CN209877895U - A Cylinder Diameter Measurement System Based on Line Structured Light - Google Patents

Abstract

The utility model provides a cylinder diameter measurement system based on line structured light, which includes an installation base plate, a line laser, an image acquisition device, and two brackets symmetrically arranged on the top of the installation base plate. The line laser and the image acquisition device are respectively arranged At the top of the two brackets, a slide rail is provided on the top of the installation base plate, and a sliding trolley for placing the cylindrical workpiece to be measured is slidably arranged on the slide rail. The utility model adopts the method of line structured light to measure the diameter of the cylindrical workpiece. The size, line structured light method uses the laser triangle method as the basic measurement principle. The laser surface emitted by the line laser is projected onto the surface of the measured cylindrical workpiece, and intersects with the cross-section of the cylindrical workpiece to be measured to form a light strip. As a carrier of information, a high-resolution camera is used to collect images, and a mathematical model is established. After system calibration, the position of the light bar pixel in the world coordinate system can be calculated, and the diameter of the measured cylinder can be obtained.

Description

A Cylinder Diameter Measurement System Based on Line Structured Light

technical field

The utility model relates to a cylinder diameter measurement system, in particular to a cylinder diameter measurement system based on line structured light.

Background technique

In the field of industrial production, it is necessary to measure the diameter of a cylindrical workpiece to determine whether the workpiece meets the requirements of the production process. At present, vernier calipers are basically used to measure the diameter of cylinders, which need to be measured multiple times at different cross-sections of the cylinder. When the inspectors use vernier calipers to measure, they are easily disturbed by human factors, such as the proficiency of the surveyors, measurement operation methods, etc., resulting in measurement results. The accuracy is low, the deviation is large, and the vernier caliper needs to be adjusted for each measurement, and the work efficiency is low.

Utility model content

The purpose of the utility model is to provide a cylinder diameter measurement system based on line structured light, which can greatly improve work efficiency and ensure measurement accuracy.

In order to achieve the above purpose, the technical solution adopted by the utility model is: a cylinder diameter measurement system based on line structured light, including a mounting base, a line laser, an image acquisition device and two brackets symmetrically arranged on the top of the mounting base, The line laser and the image acquisition device are respectively arranged on the top of the two brackets, the top of the installation base plate is provided with a slide rail and the slide rail is located between the two brackets, the slide rail is provided with slides for placing the A sliding trolley for measuring cylindrical workpieces. The bottom of the sliding trolley is provided with a slider matching the slide rail, and the head and end of the slide rail are provided with limit blocks for limiting the sliding trolley.

Further, a V-shaped groove for placing a cylindrical workpiece to be measured is opened on the top of the sliding trolley.

Further, the image acquisition device is detachably installed on its corresponding bracket through the installation disk.

Further, the image acquisition device is fixedly connected to the installation plate and the image acquisition device is located on the side of the installation plate away from the bracket. Two chutees are symmetrically opened on the installation plate, and each chute is pierced with a screw thread with the bracket. Connected T-bolts.

Further, the two chutes are arc-shaped, and the inner arc surfaces of the two are opposite to each other.

Further, the slide rail and the central axes of the two brackets are in the same vertical plane.

Further, the image acquisition device is a camera connected to a host computer.

Compared with the prior art, the beneficial effect of the utility model is that the utility model does not require the testing personnel to use a vernier caliper to measure, will not be affected by the proficiency of the testing personnel, the measurement operation method, etc., has high measurement accuracy, and is suitable for Continuous and rapid measurement, high degree of automation.

Description of drawings

Figure 1 is a schematic structural diagram of a cylinder diameter measurement system based on line structured light;

Fig. 2 is the top view of Fig. 1;

Fig. 3 is a schematic diagram of the positional relationship between the sliding car and the cylindrical workpiece to be measured;

Fig. 4 is a structural schematic diagram of the installation disk;

5 is a schematic flow chart of a measurement method using a line-structured light-based cylinder diameter measurement system;

Fig. 6 is a schematic diagram of model establishment of an image physical coordinate system, an image pixel coordinate system, and a camera coordinate system;

Fig. 7 is a schematic diagram of establishing a model with O as the center;

Fig. 8 is a schematic diagram of establishing a virtual plane perpendicular to the axis of the measured cylinder;

Marks in the figure: 1. Bracket, 2. Line laser, 3. Limiting block, 4. Slide rail, 5. Slider, 6. Sliding trolley, 7. Cylindrical workpiece to be measured, 8. Mounting base plate, 9. Image Obtaining device, 10, mounting plate, 11, chute, 12, T-bolt.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the present utility model. Obviously, the described implementation Examples are some embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the present utility model. scope of protection.

