A method, device and parameter calibration system for internal parameters of an inertial measurement unit

Abstract

The present invention relates to the field of sensor technology, and provides a method, device and parameter calibration system for calibrating the internal parameters of an inertial measurement unit. The parameter calibration system includes a turntable, a calibration plate, an inertial measurement unit, a camera and an industrial computer. Based on the calibration plate, the internal parameters of the camera are calibrated, and the time delay calibration of the camera and the inertial measurement unit is performed, so that the detection data of the inertial measurement unit is synchronized with the image data of the camera. Then, based on the internal parameters and image data of the camera, the visual odometer is applied to estimate the motion data of the camera, and the accumulated error of the visual odometer is eliminated by the PNP algorithm to obtain accurate motion data. Finally, the internal parameters of the inertial measurement unit are calibrated by the accurate motion data and the detection data. In the above method, the camera and the inertial measurement unit are controlled by an ordinary turntable for detection, and the detection data of the inertial measurement unit is calibrated by the camera, thereby saving the calibration cost while calibrating the internal parameters of the inertial measurement unit.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a method and device for calibrating the internal parameters of an inertial measurement unit, and a parameter calibration system. Background Art

[0002] The inertial measurement unit (IMU) is a crucial component of the multi-sensor system in autonomous vehicles. With the rapid development of MEMS (Micro-Electro-Mechanical System) technology in recent years, the precision and performance of IMUs based on this technology have become sufficient for application in autonomous driving algorithm tasks. A typical six-axis IMU sensor measures the degree of change in the internal MEMS mechanism to output linear acceleration measurements in the X, Y, and Z directions and angular velocity measurements around the X, Y, and Z directions. However, due to inevitable manufacturing errors in industrial production, IMU measurement units are subject to various systematic errors, such as misalignment between axes, scale factor, bias, and g-sensitivity. This phenomenon is particularly pronounced in MEMS sensors, making internal parameter calibration of inertial sensors a necessary process before actual vehicle installation and use.

[0003] Usually, IMU calibration requires a high-precision three-axis turntable to provide accurate actual motion data. However, high-precision three-axis turntables usually cost tens of millions or even millions of dollars and are expensive. They are mainly used for high-precision IMU sensors using fiber optic or laser technology. For consumer-grade MEMS technology, the application cost is too high. Summary of the Invention

[0004] The embodiments of the present invention provide a method and apparatus for calibrating the internal parameters of an inertial measurement unit, and a parameter calibration system, aiming to solve the technical problem of high cost in measuring data by an inertial measurement unit in the prior art.

[0005] To solve the above technical problems, a technical solution adopted in an embodiment of the present invention is: providing a calibration method for the intrinsic parameters of an inertial measurement unit, which is applied to a parameter calibration system, wherein the parameter calibration system includes an inertial measurement unit and a camera arranged on a turntable, a calibration board, and an industrial computer connected to the turntable, the inertial measurement unit, and the camera. The method includes: calibrating the intrinsic parameters of the camera based on the calibration board; performing time delay calibration on the camera and the inertial measurement unit to synchronize the detection data of the inertial measurement unit with the image data of the camera; estimating the motion data of the camera using a visual odometry based on the intrinsic parameters of the camera and the image data; eliminating the accumulated error of the visual odometry using a PNP algorithm to obtain precise motion data; and calibrating the intrinsic parameters of the inertial measurement unit using the precise motion data and the detection data.

[0006] Optionally, the intrinsic parameter calibration of the camera based on the calibration plate includes: controlling the camera to shoot the calibration plate in different postures to obtain at least three calibration plate images; determining the corner points of the calibration plate in each calibration plate image and the position of each corner point in the pixel coordinate system based on the at least three calibration plate images; determining the physical coordinates of each corner point in the world coordinate system based on the size and dimensions of each grid of the calibration plate; and determining the intrinsic parameter matrix of the camera based on the pixel coordinate system and the world coordinate system to complete the calibration of the camera intrinsic parameters.

