A high-precision calibration method for an end tool coordinate system of a large-scale water turbine runner chamber robot cladding-milling device

Abstract

The application provides a large water turbine runner chamber robot cladding-milling-grinding device end tool coordinate system high-precision calibration method, which comprises the following steps: moving the robot to an arbitrary position under the tool coordinate system, which is recorded as position A; collecting data points of the plane and the circumference of the sixth shaft flange coordinate system of the robot under position A; collecting data points of the plane and the circumference of the tool coordinate system installed on the robot end flange; moving the robot along the X-axis or the Y-axis of the tool coordinate system under the tool coordinate system, which is recorded as position B; repeating steps S2 and S3, and recording the relevant data of the flange coordinate system and the tool coordinate system under position B; establishing the flange coordinate system and the tool coordinate system in the data analysis software by using the relevant data of the flange coordinate system and the tool coordinate system under positions A and B of the robot; converting the flange coordinate system under position A into a reference coordinate system to obtain a conversion matrix, and the calibration of the robot tool coordinate system is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water turbine robot processing, and particularly relates to a high-precision calibration method for an end tool coordinate system of a large water turbine runner chamber robot cladding-milling device. BACKGROUND

[0002] After a long period of service, a large power generation water turbine runner chamber has a large number of cavitation defects and cracks in the inner wall and the blades. The existing defect repair method is a manual air planing and manual welding and polishing method. However, the repair cycle of the manual repair method is long, and the final polishing repair effect cannot be kept consistent. In the subsequent service process, rust is prone to occur. A large water turbine runner chamber robot cladding-milling device uses a robot to combine multiple processing tools to realize multi-process robot processing process switching, quickly realize water turbine runner chamber robot processing technology, improve the repair processing efficiency of the runner chamber, and reduce the labor input.

[0003] In the additive and subtractive repair process of the water turbine runner chamber, robot polishing, milling, laser cladding and other process procedures are included. Therefore, the robot end flange needs to replace different processing tools. When the robot processing tool is replaced, the tool coordinate system of the robot needs to be recalibrated to ensure the accuracy of the robot processing and the quality of the runner chamber repair. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a high-precision calibration method for an end tool coordinate system of a large water turbine runner chamber robot cladding-milling device. In order to achieve the above object, the present application adopts the following technical scheme:

[0005] A high-precision calibration method for an end tool coordinate system of a large water turbine runner chamber robot cladding-milling device, comprising the following steps:

[0006] S1, a quick change device is installed on the sixth axis flange of the robot for quick replacement of the grinding wheel polishing tool, the electric spindle milling tool and the laser cladding tool. After the robot completes the installation of one of the end tools, the robot is moved to an arbitrary position, which is recorded as position A;

[0007] S2, a laser tracker is erected in the open area in front of the robot, and a sensor probe is used to collect flange plane data in the plane area closely attached to the sixth axis flange, and collect sixth axis flange circumference data in the cylindrical area of the sixth axis flange;

[0008] S3, tool feature points of the three end tools are marked, including the center point of the polishing tool grinding wheel, the center point of the milling tool milling cutter and the nozzle of the laser cladding tool, and the plane data and the circumference data of the center point of each end tool at position A are recorded;

[0009] S4, switch the robot reference coordinate system to the initial tool coordinate system, which is initially defaulted to the flange coordinate system, and move a certain distance along the X axis or Y axis of the robot tool coordinate system in the forward direction, and record the current position of the robot as the B position;

[0010] S5, repeat the operation steps of steps S2 and S3, and record the flange plane, tool center data, and flange circumference of the robot at the B position of the robot, and the circumference data of the tool center;

