Self-calibration device of non-contact four-wheel aligner

Abstract

The invention discloses a self-calibration device of a non-contact four-wheel aligner, which relates to the field of automobile four-wheel detection, and comprises a single-target calibration camera (calibration camera for short) which is arranged on the side surface of a stand column and extends out of the side surface of the stand column in order to realize correction depending on a fixed target on the ground. The calibration camera can shoot a plurality of images of the ground target, computer vision processing is applied, the images are integrated and analyzed, the position change of the current stand column is calculated to calibrate the equipment, correction is carried out by relying on the ground fixed target, and during initial installation or change of the position of the stand column, rapid recovery can be realized, so that the correction result is rapid and reliable.

Description

Technical Field

[0001] The invention is applicable to the field of automobile four-wheel detection, and in particular is a non-contact four-wheel aligner self-calibration device. Background Art

[0002] Four-wheel alignment is essential in the automobile inspection and maintenance industry, and the accuracy of the detection affects the safety of automobile use. Four-wheel alignment detection technology has undergone wire-drawing, laser, CCD and 3D four-wheel alignment, and has been greatly improved in terms of accuracy. At present, the most commonly used is the 3D four-wheel alignment instrument. During the operation, auxiliary equipment such as fixtures and target plates are used. The positioning parameters of the wheel are indirectly measured through the fixture, which is prone to mechanical errors; and the fixture will cause varying degrees of damage to the wheel and the hub; due to the deformation of the rim, etc., the measurement error requires a cart to compensate, making the operation process more troublesome. The accuracy and speed of the existing non-contact measurement technology cannot meet the measurement requirements of automobile wheel alignment instruments, especially for the measurement of rim deviation, which affects the final adjustment accuracy. For the existing non-contact four-wheel alignment instrument structure, most of them are composed of an upper and lower two-layer structure, two sets of measurement units, and two sets of electrical appliances. Specific operation process: When the vehicle is parked in the middle of the four sets of columns, the wheel is detected. When the wheel position parameters meet the requirements, the vehicle is driven away. When the wheel needs to be adjusted, the vehicle is lifted and the wheel position is manually adjusted. Re-test after adjustment. Using two sets of measuring devices makes the non-contact locator very expensive and the lifting position is limited. After on-site installation, four sets of columns need to be calibrated on-site. The calibration method is mostly to calibrate multiple sets of camera targets between columns, which makes on-site installation and calibration parameters particularly cumbersome. Summary of the invention

[0003] In order to solve the above problems, that is, to solve the problems raised by the above background technology, the present invention proposes a non-contact four-wheel aligner self-calibration device, including a column, a linear guide is installed on the column through a linear guide fixing screw, a measuring unit assembly is installed on the linear guide through a linear slider fixing screw and a linear slider, a motor is installed on the back of the column through a mounting screw, a synchronous pulley is installed on the output shaft of the motor, another synchronous pulley is installed on the rotating shaft of the column, a synchronous belt is wound between the two synchronous pulleys, one side of the synchronous belt is fixed to the measuring unit assembly, and the The upper part of the column is provided with a host and an electrical component assembly, the top of the column is fixed with an upper cover and a light box by upper cover fixing screws, the upper end surface of the measuring unit assembly is fixed with a camera bracket, the lower part of the camera bracket is fixed with a calibration camera by a camera mounting screw, the column is installed with a fixed base by a base fixing screw and a base adjustment hollow bolt, a ground target is embedded in a groove of the fixed base, a locking sleeve is installed on the bottom surface of the column by a locking sleeve mounting screw, a compression spring and a locking shaft are installed inside the locking sleeve, and an upper positioning pin is also installed in the fixed base; The operation steps of the self-calibration device are as follows: Step 1: After the column is lifted or moved, before the vehicle's four-wheel alignment test, turn on the fill light first, then use the calibration camera to take multiple ground target pictures and store them; Step 2: The multiple images taken are processed and analyzed by computer vision through a host computer to obtain the changes in the spatial coordinates of the column after movement relative to the ground position.

[0004] Step 3: Based on the coordinate change of the column relative to the initial position, calculate the change values ​​of the spatial coordinates of the measurement unit component relative to the initial position after the column moves, △X, △Y and △Z. X, Y, Z are the coordinate values ​​of the measurement unit component in three directions in the spatial coordinate system.

[0005] The present invention is further configured as follows: the camera bracket extends from the notch of the column to the back side of the column.