[0007] Optionally, the application of a visual odometry to estimate the motion data of the camera based on the intrinsic parameters of the camera and the image data includes: setting the rotation range of the turntable based on the calibration plate; within the rotation range, controlling the turntable to rotate in different preset directions at a preset speed so that the turntable reaches different preset positions; in the process of the turntable rotating to the preset position, obtaining the image data of the camera at the current moment and the image data at the previous moment; obtaining two sets of one-to-one corresponding pixel point sets based on the image data at the previous moment and the image data at the current moment; and estimating the motion data of the camera based on the one-to-one corresponding pixel point sets.

[0008] Optionally, eliminating the accumulated error of the visual odometer by the PNP algorithm to obtain accurate motion data includes: obtaining image data captured by the camera, wherein the image data includes a calibration plate; determining the corner points of the calibration plate in the image data, and determining the positions of the corner points in the world coordinate system and in the pixel coordinate system; obtaining the intrinsic parameter matrix of the camera; calculating the actual motion data of the camera based on the intrinsic parameter matrix of the camera, the world coordinates of the corner points, and the pixel coordinates; and updating the motion data of the camera to the actual motion data of the camera to obtain accurate motion data.

[0009] Optionally, calibrating the internal parameters of the inertial measurement unit using the precise motion data and the detection data includes: obtaining the detection data of the inertial measurement unit at a current moment, and the precise motion data of the camera; converting the precise motion data of the camera into actual motion data of the inertial measurement unit; performing least squares calculation on the actual motion data and the detection data of the inertial measurement unit to obtain calibration parameters of the inertial measurement unit; and calibrating the internal parameters of the inertial measurement unit based on the calibration parameters.

[0010] Optionally, before obtaining the detection data of the inertial measurement unit, the method also includes: controlling the turntable to remain stationary for a preset time in different preset postures; when the turntable is stationary in different preset postures, respectively obtaining initial detection data of the inertial measurement unit on the turntable; calculating the static deviation of the inertial measurement unit in different preset postures based on the initial detection data of the inertial measurement unit; and calibrating the initial detection data of the inertial measurement unit based on the static deviation to calibrate the initial error of the inertial measurement unit.

[0011] To solve the above technical problems, another technical solution adopted in an embodiment of the present invention is: providing a calibration device for the intrinsic parameters of an inertial measurement unit, which is applied to a parameter calibration system, wherein the parameter calibration system includes an inertial measurement unit and a camera arranged on a turntable, a calibration plate, and an industrial computer connected to the turntable, the inertial measurement unit, and the camera. The device includes: a camera calibration module, which is used to calibrate the intrinsic parameters of the camera based on the calibration plate; a time delay calibration module, which is used to calibrate the time delay of the camera and the inertial measurement unit so that the detection data of the inertial measurement unit is synchronized with the image data of the camera; an estimation module, which is used to estimate the motion data of the camera using a visual odometry based on the intrinsic parameters of the camera and the image data; an acquisition module, which is used to eliminate the accumulated error of the visual odometry through a PNP algorithm to obtain precise motion data; and an intrinsic parameter calibration module, which is used to calibrate the intrinsic parameters of the inertial measurement unit through the precise motion data and the detection data.

[0012] Optionally, the estimation module is specifically used to: set the rotation range of the turntable based on the calibration plate; within the rotation range, control the turntable to rotate in different preset directions at a preset speed so that the turntable reaches different preset positions; in the process of the turntable rotating to the preset position, obtain the image data of the camera at the current moment and the image data at the previous moment; obtain two sets of one-to-one corresponding pixel point sets based on the image data at the previous moment and the image data at the current moment; and estimate the motion data of the camera based on the one-to-one corresponding pixel point sets.

[0013] Optionally, the acquisition module is specifically used to: acquire image data taken by the camera, wherein the image data includes a calibration plate; determine the corner points of the calibration plate in the image data, and determine the positions of the corner points in the world coordinate system and the pixel coordinate system; acquire the intrinsic parameter matrix of the camera; calculate the actual motion data of the camera based on the intrinsic parameter matrix of the camera, the world coordinates and the pixel coordinates of the corner points; and update the motion data of the camera to the actual motion data of the camera to obtain accurate motion data.

[0014] To solve the above technical problems, another technical solution adopted in the embodiment of the present invention is: providing a parameter calibration system, which includes: a turntable; an inertial measurement unit and a camera arranged on the turntable; a calibration board; and an industrial computer connected to the turntable, the inertial measurement unit, and the camera; wherein the industrial computer includes at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method as described above.

