A wheel arch height measuring device and method based on monocular vision

Abstract

The present application belongs to the technical field of automobile detection, and particularly relates to a wheel arch height measuring device and method based on monocular vision. The wheel arch height measuring device comprises a support, a camera and a laser are arranged on the support, and two lasers are arranged on the two sides of the camera. The wheel arch measuring device is installed at a fixed position, and visual measurement of the wheel arch height can be completed by only one camera without moving to multiple positions, so that the complexity of the measuring equipment and the demand for picture data are greatly reduced. The device has the characteristics of low cost, simple calibration, simple algorithm, fast measurement, etc. The speed and accuracy of the wheel arch height measurement are greatly improved, the equipment cost is low, and the post-maintenance is convenient.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of monocular vision-based wheel arch height measuring device and method, belong to automobile detection technical field. BACKGROUND

[0002] Automobile wheel arch, simply referred to as wheel arch, refers to the plated bright strip above the tire, i.e. a semicircular component protruding from the fender above the tire. Before assembling the wheel arch and calibrating the vehicle body sensor, the wheel arch height needs to be measured to ensure that the wheel arch installation height value is within the specified error range.

[0003] Currently, wheel arch height measurement is measured manually or by using imported binocular vision measurement devices. The former has slow measurement speed, and the measurement accuracy is greatly affected by tools and human factors. The latter uses imported binocular vision devices, which are expensive, have complex algorithms, and have high maintenance costs. Therefore, a wheel arch height measurement device with fast measurement speed and low equipment cost is needed. SUMMARY

[0004] The present application provides a monocular vision-based wheel arch height measurement device and method to address the above-mentioned deficiencies of existing technology.

[0005] The technical solution of the present application to solve the above technical problems is as follows:

[0006] One of the purposes of the present application is to provide a monocular vision-based wheel arch height measurement device, which includes a bracket, a camera and a laser are provided on the bracket, the laser is provided with two, two lasers are provided on both sides of the camera.

[0007] Based on the above technical solution, the present application can also be improved as follows:

[0008] Further, the laser is a linear laser, and the lasers emitted by the two lasers are parallel.

[0009] Further, the laser emitted by the laser is perpendicular to the ground.

[0010] The second purpose of the present application is to provide a monocular vision-based wheel arch height measurement method, which uses the monocular vision-based wheel arch height measurement device described above to measure the wheel arch height.

[0011] Further, the method comprises the following steps:

[0012] a. Place the wheel arch height measurement device on the side of the vehicle;

[0013] b. In the state that the lasers on both sides of the camera are turned on, take a photo of the wheel arch using the camera;

[0014] c. Take a photo of the wheel arch with the camera in the state that the lasers on both sides of the camera are off;

[0015] d. Process the photos of the wheel arch taken in the above steps a and b by software to obtain clear pictures of the wheel arch;

[0016] e. Calculate the height of the wheel arch;

[0017] f. Repeat the above steps b, c, d and e to measure the heights of other wheel arches of the automobile.

[0018] Further, the calculation method in the step e is as follows:

[0019] Define the distance between the imaging points of the two lasers on the photo as ab, which is calculated by pixel value;

[0020] Define the distance between the laser lines emitted by the two lasers as AB, which is measured;

[0021] Define the focal length of the camera as OC;

[0022] Define the height of the highest point of the imaging of the wheel arch on the photo as dC, which is calculated by pixel value;

[0023] Define the distance from the wheel arch to the camera as OZ;

[0024] Define the height of the wheel arch as PZ;

[0025] OZ is calculated by the following formula (1):

[0026] OZ=(OC*AB) / ab (1);

[0027] PZ is calculated by the following formula (2):

[0028] PZ=(dC*OZ) / OC (2).