[0011] S6, data fitting is performed on the robot flange and tool data at the A and B positions of the robot, and the flange coordinate system and the tool coordinate system of the robot at the A and B positions are created, and the center of the projection circumference fitting is further fitted by fitting the projection circumference of the flange cylinder and the tool body cylinder in the plane, and the flange center of the robot at the A and B positions is connected to the center of the projection circumference fitting, and the center of the projection circumference of the flange circumference at the A position is taken as the origin of the flange coordinate system, and the center of the projection circumference of the tool is taken as the origin of the tool coordinate system, and the flange center line at the A and B positions is taken as the positive X axis or positive Y axis of the flange coordinate system, and the tool projection circumference line is taken as the positive X axis or positive Y axis of the tool coordinate system, and the straight line perpendicular to the projection circumference of the robot flange at the A position and the tool circumference plane and passing through the center of the projection circumference is taken as the positive Z axis, and the robot flange coordinate system and the robot tool coordinate system are created respectively;

[0012] S7, the world coordinate system is converted from the laser tracker coordinate system to the robot flange coordinate system, that is, the robot flange coordinate system is taken as the reference coordinate system, and the robot tool coordinate system conversion matrix relative to the robot flange coordinate system can be viewed, and the robot tool coordinate system calibration can be realized through matrix conversion.

[0013] Further, in S1, the quick-change mechanism is tightly attached to the robot sixth-axis flange through the adapter flange, and the adapter flange surface and the robot sixth-axis joint surface are precisely machined to have reliable plane precision.

[0014] Further, the specific implementation process of S2 is as follows:

[0015] S21) After the robot moves to an arbitrary position, a laser tracker is erected, and a data analysis software is opened, and a device is connected in the software, and a sensor probe with a ruby at the top is kept in data communication;

[0016] S22) The ruby probe is used to collect plane point data of the adapter plate tightly attached to the robot sixth-axis tool flange, and at this time, the plane plate data is taken as the plane where the flange coordinate system is located;

[0017] S23) Collect the data points of the sixth axis flange body cylindrical area using the ruby probe, and transmit the data to the data analysis software;

[0018] S24) Project the collected flange cylindrical data and tool body cylindrical data to the respective corresponding reference planes in the data analysis software, respectively fit the data on the planes, create the circumferences and planes, and extract the circumferences and centers.

[0019] Further, in S3, the collected tool coordinate system plane and circumference data include grinding wheel circumference data and wheel plane data, milling tool handle circumference data and tool plane data, and laser cladding tool nozzle plane data and nozzle circumference data, wherein the plane data of the tool contact area is collected with the end tool and the contact area of the finishing plate specimen as the reference object, and the circumference data is collected with the regular cylinder of the tool body.

[0020] Further, the S6 specific implementation process is as follows:

[0021] S61) Fit the collected plane and circumference data at positions A and B respectively, at this time, four plane models and four circumference models on the planes are created;

[0022] S62) Connect the positions of the robot flange circumference center and the tool circumference center at positions A and B;

[0023] S63) Create a straight line through the flange circumference center and perpendicular to the flange plane at robot position A, and mark it as straight line one, and create a straight line through the tool circumference center and perpendicular to the tool auxiliary plane at robot position A, and mark it as straight line two;

[0024] S64) Create a coordinate system in the software, take the flange circumference origin at robot position A as the origin of the flange coordinate system, take the flange circumference center connection line at positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, take straight line one as the Z-axis to create the flange coordinate system, take the robot tool circumference origin at robot position A as the origin of the tool coordinate system, take the tool circumference center connection line at positions A and B as the positive X-axis or positive Y-axis of the tool coordinate system, and take straight line two as the Z-axis to create the tool coordinate system.

[0025] Further, in S6, the robot machining system needs to replace different tools for machining, and the calibration positions of different types of machining tool center points are different. The tool center point of the grinding and polishing type grinding wheel tool is at the center of the grinding wheel, the milling tool is used for milling machining by using the electric spindle, the milling type tool end face center point is defined as the tool coordinate system, the laser is used for robot additive repair machining, and the laser focal point of the laser is defined as the tool coordinate system. After the calibration of the tool center point of the cladding type, the best cladding focal length of the cladding head should be determined in combination with the process, and then the tool coordinate system is translated along the positive Z axis of the coordinate system and recorded as the cladding head tool coordinate system.