[0015] Different from the related art, the present invention provides a method, device, and parameter calibration system for calibrating the intrinsic parameters of an inertial measurement unit (IMU). The parameter calibration system includes an IMU and a camera mounted on a turntable, a calibration board, and an industrial computer connected to the turntable, the IMU, and the camera. The calibration board is used to calibrate the camera's intrinsic parameters and perform time delay calibration on the camera and IMU to synchronize the IMU's detection data with the camera's image data. A visual odometry system is then used to estimate the camera's motion data based on the camera's intrinsic parameters and the image data. The PNP algorithm eliminates the accumulated error of the visual odometry to obtain precise motion data. Finally, the precise motion data and the detection data are used to calibrate the IMU's intrinsic parameters. In this method, a conventional turntable is used to control the camera and IMU for detection, and the camera is used to calibrate the IMU's detection data. This method achieves calibration of the IMU's intrinsic parameters while saving calibration costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0017] Figure 1 This is a structural block diagram of a parameter calibration system provided by an embodiment of the present invention;

[0018] Figure 2 This is a physical diagram of a parameter calibration system provided by an embodiment of the present invention;

[0019] Figure 3 This is a structural block diagram of an industrial computer provided by an embodiment of the present invention;

[0020] Figure 4 This is a flow chart of a method for calibrating the intrinsic parameters of an inertial measurement unit provided by an embodiment of the present invention;

[0021] Figure 5 This is a structural block diagram of a device for calibrating the intrinsic parameters of an inertial measurement unit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] It should be noted that, unless there is a conflict, the various features of the embodiments of the present invention may be combined with each other and are all within the scope of protection of the present invention. In addition, although the functional modules are divided in the device schematics and the logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than the module division in the device schematics or the order in the flowcharts.

[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are intended solely for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0025] The defects in the above-mentioned solutions are the results obtained by the inventor after practice and careful research. Therefore, the process of discovering the above-mentioned problems and the solutions proposed by this application for the above-mentioned problems below should be the contributions made by the inventor to this application during the disclosure process of this application.

[0026] See also Figure 1 , Figure 1 This is a structural block diagram of a parameter calibration system provided by an embodiment of the present invention. Figure 1As shown, the parameter calibration system 100 includes a turntable 11, an inertial measurement unit 12, a camera 13, an industrial computer 14, and a calibration plate 15. The inertial measurement unit 12 and the camera 13 are arranged on the turntable 11, the industrial computer 14 is connected to the turntable 11, the inertial measurement unit 12, and the camera 13 respectively, and the calibration plate 15 is arranged directly opposite the camera 13.

[0027] During the operation of the parameter calibration system 100, the industrial computer 14 controls the turntable 11 to start moving, thereby driving the inertial measurement unit 12 and the camera 13 to move synchronously. During the movement of the inertial measurement unit 12 and the camera 13, the inertial measurement unit 12 will measure data in real time and send the measurement data to the industrial computer 14. The camera 13 will also capture image data including the calibration plate 15 in real time and send the image data to the industrial computer 14. After receiving the image data, the industrial computer 14 will process the image data to complete the calibration of the inertial measurement unit through the processed image data. The rotation direction of the turntable 11 includes 180 degrees along the X-axis, 180 degrees along the Y-axis, and 180 degrees along the Z-axis. By setting the rotation angle of the turntable 11, it is ensured that the calibration plate 15 is included in the photos captured by the camera 13 during the rotation of the turntable 11. It should be noted that, if the photo taken by the camera 13 does not include the calibration plate 15 during the rotation of the turntable 11 , the photo currently taken by the camera 13 is considered to be an unqualified photo.

[0028] In some embodiments, the calibration plate 15 is a checkerboard calibration plate, and the camera 13 is calibrated by the checkerboard calibration plate, thereby removing the eccentricity error that occurs during the camera calibration process.

[0029] like Figure 2 As shown, Figure 2 This is a physical diagram of a parameter calibration system provided by an embodiment of the present invention, such as Figure 2 As shown, 1 refers to the inertial measurement unit 12 , 2 refers to the camera 13 , 3 refers to the turntable 11 , 4 refers to the industrial computer 14 , and 5 refers to the checkerboard calibration plate 15 .

