A dual-station five-axis mechanism correlation calibration method

Abstract

The application discloses a double-station five-axis mechanism correlation calibration method, solves the calibration problem of the cooperative work of the double-station five-axis mechanism, realizes the accurate correlation of a visual tool and a work tool by establishing a unified base coordinate system and a shared mark point calibration reference, greatly improves the cooperative work precision of the double-station, and has the advantages of simple calibration process and strong operability, does not need complex equipment modification and additional calibration tools, can be completed only by conventional visual calibration and position collection, reduces calibration cost and operation difficulty, and is suitable for various types of tool head combinations and can meet the needs of different process scenes.

Description

Technical Field

[0001] This invention relates to the field of industrial automation control technology, specifically to a method for calibrating a dual-station five-axis mechanism. Background Technology

[0002] A five-axis mechanism generally refers to a mechanical system that enables a tool head or workpiece to move in coordination across five degrees of freedom. It typically includes three linear axes (X-axis, Y-axis, and Z-axis) and two rotary axes (B-axis rotating around the Y-axis and C-axis rotating around the Z-axis). Through the coordinated operation of these five axes, the tool head can perform machining relative to the workpiece from any direction. The tool head is generally fixed to the Z-axis. Different tool heads are used for different workpieces or processes, such as dispensing tool heads, laser tool heads, and inspection tool heads.

[0003] Based on the above structure, in special industry applications, processing the same workpiece may require two different tool heads, such as a 2D vision tool and a working tool. Due to actual situations such as interference or sensor interference, they need to be installed on different Z axes. The 2D vision is used for workpiece positioning or guidance, while the working tool may be a dispensing tool or a laser tool, etc.

[0004] Based on the above, two five-axis mechanisms are generally required to operate. However, in order to ensure the processing technology and equipment utilization rate, the structural design considers adding a set of linear axes (X-axis and Z-axis) to the standard five-axis mechanism to form a seven-axis structure. The two sets of XZ axes and one set of YBC axes are combined in pairs to form two five-axis mechanisms, namely a dual-station five-axis mechanism. The two sets of Z axes meet the needs of two sets of tool installation and multi-process operation, while also improving the equipment utilization rate.

[0005] However, the above dual-station five-axis mechanism will encounter the challenge of how to make the two stations of the two five-axis work together in terms of control. Summary of the Invention

[0006] The purpose of this invention is to provide a method for calibrating a dual-station five-axis mechanism to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for correlation calibration of a dual-station five-axis mechanism, comprising the following steps: Step 1: Model design, determine the axis system composition of the dual-station five-axis mechanism. The mechanism is a seven-axis structure, including X1 axis, Z1 axis, X2 axis, Z2 axis, Y axis, B axis, and C axis. Step 2: Model allocation, combining the X1 axis, Z1 axis with the Y axis, B axis, and C axis to form station 1; Step 3: Model allocation, combining the X2 axis, Z2 axis with the Y axis, B axis, and C axis to form station 2; Step 4: Set the zero point of station 1, adjust the B axis to make the worktable level, and set the joint values ​​of the X1 axis, Z1 axis, Y axis, B axis, and C axis to 0. Step 5: Set the zero point of station 2, keep the worktable level, and set the joint values ​​of X2 axis, Z2 axis, Y axis, B axis and C axis to 0; Step 6: Fix a 2D camera on the Z1 axis as a vision tool ; Step 7: Fix the tool head on the Z2 axis, tool coordinates ; Step 8: Set a mark point on the workbench; Step 9: Set workstation 1 and workstation 2 to share the same base coordinate system (Base); Step 10: Perform 9-point calibration of the 2D camera and vision tool calibration using conventional calibration methods to obtain the position parameters of the vision coordinate system relative to the workstation 1 flange coordinate system; Step 11: Move station 1 to ensure the mark point is clearly imaged within the 2D camera's field of view, and record the flange position of station 1. Parameters, to obtain the position of the mark point in the visual coordinate system. coordinate; Step 12: Using formula ①: Calculate the position coordinates of the mark point in the base coordinate system Base; Step 13: Move station 2 so that the tool head is aligned with the mark point, and record the flange position of station 2. parameter; Step Fourteen: Using Formula ②: To establish the association between the visual tool and the operational tool, formulas ① and ② are combined to achieve dual-station association calibration. The combined formulas are as follows: .