[0006] The patent of the present invention is further configured as follows: the ground target is made of ceramic material.

[0007] The further configuration of the present invention is as follows: The specific implementation method of the self-calibration device is as follows: a. After the first installation or the column is raised and lowered, the system will turn on the fill light, and then use the calibration camera to take pictures of the ground target. This process is repeated many times, and the pictures taken are stored in the computer; b. Read the RGB value of each pixel of each image captured, and process the image into grayscale according to the formula Grey = 0.299*R + 0.587*G + 0.114*B.

[0008] c. Binarize the grayscale processed image. First, select the appropriate offset adjustment value (here assumed to be a) according to the shooting effects of multiple images, then perform Gaussian filtering on the image, calculate the Gaussian mean in the 3*3 area around each pixel (here assumed to be b), and calculate the final binarization threshold based on these two parameters to binarize the image. d. Perform connected region detection on the obtained binary image and calculate the area of ​​the connected region within the specified contour. If the area is too small, perform secondary filtering and delete the small connected region. e. Perform edge search on the processed image to find the contour features of the pattern inside the target; f. Superimpose multiple processed target patterns taken continuously, and eliminate the errors generated during shooting through algorithm calculation; g. Search for feature points on the final image, use Hough transform to find the straight line, derive the target value to get the feature points, and record and save the coordinates of the found feature points in sequence. According to the coordinate change of the feature point relative to the initial position, the change of the projection of the plane where the calibration camera is located parallel to the target plane is obtained, and based on this, the change of the X, Y, and Z axes that should be corrected for each pixel point when the main camera is shooting is obtained to complete the self-correction of the camera. At this point, the self-calibration device has completed its work.

[0009] The beneficial technical effects of the patent of this invention are as follows: This product is based on a single column that can conveniently and reliably track, measure and lift vehicles of different heights through a lifting device for automatic measurement and calculation. Each column independently searches for a target fixed on the ground, collects images through a camera, and automatically corrects the measurement unit through an algorithm, instead of relying on the relative position relationship between the four columns to correct the measurement unit. This can save a set of measurement units and save costs. Correction is made by relying on a fixed target on the ground, and can be quickly restored during initial installation or when the column position is changed, making the correction result fast and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is the overall front view of the present invention.

[0011] Figure 2 It is an overall side view of the present invention.

[0012] Figure 3 It is an overall top view of the present invention.

[0013] Figure 4 It is a cross-sectional view of the locking device of the present invention.

[0014] Figure 5 It is a top view of the base of the present invention.

[0015] : 1. column, 2. linear guide, 3. linear guide fixing screw, 4. linear slider, 5. linear slider fixing screw, 6. measuring unit assembly, 7. synchronous belt, 8. synchronous pulley, 9. main machine, 10. electrical component assembly, 11. upper cover, 12. upper cover fixing screw, 13. light box, 14. motor mounting screw, 15. motor, 16. camera bracket, 17. camera mounting screw, 18. calibration camera, 19. base fixing screw, 20. base adjustment hollow bolt, 21. positioning pin, 22. fixing base, 23. ground target, 24. locking sleeve mounting screw, 25. locking sleeve, 26. compression spring, 27. locking shaft. DETAILED DESCRIPTION

[0016] Please refer to the attached Figure 1-5To describe the preferred embodiments of the present invention. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0017] The patent of this invention proposes a non-contact four-wheel aligner self-calibration device. In order to realize correction by relying on a fixed target on the ground, a single-target calibration camera (referred to as the calibration camera) is provided on the side of the column 1 and protrudes out of the side of the column 1. When the column 1 is raised or lowered or moved, the calibration camera will take multiple images of the ground target 23, and use computer vision processing to integrate and analyze the images, calculate the current position change of the column 1, and calibrate the equipment.

[0018] The self-calibration correction unit mainly includes the following parts: A single-target positioning camera, an auxiliary LED fill light, and a target fixed on the ground. The camera is placed parallel to the ground target 23, and the position of the ground target is fixed relative to the column 1.

[0019] Self-calibration device operation steps: Step 1: After the column is lifted or moved, before the four-wheel alignment test of the vehicle is performed, the fill light is turned on first, and then the calibration camera 18 takes multiple ground target pictures and stores them.

[0020] Step 2: The multiple images taken are processed and analyzed by computer vision through the host 9 to obtain the change of the spatial coordinates of the column after the movement relative to the ground position.

