CN110645910A - A system and method for automatic detection of three-dimensional dimensions of workpieces based on laser scanning - Google Patents

Abstract

The invention is an automatic detection system and method for the three-dimensional size of a workpiece based on laser scanning. The detection software belongs to the technical field of three-dimensional scanning and digital analysis. In the present invention, a numerically controlled three-dimensional moving platform is used to realize dynamic measurement in the whole process, which replaces manual movement detection and improves the detection efficiency; the air-floating guide rail is adopted to improve the moving accuracy; The deflection of the laser scanning sensor is realized, and the workpiece is scanned at different angles; the blue line scanning laser scanning sensor is selected, which has strong anti-interference ability and high measurement accuracy.

Description

A system and method for automatic detection of three-dimensional dimensions of workpieces based on laser scanning

technical field

The invention relates to an automatic detection system and method for the three-dimensional size of a workpiece based on laser scanning, and belongs to the technical field of three-dimensional scanning and digital analysis.

Background technique

At present, there are many types of workpieces in aerospace systems, complex structures and small batches. If its shape and position parameters are all detected by inspectors through traditional general-purpose measuring tools such as vernier calipers and micrometers, a medium-complex workpiece needs to measure about 300 to 400 dimensions, and dimensions such as wall thickness need to be measured at multiple locations. Skilled operators need (3 to 5) hours to complete, and many inspectors are required. At present, there are problems such as a large amount of workpieces, low test efficiency, human judgment of qualification, untraceable quality, a lot of manpower and material resources, and error-prone factors, which have become factors restricting the quality and progress of workpiece products.

The workpiece is made of high-brightness materials. Therefore, the traditional photogrammetry method is not suitable. The original image collected is not clear enough, and there are many interferences, so it is impossible to accurately measure the shape and position parameters; due to the restriction of measurement efficiency, the contact measurement of the CMM The method is also not applicable; in addition, according to the tolerance of the workpiece, the accuracy of the instruments and equipment used to detect the workpiece is required to be better than ±0.03mm, and the errors of other scanning methods such as articulated arm laser scanning measurement, rotary table scanning measurement method, and 3D scanning method are all greater than ±0.05 mm does not meet the requirements.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: in view of the problems of low detection efficiency and low automation level of the existing workpiece measurement method, the present invention provides an automatic detection system and method for the three-dimensional size of the workpiece based on laser scanning, which improves detection efficiency and automation level.

The technical scheme of the present invention is: an automatic detection system for the three-dimensional size of a workpiece based on laser scanning, the automatic detection system includes a three-dimensional mobile platform, a three-dimensional mobile platform numerical control module, a laser scanning sensor, a laser scanning sensor numerical control module and detection software; wherein:

Three-dimensional mobile platform, including X-axis air-bearing guide, Y-axis air-bearing guide, Z-axis air-bearing guide and displacement platform, the workpiece to be measured is placed on the displacement platform; X-axis air-bearing guide drives the displacement platform along the X-axis of the measurement coordinate system Axial movement; a laser scanning sensor is installed at the end of the Z-axis air-bearing guide rail, and the Y-axis air-bearing guide and Z-axis air-bearing guide drive the laser scanning sensor to move relative to the displacement platform along the Y-axis and Z-axis of the measurement coordinate system;

The CNC module of the three-dimensional mobile platform controls the movement of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide in the three-dimensional direction according to the preset motion trajectory and speed, and obtains the position information of the measured workpiece in real time. To the detection software, each time the workpiece to be tested moves a certain distance, a measurement pulse signal is sent to the CNC module of the laser scanning sensor;

The laser scanning sensor numerical control module, after receiving the measurement pulse signal, generates a collection drive signal and sends it to the laser scanning sensor;

The laser scanning sensor, under the control of the acquisition drive signal, scans the measured workpiece, obtains the distance information from the scanning point on the measured workpiece to the sensor head, and sends it to the detection software;

The detection software is used to set the movement speed of the X-axis air-bearing guide, Y-axis air-bearing guide and Z-axis air-bearing guide of the 3D mobile platform, set the initial position information of the laser scanning sensor probe, and generate the X-axis air-bearing guide, Y-axis air bearing The movement trajectory of the shaft air-bearing guide and the Z-axis air-bearing guide; set the angle information of the laser scanning sensor and send it to the numerical control module of the laser scanning sensor; according to the position information of the measured workpiece and the distance from the scanning point on the measured workpiece to the sensor head information, obtain the 3D coordinate point cloud data of the scanning points on the workpiece under test, and then perform denoising, simplification, and splicing processing on the 3D coordinate point cloud data. Select the point cloud data corresponding to the geometric feature of the workpiece to be measured, and then generate the image of the geometric feature, measure the size of the geometric feature, and then compare the measured size of the geometric feature with the standard size to obtain the shape and position error of the geometric feature of the workpiece. , according to the shape and position error results to judge the qualification of the workpiece to be tested, generate a test report, save and display the test report.