[0026] Further, 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, and the collected point data and the created workpiece coordinate system space pose 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, the tool coordinate system is converted relative to the flange coordinate system in the space pose, and then the calibration of the robot tool coordinate system is realized.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The large hydroelectric generator runner chamber in-situ additive and subtractive repair system high-precision calibration method of the present application can realize rapid switching of the robot multi-process machining tool of the large hydroelectric generator runner chamber in-situ additive and subtractive repair system without the need for secondary calibration, improve the machining efficiency and ensure that the machining trajectory is accurately reached. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present application will be further described below in conjunction with the drawings and embodiments:

[0030] Figure 1 is a robot tool coordinate system calibration process schematic diagram of the present application;

[0031] Figure 2 is a robot end flange schematic diagram of the present application;

[0032] Figure 3 is a grinding and polishing type tool coordinate system calibration schematic diagram of the present application;

[0033] Figure 4 is a milling type tool coordinate system calibration schematic diagram of the present application;

[0034] Figure 5 is a laser cladding type tool coordinate system calibration schematic diagram of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the present application will be further described below in conjunction with the drawings and embodiments.

[0036] Referring to FIGS. 1-3, a high-precision calibration method for an end tool coordinate system of a robot cladding-milling device for a large water turbine runner chamber is shown, including the following steps: Figure 1 、 Figure 2 (1) A stable connection quick-change tool flange is designed at the end of the robot to ensure quick replacement of the robot and stable connection of the robot end tool. After the robot completes the installation of the end tool, the robot is moved to an arbitrary position, denoted as position A.

[0037] (2) A laser tracker is erected in the open area in front of the robot, and a data acquisition and analysis software is opened. A high-precision probe with a ruby is used to collect data points on the plane where the sixth-axis flange of the robot is located and the cylindrical body of the sixth-axis flange. The specific steps are as follows:

[0038] 1) After the robot is moved to an arbitrary position, the laser tracker is erected and the data analysis software is opened. In the software, the device is connected with the ruby probe to maintain data communication.

[0039] 2) The ruby probe is used to collect data points on the closely fitted adapter plate connected to the sixth-axis tool flange of the robot. At this time, the plane plate data is taken as the plane where the flange coordinate system is located.

[0040] 3) The ruby probe is used to collect data points on the cylindrical surface of the sixth-axis flange body, and the data is transmitted to the data analysis software.

[0041] In the data analysis software, the collected flange cylindrical data and tool body cylindrical data are projected onto their respective reference planes. The data on the planes are respectively fitted with features to create a circle and extract the circle center.

[0042] (3) The laser tracker and ruby probe are used to collect data on the body cylinder of the robot tool. At the same time, an auxiliary plane is designed on the end face of the tool to ensure that the tool center point, i.e., the TCP, is completely fitted with the auxiliary tool plane, and the plane has high precision. The ruby probe is used to collect point cloud data of the auxiliary plane and transmit it to the data analysis software.

[0043] (4) In the robot teach pendant, the robot reference coordinate system is switched to the tool coordinate system (i.e., the initial flange coordinate system). The robot is controlled to move a certain distance along the positive X-axis or positive Y-axis direction of the tool coordinate system and then stopped, denoted as position B.

[0044]

[0045] ​(5) Reuse laser tracker ruby probe and tool auxiliary tool to collect point position of robot sixth axis flange cylinder data, plane data, end tool cylinder data and auxiliary tool plane data, that is, repeat steps (2) and (3), and group the collected data in the data analysis software.

[0046] (6) In the data analysis software, feature fitting is performed on the robot flange cylinder data, plane data, robot tool aid data and tool auxiliary plane data under positions A and B respectively, and the robot flange coordinate system and the tool coordinate system are created. The specific implementation steps are as follows:

[0047] 1) Feature fitting is performed on the collected plane and circumference data under positions A and B respectively, at which time four plane models and four circumference models on the planes are created.

[0048] 2) The positions of the robot flange circumference center under positions A and B and the positions of the tool circumference center are connected.