[0030] See also Figure 3 , Figure 3 This is a structural block diagram of an industrial computer provided by an embodiment of the present invention. The industrial computer 14 includes: at least one processor 141, Figure 3 In the example, a processor 141 is used; the memory 142 connected to the at least one processor 141 is communicated with, Figure 3 The bus connection is taken as an example.

[0031] The memory 142 stores instructions that can be executed by the at least one processor 141, and the instructions are executed by the at least one processor 141 so that the at least one processor 141 can perform the following method for calibrating the internal parameters of the inertial measurement unit.

[0032] Memory 142, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the method for calibrating the intrinsic parameters of an inertial measurement unit in the embodiments of the present invention. Processor 141 executes the non-volatile software programs, instructions, and modules stored in memory 142 to execute various functional applications and data processing of industrial computer 14, thereby implementing the method for calibrating the intrinsic parameters of an inertial measurement unit in the following method embodiment.

[0033] The memory 142 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and application programs required for at least one function. In addition, the memory 142 may include a high-speed random access memory and may also include a non-volatile memory. For example, it may include at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 142 may optionally include a memory remotely located relative to the processor 141.

[0034] The one or more modules are stored in the memory 142, and when executed by the one or more processors 141, perform the calibration method of the inertial measurement unit internal parameter in any of the following method embodiments, for example, perform the following description Figure 4 The method steps in .

[0035] See also Figure 4 , Figure 4 This is a flow chart of a method for calibrating the internal parameters of an inertial measurement unit provided by an embodiment of the present invention, wherein the method is applied to the parameter calibration system as described above, such as Figure 4 As shown, the method includes:

[0036] S01. Performing intrinsic parameter calibration on the camera based on the calibration board.

[0037] During camera capture, a geometric model of camera imaging must be established to determine the relationship between the three-dimensional geometric position of a point on the surface of a spatial object and its corresponding point in the image. The parameters of this geometric model are the camera parameters, which are obtained by calibrating the camera. These camera parameters include intrinsic parameters and extrinsic parameters. The intrinsic parameters determine the projection relationship from three-dimensional space to a two-dimensional image, while the extrinsic parameters determine the relative positional relationship between the camera coordinates and the world coordinate system.

[0038] Specifically, the turntable is first controlled to rotate in different directions to position the camera in different postures. The camera then captures at least three images containing the calibration plate in different postures. Based on the at least three calibration plate images, the corner points of the calibration plate in each calibration plate image and the position of each corner point in the pixel coordinate system are determined. In the image, the origin of the pixel is generally in the upper left corner of the image. Based on the pixel origin, the position of each corner point in the pixel coordinate system can be determined. The total size of the calibration plate and the size of each grid are then obtained. Based on these sizes and sizes, the physical coordinates of the corner points in the world coordinate system are determined. Based on the positions of the corner points in the physical coordinate system and the pixel coordinate system, the intrinsic parameter matrix of the camera is determined. Finally, based on the intrinsic parameter matrix, the intrinsic parameters of the camera are determined. It should be noted that capturing at least three images containing the calibration plate eliminates errors caused by shooting angles.

[0039] S02: The camera and the inertial measurement unit perform time delay calibration to synchronize the detection data of the inertial measurement unit with the image data of the camera.

[0040] Specifically, during the synchronous operation of the camera and the inertial measurement unit, the camera may have problems such as trigger delay and transmission delay, so that at the same moment, the detection data of the inertial measurement unit and the image data taken by the camera are not data at the same position. Therefore, before performing internal parameter correction on the inertial measurement unit, it is necessary to perform time delay calibration on the camera and the inertial measurement unit so that the information obtained by the camera and the inertial measurement unit at the same moment is information at the same position, thereby ensuring that the detection data of the inertial measurement unit is synchronized with the image data of the camera.

[0041] S03: Estimate the motion data of the camera using a visual odometry according to the intrinsic parameters of the camera and the image data.

[0042] The visual odometry refers to recovering the camera's motion pose from a series of image streams.

