equation;

[0088] S404. After every Δt time, use the true displacement [S obtained by the method of step S200 cx , S cy , S cz and Euler angles [α c , β c , γ c to correct the three-axis displacement [S obtained by electronic measurement xk , S yk , S zk and Euler angles [α k , β k , γ k to eliminate the deviation introduced in the integration process;

[0089] S405. Repeat the above steps in sequence until the calibration ends.

[0090] The shell-shaped IMU provided by the present invention can obtain two sets of data of electronic measurement and optical test respectively through the MEMS chip and the dyed shell, and the two measurement methods are carried out synchronously, which can avoid the deviation of IMU data.

[0091] The above embodiments are only exemplary embodiments of the present application and are not used to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements within the essence and protection scope of the present application, and such modifications or equivalent replacements should also be regarded as falling within the protection scope of the present application.

Claims

1. A shell-shaped IMU based on MEMS and optical synchronous measurement, characterized in that the shell-shaped IMU includes a MEMS chipset, a battery pack and an external housing, and the MEMS chipset and the battery pack are connected and fixed inside the external housing; the outer surface of the external housing is dyed with a Boolean image with alternating black and white colors, so that the shell-shaped IMU is suitable for MEMS and optical synchronous measurement, and the obtained optical measurement data and electronic measurement data are calibrated with each other; inside the MEMS chipset, a microprocessor and a kinetic solution and Kalman dynamic filtering algorithm are used to quickly solve the real-time motion attitude of the shell-shaped IMU; a digital filtering technology is used to reduce measurement noise; an attitude resolver is integrated inside the MEMS chipset to cooperate with the dynamic Kalman filtering algorithm to accurately output measurement data in a dynamic environment; an optical measurement is completed with the help of a camera; the process of mutual calibration is as follows: S401. Control the camera and the shell-shaped IMU to work synchronously. In the same scene, the two cameras respectively obtain the color images I and J of the shell-shaped IMU, and the MEMS chip obtains the three-axis motion acceleration [a x , a y , a z and the three-axis motion angular velocity [w x , w y , w z ; S402. Obtain the three-dimensional motion trajectory of the shell-shaped IMU by using the method of step S200, that is, obtain the true displacement of the shell-shaped IMU[S cx ,S cy ,S cz and Euler angles [α c , β c , γ c ; S403. Use the Kalman filter algorithm to filter the three-axis motion accelerations x , a y , a z and the three-axis motion angular velocities x , w y , w z of the shell-shaped IMU, and obtain the three-axis motion accelerations estimated by the Kalman filter and the three-axis motion angular velocities estimated by the Kalman filter. Convert them into three-axis displacements xk , S yk , S zk using the uniformly accelerated motion formula, and convert the three-axis motion angular velocities estimated by the Kalman filter into Euler angles k , β k , γ k using Euler's dynamics equation; After every Δt time, the true displacement [S cx ,S cy ,S cz and Euler angles [α c ,β c ,γ c obtained by the method of step S200 are used to correct the triaxial 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 in the integration process; S405. Repeat the above steps in sequence until the calibration ends.

2. The shell-shaped IMU based on MEMS and optical synchronous measurement according to claim 1, characterized in that the external housing is spherical, and the shell-shaped IMU is a spherical IMU.

3. A method for using a shell-shaped IMU based on MEMS and optical synchronous measurement according to any one of claims 1-2, characterized in that, The method includes the following steps: S100: Two cameras are arranged orthogonally adjacent to each other, and the imaging ports are respectively facing the solid wall surface of the motion place where the shell-shaped IMU is located, and the motion images of the shell-shaped IMU are collected; S200: Obtain the two-dimensional motion trajectory of the shell-shaped IMU according to the motion images collected by the two cameras, and use the redundant data in the vertical direction in the motion images of the two cameras to compare the motion trajectory in the third dimension, and then generate the three-dimensional motion trajectory of the shell-shaped IMU to obtain the three-axis motion acceleration of the shell-shaped IMU; S300: Synthesize the projection of the outer surface of the shell-shaped IMU during the motion process into a two-dimensional image, compare it with the Boolean image on the outer surface of the shell-shaped IMU, generate the three-dimensional rotation trajectory of the shell-shaped IMU, and obtain the three-axis motion angular velocity of the shell-shaped IMU; S400: Obtain the optical measurement data through steps S200 and S300, and based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained by the camera, the electronic measurement data and the optical measurement data are calibrated with each other.

4. The usage method according to claim 3, characterized in that the specific process of generating the three-dimensional rotation trajectory of the shell-shaped IMU is as follows: Create a piecewise constant analytical function describing the Boolean image on the outer surface of the shell-shaped IMU. Given any coordinate on the outer surface, the piecewise constant analytical function returns 0 or 1; Use the projection of the outer surface of the shell-shaped IMU during the motion process to synthesize a two-dimensional image; Compare the synthesized two-dimensional image of one frame with the Boolean image on the outer surface of the shell-shaped IMU, and use the minimization function to determine the best match to obtain the three-dimensional rotation trajectory of this frame of image; Repeat the above process until all frames of two-dimensional images are compared to generate the three-dimensional rotation trajectory of the shell-shaped IMU.

5. The usage method according to claim 4, characterized in that The Boolean image of the outer surface of the shell-shaped IMU consists of multiple infinitesimal surface elements. Any coordinate on the outer surface of the shell-shaped IMU corresponds to the color of the infinitesimal surface element, and the color of each infinitesimal surface element is a single color.

6. The usage method according to claim 3, wherein The specific process of generating the three-dimensional motion trajectory of the shell-shaped IMU is as follows: cross-correlate the vertical acceleration time series from the motion images of two cameras, and generate the three-dimensional motion trajectory of the shell-shaped IMU when the cross-correlation coefficient of the two acceleration time series is greater than 98%.

7. The usage method according to claim 3, wherein Based on the electronic measurement data of the shell-shaped IMU itself and the optical measurement data obtained by the camera, it can be applicable to the calibration of the shell-shaped IMU, or can be applicable to inertial measurement work, or can be applicable to the calibration and inertial measurement work of the shell-shaped IMU.

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