[0021] Step 3: Based on the coordinate change of the column relative to the initial position, calculate the spatial coordinate change values ​​△X, △Y and △Z of the measuring unit component 6 relative to the initial position after the column moves. (X, Y, Z are the coordinate values ​​of the measuring unit component 6 in three directions in the spatial coordinate system respectively).

[0022] Step 4: According to the obtained values ​​of △X, △Y and △Z, the picture taken by the camera in the measuring unit component 6 is subjected to secondary correction.

[0023] The column 1 serves as a fixed foundation for the entire mechanism, and other parts are installed on the column 1. The linear guide 2 is fixed to the column 1 by the linear guide fixing screws 3. The back of the measuring unit assembly 6 is fixed with a linear slider 4 by the linear slider fixing screws 5, so that the measuring unit assembly 6 can move up and down along the linear guide 2 to meet the detection of vehicles of different heights. The motor 15 is installed on the back of the column 1 by the motor mounting screws 14, and the synchronous pulley 8 is fixed on the output shaft of the motor 15. The lower synchronous pulley 8 is fixed on the rotating shaft of the column 1. A synchronous belt 7 is wound between the two synchronous pulleys, and one side of the synchronous belt 7 is fixed to the measuring unit assembly 6. In this way, the measuring unit assembly 6 can be automatically lifted and lowered to track the target vehicle through the synchronous belt 7 driven by the motor 15. The upper part of the column 1 is placed with a host 9 electrical component assembly 10, and the host 9 is used to realize the calculation and command output of the entire measurement and calibration process. The top of the column 1 is fixed with the upper cover 11 and the light box 13 by the upper cover fixing screws 12. The function of the light box 13 is to provide lights of different colors to indicate different working states. A camera bracket 16 is fixed on the upper end surface of the measuring unit assembly 6. The camera bracket 16 extends from the notch of the column 1 to the back of the column 1. A calibration camera 18 is fixed below the camera bracket 16 by the camera mounting screws 17. The calibration camera 18 can be raised and lowered with the measuring unit assembly 6. The entire column 1 is fastened and horizontally adjusted with the base fixing screws 19, the base adjustment hollow bolts 20 and the fixed base 22. The ceramic The ground target 23 of the material is embedded in the groove of the fixed base 22. The calibration camera 18 recognizes the pattern of the ground target 23 to correct its own position parameters and automatically correct the calculated values. The locking sleeve 25 is fixed to the bottom surface of the column 1 through the locking sleeve mounting screw 24. The locking sleeve 25 is installed with a compression spring 26 inside to provide an upward thrust for the locking shaft 27. When installing the column, put the positioning hole on the base of the column 1 into the positioning pin 21 fixed on the fixed base 22, and then manually press the locking shaft 27 and rotate it 90° to complete the fixation of the column 1 and the fixed base 22. The specific implementation method of the self-calibration device is as follows: 1. After the first installation or the column 1 is raised and lowered, the system will turn on the fill light, and then the calibration camera 18 will take pictures of the ground target. This process is repeated many times, and the pictures taken are stored in the computer. 2. Read the RGB value of each pixel of each picture taken, and process the picture in grayscale according to the formula Grey = 0.299*R + 0.587*G + 0.114*B. 3. Binarize the grayscale processed image. First, select the appropriate offset adjustment value (here assumed to be a) according to the shooting effects of multiple images, then perform Gaussian filtering on the image, calculate the Gaussian mean in the 3*3 area around each pixel (here assumed to be b), and calculate the final binarization threshold based on these two parameters to binarize the image. 4. Perform connected region detection on the obtained binary image and calculate the area of ​​the connected region within the specified contour. If the area is too small, perform secondary filtering and delete the small connected region. 5. Perform edge search on the processed image to find the contour features of the target's internal pattern. 6. Overlay the processed target patterns taken continuously and eliminate the errors generated during shooting through algorithm calculation. 7. Search for feature points in the final image, use Hough transform to find the straight line, derive the target value to get the feature points, and record and save the coordinates of the found feature points in sequence. According to the coordinate change of the feature point relative to the initial position, the change of the projection of the plane where the calibration camera is located parallel to the target plane is obtained. Based on this, the change of the X, Y, and Z axes that should be corrected for each pixel point when the main camera is shooting is obtained, and the self-calibration of the camera is completed. At this point, the self-calibration device has completed its work Although the present invention has been described with reference to the preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0024] In the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0026] The term "comprise" or any other similar term is intended to cover a non-exclusive inclusion, such that a process, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, article, or apparatus / device.

