Three-dimensional automatic scanning and measuring device and method for parts

Abstract

The invention discloses a part three-dimensional automatic scanning and measuring device and method. The device comprises a collaborative robot, a multi-line laser scanner, an electric rotary table and an information exchange processing device. The multi-line laser scanner is used for scanning the part to obtain an actual measurement model of the part; the collaborative robot is used for clamping and fixing the multi-line laser scanner; the electric rotary table is used for bearing a tested part and can adjust the rotation angle. The information exchange processing device is used for controlling the multi-line laser scanner, the collaborative robot and the electric turntable to execute a planned scanning path to obtain an actual measurement model, identifying hole features and scanning a missing area, calculating a scanning effective rate and planning a secondary scanning path until the scanning effective rate reaches a set value; the information processing device comprises a coordinate system calibration and conversion module, a coarse scanning path planning module and a secondary fine scanning path module. According to the invention, the rough scanning path and the secondary scanning path can be automatically planned, the automatic scanning efficiency is improved, and the error of manual operation is reduced.

Description

Technical Field

[0001] The invention belongs to the field of automatic control and three-dimensional scanning, and in particular relates to a three-dimensional automatic scanning and measuring device and method for parts. Background Art

[0002] With the development of the manufacturing industry, the requirements for the measurement accuracy, efficiency, stability and field adaptability of geometric measurement equipment are getting higher and higher. As an important link in the digital measurement process of geometric quantities, three-dimensional scanning measurement of parts can provide an effective means to ensure the design and production quality of complex parts and shorten the development cycle. At present, the three-dimensional scanning measurement of most aviation parts is still in a semi-automatic state, using manual selection of scanning points, manual dragging of scanning probes, and manual splicing and processing of point clouds. Due to the complex structure and surface shape of aviation parts, the speed of traditional manual inspection can not keep up with the pace of the automated production line, and the inspectors may feel fatigued due to the cumbersome inspection steps, resulting in large errors in the inspection results. The automatic scanning instruments developed by some foreign companies are expensive, and the key technologies are in a blocked state, and it is impossible to customize personalized scanning solutions according to actual scanning needs. Therefore, the existing three-dimensional scanning technology still cannot meet the expectations of digital measurement and intelligent manufacturing, and an automated three-dimensional scanning measurement device and method is needed. Summary of the invention

[0003] The purpose of the present invention is to provide a three-dimensional automatic scanning and measuring device for parts, which can automatically plan a rough scanning path and a secondary scanning path, improve the efficiency of three-dimensional automatic scanning, and reduce errors caused by human operation.

[0004] In order to achieve the above-mentioned object, one aspect of the present invention provides a three-dimensional automatic scanning and measuring device for parts, including a collaborative robot, a multi-line laser scanner, an electric turntable, and an information exchange processing device;

[0005] The multi-line laser scanner is used to project the projection formed by the cross lines of multiple beams of blue laser onto the measured part, and generate a three-dimensional grid of the part surface by performing signal processing on the area where the cross line projection is projected, so as to obtain a measured model of the part; the collaborative robot has six degrees of freedom, which is used to clamp and fix the multi-line laser scanner; the electric turntable is used to carry the measured part and can adjust the rotation angle;

[0006] The information exchange processing device is used to control the multi-line laser scanner, the collaborative robot and the electric turntable to execute the planned scanning path to obtain the measured model, identify the hole features and the scanned missing area, calculate the scanning efficiency, and plan the secondary scanning path until the scanning efficiency reaches the set value. The information processing device includes a coordinate system calibration and conversion module, a rough scanning path planning module and a secondary fine scanning path module.

[0007] The coordinate system calibration and conversion module is used to calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, unify the three into a global coordinate system, and convert the local coordinate system of the end of the collaborative robot into the global coordinate system, so that the robot can reach the planned scanning viewpoint and maintain the corresponding posture;

[0008] The coarse scanning path planning module is used to establish a part bounding box according to the part theoretical model, calculate the initial scanning viewpoint, connect the viewpoints and plan the path in the global coordinate system to form a coarse scanning path;

[0009] The secondary fine scanning path module is used to analyze the measured model of the part, extract the position and contour of the hole features and the scanned missing area, generate secondary scanning viewpoints, connect the viewpoints and plan the path in the global coordinate system to form a secondary fine scanning path.