The automatic detection system for the three-dimensional size of the workpiece further includes a laser scanning sensor rotating mechanism;

One end of the rotating mechanism of the laser scanning sensor is connected with the Z-axis air-floating guide rail, and the other end is connected with the laser scanning sensor, which is used to drive the laser scanning sensor to swing in the two directions of the Y-axis and the Z-axis of the measurement coordinate system;

The laser line scan sensor numerical control module is used to realize the motion control of the laser scan sensor rotation mechanism, and to set the deflection angle and speed of the laser scan sensor.

The rotating mechanism of the laser scanning sensor includes an upper column, a servo motor, and a lower column; the upper column is fixedly installed on the air-floating block of the Z-axis air-floating guide along the Z-axis direction, the main body of the servo motor is installed on the upper column, and the rotating shaft of the servo motor Parallel to the X-axis direction of the measurement coordinate system, there is an interference fit between the rotating shaft of the servo motor and the lower column, and the shaft and the upper column are not in contact with each other. The laser line scanning sensor is fixedly connected with the other end of the lower column, and the lower column is rotated by a certain deflection angle under the drive of the servo motor, that is, the laser scanning sensor is driven to deflect together to scan the workpiece at different angles.

The laser scanning sensor is a line scanning sensor.

The laser scanning sensor is a blue laser line scanning sensor.

A grating ruler is installed on the X-axis air-bearing guide, Y-axis air-bearing guide and Z-axis air-bearing guide, respectively, and the three-dimensional mobile platform numerical control module and the grating scale form a closed-loop feedback system: the grating scale is used to measure the three-dimensional direction of the workpiece to be measured. The position information on the 3D mobile platform is fed back to the numerical control module of the three-dimensional mobile platform; the numerical control module of the three-dimensional mobile platform continuously compares the theoretical position of the measured workpiece with the actual measured position of the workpiece fed back by the grating ruler, and adjusts X at any time through the control of PID parameters. The movement of the shaft air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide in the three-dimensional direction.

The detection software includes a data acquisition and processing module, a size measurement and error identification module, and a parameter setting module;

The data acquisition and processing module, according to the movement trajectory of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide, and the distance information from the scanning point on the measured workpiece to the sensor head, obtains the scanning point on the measured workpiece. 3D coordinate point cloud data, and then perform denoising, streamlining, and splicing processing on the 3D coordinate point cloud data of the scanning points on the measured workpiece, and send the processed 3D coordinate point cloud data of the scanning points on the measured workpiece to the size measurement. and error identification module;

The dimension measurement and error recognition module selects the point cloud data corresponding to the geometric features of the measured workpiece according to the drawing files of the measured workpiece, and then generates an image of the geometric feature, measures the size of the geometric feature, and then measures the geometric feature. The size is compared with the standard size to obtain the shape and position error of the geometric features of the workpiece. According to the error result, the qualification of the tested workpiece is judged, and a test report is generated, and the test report is saved and displayed.

Parameter setting module, set the movement speed of the X-axis air-bearing guide, Y-axis air-bearing guide and Z-axis air-bearing guide of the 3D mobile platform, set the initial position information of the laser scanning sensor probe, and generate the X-axis air-bearing guide, Y-axis The motion trajectories of the air-bearing guide rail and the Z-axis air-bearing guide rail are sent to the numerical control module of the 3D mobile platform. Set the angle information of the laser scanning sensor and send it to the numerical control module of the laser scanning sensor.

The laser scanning-based automatic detection system for the three-dimensional size of the workpiece further includes a quality traceability module, which can query the historical detection data of the corresponding detection samples according to the user's needs, and perform statistical analysis on the historical detection data of the detection samples.

Another technical solution of the present invention is: an automatic detection method for the three-dimensional size of a workpiece based on laser scanning, which is characterized by comprising the following steps:

S1, carry out the scanning work of the workpiece, and obtain the multi-layer three-dimensional coordinate point cloud data of the front, back and side of the tested workpiece;

S2: After scanning, the multi-layer three-dimensional coordinate point cloud data of the front, back and side of the workpiece to be tested are denoised, simplified and combined, and finally synthesized into the same coordinate system;

S3: According to the drawing file of the workpiece to be tested, select the point cloud data corresponding to the geometric feature of the workpiece to be tested from the processed 3D coordinate point cloud data, and then generate an image of the geometric feature to measure the size of the geometric feature.

S4: Compare the measured size of the geometric feature with the standard size to obtain the geometrical error of the geometrical feature of the workpiece, judge the eligibility of the tested workpiece according to the result of the geometrical error, generate a test report, save and display the test report.

