Large water turbine runner chamber robot cladding-milling device end tool coordinate system high-precision calibration method

Abstract

The invention provides a high-precision calibration method for a tool coordinate system at the tail end of a robot cladding-milling device for a runner chamber of a large water turbine. The high-precision calibration method comprises the following steps that any position of a mobile robot under the tool coordinate system is marked as a position A; data point collection is conducted on the plane and the circumference where a robot sixth-axis flange coordinate system is located at the position A; data point collection is conducted on the plane and the circumference where a tool coordinate system installed on a flange at the tail end of the robot is located; the mobile robot moves along the X axis or the Y axis of the tool coordinate system under the tool coordinate system and is recorded as a position B; the step S2 and the step S3 are repeated, and related data of the flange coordinate system and the tool coordinate system at the position B are recorded; establishing a flange coordinate system and a tool coordinate system according to related data of the flange coordinate system and the tool coordinate system under the positions A and B of the robot in data analysis software; and the flange coordinate system at the position A is converted into a reference coordinate system, a conversion matrix is obtained, and calibration of the robot tool coordinate system is completed.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic turbine robot processing, and in particular to a high-precision calibration method for a tool coordinate system at the end of a large hydraulic turbine runner chamber robot cladding-milling device. Background Art

[0002] After a long period of service, the runner chamber of a large-scale power generation turbine has a large number of cavitation defects and cracks on the inner wall and blades of the runner chamber. The existing defect repair method is to repair it by manual air planing plus manual welding and grinding. However, the manual repair method has a long initial repair cycle and the final grinding and polishing repair effect cannot maintain good consistency, which is prone to rust during subsequent service. A large-scale turbine runner chamber robot cladding-milling device uses a robot combined with a variety of processing tools to realize multi-process robot processing process switching, quickly realize the turbine runner chamber robot processing technology, improve the runner chamber repair processing efficiency and reduce manpower input.

[0003] The in-situ additive and subtractive material repair process of the turbine runner chamber includes robot grinding, milling, laser cladding and other process steps. Therefore, the robot end flange needs to be replaced with different processing tools. When replacing the robot processing tools, the robot's tool coordinate system needs to be recalibrated to ensure the accuracy of the robot processing and the quality of the runner chamber repair. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a high-precision calibration method for the tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device. In order to achieve the above purpose, the present invention adopts the following technical solutions: A high-precision calibration method for the tool coordinate system of a robot cladding-milling device at the end of a large turbine runner chamber comprises the following steps: S1. Install a quick-change device on the sixth axis flange of the robot for quick replacement of grinding wheel grinding and polishing tools, electric spindle milling tools, and laser cladding tools. After the robot completes the installation of one of the end tools, move the robot to any position recorded as position A; S2. Set up a laser tracker in an open area in front of the robot, use a sensor probe to collect flange plane data in the plane area where the robot's sixth-axis flange surface is tightly fitted, and collect sixth-axis flange circumference data in the robot's sixth-axis flange cylindrical area; S3, marking the tool feature points of the three end tools, including the center point of the grinding wheel of the grinding and polishing tool, the center point of the milling cutter of the milling tool, and the nozzle of the laser cladding tool, and recording the plane data and circumference data of the center point of each end tool at position A; S4, switch the robot reference coordinate system to the initial tool coordinate system, which is initially the flange coordinate system by default, and move a certain distance in the positive direction along the X-axis or Y-axis of the robot tool coordinate system, and record the current position of the robot as position B; S5. Repeat the operation steps of steps S2 and S3 to record the flange plane, tool center data, flange circumference, and tool center circumference data of the robot at position B; S6. Fit the robot flange and tool data at the robot positions A and B, respectively create the planes where the robot flange coordinate system and the robot tool coordinate system are located at the A and B positions, and further fit the projection fitting circle of the flange cylinder and the tool body cylinder on the plane to create the center of the projection circle, connect the centers of the robot flange and the processing tool at the A and B positions on the projection circle fitting, take the center of the robot flange circle at the A position on the projection surface circle as the origin of the flange coordinate system, take the center of the tool circle on the projection surface circle as the origin of the tool coordinate system, take the line connecting the flange centers at the A and B positions as the positive X-axis or positive Y-axis of the flange coordinate system, take the line connecting the tool projection circle as the positive X-axis or positive Y-axis of the tool coordinate system, take the straight line perpendicular to the robot flange projection circle and the tool circle plane at the A position and passing through the center of the projection circle as the positive Z-axis, and respectively create the robot flange coordinate system and the robot tool coordinate system; S7. Convert the world coordinate system from the laser tracker coordinate system to the robot flange coordinate system, that is, take the robot flange coordinate system as the reference coordinate system, and then you can view the robot tool coordinate system conversion matrix relative to the robot flange coordinate system. The robot tool coordinate system calibration can be achieved through matrix conversion.