A cylinder diameter measurement system based on line structured light, as shown in Figure 1 and Figure 2, includes an installation base plate 8, a line laser 2, an image acquisition device 9 and two brackets 1 symmetrically arranged on the top of the installation base plate, the The line laser 2 and the image acquisition device 9 are respectively arranged on the tops of the two brackets 1, the top of the installation base plate 8 is provided with a slide rail 4 and the slide rail 4 is located between the two brackets 1, on the slide rail 4 Slidingly provided with a sliding trolley 6 for placing the cylindrical workpiece 7 to be measured, the bottom of the sliding trolley 6 is provided with a slider 5 matching the slide rail 4, and the head end and the end of the slide rail 4 are provided with a sliding trolley 6 Carry out the limit block 3 of limit.

To further optimize this solution, as shown in FIG. 3 , the top of the sliding trolley 6 is provided with a V-shaped groove for placing the cylindrical workpiece 7 to be measured.

To further optimize this solution, the image acquisition device 9 is detachably installed on its corresponding bracket 1 through the installation disk 10 .

To further optimize this solution, the image acquisition device 9 is fixedly connected to the installation disk 10 and the image acquisition device 9 is located on the side of the installation disk 10 away from the bracket 1. As shown in FIG. 4 , two slide grooves are symmetrically opened on the installation disk 10 11. A T-bolt 12 threaded with the bracket 1 is threaded in each chute 11 .

To further optimize this solution, the two chutes 11 are both arc-shaped and the inner arc surfaces of the two are oppositely arranged.

To further optimize this solution, the central axes of the slide rail 4 and the two brackets 1 are in the same vertical plane.

To further optimize this solution, the image acquisition device 9 is a camera connected to a host computer.

Using the utility model, that is, a measuring method of a cylinder diameter measuring system based on line structured light, comprises the following steps:

Step 1: Place the cylindrical workpiece 7 to be measured in the V-shaped groove opened on the sliding trolley 6;

Step 2: Turn on the line laser 2 and slide the sliding trolley 6 back and forth in the slide rail 4, so that the laser surface emitted by the line laser 2 intersects with the cross-section of the cylindrical workpiece 7 to be measured to form a light strip;

Step 3: Adjust the T-shaped bolt 12 to separate the mounting plate 10 from the bracket 1, then turn the mounting plate 10 so that the light bar generated in step 2 is within the field of view of the image acquisition device 9, and then adjust the T-shaped bolt 12 to fix the mounting plate 10 on the On bracket 1;

Step 4: collect picture information by the image acquisition device 9 and upload the collected picture information to the host computer;

Step 5: After the host computer processes the collected image information, the diameter of the cylindrical workpiece 7 to be measured can be obtained.

To further optimize this scheme, the process of the host computer processing the collected image information to obtain the diameter of the cylindrical workpiece 7 to be measured includes the following steps:

Step 1: Use filtering and morphological processing methods to preprocess the collected picture information, so that the light strips are complete and accurate at the boundary;

Step 2: Extract the center of the light bar and fit the center of the light bar;

Step 3: Calculate the diameter of the cylindrical workpiece to be measured according to the fitted ellipse.

The following is a detailed description of the processing flow of the host computer:

The principle of the utility model is as follows: select the method of line structured light to measure the diameter of the cylindrical workpiece, the line structured light method takes the laser triangle method as the basic measurement principle, and the laser surface emitted by the line laser 2 is projected onto the surface of the measured cylindrical workpiece 7 The surface intersects with the section of the cylindrical workpiece 7 to be measured to form a light strip, using the laser as the carrier of information transmission, using a high-resolution camera to collect images, establishing a mathematical model, and calculating the pixel points of the light strip after system calibration The position in the world coordinate system can get the diameter of the measured cylinder.