The specific steps of the step S1 are:

S1.1. Define the processing base surface of the workpiece to be measured as the front of the workpiece to be measured, and use it as the initial surface to be measured. Place the workpiece to be measured on the moving platform, the surface to be measured faces upward, and the laser line scan sensor vertically downward;

S1.2. According to the known size of the measured surface of the workpiece to be measured, set the X-axis air-bearing guide rail, Y-axis air-bearing guide rail movement speed and trajectory of the three-dimensional mobile platform, and the initial position of the laser line scan sensor in the Z-axis direction. Height, the angle of the laser line scan sensor, according to the height range of the laser line scan sensor and the measured surface of the workpiece to be measured, set the number of scanning layers of the measured surface;

S1.3: Place the workpiece to be tested on the displacement platform, the workpiece to be tested performs a reciprocating smooth and uniform motion along the X-axis and the Y-axis relative to the laser line scan sensor, and the laser line scan sensor performs the measurement on the surface of the workpiece to be tested. Uninterrupted scanning until the first layer of the surface to be measured of the workpiece to be measured within the ranging range of the scanning sensor is scanned, and the 3D point cloud data of the first layer of the surface to be measured of the workpiece to be measured is obtained;

S1.4: Control the scanning sensor to move a certain distance in the Z-axis direction according to the height of the workpiece to be measured and the distance measurement range of the laser line scanning sensor, and scan the second layer according to the scanning method in step 2, and repeat the cycle until Obtain the multi-layer 3D point cloud data of the surface to be measured of the workpiece to be measured;

S1.5: Turn the workpiece to be tested by 180°, with the reverse side as the surface to be tested facing up, place the workpiece to be tested on the moving platform, and the laser line scan sensor vertically downward, repeat steps S1.2, S1.3, and S1. 4. Obtain multi-layer 3D point cloud data on the reverse side of the tested workpiece;

S1.6: Control the laser line scanning sensor to deflect a certain angle, scan the side of the workpiece, and obtain multi-layer 3D point cloud data on the side of the workpiece to be tested.

The advantages of the present invention compared with the prior art are:

(1) In the present invention, a numerically controlled three-dimensional moving platform is used to realize the movement of the workpiece to be measured relative to the laser sensor in the X-axis direction, as well as the movement of the laser line scanning sensor in the Y-axis and Z-axis directions, to realize full dynamic measurement , which replaces manual movement detection and improves detection efficiency.

(2) The three-dimensional mobile platform of the present invention adopts the air-floating guide rail to realize three-dimensional movement, realizes the advantages of no friction and no vibration in translational sliding, and achieves the effect of high moving precision. The whole set of three-dimensional mobile platform can control the measurement error within ± within 5μm.

(3) In the present invention, a laser scanning sensor rotating mechanism is installed on the Z-axis air-floating guide rail, which can realize the deflection of the laser scanning sensor and scan the workpiece at different angles.

(4) The present invention adopts a laser scanning sensor, and its measurement method is non-contact measurement. Compared with the traditional contact measurement method, the detection time can be greatly shortened and the detection efficiency can be improved.

(5), the present invention selects blue line scanning laser scanning sensor, which has strong anti-interference ability and high measurement accuracy;

(6) After the detection of the tested sample is completed, the present invention can realize that the detection result of the tested sample is stored in the database server, establish a database, can realize the product quality process traceability and data analysis, and can automatically generate the corresponding tested sample. Sample test report.

(7) The present invention does not need to be reprogrammed for different products, has no workload of repeated programming, is suitable for the detection of workpiece products with less batches, and improves the detection efficiency.

Description of drawings

FIG. 1 is a system block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a detection software module according to an embodiment of the present invention.

FIG. 3 is a three-dimensional effect diagram of an automatic detection system according to an embodiment of the present invention.

FIG. 4 is a three-dimensional effect diagram of a part of the air-floating guide rail according to the embodiment of the present invention.

FIG. 5 is a three-dimensional effect diagram of a rotating column according to an embodiment of the present invention.

FIG. 6 is a flowchart of a data stitching algorithm according to an embodiment of the present invention.

FIG. 7 is a detection flow chart of an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , the present invention provides an automatic detection system for the three-dimensional size of a workpiece based on laser scanning. The system includes a three-dimensional mobile platform, a three-dimensional mobile platform numerical control module, a laser scanning sensor, a laser scanning sensor numerical control module, a laser scanning sensor rotating mechanism 3, a power supply module and detection software. in:

Three-dimensional mobile platform, including X-axis air-bearing guide, Y-axis air-bearing guide, Z-axis air-bearing guide and displacement platform, the workpiece to be measured is placed on the displacement platform; X-axis air-bearing guide drives the displacement platform along the X-axis of the measurement coordinate system Axial movement; a laser scanning sensor is installed at the end of the Z-axis air-bearing guide rail, and the Y-axis air-bearing guide rail and Z-axis air-bearing guide rail drive the laser scanning sensor to move relative to the displacement platform along the Y-axis and Z-axis of the measurement coordinate system.

The CNC module of the three-dimensional mobile platform controls the movement of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide in the three-dimensional direction according to the preset motion trajectory and speed, and obtains the position information of the measured workpiece in real time. To the detection software, every time the workpiece to be tested moves a certain distance, a measurement pulse signal is sent to the CNC module of the laser scanning sensor.