[0005] Furthermore, in S1, the quick-change mechanism is tightly fitted with the robot's sixth-axis flange through the adapter flange, and the precision of the fine-machined plane between the adapter flange surface and the robot's sixth-axis joint surface is reliable.

[0006] Furthermore, the specific implementation process of S2 is as follows: S21) After the robot moves to any position, set up the laser tracker and open the data analysis software, and connect the device with the sensor probe with the ruby ​​installed on the top to maintain data communication in the software; S22) Use a ruby ​​probe to collect plane point data of the adapter plate that is tightly connected to the robot's sixth-axis tool flange. At this time, the plane plate data is used as the plane where the flange coordinate system is located; S23) using a ruby ​​probe to collect cylindrical surface data points of the cylindrical area of ​​the sixth-axis flange body, and transmitting the data to the data analysis software; S24) In the data analysis software, the collected flange cylindrical data and tool body cylindrical data are projected onto their respective corresponding reference planes, and feature fitting is performed on the data on the planes to create circles and planes and extract the circumference and the center of the circle.

[0007] Furthermore, in S3, the plane and circumferential data of the tool coordinate system collected include the circumferential data and plane data of the grinding wheel, the circumferential data and plane data of the milling tool holder, the nozzle plane data and circumferential data of the laser cladding tool, among which the plane data of the tool contact area is collected with the contact area between the end tool and the fine-machined flat plate specimen as the reference object, and the circumferential data is collected with the regular cylinder of the tool body.

[0008] Furthermore, the specific implementation process of S6 is as follows: S61) Perform feature fitting on the collected plane and circular data at positions A and B respectively. At this time, 4 plane models and circular models on 4 planes should be created; S62) connecting the center position of the robot flange circle at positions A and B with the center position of the tool circle; S63) Create a straight line passing through the center of the circle where the flange circumference is located and perpendicular to the flange plane at the robot A position, record it as straight line 1, and create a straight line passing through the center of the circle where the tool circumference is located and perpendicular to the tool auxiliary plane, record it as straight line 2; S64) Create a coordinate system in the software, with the flange circumference origin at the robot's position A as the flange coordinate system origin, the line connecting the flange circumference centers at positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, and straight line 1 as the Z-axis to create the flange coordinate system. The robot tool circumference origin at the robot's position A is the tool coordinate system origin, the line connecting the tool circumference centers at positions A and B is the positive X-axis or positive Y-axis of the tool coordinate system, and straight line 2 as the Z-axis to create the tool coordinate system.

[0009] Furthermore, in S6, the robot processing system needs to replace different tools for processing, and the calibration positions of the center points of different types of processing tools are different. The tool center point of the grinding wheel tool is at the center of the grinding wheel. The electric spindle and milling cutter are used for milling processing. The center point of the end face of the milling tool is defined as the tool coordinate system. The laser is used for robot additive repair processing, and the laser focal point is defined as the tool coordinate system. After the tool center point of the cladding tool is calibrated, the optimal cladding focal length of the cladding head should be determined in combination with the process, and then it is translated along the positive Z axis of the coordinate system on the calibrated tool coordinate system and recorded as the cladding head tool coordinate system.

[0010] Furthermore, in S7, in the data analysis software of the laser tracker, the original reference coordinate system is the initial coordinate system of the laser tracker. The collected point data and the created workpiece coordinate system spatial posture are established relative to the reference coordinate system. In the data analysis software, the reference coordinate system is converted from the coordinate system of the laser tracker to the created robot flange coordinate system by using the coordinate system conversion method, thereby realizing the conversion of the tool coordinate system in space posture relative to the flange coordinate system, and then realizing the calibration of the robot tool coordinate system.