In the online structured light measurement method, in order to find the pixel coordinates of the light stripe points and the corresponding specific coordinates in the world coordinate system, it is necessary to establish a suitable measurement model. In the online structured light measurement method, the common mathematical models include: analytical geometry model, artificial neural network model and pinhole imaging model. When the utility model is used, the most commonly used pinhole imaging model is used.

1. First, establish the image physical coordinate system, image pixel coordinate system and camera coordinate system. The principle of the model is shown in Figure 6.

1. Image physical coordinate system

O-xy is the physical coordinate system of the image. The origin is the intersection point O of the camera optical axis and the image plane captured by the camera. O is also the intersection point of the camera optical axis and the image plane, also known as the principal point.

2. Image pixel coordinate system

The image pixel coordinate system takes the upper left corner of the image captured by the camera as the coordinate origin, and (u, v) represent the column and row coordinates of a point on the image.

3. Camera coordinate system

The O _c -X _c Y _c Z _c coordinate system is the camera coordinate system, the coordinate system takes the camera optical center O _c as the origin, O _c Z _c is the optical axis, O _c x _c and O _c Y _c are respectively related to the image physical coordinate system The x and y axes are parallel.

4. World coordinate system

The O _w -X _w Y _w ^Z _w coordinate system is the world coordinate system, and the position needs to be selected according to the system calibration method and system measurement.

Let the coordinates of a point P in the space be (x _w , y _w , z _w ) in the world coordinate system, the coordinates in the camera coordinate system be (x _c , y _c , z _c ), and the coordinates in the image pixel coordinate system is (u, v), the transformation relationship between (u, v) and (x _c , y _c , z _c ) is:

When using the above formula to calculate (x _c , y _c , z _c ) from (u, v), a unique solution cannot be obtained. Therefore, light plane constraints need to be added to the online structured light measurement method, and the points on the light strip satisfy both the pinhole imaging model and the light plane constraints.

Let the equation of the light plane in the camera coordinate system be ax _c +by _c +cz _c +d=0, and combine this equation with (1) to get:

From this, the one-to-one correspondence between (u, v) and (x _c , y _c , z _c ) can be obtained, and the coordinates of point P in the camera coordinate system (x _c , y _c , z _c ) and the world coordinate system The relationship between the lower coordinates ( x _w , y _w , z _w ) is as follows:

R and T are the rotation matrix and translation matrix respectively when the camera coordinate system is converted to the world coordinate system, so that the coordinate value of the point in the world coordinate system (x _w , y _w , z _w ).

Two, the concrete method of operation of the present utility model is as shown in Figure 5, below with regard to the specific method used in conjunction with Figure 5, describe in detail:

1. The cylinder diameter measurement system based on line structured light is mainly designed by oblique laser triangulation method. According to the method used and the convenience, practicability and operability of cylinder measurement, the above measurement system is built;

2. Using the slide rail 4 and slider 5 mechanism, the sliding trolley 6 can move horizontally along the slide rail 4 to measure the diameters of different sections of the cylindrical workpiece to be measured;

3. In order to make the edges of the collected light strips complete and accurate, filter and morphological processing methods are used for preprocessing, and then the light strips are processed according to the sub-pixel edge detection algorithm (this method is based on the improved method of the gray center of gravity method). center fit.

This method regards the gray barycenter of the light bar as the center point of the light bar and uses the idea of weighted average. Assuming that the pixel coordinates of the center pixel of the light strip extracted in the i-th column of the image are (u _id , v _id ), and the gray value of the light-strip point on the i-th column and row j is G(j, i), the following relationship exists:

However, due to the uneven brightness distribution of the arc-shaped light strip, the effect of the center of the light strip extracted by the gray-scale center of gravity method is not ideal. The utility model improves the above situation. First, the image is opened to remove the burrs around the light strip and smooth the image. Then use the Zhang parallel fast thinning algorithm to thin the image, and finally continue to use the gray-scale center of gravity method to process the thinned image to obtain the center of the light bar with relatively high precision.