[0010] Another aspect of the present invention provides a method for three-dimensional automatic scanning and measuring of parts, using the above-mentioned device to perform three-dimensional automatic scanning and measuring of parts, the method comprising:

[0011] Step S1, calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, unify the three into a global coordinate system, convert the local coordinate system of the end of the collaborative robot into the global coordinate system, and place the part at the center of the electric turntable, with the placement posture consistent with the orientation of the calibrated coordinate system;

[0012] Step S2, establishing a part bounding box according to the part theoretical model, calculating the initial scanning viewpoint, generating a rough scanning path and executing it;

[0013] Step S3, for the measured model obtained by executing the rough scanning path, identifying the holes and the scanned missing areas therein, calculating the corresponding secondary precise scanning viewpoints, generating the secondary scanning path and executing it;

[0014] Step S4, obtaining the measured model obtained by executing the secondary scanning path, and calculating whether its scanning efficiency reaches the set value. If it reaches the set value, the scanning is completed, otherwise step S3 is repeated until the scanning efficiency reaches the set value.

[0015] The three-dimensional automatic scanning and measuring device for parts according to the above aspects of the present invention can automatically plan a rough scanning path and a secondary scanning path, improve the efficiency of three-dimensional automatic scanning, and reduce errors caused by human operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0017] Figure 1 It is a schematic structural diagram of a three-dimensional automatic scanning and measuring device for parts according to an embodiment of the present invention;

[0018] Figure 2 It is a flow chart of a method for automatic three-dimensional scanning and measuring of parts according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] One embodiment of the present invention provides a three-dimensional automatic scanning and measuring device for parts, such as Figure 1 As shown, the three-dimensional automatic scanning and measuring device for parts according to an embodiment of the present invention includes a collaborative robot 1, a multi-line laser scanner 2, an electric turntable 4 and an information exchange processing device.

[0021] The collaborative robot 1 is used to clamp the multi-line laser scanner 2. The collaborative robot 1 has six degrees of freedom. The flange end clamps the multi-line laser scanner 2 through a connecting fixture. The collaborative robot 1 is used to automatically clamp the multi-line laser scanner 2 to complete the scanning path and provide real-time feedback on status and position information.

[0022] The multi-line laser scanner 2 has a multi-line laser emission source and two receiving lenses, which are used to reconstruct the surface mesh information of the part. The multi-line laser emission source can emit three light sources: 26-line cross blue laser, 7-line parallel blue laser and single-line blue laser. It is suitable for high-speed scanning and deep hole scanning, with a large scanning range. At the same time, it has a better scanning effect on metal parts with smooth and reflective surfaces.

[0023] The multi-line laser scanner 2 projects a projection consisting of multiple blue laser cross lines onto the part to be measured. The area irradiated by the cross line projection can generate a three-dimensional grid of the part surface after signal processing, and a comprehensive scan of the part can be achieved by combining the planned path.

[0024] The electric turntable 4 is used to carry the part 3 to be tested, and the rotation angle can be flexibly adjusted to facilitate scanning of the part. By rotating at a specific angle, it cooperates with the collaborative robot 1 to complete the automatic scanning path.

[0025] The information exchange processing device is connected to the multi-line laser scanner 2, the collaborative robot 1 and the electric turntable 4. The information exchange processing device is a computer, etc., which supports the TCP / IP communication protocol and can also be externally connected to the three-dimensional automatic scanning measurement device. The information exchange processing device is used to control the multi-line laser scanner, the collaborative robot and the electric turntable to execute the planned scanning path to obtain the measured model, identify the hole features and the scan missing area, calculate the scanning efficiency, and plan the secondary scanning path until the scanning efficiency reaches the set value.

[0026] The information exchange processing device and the collaborative robot 1 communicate via the EtherNet / IP protocol to transmit control instructions and to call back the status information of the collaborative robot 1; the information exchange processing device and the multi-line laser scanner 2 communicate via the TCP protocol to transmit control instructions and to call back the status information of the multi-line laser scanner 2; the information exchange processing device and the electric turntable 4 are connected via a motion controller, which controls the rotation of the electric turntable 4 by sending pulse signals, and the motion controller is, for example, a stepper motor controller.