[0011] Compared with the prior art, the present invention has the following beneficial effects: By adopting the high-precision calibration method of the in-situ additive and subtractive material repair system for the runner chamber of a large hydropower unit of the present invention, it is possible to realize rapid switching of multi-process processing tools of the robot of the in-situ additive and subtractive material repair system for the runner chamber of a large hydropower unit without the need for secondary calibration, thereby improving processing efficiency and ensuring accurate arrival of the processing trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 A schematic diagram of the robot tool coordinate system calibration process of the present invention; Figure 2 is a schematic diagram of the robot end flange of the present invention; Figure 3 It is a schematic diagram of the calibration of the coordinate system of the grinding and polishing tools of the present invention; Figure 4 It is a schematic diagram of the calibration of the coordinate system of the milling tool of the present invention; Figure 5 It is a schematic diagram of the calibration of the coordinate system of the laser cladding tool of the present invention. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0014] Please refer to Figure 1 , Figure 2 As shown, a high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device comprises the following steps: (1) Design a stable connection quick-change tooling flange at the end of the robot to ensure the rapid replacement of the robot and the end tool and the stable connection of the robot end tool. After the robot completes the installation of the end tool, move the robot to any position recorded as position A.

[0015] (2) Set up a laser tracker in an open area in front of the robot and open the data acquisition and analysis software. Use a high-precision probe with a ruby ​​to collect data points on the plane where the robot's sixth-axis flange is located and the cylinder of the robot's sixth-axis flange. The specific steps are as follows: 1) After the robot moves to any position, set up the laser tracker and open the data analysis software. In the software, connect the device and the ruby ​​probe to maintain data communication.

[0016] 2) Use a ruby ​​probe to collect plane point data on the adapter plate that is tightly connected to the robot's sixth-axis tool flange. At this time, the plane plate data is used as the plane where the flange coordinate system is located.

[0017] 3) Use a ruby ​​probe to collect data points on the cylindrical surface of the sixth-axis flange body and transmit the data to the data analysis software.

[0018] In the data analysis software, the collected flange cylindrical data and tool body cylindrical data are projected onto their respective corresponding reference planes, and the data on the planes are fitted with features to create circles and planes and extract the center of the circles.

[0019] (3) The cylindrical data of the robot tool body is collected using a laser tracker and a ruby ​​probe. At the same time, the auxiliary plane of the end tool face is designed to ensure that the plane where the tool center point, i.e., TCP, is located, is completely aligned with the auxiliary tooling plane and that the plane accuracy is high. The ruby ​​probe is used to collect the auxiliary plane point cloud data and transmit it to the data analysis software.

[0020] (4) In the robot teach pendant, switch the robot reference coordinate system to the tool coordinate system (i.e., the initial flange coordinate system), control the robot to move a certain distance along the positive X-axis or positive Y-axis direction of the tool coordinate system, and then stop the robot, which is recorded as position B.

[0021] (5) Re-use the laser tracker ruby ​​probe and tool auxiliary fixture to collect the cylindrical data and plane data of the robot's sixth-axis flange, the cylindrical data of the end tool, and the plane data of the auxiliary fixture, that is, repeat steps (2) and (3), and group the collected data in the data analysis software.

[0022] (6) In the data analysis software, feature fitting is performed on the robot flange cylindrical data, plane data, robot tool assistance data, and tool auxiliary plane data at positions A and B respectively to create the robot flange coordinate system and tool coordinate system. The specific implementation steps are as follows: 1) Perform feature fitting on the collected plane and circular data at positions A and B respectively. At this time, 4 plane models and circular models on 4 planes should be created.

[0023] 2) Draw a line between the center of the robot flange circle and the center of the tool circle at positions A and B.

[0024] 3) At robot position A, create a straight line passing through the center of the flange circumference and perpendicular to the flange plane, which is called Line 1; create a straight line passing through the center of the tool circumference and perpendicular to the tool auxiliary plane, which is called Line 2. 4) Create a coordinate system in the software, with the flange circumference origin at the robot's position A as the flange coordinate system origin, the line connecting the flange circumference centers at positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, and straight line 1 as the Z-axis to create the flange coordinate system; with the robot tool circumference origin at the robot's position A as the tool coordinate system origin, the line connecting the tool circumference centers at positions A and B as the positive X-axis or positive Y-axis of the tool coordinate system, and straight line 2 as the Z-axis to create the tool coordinate system.