The laser scanning sensor numerical control module, after receiving the measurement pulse signal, generates a collection drive signal and sends it to the laser scanning sensor; realizes the motion control of the laser scanning sensor rotating mechanism 3, and sets the laser scanning sensor deflection angle and speed.

The laser scanning sensor is a blue laser line scanning sensor. The blue laser line scanning sensor scans the measured workpiece under the control of the collected driving signal, and obtains the distance information from the scanning point on the measured workpiece to the sensor head. Sent to inspection software.

One end of the laser scanning sensor rotating mechanism 3 is connected with the Z-axis air-floating guide rail 2, and the other end is connected with the laser scanning sensor, which is used to drive the laser scanning sensor to swing in the two directions of the Y-axis and the Z-axis of the measurement coordinate system;

The detection software is used to set the movement speed of the X-axis air-bearing guide, Y-axis air-bearing guide and Z-axis air-bearing guide of the 3D mobile platform, set the initial position information of the laser scanning sensor probe, and generate the X-axis air-bearing guide, Y-axis air bearing The movement trajectory of the shaft air-bearing guide and the Z-axis air-bearing guide; set the angle information of the laser scanning sensor and send it to the numerical control module of the laser scanning sensor; according to the position information of the measured workpiece and the distance from the scanning point on the measured workpiece to the sensor head information, obtain the 3D coordinate point cloud data of the scanning points on the workpiece under test, and then perform denoising, simplification, and splicing processing on the 3D coordinate point cloud data. Select the point cloud data corresponding to the geometric features of the workpiece to be measured, and then generate an image of the geometric feature, measure the size of the geometric feature, and then compare the measured size of the geometric feature with the standard size (drawing size) to obtain the geometric feature of the workpiece. According to the shape and position error results, the qualification of the tested workpiece is judged, a test report is generated, and the test report is saved and displayed.

The power supply module supplies power for the three-dimensional mobile platform, the numerical control module of the three-dimensional mobile platform, the laser scanning sensor, and the numerical control module of the laser scanning sensor.

The power module includes a switching power supply, a power filter, and a power conversion circuit. Among them, the switching power supply generates the power supply voltage and outputs it to the power supply filter; the power supply filter filters out the interference generated when the switching power supply is turned on or off to make it work normally and stably; the power conversion circuit converts the power supply voltage after filtering out the interference into a three-dimensional mobile platform , 3D mobile platform numerical control module, laser scanning sensor, laser scanning sensor numerical control module, etc.

The X-axis air-bearing guide rail, the Y-axis air-bearing guide rail and the Z-axis air-bearing guide rail have the same structure. As shown in FIG. 4 , the air-bearing guide rail includes an air inlet 8 , a guide rail seat 9 , a guide rail servo motor 10 , a first lead screw support seat 11 and a first lead screw support seat 14 , a precision ball screw 12 , and an air floating block 13 , grating probe 15, grating ruler 16.

The air cylinder 5 injects air into the air float block 13 through the air inlet 8, so that a layer of air film is formed between the air float block 13 and the guide seat 9. The precision ball screw 12 is driven by the guide rail servo motor 10 to rotate, which in turn drives the air flotation block 13 to perform translational movement. Due to the existence of the air film, the air flotation block 13 has no friction and vibration during translation, and has extremely high translation accuracy. The air flotation blocks of the X-axis air flotation guide rail 6 are connected to the displacement platform 22 , and air flotation blocks are installed on the bottom surfaces of both sides of the displacement platform 22 , which can form a layer of air film with the control empty seat platform 7 during the translation process. The air-floating block of the Y-axis air-bearing guide 4 is connected to the guide seat of the Z-axis air-bearing guide 2, and the air-bearing block of the Z-axis air-bearing guide 2 is connected to the laser line scanning sensor rotating mechanism 3, so that the laser line scanning sensor can be positioned on the Y-axis. and Z-axis for high-precision movement in both directions.

A grating ruler, a controller and a motor are respectively installed on the X-axis air-bearing guide rail, Y-axis air-bearing guide rail and Z-axis air-bearing guide rail. The three-dimensional mobile platform numerical control module and the grating ruler form a closed-loop feedback system: Measure the position information of the workpiece in the three-dimensional direction, and feed it back to the numerical control module of the three-dimensional mobile platform; Control, adjust the movement of the X-axis air-bearing guide, Y-axis air-bearing guide and Z-axis air-bearing guide in the three-dimensional direction at any time by controlling the three guide rail servo motors, and try to make the actual position of the movement match the theoretical position required by the computer, improve the control precision.

The laser line scanning sensor rotating mechanism 3 is connected with the air-floating block of the Z-axis air-bearing guide 2, which can realize high-precision movement in the two directions of the Y-axis and the Z-axis; the air-bearing guide cylinder 5 provides a stable air source.