[0029] The present application has the following advantages:

[0030] The application combines monocular camera and parallel structured light, and takes two images in the case that the measuring device is fixed, one is taken in the state that the parallel structured light is opened, and the other is taken in the state that the parallel structured light is closed, and the purpose of measuring the wheel arch height of the vehicle by monocular vision and parallel structured light is realized through the calculation of the processing of the two images. The wheel arch measuring device is installed by fixing the position, and does not need to move in multiple positions during measurement. In addition, only one camera is needed to complete the visual measurement of the wheel arch height, which greatly reduces the complexity of the measuring equipment and the demand for picture data. The device has the characteristics of low cost, simple calibration, simple algorithm, fast measurement speed, etc. The speed and accuracy of the wheel arch height measurement are greatly improved, the equipment cost is low, and the post-maintenance is convenient. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the wheel arch height measuring device based on monocular vision of the application.

[0032] Figure 2 It is a camera coordinate system for measuring the wheel arch height without the help of a laser for a single camera in the specific embodiment.

[0033] Figure 3 It is a camera coordinate system for measuring the wheel arch height of the wheel arch height measuring device based on monocular vision of the application.

[0034] The following records the reference signs: 1, camera; 2, laser; 3, support. DETAILED DESCRIPTION

[0035] The principles and characteristics of the application are described below in combination with the drawings, and the examples are only used to explain the application, and are not used to limit the scope of the application.

[0036] Referring to Figure 1 The wheel arch height measuring device based on monocular vision of the embodiment comprises a support 3, the support 3 is provided with a camera 1 and a laser 2, the laser 2 is provided with two, and the two lasers 2 are arranged on the two sides of the camera 1. The laser 2 is a linear laser, and the lasers 2 emit parallel laser beams; the laser beams emitted by the laser 2 are perpendicular to the ground.

[0037] The wheel arch height measuring method based on monocular vision of the embodiment adopts the above measuring device to measure the wheel arch height of the vehicle, and mainly comprises the following steps:

[0038] a. placing the wheel arch height measuring device on the side of the vehicle;

[0039] b. taking one photo of the wheel arch by the camera in the state that the lasers on the two sides of the camera are opened;

[0040] c. Take a photo of the wheel arch with the camera in the state that the lasers on both sides of the camera are off;

[0041] d. Process the photos of the wheel arch taken in step a and step b to make them;

[0042] e. Calculate the height of the wheel arch by the following method:

[0043] Define the distance between the imaging points of the two lasers on the photo as ab, which is calculated by pixel value;

[0044] Define the distance between the laser lines emitted by the two lasers as AB, which is measured;

[0045] Define the focal length of the camera as OC;

[0046] Define the height of the highest point of the imaging of the wheel arch on the photo as dC, which is calculated by pixel value;

[0047] Define the distance from the wheel arch to the camera as OZ;

[0048] Define the height of the wheel arch as PZ;

[0049] OZ is calculated by the following formula (1):

[0050] OZ = (OC x AB) / ab (1);

[0051] PZ is calculated by the following formula (2):

[0052] PZ = (dC x OZ) / OC (2);

[0053] f. Repeat the above steps b, c, d and e to measure the height of other wheel arches of the vehicle.

[0054] The process of measuring and calculating the height of the wheel arch in this embodiment is as follows:

[0055] The measuring device of the embodiment is composed of a camera and two linear lasers, the laser lines emitted by the two linear lasers are parallel light lines perpendicular to the ground, and the distance between the parallel light lines is fixed as a known value AB = 100 mm. The monocular camera (i.e. one camera) of the embodiment is fixedly installed, the image of the eyebrow region is shot, then image processing is performed, the picture is transmitted to the upper computer, the picture is processed by the OpenCV program, the picture is first sharpened, then the Canny() function is used for edge detection, the findContours() function is used for contour extraction, and finally the drawContours() function is used for drawing the contour to obtain the picture of the eyebrow contour. Since the image of the monocular camera is a two-dimensional plane, if the parallel structured light of the lasers on the two sides of the camera is not used, only one picture shot at one position cannot directly calculate the height of the eyebrow through the contour of the eyebrow on the image. Because the depth of field of the object cannot be calculated through one picture, see Figure 2 , the model of camera imaging is shown in the figure, and the model is simplified for convenient calculation. It is assumed that the height of the eyebrow is PZ, and the image point coordinate of P on the image is d when the eyebrow with the same height PZ is shot at a distance of CZ from the image plane. When the eyebrow with the same height PZ moves to the position of Z', the highest point P' of the eyebrow is shot by the camera, and the point coordinate of P' on the image is d' at this time. Through the model, the following conclusion can be drawn: the point coordinates of the height of the object on the image are different as long as the distance between the object and the camera is different when a single camera shoots the same height of the object at the same position.