[0043] Specifically, when the turntable controls the movement of the camera, it is necessary to ensure that the calibration plate is included in the photos taken by the camera, wherein the camera determines the camera's motion data based on the calibration plate. Therefore, when setting the rotation range of the turntable, it is necessary to ensure that the photos taken by the camera include the calibration plate regardless of the camera's position. After setting the rotation range of the turntable, the industrial control table controls the turntable to rotate in different preset directions at a preset speed within the rotation range, so that the turntable reaches different preset positions. The preset speed is set so that the turntable rotates at a constant speed to prevent measurement errors caused by speed changes. The preset directions include controlling the turntable to move along the X-axis, along the Y-axis, and along the Z-axis. During the process of the turntable rotating to the preset position, the industrial control computer will also control the camera in real time to acquire image data including the calibration plate, and record the time of acquiring the image data. When calculating the camera's motion data, the image data and the time at which the image data was acquired are first acquired. Image data at adjacent moments are then acquired based on the time. The same set of pixels in the image data and the adjacent image data are then acquired. Finally, the camera's motion data is estimated based on the same set of pixels. The motion data includes the camera's acceleration and angular velocity.

[0044] S04. Eliminate the accumulated error of the visual odometer by using a PNP algorithm to obtain accurate motion data.

[0045] The PNP algorithm is a method for solving the motion of 3D to 2D point pairs, and its purpose is to solve the pose of the camera coordinate system relative to the world coordinate system.

[0046] Specifically, first, the image data captured by the camera and containing the calibration plate is obtained, and the corner points of the calibration plate are determined according to the image data, and the positions of each corner point in the world coordinate system and the pixel coordinate system are determined respectively, and then the intrinsic parameter matrix of the camera is obtained, and according to the intrinsic parameter matrix, the corner points are converted from the pixel coordinate system to the image coordinate system, and then based on the positions of the corner points in the image coordinate system and the world coordinate system, the actual motion data of the camera is calculated, and finally the motion data of the camera is updated to the actual motion data of the camera, so as to obtain the precise motion data of the camera.

[0047] S05. Calibrate the internal parameters of the inertial measurement unit using the precise motion data and the detection data.

[0048] Specifically, after obtaining the precise motion data of the camera, the industrial control machine converts the precise motion data of the camera into the actual motion data of the inertial measurement unit, and obtains the detection data of the inertial measurement unit at the same time as the precise motion data of the camera. Then, the least squares method is performed on the actual motion data and the detection data of the inertial measurement unit to obtain the calibration parameters of the inertial measurement unit. Finally, based on the calibration parameters, the internal parameters of the inertial measurement unit are calibrated. Among them, the least squares method (also known as the least square method) is a mathematical optimization technique that mainly finds the best function matching of the data by minimizing the sum of squares of errors. Using the least squares method, unknown data can be easily obtained, and the sum of squares of errors between the obtained data and the actual data can be minimized.

[0049] In some embodiments, before obtaining the detection data of the inertial measurement unit, the industrial computer will also control the turntable to stand still for a preset time in different preset postures, and when the turntable is stationary in different preset postures, respectively obtain the initial detection data of the inertial measurement unit on the turntable, and then calculate the static deviation of the inertial measurement unit in different preset postures based on the initial detection data of the inertial measurement unit. Finally, based on the static deviation, the initial detection data of the inertial measurement unit is calibrated to calibrate the initial error of the inertial measurement unit.

[0050] An embodiment of the present invention provides a method for calibrating the intrinsic parameters of an inertial measurement unit (IMU), applicable to a parameter calibration system. The system includes an IMU and a camera mounted on a turntable, a calibration board, and an industrial computer connected to the turntable, the IMU, and the camera. The method primarily calibrates the camera's intrinsic parameters using the calibration board and performs time delay calibration on the camera and IMU to synchronize the IMU's detection data with the camera's image data. A visual odometry algorithm is then used to estimate the camera's motion data based on the camera's intrinsic parameters and the image data. Accumulated errors in the visual odometry are then eliminated using a PNP algorithm to obtain precise motion data. Finally, the precise motion data and the detection data are used to calibrate the IMU's intrinsic parameters. In this method, a conventional turntable is used to control the camera and IMU for detection, and the camera is used to calibrate the IMU's detection data, thereby calibrating the IMU's intrinsic parameters while saving calibration costs.