As shown in FIG. 5, the laser scanning sensor rotating mechanism 3 includes an upper column 17, a servo motor 18, and a lower column 23; the upper column 17 is fixedly installed on the air-floating block of the Z-axis air-bearing guide 2 along the Z-axis direction, and the servo The main body of the motor 18 is installed on the upper column 17, the rotating shaft of the servo motor 18 is parallel to the X-axis direction of the measuring coordinate system, the rotating shaft of the servo motor 18 and the lower column are interference fit, and the shaft and the upper column 17 do not contact each other , the laser line scanning sensor 19 is fixedly connected with the other end of the lower column, and the lower column is rotated by a certain deflection angle under the drive of the servo motor 18, that is, the laser scanning sensor 19 is driven to deflect together to scan the workpiece at different angles.

As shown in Figure 2, the detection software includes a data acquisition and processing module, a dimension measurement and error identification module, a parameter setting module, a measuring tool calibration module, and a quality traceability module.

The data acquisition and processing module, according to the movement trajectory of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide, and the distance information from the scanning point on the measured workpiece to the sensor head, obtains the scanning point on the measured workpiece. 3D coordinate point cloud data, and then perform denoising, streamlining, and splicing processing on the 3D coordinate point cloud data of the scanning points on the measured workpiece, and send the processed 3D coordinate point cloud data of the scanning points on the measured workpiece to the size measurement. and error identification module;

The dimension measurement and error recognition module selects the point cloud data corresponding to the geometric features of the workpiece to be measured (for example, circles, steps, straight segments, holes, etc.) The square method or Hough transform method generates an image of a geometric feature (eg, a circle, a line), and measures the size of the geometric feature (eg, the length, width, height of the workpiece, the diameter of the circle on the workpiece, the height of the step, and the hole spacing, etc. ), and then compare the measured size of the geometric feature with the standard size (drawing size) to obtain the shape and position error of the geometric feature of the workpiece, judge the eligibility of the tested workpiece according to the error result, generate a test report, save and display the test report.

The parameter setting module is used to set the movement speed of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide of the 3D mobile platform. Combined with the height characteristics of the workpiece surface topography and the effective range of the probe scanning height, set the laser scanning sensor measurement. The initial position information of the head is used to generate the motion trajectories of the X-axis air-bearing guide, the Y-axis air-bearing guide and the Z-axis air-bearing guide, and send it to the numerical control module of the 3D mobile platform. Set the angle information of the laser scanning sensor and send it to the numerical control module of the laser scanning sensor.

The quality traceability module, according to user needs, saves all measurement data and establishes a database. It can be used to query the historical testing data of the corresponding testing samples; perform statistical analysis on the historical testing data of the testing samples.

The measuring tool calibration module obtains the measured dimensions (including length, width, height, hole diameter, hole spacing, straightness, perpendicularity, etc.) The size (drawing size) is compared to obtain the compensation coefficient, and the size parameters are compensated according to the compensation coefficient. Standard parts are flat plate standard parts and step standard parts.

Based on the above system, the present invention also provides an automatic detection method for the three-dimensional size of a workpiece based on laser scanning, as shown in FIG. 7 , the method includes the following steps:

As shown in Figure 7 is the detection flow of the device of the present invention, and its concrete steps are:

S1: Equipment initialization: Before starting the detection work, prepare for initialization, first power on the device, and then start the 3D mobile platform, the laser line scanning sensor, and the detection software one after another. The detection software performs system self-check and completes the initialization work. After the initialization preparation is completed, start scanning the workpiece, as shown in Figure 3, to obtain the multi-layer 3D coordinate point cloud data of the front, back and side of the tested workpiece:

S1.1. Define the processing base surface of the workpiece to be measured as the front of the workpiece to be measured, and use it as the initial surface to be measured. Place the workpiece to be measured on the moving platform, the surface to be measured faces upward, and the laser line scan sensor vertically downward;

S1.2. According to the known size of the measured surface of the workpiece to be measured, set the X-axis air-bearing guide rail, Y-axis air-bearing guide rail movement speed and trajectory of the three-dimensional mobile platform, and the initial position of the laser line scan sensor in the Z-axis direction. Height, the angle of the laser line scan sensor, according to the height range of the laser line scan sensor and the measured surface of the workpiece to be measured, set the number of scanning layers of the measured surface;

S1.3: Place the workpiece to be tested on the displacement platform, the workpiece to be tested performs a reciprocating smooth and uniform motion along the X-axis and the Y-axis relative to the laser line scan sensor, and the laser line scan sensor performs the measurement on the surface of the workpiece to be tested. Uninterrupted scanning until the first layer of the surface to be measured of the workpiece to be measured within the ranging range of the scanning sensor is scanned, and the 3D point cloud data of the first layer of the surface to be measured of the workpiece to be measured is obtained;

S1.4: Control the scanning sensor to move a certain distance in the Z-axis direction according to the height of the workpiece to be measured and the distance measurement range of the laser line scanning sensor, and scan the second layer according to the scanning method in step 2, and repeat the cycle until Obtain the multi-layer 3D point cloud data of the surface to be measured of the workpiece to be measured;