[0056] The embodiment sets one linear laser on the left and right sides of the camera respectively, the two linear lasers emit parallel structured light lines perpendicular to the ground, and the distance between the two laser lines is known. As shown in Figure 3 , AB is the distance between the two horizontal laser lines emitted by the two lasers and irradiating the car, and the distance between the two horizontal laser lines and the points on the edge of the eyebrow. Since the distance AB is the distance between the parallel laser lines, i.e. the known value, combined with the imaging principle of the object, the similar triangles ΔOab ∽ ΔOAB and the triangles ΔOCa ∽ ΔODA can be obtained. According to the similar principle of the two groups of triangles, the following can be obtained: ① ab / AB = Oa / OA; ② Oa / OA = OC / OD. From ① and ②, ab / AB = OC / OD is obtained, wherein ab is the distance between the imaging points of the two laser lines on the picture, which can be calculated from the pixel value of the picture, AB is known as 100 mm, and OC is the focal length f of the camera, which can be obtained by camera calibration. Therefore Figure 3The formula is OD = (OC × AB) / ab. This allows us to measure the distance between the camera and the wheel arch (i.e., depth of field). After obtaining the distance data, the two parallel laser lines are turned off, and an image of the wheel arch outline is taken. This image is then processed to obtain a clear, curved outline. Figure 2 Based on the camera imaging principle and the principle of similar triangles, PZ / dC = OZ / OC, then the height of the brow is PZ = (dC × OZ) / OC. Where dC is the height of the highest point of the brow image on the photograph, calculated using the formula y = (v - cy) * dy, where y represents the image height (i.e., dC), cy is the coordinate of the principal point in the (u, v) coordinate system, v represents the pixel value at that height, and dy represents the physical size of the pixel in the y-direction. The OZ value is then calculated. Figure 3 In this context, OD and OC represent the camera's focal length, which can be obtained through the camera's intrinsic parameter calibration. From this, the height PZ of the wheel arch can be calculated.

[0057] The measuring device in this embodiment is fixed on both sides of the vehicle. A monocular camera takes an image when the parallel laser line is turned on, and then takes another image when the parallel laser line is turned off. After image processing of the two images, the height of the vehicle wheel arch can be calculated using a formula. The monocular vision plus structured light measurement algorithm in this embodiment is simple, fast in calculation, and low in equipment cost.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A monocular vision-based wheel arch height measurement method, characterized in that, The wheel arch height is measured by a wheel arch height measuring device, including the following steps: a. placing the wheel arch height measuring device on the side of the vehicle; b. taking a photo of the wheel arch by the camera under the condition that the lasers on both sides of the camera are turned on; c. taking a photo of the wheel arch by the camera under the condition that the lasers on both sides of the camera are turned off; d. processing the wheel arch photos taken in steps a and b by software to obtain a clear wheel arch picture; e. calculating the height of the wheel arch, the calculation method being as follows: defining the distance between the imaging points of the two lasers on the photo as ab, which is calculated by pixel value; defining the distance between the emitted laser lines of the two lasers as AB, which is measured; defining the focal length of the camera as OC; defining the height of the highest point of the imaging of the wheel arch on the photo as dC, which is calculated by pixel value; defining the distance from the wheel arch to the camera as OZ; defining the height of the wheel arch as PZ; OZ is calculated by formula (1) as follows: OZ=(OC×AB) / ab (1); PZ is calculated by formula (2) as follows: PZ=(dC×OZ) / OC (2); f. repeating steps b, c, d and e to measure the height of other wheel arches of the vehicle; The wheel arch height measuring device comprises a support, a camera and two lasers on the support, the two lasers being arranged on both sides of the camera.

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