[0051] See also Figure 5 , Figure 5 This is a structural block diagram of a calibration device for an inertial measurement unit internal parameter provided by an embodiment of the present invention, wherein the device is applied to the parameter calibration system as described above, such as Figure 5As shown, the inertial measurement unit intrinsic parameter calibration device 40 includes a camera calibration module 41 , a time delay calibration module 42 , an estimation module 43 , an acquisition module 44 and an intrinsic parameter calibration module 45 .

[0052] The camera calibration module 41 is used to perform intrinsic parameter calibration on the camera based on the calibration board.

[0053] The time delay calibration module 42 is used to perform time delay calibration on the camera and the inertial measurement unit to synchronize the detection data of the inertial measurement unit with the image data of the camera.

[0054] The estimation module 43 is configured to estimate the motion data of the camera using a visual odometer based on the intrinsic parameters of the camera and the image data.

[0055] The estimation module 43 is specifically used to: set the rotation range of the turntable based on the calibration plate; within the rotation range, control the turntable to rotate in different preset directions at a preset speed so that the turntable reaches different preset positions; in the process of the turntable rotating to the preset position, obtain the image data of the camera at the current moment and the image data at the previous moment; obtain two sets of one-to-one corresponding pixel point sets based on the image data at the previous moment and the image data at the current moment; and estimate the motion data of the camera based on the one-to-one corresponding pixel point sets.

[0056] The acquisition module 44 is used to eliminate the cumulative error of the visual odometer through the PNP algorithm to obtain accurate motion data.

[0057] The acquisition module 44 is specifically used to: acquire image data captured by the camera, wherein the image data includes a calibration plate; determine the corner points of the calibration plate in the image data, and determine the positions of the corner points in the world coordinate system and the pixel coordinate system; acquire the intrinsic parameter matrix of the camera; calculate the actual motion data of the camera based on the intrinsic parameter matrix of the camera, the world coordinates and the pixel coordinates of the corner points; and update the motion data of the camera to the actual motion data of the camera to obtain accurate motion data.

[0058] The internal parameter calibration module 45 is used to calibrate the internal parameters of the inertial measurement unit using the precise motion data and the detection data.

[0059] It should be noted that the aforementioned apparatus for calibrating the intrinsic parameters of an inertial measurement unit can execute the method for calibrating the intrinsic parameters of an inertial measurement unit provided in an embodiment of the present invention, and has the corresponding functional modules and beneficial effects of executing the method. For technical details not fully described in the embodiment of the apparatus for calibrating the intrinsic parameters of an inertial measurement unit, please refer to the method for calibrating the intrinsic parameters of an inertial measurement unit provided in an embodiment of the present invention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Under the idea of ​​the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for calibrating the internal parameters of an inertial measurement unit, characterized in that: Applied to a parameter calibration system, the parameter calibration system includes an inertial measurement unit and a camera arranged on a turntable, a calibration plate, and an industrial computer connected to the turntable, the inertial measurement unit, and the camera. The method includes: Performing intrinsic parameter calibration on the camera based on the calibration plate; performing time delay calibration on the camera and the inertial measurement unit to synchronize detection data of the inertial measurement unit with image data of the camera; estimating motion data of the camera using a visual odometry based on the camera's intrinsic parameters and the image data; Eliminate the accumulated error of the visual odometer through the PNP algorithm to obtain accurate motion data; Calibrate the internal parameters of the inertial measurement unit using the precise motion data and the detection data; The method of eliminating the accumulated error of the visual odometer by the PNP algorithm to obtain accurate motion data includes: Acquire image data captured by the camera, wherein the image data includes a calibration plate; Determining corner points of a calibration plate in the image data, and determining positions of the corner points in a world coordinate system and a pixel coordinate system; Obtaining the intrinsic parameter matrix of the camera; Calculating actual motion data of the camera according to the intrinsic parameter matrix of the camera, the world coordinates of the corner points, and the pixel coordinates; The motion data of the camera is updated to the actual motion data of the camera to obtain accurate motion data.