S1.5: Turn the workpiece to be tested by 180°, with the reverse side as the surface to be tested facing up, place the workpiece to be tested on the moving platform, and the laser line scan sensor vertically downward, repeat steps S1.2, S1.3, and S1. 4. Obtain multi-layer 3D point cloud data on the reverse side of the tested workpiece;

S1.6: Control the laser line scanning sensor to deflect a certain angle, scan the side of the workpiece, and obtain multi-layer 3D point cloud data on the side of the workpiece to be tested;

和点集

i＝0,1,...,N。S2: After scanning, the multi-layer 3D coordinate point cloud data on the front, back and side of the workpiece to be tested are denoised, simplified and combined, and finally synthesized into the same coordinate system. As shown in FIG. 6 , the S2 adopts the following method to combine data. It is assumed that in different viewing angles, the laser line scanning sensor 19 collects two sets of point cloud data, that is, the reference point cloud data and the target point cloud data. Extract the initial corresponding point set, point set μ ^k = {μ ^k }

and point set

i=0,1,...,N.

The spatial coordinate transformation of a point set can be expressed as the following transformation:

μ ^(k+1)' =Rμ ^k+1 +T (1)

where R is the rotation matrix and T is the translation vector.

The two sets of laser data points collectively represent the same part of the environment and are called the common part. The basis of flattening is to obtain the transformation parameters (R, T) (R, T) between the data point sets μ ^(k+1)° and μ ^(k+1) , so that the common difference between the two sets of data point sets and partially overlapped. Expressed as a formula:

com(|μ ^k -μ ^(k+1)' |)=0 (2)

Among them, com(·) represents the operator that takes the common part of the two sets of points, and |·| is the Euclidean distance operator. In general, only some of the two sets of laser data point sets collected by the laser scanning probe from different viewing angles can overlap, so Equation 2 can be written in the following form:

min(|μ ^k -μ ^(k+1)' |)=0 (3)

where min(.) is the minimum operator.

Let {a _i } be the point set selected from μ ^k ={μ ^k }, {b _i } be the point set selected from μ ^k ={μ ^k+1 }, where i=0,1, ...m. Use {a _i } and {b _i } to form a corresponding point set {a _i ,b _i |i=1,2,...m}. Combining equations (1) and (3), and considering all the points in the point set, we get:

The problem of laser data point set registration and splicing under multi-view can be described as: solving the changing parameters R and T, so that the objective evaluation function g(R, T) shown in equation (4) reaches the minimum value. When the rotation matrix R and the translation vector T are solved, the data point sets from different perspectives can be registered in the same spatial coordinate system to complete the stitching of the spatial point cloud data of the three-dimensional model of the workpiece.

S3: According to the drawing file of the workpiece to be tested, select the point cloud data corresponding to the geometric feature of the workpiece to be tested from the processed 3D coordinate point cloud data, and then generate an image of the geometric feature to measure the size of the geometric feature.

S4: Compare the measured size of the geometric feature with the standard size (drawing size) to obtain the shape and position error of the geometric feature of the workpiece, judge the eligibility of the tested workpiece according to the shape and position error result, generate a test report, save and display the test report .

The device of the invention greatly shortens the detection time of a single workpiece, can automatically generate a test result report, and can also establish a workpiece size, shape and position parameter database, which can not only solve the problem of workpiece testing automation, improve testing efficiency and reliability, but also form workpieces. Product quality traceability system and process parameter improvement analysis data

Example:

误差合成后能够优于±0.03mm。In a specific embodiment of the present invention, the laser scanning sensor scans the workpiece to obtain point cloud data including its key dimensions and position parameters, and the measurement error of the three-dimensional mobile platform is controlled within ±5 μm. The measurement error of the selected laser scanning sensor is better than ±0.02mm. The detection software denoises, simplifies, and merges the massive point cloud data obtained by the laser scanning sensor to obtain the key dimensions and position parameters of the workpiece. In the process of data processing, the lack of data, the generation of singular points and other factors will affect the accuracy of the detection results, and the error introduced by data processing is controlled within ±10μm. During the detection process, changes in environmental factors such as temperature, humidity, air pressure, etc. will cause the expansion and contraction of the measured object and the measuring device to be controlled within ±5μm. according to

The error can be better than ±0.03mm after synthesis.

The sampling period of the laser scanning sensor is set to 1000Hz, and the three-dimensional mobile platform moves at a speed of 20mm/s. The length of the scanned workpiece is 500mm, the width is 400mm, the length of the laser line is 15mm, the height of the workpiece is 50mm, and the measuring height range of the sensor is ±8mm. In fact, a total of 2 measurements are required. The time required to switch the position of adjacent laser lines and the time required to adjust the sensor height are not considered. The scan time is calculated as follows:

A single scan requires time t1=500mm÷20mm/s=25s.

According to each adjacent parallel laser line overlapping 2mm, it needs to scan 400mm÷13mm≈31 times.

Then, it takes time t2=t1×31 times=775s to scan a surface of 500mm×400mm.

The total estimated scanning time t3=t2×2 times=1550s≈26min.

Based on the above analysis, the estimated scanning test time for a workpiece product is 30 minutes.