[0025] 5) Note that this robot processing system uses different tools for processing, so the calibration position of the center point, TCP, of different types of processing tools is different. The TCP of grinding and polishing wheel tools is at the center of the grinding wheel, such as Figure 3 The electric spindle and milling cutter are used for milling processing, and the center point of the end face of the milling tool is defined as the tool coordinate system (TCP), as shown in Figure 4 When using laser for robot additive repair processing, the laser focal point is defined as the tool coordinate system (TCP), as shown in Figure 5 Therefore, after the tool center point of the cladding type, namely TCP, is calibrated, the optimal cladding focal length of the cladding head should be determined in combination with the process, and then the calibrated tool coordinate system should be translated along the positive Z axis of the coordinate system to be recorded as the cladding head tool coordinate system.

[0026] (7) In the data analysis software, all point data are referenced by the world coordinate system of the laser tracker. Therefore, by changing the reference coordinate system from the laser tracker coordinate system to the flange coordinate system in the software, the tool coordinate system of the robot calibration can be transformed relative to the flange coordinate system. The tool coordinate system transformation relationship relative to the flange coordinate system can be viewed in the data analysis software.

[0027] By adopting the high-precision calibration method of the in-situ additive and subtractive material repair system for the runner chamber of a large hydropower unit of the present invention, it is possible to realize rapid switching of multi-process processing tools of the robot of the in-situ additive and subtractive material repair system for the runner chamber of a large hydropower unit without the need for secondary calibration, thereby improving processing efficiency and ensuring accurate arrival of the processing trajectory.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A high-precision calibration method for the tool coordinate system of a robot cladding-milling device for a large turbine runner chamber, characterized in that: The following steps are involved: S1. Install a quick-change device on the sixth axis flange of the robot for quick replacement of grinding wheel grinding and polishing tools, electric spindle milling tools, and laser cladding tools. After the robot completes the installation of one of the end tools, move the robot to any position recorded as position A; S2. Set up a laser tracker in an open area in front of the robot, use a sensor probe to collect flange plane data in the plane area where the robot's sixth-axis flange surface is tightly fitted, and collect sixth-axis flange circumference data in the robot's sixth-axis flange cylindrical area; S3, marking the tool feature points of the three end tools, including the center point of the grinding wheel of the grinding and polishing tool, the center point of the milling cutter of the milling tool, and the nozzle of the laser cladding tool, and recording the plane data and circumference data of the center point of each end tool at position A; S4, switch the robot reference coordinate system to the initial tool coordinate system, which is initially the flange coordinate system by default, and move a certain distance in the positive direction along the X-axis or Y-axis of the robot tool coordinate system, and record the current position of the robot as position B; S5. Repeat the operation steps of steps S2 and S3 to record the flange plane, tool center data, flange circumference, and tool center circumference data of the robot at position B; S6. Fit the robot flange and tool data at the robot positions A and B, respectively create the planes where the robot flange coordinate system and the robot tool coordinate system are located at the A and B positions, and further fit the projection fitting circle of the flange cylinder and the tool body cylinder on the plane to create the center of the projection circle, connect the centers of the robot flange and the processing tool at the A and B positions on the projection circle fitting, take the center of the robot flange circle at the A position on the projection surface circle as the origin of the flange coordinate system, take the center of the tool circle on the projection surface circle as the origin of the tool coordinate system, take the line connecting the flange centers at the A and B positions as the positive X-axis or positive Y-axis of the flange coordinate system, take the line connecting the tool projection circle as the positive X-axis or positive Y-axis of the tool coordinate system, take the straight line perpendicular to the robot flange projection circle and the tool circle plane at the A position and passing through the center of the projection circle as the positive Z-axis, and respectively create the robot flange coordinate system and the robot tool coordinate system; S7. Convert the world coordinate system from the laser tracker coordinate system to the robot flange coordinate system, that is, take the robot flange coordinate system as the reference coordinate system, and then you can view the robot tool coordinate system conversion matrix relative to the robot flange coordinate system. The robot tool coordinate system calibration can be achieved through matrix conversion.