2. The method according to claim 1, characterized in that The performing intrinsic parameter calibration on the camera based on the calibration plate includes: Controlling the camera to photograph the calibration plate in different postures to obtain at least three calibration plate images; Determining, based on the at least three calibration plate images, corner points of the calibration plate in each calibration plate image and positions of the corner points in a pixel coordinate system; Determine the physical coordinates of each corner point in the world coordinate system based on the size and dimensions of each grid of the calibration plate; Based on the pixel coordinate system and the world coordinate system, an intrinsic parameter matrix of the camera is determined to complete the calibration of the camera intrinsic parameters.

3. The method according to claim 2, characterized in that The step of estimating the motion data of the camera by applying a visual odometry according to the intrinsic parameters of the camera and the image data comprises: Based on the calibration plate, setting the rotation range of the turntable; Within the rotation range, controlling the turntable to rotate in different preset directions at a preset speed so that the turntable reaches different preset positions; During the process of the turntable rotating to the preset position, acquiring image data of the camera at the current moment and image data at the previous moment; Obtain two sets of one-to-one corresponding pixel point sets based on the image data at the previous moment and the image data at the current moment; The motion data of the camera is estimated according to the one-to-one corresponding pixel point set.

4. The method according to claim 3, characterized in that The calibrating the internal parameters of the inertial measurement unit using the precise motion data and the detection data includes: Acquire detection data of the inertial measurement unit and precise motion data of the camera at the current moment; Converting the precise motion data of the camera into actual motion data of the inertial measurement unit; performing a least squares calculation on the actual motion data and the detection data of the inertial measurement unit to obtain calibration parameters of the inertial measurement unit; Based on the calibration parameters, the intrinsic parameters of the inertial measurement unit are calibrated.

5. The method according to claim 1, wherein Before acquiring the detection data of the inertial measurement unit, the method further includes: Controlling the turntable to stand still for a preset time in different preset postures; When the turntable is stationary at different preset postures, respectively acquiring initial detection data of an inertial measurement unit on the turntable; Calculating the static deviation of the inertial measurement unit under different preset postures according to the initial detection data of the inertial measurement unit; Based on the static deviation, initial detection data of the inertial measurement unit is calibrated to calibrate an initial error of the inertial measurement unit.

6. A calibration device for an inertial measurement unit internal parameter, characterized in that: Applied to a parameter calibration system, the parameter calibration system includes an inertial measurement unit and a camera arranged on a turntable, a calibration plate, and an industrial computer connected to the turntable, the inertial measurement unit, and the camera. The device includes: A camera calibration module, configured to perform intrinsic parameter calibration on the camera based on the calibration board; a time delay calibration module, configured to perform time delay calibration on the camera and the inertial measurement unit so as to synchronize detection data of the inertial measurement unit with image data of the camera; an estimation module, configured to estimate the motion data of the camera using a visual odometry based on the intrinsic parameters of the camera and the image data; An acquisition module, configured to eliminate the accumulated error of the visual odometer by using a PNP algorithm to obtain accurate motion data; an internal parameter calibration module, configured to calibrate the internal parameters of the inertial measurement unit using the precise motion data and the detection data; The acquisition module is specifically used for: Acquire image data captured by the camera, wherein the image data includes a calibration plate; Determining corner points of a calibration plate in the image data, and determining positions of the corner points in a world coordinate system and a pixel coordinate system; Obtaining the intrinsic parameter matrix of the camera; Calculating actual motion data of the camera according to the intrinsic parameter matrix of the camera, the world coordinates of the corner points, and the pixel coordinates; The motion data of the camera is updated to the actual motion data of the camera to obtain accurate motion data.

7. The device according to claim 6, characterized in that The estimation module is specifically used for: Based on the calibration plate, setting the rotation range of the turntable; Within the rotation range, controlling the turntable to rotate in different preset directions at a preset speed so that the turntable reaches different preset positions; During the process of the turntable rotating to the preset position, acquiring image data of the camera at the current moment and image data at the previous moment; Obtain two sets of one-to-one corresponding pixel point sets based on the image data at the previous moment and the image data at the current moment; The motion data of the camera is estimated according to the one-to-one corresponding pixel point set.

8. A parameter calibration system, characterized in that: The parameter calibration system includes: Turntable; An inertial measurement unit and a camera are arranged on the turntable; Calibration plates; and an industrial computer connected to the turntable, the inertial measurement unit, and the camera; Wherein, the industrial computer includes at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 5.

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