To sum up, the time for the device of the present invention to detect workpieces within the range of 500mm×400mm×50mm in length, width and height is less than 30 minutes, which is (3 to 5) hours compared to manual detection. Greatly improve the detection efficiency.

The parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (10)

1. The utility model provides a three-dimensional size automatic check out system of work piece based on laser scanning which characterized in that: the system comprises a three-dimensional mobile platform, a three-dimensional mobile platform numerical control module, a laser scanning sensor numerical control module and detection software; wherein:

the three-dimensional moving platform comprises an X-axis air-floating guide rail, a Y-axis air-floating guide rail, a Z-axis air-floating guide rail and a displacement platform, and the workpiece to be measured is horizontally placed on the displacement platform; the X-axis air floatation guide rail drives the displacement platform to move along the X-axis direction of the measurement coordinate system; the tail end of the Z-axis air-floating guide rail is provided with a laser scanning sensor, and the Y-axis air-floating guide rail and the Z-axis air-floating guide rail drive the laser scanning sensor to move relative to the displacement platform along the Y-axis direction and the Z-axis direction of the measurement coordinate system;

the three-dimensional moving platform numerical control module controls the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail to move in the three-dimensional direction according to a preset movement track and speed, acquires the position information of the workpiece to be detected in real time and sends the position information to the detection software, and sends a measuring pulse signal to the laser scanning sensor numerical control module when the workpiece to be detected moves for a certain distance;

the laser scanning sensor numerical control module generates an acquisition driving signal after receiving the measurement pulse signal and sends the acquisition driving signal to the laser scanning sensor;

the laser scanning sensor scans the workpiece to be detected under the control of the acquisition driving signal to obtain the distance information from a scanning point on the workpiece to be detected to the sensing head, and sends the distance information to the detection software;

the detection software is used for setting the movement speeds of an X-axis air-floating guide rail, a Y-axis air-floating guide rail and a Z-axis air-floating guide rail of the three-dimensional moving platform, setting initial position information of a measuring head of the laser scanning sensor and generating the movement tracks of the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail; setting angle information of a laser scanning sensor and sending the angle information to a numerical control module of the laser scanning sensor; obtaining three-dimensional coordinate point cloud data of scanning points on a measured workpiece according to position information of the measured workpiece and distance information from the scanning points on the measured workpiece to a sensing head, denoising, simplifying and splicing the three-dimensional coordinate point cloud data, selecting point cloud data corresponding to geometric features of the measured workpiece from the processed three-dimensional coordinate point cloud data according to a drawing file of the measured workpiece, then generating an image of the geometric features, measuring the size of the geometric features, comparing the measured size of the geometric features with a standard size to obtain form and position errors of the geometric features of the workpiece, judging the qualification of the measured workpiece according to the form and position error result, generating a detection report, and storing and displaying the detection report.

2. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 1, characterized in that: the laser scanning sensor rotating mechanism (3) is also included;

one end of a laser scanning sensor rotating mechanism (3) is connected with the Z-axis air-floating guide rail (2), and the other end of the laser scanning sensor rotating mechanism is connected with the laser scanning sensor and is used for driving the laser scanning sensor to swing in two directions of a Y axis and a Z axis of a measurement coordinate system;

and the laser line scanning sensor numerical control module is used for realizing the motion control of the laser scanning sensor rotating mechanism (3) and setting the deflection angle and speed of the laser scanning sensor.

3. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 2, characterized in that: the laser scanning sensor rotating mechanism (3) comprises an upper upright post (17), a servo motor (18) and a lower upright post (23); the upper upright post (17) is fixedly arranged on an air floatation block of the Z-axis air floatation guide rail (2) along the Z-axis direction, a servo motor (18) main body is arranged on the upper upright post (17), a rotating shaft of the servo motor (18) is parallel to the X-axis direction of a measurement coordinate system, the rotating shaft of the servo motor (18) is in interference fit with the lower upright post, and the shaft is not contacted with the upper upright post (17). The laser line scanning sensor (19) is fixedly connected with the other end of the lower upright post, and the lower upright post rotates by a certain deflection angle under the driving of the servo motor (18), namely, the laser line scanning sensor (19) is driven to deflect together, so as to scan workpieces at different angles.

4. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 1 or 2, characterized in that: the laser scanning sensor is a line scanning sensor.

5. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 4, wherein: the laser scanning sensor is a blue laser line scanning sensor.

6. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 1, characterized in that: grating rulers are respectively installed on the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail, and the three-dimensional moving platform numerical control module and the grating rulers form a closed-loop feedback system: the grating ruler is used for measuring the position information of the measured workpiece in the three-dimensional direction and feeding the position information back to the three-dimensional moving platform numerical control module; the three-dimensional moving platform numerical control module continuously compares the theoretical position of the workpiece to be measured with the actual position of the workpiece fed back by the grating ruler, and adjusts the movement of the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail in the three-dimensional direction at any time through the control of PID parameters.

7. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 1, characterized in that: the detection software comprises a data acquisition and processing module, a size measurement and error identification module and a parameter setting module;

the data acquisition and processing module is used for obtaining three-dimensional coordinate point cloud data of scanning points on a measured workpiece according to the movement tracks of the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail and the distance information from the scanning points on the measured workpiece to the sensing head, then carrying out denoising, simplification and splicing processing on the three-dimensional coordinate point cloud data of the scanning points on the measured workpiece, and sending the processed three-dimensional coordinate point cloud data of the scanning points on the measured workpiece to the size measurement and error identification module;

the size measurement and error identification module selects point cloud data corresponding to the geometric features to be measured of the workpiece to be measured according to a drawing file of the workpiece to be measured, then generates an image of the geometric features, measures the sizes of the geometric features, compares the measured sizes of the geometric features with standard sizes to obtain form and position errors of the geometric features of the workpiece, judges the qualification of the workpiece to be measured according to error results, generates a detection report, and stores and displays the detection report.

And the parameter setting module is used for setting the movement speeds of an X-axis air-floating guide rail, a Y-axis air-floating guide rail and a Z-axis air-floating guide rail of the three-dimensional moving platform, setting the initial position information of a measuring head of the laser scanning sensor, generating the movement tracks of the X-axis air-floating guide rail, the Y-axis air-floating guide rail and the Z-axis air-floating guide rail and sending the movement tracks to the numerical control module of the three-dimensional moving platform. And setting angle information of the laser scanning sensor and sending the angle information to the numerical control module of the laser scanning sensor.

8. The automatic detection system for the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 1, characterized in that: the quality tracing module is used for inquiring the historical detection data of the corresponding detection sample according to the user requirement; and carrying out statistical analysis on historical detection data of the detected sample.

9. A method for automatically detecting the three-dimensional size of a workpiece based on laser scanning is characterized by comprising the following steps:

s1, carrying out scanning work on the workpiece to obtain multilayer three-dimensional coordinate point cloud data of the front surface, the back surface and the side surface of the workpiece to be detected;

s2: after scanning, carrying out denoising, simplification and splicing treatment on the multi-layer three-dimensional coordinate point cloud data of the front surface, the back surface and the side surface of the workpiece to be detected, and finally synthesizing the data to be detected in the same coordinate system;

s3: and according to the drawing file of the measured workpiece, selecting point cloud data corresponding to the geometric features of the measured workpiece from the processed three-dimensional coordinate point cloud data, then generating an image of the geometric features, and measuring the size of the geometric features.

S4: and comparing the measured size of the geometric features with the standard size to obtain the form and position errors of the geometric features of the workpiece, judging the qualification of the workpiece to be detected according to the form and position error result, generating a detection report, and storing and displaying the detection report.

10. The method for automatically detecting the three-dimensional size of the workpiece based on the laser scanning as claimed in claim 9, wherein the step S1 comprises the following steps:

s1.1, defining a processing base surface of a workpiece to be detected as the front surface of the workpiece to be detected, taking the processing base surface as an initial surface to be detected, placing the workpiece to be detected on a mobile platform, wherein the surface to be detected is upward, and a laser line scanning sensor is downward vertically;

s1.2, setting the X-axis air-floating guide rail, the Y-axis air-floating guide rail movement speed and movement track of the three-dimensional moving platform, the initial height of the laser line scanning sensor in the Z-axis direction and the angle of the laser line scanning sensor according to the known size of the surface to be measured of the workpiece to be measured, and setting the scanning layer number of the surface to be measured according to the height ranges of the laser line scanning sensor and the surface to be measured of the workpiece to be measured;

s1.3: placing a workpiece to be detected on a displacement platform, wherein the workpiece to be detected alternately performs reciprocating stable uniform motion along an X axis and a Y axis relative to a laser line scanning sensor, and the laser line scanning sensor performs uninterrupted scanning on the surface to be detected of the workpiece to be detected until the first layer of scanning on the surface to be detected of the workpiece to be detected within the range of the scanning sensor is finished, so as to obtain first layer of three-dimensional point cloud data of the surface to be detected of the workpiece to be detected;

s1.4: controlling the scanning sensor to move a certain distance in the Z-axis direction according to the height of the surface to be measured of the measured workpiece and the distance measurement range of the laser line scanning sensor, scanning the second layer according to the scanning method in the step two, and repeating the steps until multilayer three-dimensional point cloud data of the surface to be measured of the measured workpiece are obtained;

s1.5: turning the tested workpiece by 180 degrees, taking the reverse side as the side to be tested to be upward, placing the tested workpiece on a mobile platform, enabling a laser line scanning sensor to be vertical to be downward, repeating the steps S1.2, S1.3 and S1.4, and obtaining multilayer three-dimensional point cloud data of the reverse side of the tested workpiece;

s1.6: and controlling the laser line scanning sensor to deflect by a certain angle, scanning the side surface of the workpiece, and acquiring multilayer three-dimensional point cloud data of the side surface of the workpiece to be detected.

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