[0027] The information exchange processing device includes a coordinate system calibration and conversion module, a coarse scanning path planning module and a secondary fine scanning path module.

[0028] The coordinate system calibration and conversion module is used to calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, and unify the three into a global coordinate system. When calibrating the coordinate system of the collaborative robot 1, the center of the electric turntable 4 is used as the coordinate origin, the vertical upward is the Z axis, the direction pointing to the collaborative robot 1 is the Y axis, and the direction of the X axis is determined according to the right-hand rule. In order to unify the coordinate systems of the robot and the parts, when placing the parts, the origin of the part 3 is placed at the center of the electric turntable 4, and its posture direction is consistent with the calibrated coordinate system.

[0029] The coordinate system calibration and conversion module is also used to convert the local coordinate system of the end of the collaborative robot 1 into a global coordinate system so that the robot reaches the planned scanning viewpoint and maintains the corresponding posture.

[0030] The robot's position and posture are expressed as p(x, y, z, α, β, γ), where the first three components represent the position and the last three components represent the posture. In order for the robot to reach the planned scanning viewpoint and maintain the corresponding posture, it is necessary to calculate the transformation matrix between the local coordinate system and the global coordinate system, and finally calculate the rotation vector. A set of three unit vectors pointing relative to the global coordinate system can form a 3×3 matrix, which is called a rotation matrix and is expressed as follows:

[0031]

[0032] In the formula, (a x , a y , a z ) represents the direction of the X′ axis in the robot coordinate system O′-X′Y′Z′ in the global coordinate system O-XYZ, (b x , b y , b z ) represents the direction of the Y′ axis in the robot coordinate system O′-X′Y′Z′ in the global coordinate system O-XYZ, (c x , c y , c z ) represents the direction of the Z′ axis in the robot coordinate system O′-X′Y′Z′ in the global coordinate system O-XYZ,

[0033] In a collaborative robot, the local coordinate system of its end is Composition, order Then the rotation matrix is:

[0034]

[0035] When β is in the interval (-π / 2, π / 2), the solution is:

[0036] α=Atan2(r 21 , r 11 )

[0037]

[0038] γ=Atan2(r 32 , r 33 )

[0039] When β is in the interval (π / 2, 3π / 2), the solution is:

[0040] α=Atan2(-r 21 , -r 11 )

[0041]

[0042] γ=Atan2(-r 32 , -r 33 )

[0043] If the position coordinates of the scanning viewpoint P are (P x , P y , P z ), then the robot posture is expressed as (P x , P y , Pz , α, β, γ).

[0044] The rough scanning path planning module is used to discretize the 3D grid into a point cloud according to the theoretical model of the part, automatically calculate its bounding box, center of mass, main normal direction and other information, generate scanning viewpoints, connect the viewpoints and plan the path in a unified coordinate system, and send it to the collaborative robot and electric turntable to form a rough scanning path. The rough scanning path planning module includes the analysis of the theoretical model of the part, sampling function, establishment of the part bounding box function, calculation of the scanning viewpoint and generation of the scanning path.

[0045] The secondary fine scanning path module is used to identify the holes and missing areas of the measured model obtained by executing the scanning path and plan the secondary scanning path. Among them, the hole features and the position and contour of the scanned missing area are extracted through the K nearest neighbor point set method, and the secondary scanning viewpoints are generated. The viewpoints are connected and the path in the unified coordinate system is planned and sent to the collaborative robot and the electric turntable to form a secondary fine scanning path.

[0046] In the K nearest neighbor point set method, point pi (i = 1, 2, 3, ..., N) in the input point cloud (measured model) is selected as the center point, and the neighborhood point set is searched to calculate the centroid C i . In general, different point clouds have different scales. In order to ensure that the same number of neighborhood points can be obtained each time, the present invention uses the K nearest neighbor algorithm to obtain the K nearest neighbor point set m of pt. The position vector components of the center of mass in the rectangular coordinate system are as follows:

[0047]

[0048] Where m = ∑m i , the centroid C of each point set can be obtained through the above formula i (x c ,y c , z c ). Then calculate the center point p i Its corresponding centroid C i The distance is calculated and the mean is used as the threshold L for extracting the boundary:

[0049]

[0050] Where N is the number of points in the input point cloud, assuming L i =|p i -c i |, if L i ≥θ*L, then it is considered that p t is a boundary node, and θ is a controllable parameter that can control the number of extracted boundary points, hole features, and scanned missing areas.