[0049] 3) A straight line passing through the flange circumference center and perpendicular to the flange plane is created under the robot position A and is denoted as straight line one, and a straight line passing through the tool circumference center and perpendicular to the tool auxiliary plane is created and is denoted as straight line two.

[0050] 4) In the software, a coordinate system is created, the flange coordinate system origin under the robot position A is taken as the flange coordinate system origin, the flange coordinate system positive X axis or positive Y axis is taken as the flange circumference center connection line under positions A and B, and the flange coordinate system is created with straight line one as the Z axis; the robot tool coordinate system origin under the robot position A is taken as the tool coordinate system origin, the tool coordinate system positive X axis or positive Y axis is taken as the tool circumference center connection line under positions A and B, and the tool coordinate system is created with straight line two as the Z axis.

[0051] 5) Note that different tools are used in the present robot machining system for machining, so the calibration positions of different types of tool center points (TCP) are different. The TCP of the grinding and polishing type grinding wheel tool is at the center of the grinding wheel, as shown in Figure 3 The center point of the end face of the milling type tool is defined as the tool coordinate system (TCP) when the electric spindle and milling cutter are used for milling machining, as shown in Figure 4 The laser focal point of the laser is defined as the tool coordinate system (TCP) when the laser is used for robot additive repair machining, as shown in Figure 5 Therefore, after the tool center point (TCP) of the cladding type is calibrated, the best cladding focal length of the cladding head should be determined in combination with the process, and then the tool coordinate system is translated along the positive Z axis of the coordinate system to obtain the cladding head tool coordinate system.

[0052] (7) all point data in the data analysis software are referenced by the world coordinate system of the laser tracker, thus modifying the reference coordinate system from the laser tracker coordinate system to the flange coordinate system in the software can realize the conversion of the tool coordinate system of the robot calibration relative to the flange coordinate system. The tool coordinate system transformation relative to the flange coordinate system can be checked in the data analysis software.

[0053] The large hydroelectric generating unit runner chamber in-situ additive and subtractive repair system high-precision calibration method can realize quick switching of the robot of the large hydroelectric generating unit runner chamber in-situ additive and subtractive repair system in multiple machining processes without secondary calibration, improves machining efficiency and ensures that the machining track is accurately reached.

[0054] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A high-precision calibration method for the end-effector coordinate system of a robotic cladding-milling device for a large turbine runner, characterized in that, Includes the following steps: S1. Install a quick-change device on the flange of the sixth axis of the robot for quick replacement of grinding wheel 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, which is marked as position A. S2. Set up a laser tracker in an open area in front of the robot, and use the sensor probe to collect flange plane data in the plane area where the flange face of the sixth axis of the robot is tightly fitted, and collect circumferential data of the sixth axis flange in the cylindrical area of ​​the sixth axis flange of the robot. S3. Mark the tool feature points of the three end tools, including the center point of the grinding wheel of the polishing tool, the center point of the milling cutter of the milling tool, and the nozzle of the laser cladding tool. Record the plane data and circumferential 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. The default is the flange coordinate system. Move a certain distance in the positive direction along the X-axis or Y-axis of the robot tool coordinate system and record the robot's current position as position B. S5. Repeat steps S2 and S3 to record the data of the robot's flange plane, tool center, flange circumference, and the circumference of the tool center at position B. S6. Perform data fitting on the robot flange and tool data at robot positions A and B. Create the plane containing the robot flange coordinate system and the robot tool coordinate system at positions A and B respectively. Further fit the projected circumference of the flange cylinder and the tool body cylinder on the plane to create the center of the projected circumference. Connect the centers of the robot flange and the machining tool at positions A and B respectively on the projected circumference. Take the center of the robot flange circumference at position A on the projected circumference as the origin of the flange coordinate system, and take the center of the tool circumference on the projected circumference as the origin of the tool coordinate system. Take the line connecting the centers of the flange at positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, and take the line connecting the projected circumference of the tool as the positive X-axis or positive Y-axis of the tool coordinate system. Take the straight line perpendicular to the plane of the projected circumference of the robot flange at position A and the tool circumference and passing through the center of the projected circumference as the positive Z-axis. Create the robot flange coordinate system and the robot tool coordinate system respectively. S7. Convert the world coordinate system from the laser tracker coordinate system to the robot flange coordinate system. That is, use the robot flange coordinate system as the reference coordinate system. You can then view the robot tool coordinate system transformation matrix relative to the robot flange coordinate system. The robot tool coordinate system can be calibrated through matrix transformation.