Fitting the center line of the light strip obtained, because there is a certain angle between the incident direction of the line laser and the cylinder to be measured, the center line of the light strip obtained is an ellipse after fitting. In order to solve this problem, the utility model A cylinder diameter measurement algorithm based on the constraint of the center of the circle is proposed, and a model with O as the center of the circle is established. As shown in Figure 7, A, B, C, and D are points on the circle, and H is the intersection of AC and BD. According to The geometric relationship of a circle can be obtained:

AH×CH=BH×DH=r ² -OH ² (5)

Among them, r is the radius of the circle, let the coordinates of point O of the center of the circle be (x ₀ y ₀ ), the coordinates of points A, B, C, and D are respectively (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ), (x ₄ , y ₄ ), using the coordinates of points A, B, C, and D, the coordinates (x ₅ , y ₅ ) of point H can be obtained.

In order to improve the measurement accuracy, a virtual plane perpendicular to the axis of the measured cylinder is established, as shown in Figure ₈ , where π2 is the virtual plane perpendicular to MN, P _i is the measured point on the cylinder, Q _i The point is the projection of point P _i on the π ₂ plane, and the point Q _i on the arc cd on the virtual plane is divided into 4 areas equally, and the number of points on each area is n, A, B, C, D corresponds to the points of the 4 regions respectively. Let A _i be the i-th point, then B _i is the i+n-th point, C _i is the i+2n-th point, and D _i is the i+3n-th point. Bringing the local coordinates of point Q _i into Equation (5), the objective function of the optimized circle center point can be obtained:

where r is an estimate of the radius of the cylinder.

In Fig. 7, L is a chord on the circle, F is the midpoint of the chord, OF⊥L, namely OF·L=0. Therefore, the objective function of optimizing the center point can also be expressed as:

Combining equations (6) and (7), the optimization function of the optimized circle center point is obtained as:

Finding the minimum value of formula (8) is a nonlinear optimization problem. Find the optimal solution of the objective function and get the optimized center of circle O _c . Let the coordinates of O _c be (x _c , y _c ), and combine O _c and The local coordinates of point Q _i are substituted into formula (9) to obtain the diameter of the measured cylinder:

where N=4×n.

The above description of the disclosed embodiments enables those skilled in the art to realize or use the utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. The utility model provides a cylinder diameter measurement system based on line structure light, includes mounting plate (8), line laser (2), image acquisition device (9) and symmetry set up two supports (1) at the mounting plate top, its characterized in that: line laser ware (2) and image acquisition device (9) set up respectively on the top of two supports (1), the top of mounting plate (8) is provided with slide rail (4) and slide rail (4) are located two supports (1) between, slide on slide rail (4) and be provided with slip dolly (6) that are used for placing cylinder work piece (7) that await measuring, the bottom of slip dolly (6) be provided with slide rail (4) assorted slider (5), the head end and the end of slide rail (4) all are provided with and are used for carrying out spacing stopper (3) to slip dolly (6).

2. The line structured light based cylinder diameter measurement system of claim 1, wherein: the top end of the sliding trolley (6) is provided with a V-shaped groove for placing a cylindrical workpiece (7) to be tested.

3. The line structured light based cylinder diameter measurement system of claim 1, wherein: the image acquisition device (9) is detachably mounted on the corresponding support (1) through a mounting disc (10).

4. The line structured light based cylinder diameter measurement system of claim 3, wherein: image acquisition device (9) and mounting disc (10) fixed connection and image acquisition device (9) are located one side that support (1) were kept away from in mounting disc (10), and two spout (11) have been seted up to the symmetry on mounting disc (10), all wear to be equipped with in each spout (11) one with support (1) threaded connection's T type bolt (12).

5. The line structured light based cylinder diameter measurement system of claim 4, wherein: the two sliding grooves (11) are arc-shaped, and the inner arc surfaces of the two sliding grooves are arranged oppositely.

6. The line structured light based cylinder diameter measurement system of claim 1, wherein: the central axes of the slide rail (4) and the two brackets (1) are in the same vertical plane.

7. The line structured light based cylinder diameter measurement system of claim 1, wherein: the image acquisition device (9) is a camera connected with an upper computer.