[0051] The secondary fine scanning path module also has a scanning efficiency judgment function. By setting the efficiency threshold, it determines whether the measured model obtained by each fine scanning meets the requirements. If not, the function of this module is repeatedly executed until the efficiency of the measured model of the part reaches the set threshold. The measured model can be output for the next step of evaluation.

[0052] The calculation method of scanning efficiency is as follows: respectively calculate the number of points in the theoretical model (theoretical point cloud) and the measured model (measured point cloud), sample the measured model according to the number of points in the theoretical model, and establish a K-dimensional tree to quickly find the points that exist in the theoretical model but not in the measured model, that is, the number of missing points in the measured model. Calculate the ratio of the number of points in the measured model to the number of points in the theoretical model, which is the scanning efficiency, and calculate the ratio of the number of missing points to the total number of points in the measured model, which is the scanning missing rate. The scanning effect is judged by these two indicators.

[0053] The information exchange processing device receives the status information of the collaborative robot 1, the multi-line laser scanner 2 and the electric turntable 4 in real time as a callback signal, coordinates and controls each module according to the callback signal, and finally realizes three-dimensional automatic scanning measurement.

[0054] Another embodiment of the present invention provides a three-dimensional automatic scanning and measuring method for parts, using the three-dimensional automatic scanning and measuring device for parts of the above embodiment to perform three-dimensional automatic scanning and measuring of parts. Figure 2 As shown, the method of the embodiment of the present invention includes the following steps:

[0055] Step S1, calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, unify the three into a global coordinate system, convert the local coordinate system of the end of the collaborative robot into the global coordinate system, and place the part 3 at the center of the electric turntable 4.

[0056] Step S2, establish the part bounding box according to the part theoretical model, calculate the center of mass, main normal direction and other information, obtain the initial scanning viewpoint, generate a rough scanning path, and send it to the collaborative robot 1 and the electric turntable 4 to execute the path,

[0057] Step S3, for the rough scan model obtained by executing the rough scan path, identify the holes and scan-missing areas therein, calculate the corresponding secondary precision scan viewpoints, generate the secondary scan path, and send it to the collaborative robot 1 and the electric turntable 4 to execute the scan path.

[0058] Step S4, obtain the secondary scanning model obtained by executing the secondary scanning path, calculate whether its scanning efficiency reaches the set value, if it reaches the set value, complete the scanning, otherwise repeat step S3 until the scanning efficiency requirement is met, and save the measured model data.

[0059] In one embodiment, before step S1, a communication establishment step is also included, in which the information exchange processing device establishes IP communication with the collaborative robot 1 through a network cable, establishes TCP communication with the multi-line laser scanner 2, and establishes a communication connection with the electric turntable 4 through a motion controller.

[0060] The three-dimensional automatic scanning and measuring device and method of parts according to the embodiment of the present invention have the following beneficial effects:

[0061] The present invention analyzes the theoretical model of the part, automatically plans the rough scanning viewpoint and path, calls the collaborative robot equipped with a multi-line laser scanner to execute the scanning path and measure the part, automatically processes the measured data of the part, automatically identifies the hole features and scanning missing parts on the measured model, plans the secondary scanning viewpoint for fine scanning, calculates the scanning efficiency of the obtained measured model, and realizes automatic planning and execution of the three-dimensional scanning route of the part. The present invention is suitable for smaller parts with sizes between 5×5×5cm and 20×20×20cm, has high practicality on the aviation parts production line, can be used in the measurement and inspection of aviation parts, etc., can improve the automation level of the factory, reduce errors caused by human factors, and improve the production and inspection efficiency of aviation parts.