2. According to claim 1, a high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device is characterized in that: In S1, the quick-change mechanism is tightly fitted with the robot's sixth-axis flange through the adapter flange, and the precision of the fine-machined plane between the adapter flange surface and the robot's sixth-axis joint surface is reliable.

3. According to claim 1, a high-precision calibration method for the end tool coordinate system of a robot cladding-milling device for a large turbine runner chamber, characterized in that: The specific implementation process of S2 is as follows: S21) After the robot moves to any position, set up the laser tracker and open the data analysis software, and connect the device with the sensor probe with the ruby ​​installed on the top to maintain data communication in the software; S22) Use a ruby ​​probe to collect plane point data of the adapter plate that is tightly connected to the robot's sixth-axis tool flange. At this time, the plane plate data is used as the plane where the flange coordinate system is located; S23) using a ruby ​​probe to collect cylindrical surface data points of the cylindrical area of ​​the sixth-axis flange body, and transmitting the data to the data analysis software; S24) In the data analysis software, the collected flange cylindrical data and tool body cylindrical data are projected onto their respective corresponding reference planes, and feature fitting is performed on the data on the planes to create circles and planes and extract the circumference and the center of the circle.

4. According to claim 1, a high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device is characterized in that: In S3, the collected plane and circumferential data of the tool coordinate system include the circumferential data and plane data of the grinding wheel, the circumferential data and plane data of the milling tool holder, the nozzle plane data and circumferential data of the laser cladding tool, among which the plane data of the tool contact area is collected with the contact area between the end tool and the fine-machined flat plate specimen as the reference object, and the circumferential data is collected with the regular cylinder of the tool body.

5. The high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device according to claim 1 is characterized in that: The specific implementation process of S6 is as follows: S61) Perform feature fitting on the collected plane and circular data at positions A and B respectively. At this time, 4 plane models and circular models on 4 planes should be created; S62) connecting the center position of the robot flange circle at positions A and B with the center position of the tool circle; S63) Create a straight line passing through the center of the circle where the flange circumference is located and perpendicular to the flange plane at the robot A position, record it as straight line 1, and create a straight line passing through the center of the circle where the tool circumference is located and perpendicular to the tool auxiliary plane, record it as straight line 2; S64) Create a coordinate system in the software, with the flange circumference origin at the robot's position A as the flange coordinate system origin, the line connecting the flange circumference centers at positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, and straight line 1 as the Z-axis to create the flange coordinate system. The robot tool circumference origin at the robot's position A is the tool coordinate system origin, the line connecting the tool circumference centers at positions A and B is the positive X-axis or positive Y-axis of the tool coordinate system, and straight line 2 as the Z-axis to create the tool coordinate system.

6. The high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device according to claim 1 is characterized in that: In S6, the robot processing system needs to replace different tools for processing, and the calibration positions of the center points of different types of processing tools are different. The tool center point of the grinding wheel tool is at the center of the grinding wheel. The electric spindle and milling cutter are used for milling processing. The center point of the end face of the milling tool is defined as the tool coordinate system. The laser is used for robot additive repair processing, and the laser focal point is defined as the tool coordinate system. After the tool center point of the cladding tool is calibrated, the optimal cladding focal length of the cladding head should be determined in combination with the process, and then it is translated along the positive Z axis of the coordinate system on the calibrated tool coordinate system and recorded as the cladding head tool coordinate system.

7. The high-precision calibration method for the end tool coordinate system of a large-scale turbine runner chamber robot cladding-milling device according to claim 1 is characterized in that: In S7, in the data analysis software of the laser tracker, the original reference coordinate system is the initial coordinate system of the laser tracker. The collected point data and the created workpiece coordinate system spatial posture are established relative to the reference coordinate system. In the data analysis software, the reference coordinate system is converted from the coordinate system of the laser tracker to the created robot flange coordinate system by using the coordinate system conversion method, so as to realize the conversion of the tool coordinate system in space posture relative to the flange coordinate system, and then realize the calibration of the robot tool coordinate system.

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