[0027] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A non-contact four-wheel aligner self-calibration device, comprising a column (1), characterized in that: A linear guide rail (2) is mounted on the column (1) via a linear guide rail fixing screw (3); a measuring unit assembly (6) is mounted on the linear guide rail (2) via a linear slider fixing screw (5) and a linear slider (4); a motor (15) is mounted on the back of the column (1) via a mounting screw (14); a synchronous pulley (8) is mounted on the output shaft of the motor (15); another synchronous pulley (8) is mounted on the rotating shaft of the column (1); a synchronous belt (7) is wound between the two synchronous pulleys (8); one side of the synchronous belt (7) is fixed to the measuring unit assembly (6); a main machine (9) and an electrical component assembly (10) are placed on the upper half of the column (1); and the top of the column (1) is fixed via an upper cover. The upper cover (11) and the light box (13) are fixed by screws (12); a camera bracket (16) is fixed to the upper end surface of the measuring unit assembly (6); a calibration camera (18) is fixed below the camera bracket (16) by camera mounting screws (17); a fixed base (22) is installed on the column (1) by base fixing screws (19) and base adjustment hollow bolts (20); a ground target (23) is embedded in a groove of the fixed base (22); a locking sleeve (25) is installed on the bottom surface of the column (1) by locking sleeve mounting screws (24); a compression spring (26) and a locking shaft (27) are installed inside the locking sleeve (25); an upper positioning pin (21) is also installed in the fixed base (22); The operation steps of the self-calibration device are as follows: Step 1: After the column (1) is lifted or moved, before the four-wheel alignment test of the vehicle is performed, the fill light is turned on, and then a calibration camera (18) is used to take a plurality of ground target images and store them; Step 2: The multiple images taken are processed and analyzed by computer vision through the host (9) to obtain the change in the spatial coordinates of the column after the movement relative to the ground position; Step 3: Based on the coordinate change of the column (1) relative to the initial position, calculate the spatial coordinate change values ​​△X, △Y and △Z of the measuring unit component (6) relative to the initial position after the column moves. (X, Y, Z are the coordinate values ​​of the measuring unit component (6) in three directions in the spatial coordinate system respectively); Step 4: Based on the obtained values ​​of △X, △Y and △Z, perform secondary correction on the measurement unit component (6) and the image captured by the camera.

2. The non-contact four-wheel aligner self-calibration device according to claim 1, characterized in that: The camera bracket (16) extends from the notch of the column (1) to the back side of the column (1).

3. The non-contact four-wheel aligner self-calibration device according to claim 1, characterized in that: The ground target (23) is made of ceramic material.

4. The non-contact four-wheel aligner self-calibration device according to claim 1, characterized in that: The specific implementation method of the self-calibration device is as follows: a. After the first installation or the column (1) is lifted, the system will turn on the fill light, and then the calibration camera (18) will take pictures of the ground target. This process is repeated several times, and the pictures taken are stored in the computer; b. Read the RGB value of each pixel of each captured image, and process the image into grayscale according to the formula Grey = 0.299*R+ 0.587*G + 0.114*B; c. Binarize the grayscale processed image. First, select the appropriate offset adjustment value (here assumed to be a) according to the shooting effects of multiple images, then perform Gaussian filtering on the image, calculate the Gaussian mean in the 3*3 area around each pixel (here assumed to be b), and calculate the final binarization threshold based on these two parameters to binarize the image. d. Perform connected region detection on the obtained binary image and calculate the area of ​​the connected region within the specified contour. If the area is too small, perform secondary filtering and delete the small connected region. e. Perform edge search on the processed image to find the contour features of the pattern inside the target; f. Superimpose multiple processed target patterns taken continuously and eliminate the errors generated during shooting through algorithm calculation; g. Search for feature points in the final image, use Hough transform to find straight lines, derive the target value to get feature points, record and save the coordinates of the found feature points in sequence, and obtain the change of the projection of the plane where the calibration camera is located parallel to the target plane based on the change of the coordinates of the feature points relative to the initial position. Based on this, the change of the X, Y, and Z axes that should be corrected for each pixel point when the main camera is shooting is obtained, and the camera's self-correction is completed. At this point, the self-calibration device completes its work.

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