[0062] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional automatic scanning and measuring device for parts, characterized in that: It includes collaborative robots, multi-line laser scanners, electric turntables, and information exchange processing devices; The multi-line laser scanner is used to project the projection formed by the cross lines of multiple beams of blue laser onto the measured part, and generate a three-dimensional grid of the part surface by performing signal processing on the area where the cross line projection is projected, so as to obtain a measured model of the part; the collaborative robot has six degrees of freedom, which is used to clamp and fix the multi-line laser scanner; the electric turntable is used to carry the measured part and can adjust the rotation angle; The information exchange processing device is used to control the multi-line laser scanner, the collaborative robot and the electric turntable to execute the planned scanning path to obtain the measured model, identify the hole features and the scanned missing area, calculate the scanning efficiency, and plan the secondary scanning path until the scanning efficiency reaches the set value. The information processing device includes a coordinate system calibration and conversion module, a rough scanning path planning module and a secondary fine scanning path module. The coordinate system calibration and conversion module is used to calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, unify the three into a global coordinate system, and convert the local coordinate system of the end of the collaborative robot into the global coordinate system, so that the robot can reach the planned scanning viewpoint and maintain the corresponding posture; The coarse scanning path planning module is used to establish a part bounding box according to the part theoretical model, calculate the initial scanning viewpoint, connect the viewpoints and plan the path in the global coordinate system to form a coarse scanning path; The secondary fine scanning path module is used to analyze the measured model of the part, extract the position and contour of the hole features and the scanned missing area, generate secondary scanning viewpoints, connect the viewpoints and plan the path in the global coordinate system to form a secondary fine scanning path.

2. A three-dimensional automatic scanning and measuring method for parts, characterized in that: The device of claim 1 is used to perform three-dimensional automatic scanning and measurement of parts, the method comprising: Step S1, calibrate the robot coordinate system, the part coordinate system, and the turntable coordinate system, unify the three into a global coordinate system, convert the local coordinate system of the end of the collaborative robot into the global coordinate system, and place the part at the center of the electric turntable, with the placement posture consistent with the orientation of the calibrated coordinate system; Step S2, establishing a part bounding box according to the part theoretical model, calculating the initial scanning viewpoint, generating a rough scanning path and executing it; Step S3, for the measured model obtained by executing the rough scanning path, identifying the holes and the scanned missing areas therein, calculating the corresponding secondary precise scanning viewpoints, generating the secondary scanning path and executing it; Step S4, obtaining the measured model obtained by executing the secondary scanning path, and calculating whether its scanning efficiency reaches the set value. If it reaches the set value, the scanning is completed, otherwise step S3 is repeated until the scanning efficiency reaches the set value.

3. The method according to claim 2, characterized in that In step S4, the scanning efficiency is calculated as follows: The number of points in the theoretical model and the measured model are calculated respectively, and the measured model is sampled according to the number of points in the theoretical model. A K-dimensional tree is established to quickly find the points that exist in the theoretical model but not in the measured model. The ratio of the points in the measured model to the points in the theoretical model is calculated as the scanning efficiency.

4. The method according to claim 2 or 3, characterized in that: In step S3, select point p in the measured model i As the center point, i = 1, 2, 3, ..., N, N is the number of points in the measured model, and the K nearest neighbor algorithm is used to search for p i The neighborhood point set is used to calculate the centroid C i , calculate the center point p i Its corresponding centroid C i The distance is calculated and the mean is used as the threshold L for extracting the boundary: Assume that L i =|p i -c i |, if L i ≥θ*L, then it is considered that p i is a boundary node, and θ is a controllable parameter used to control the number of extracted boundary nodes, hole features, and scanned missing areas.

5. The method according to claim 2 or 3, characterized in that: In step S1, the local coordinate system of the end of the collaborative robot is converted to the global coordinate system as follows: The posture of the collaborative robot is represented by α, β, and γ. When β is in the interval (-π / 2, π / 2), the posture of the collaborative robot is: α=Atan2(r 21 ,r 11 ) γ=Atan2(r 32 ,r 33 ) When β is in the interval (π / 2, 3π / 2), the posture of the collaborative robot is: α=Atan2(-r 21 ,-r 11 ) γ=Atan2(-r 32 ,-r 33 ) Among them, the local coordinate system of the collaborative robot is Composition, order Then the rotation matrix is:

6. The method according to claim 2 or 3, characterized in that: Before step S1, a communication establishment step is also included. In the communication establishment step, the information exchange processing device establishes IP communication with the collaborative robot, TCP communication with the multi-line laser scanner, and communication connection with the electric turntable through the motion controller.

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