2. The high-precision calibration method for the end-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, characterized in that, In S1, the quick-change mechanism is tightly fitted with the sixth axis flange of the robot through the adapter flange, and the surface of the adapter flange and the mating surface of the sixth axis of the robot are reliably precision machined.

3. The high-precision calibration method for the end-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, characterized in that, The specific implementation process of its S2 is as follows: S21) After the robot moves to any position, set up a laser tracker, open the data analysis software, and connect the device to the sensor probe with ruby ​​installed at the top in the software to maintain data communication. S22) Use a ruby ​​probe to collect planar point data on the adapter plate that is tightly fitted to the sixth axis tool flange of the connecting robot. At this time, the planar plate data is used as the plane where the flange coordinate system is located. S23) 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; S24) In the data analysis software, the collected flange cylindrical data and tool body cylindrical data are projected onto their respective reference planes. Feature fitting is performed on the data on the planes to create the circumference and the plane, and the circumference and center are extracted.

4. The high-precision calibration method for the end-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, 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, and the plane data and circumferential data of the laser cladding tool nozzle. The plane data of the tool contact area is collected with the contact area between the end tool and the finished 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-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, characterized in that, The specific implementation process of S6 is as follows: S61) Perform feature fitting on the collected planar and circular data at positions A and B respectively. At this time, four planar models and four circular models on the plane should be created. S62) Connect the center of the robot flange circumference at positions A and B with the center of the tool circumference; S63) A straight line created at position A that passes through the center of the flange circumference and is perpendicular to the flange plane is called line one, and a straight line created at the center of the tool circumference and is perpendicular to the tool auxiliary plane is called line two. S64) Create a coordinate system in the software. Take the origin of the flange circumference under robot position A as the origin of the flange coordinate system, take the line connecting the centers of the flange circumference under positions A and B as the positive X-axis or positive Y-axis of the flange coordinate system, and take line one as the Z-axis to create the flange coordinate system. Take the origin of the robot tool circumference under robot position A as the origin of the tool coordinate system, take the line connecting the centers of the tool circumference under positions A and B as the positive X-axis or positive Y-axis of the tool coordinate system, and take line two as the Z-axis to create the tool coordinate system.

6. The high-precision calibration method for the end-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, characterized in that, In S6, this robotic machining system requires the use of different tools for machining. The center point of different types of machining tools is calibrated differently. For grinding and polishing tools, the tool center point is at the center of the grinding wheel. Milling is performed using an electric spindle and a milling cutter. The center point of the end face of the milling tool is defined as the tool coordinate system. Robotic additive repair machining is performed using a laser. The laser focal point is defined as the tool coordinate system. After the center point of the cladding tool is calibrated, the optimal cladding focal length of the cladding head should be determined in conjunction with the process. Then, the cladding head tool coordinate system is translated along the positive Z-axis of the calibrated tool coordinate system.

7. The high-precision calibration method for the end-effector coordinate system of a large-scale hydro turbine runner robot cladding-milling device according to claim 1, characterized in that, In S7, the original reference coordinate system in the laser tracker's data analysis software is the initial coordinate system of the laser tracker. The collected data at each point and the spatial pose of the created workpiece coordinate system are all established relative to the reference coordinate system. In the data analysis software, the reference coordinate system is transformed from the laser tracker's coordinate system to the created robot flange coordinate system through coordinate system transformation. This achieves the transformation of the tool coordinate system relative to the flange coordinate system in spatial pose, thereby realizing the calibration of the robot tool coordinate system.

Images