[0008] Furthermore, in step one, the X1 axis and X2 axis are horizontal linear axes, the Z1 axis and Z2 axis are vertical linear axes, the Y axis is a longitudinal linear axis, the B axis is a rotation axis about the Y axis, and the C axis is a rotation axis about the Z axis.

[0009] Furthermore, the 2D camera in step six is ​​used to acquire image information of the mark points and establish a visual coordinate system, and the working tool head in step seven includes any one of a dispensing tool head, a laser tool head, and a detection tool head.

[0010] Furthermore, the mark points in step eight have clear outline features, can be accurately identified by a 2D camera, and can be precisely aligned by the tool head.

[0011] Furthermore, the visual tool calibration in step ten is performed simultaneously with the 9-point calibration, and the calibration results are used to determine the relative positional relationship between the visual coordinate system and the workstation 1 flange coordinate system.

[0012] Furthermore, in step eleven, the position coordinates of the mark point in the visual coordinate system are calculated by an image processing algorithm based on the image captured by the 2D camera.

[0013] Furthermore, formula ① in step twelve is derived based on the coordinate transformation relationship between the visual coordinate system, the workstation 1 flange coordinate system, and the base coordinate system Base, and is used to calculate the absolute position of the mark point in the base coordinate system Base.

[0014] Furthermore, formula ② in step fourteen is derived based on the principle that the position of the mark point remains unchanged in the base coordinate system Base, and is used to establish the positional association between the vision tool at workstation 1 and the operation tool at workstation 2.

[0015] Furthermore, the method can be extended to multi-station five-axis mechanisms. By adding Xn-axis, Zn-axis and Y-axis, B-axis and C-axis to form multiple stations, the multi-station correlation calibration is completed with a unified base coordinate system Base and mark points as the reference.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention solves the calibration challenge of collaborative operation of dual-station five-axis mechanisms. By establishing a unified base coordinate system and shared mark point calibration benchmarks, it achieves precise correlation between vision tools and operational tools, significantly improving the accuracy of collaborative operation between dual stations. The calibration process is simple and highly operable, requiring no complex equipment modifications or additional calibration tools. It can be completed simply through conventional vision calibration and position acquisition, reducing calibration costs and operational difficulty. It is applicable to various tool head combinations, meeting the needs of different process scenarios. It has good scalability, easily extending to multi-station five-axis mechanisms, achieving multi-station collaborative control through the same calibration logic, and providing technical support for the construction of complex automated production lines. Attached Figure Description

[0017] Figure 1 This is a simplified structural diagram of the seven-axis dual-station five-axis mechanism of the present invention; Figure 2 This is a flowchart illustrating the implementation of the dual-station five-axis mechanism correlation calibration method of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-2 This invention provides a method for calibrating a dual-station five-axis mechanism, comprising the following steps: Step 1: Model design, determine the axis system composition of the dual-station five-axis mechanism. The mechanism is a seven-axis structure, specifically including the X1 axis, Z1 axis, X2 axis, Z2 axis, Y axis, B axis, and C axis. Among them, the X1 axis and X2 axis are horizontal linear axes, the Z1 axis and Z2 axis are vertical linear axes, the Y axis is a longitudinal linear axis, the B axis is a rotation axis about the Y axis, and the C axis is a rotation axis about the Z axis. Step 2: Model allocation. Combine the X1 axis, Z1 axis with the Y axis, B axis, and C axis to form the first five-axis mechanism, which is defined as station 1. Station 1 is used to carry vision tools to realize workpiece positioning and guidance. Step 3: Model allocation. Combine the X2 axis, Z2 axis with the Y axis, B axis, and C axis to form a second five-axis mechanism, which is defined as station 2. Station 2 is used to carry the working tools to realize specific processing or inspection operations. Step 4: Set the zero point of station 1, adjust the B axis to keep the worktable horizontal, and then adjust the joint values ​​of the X1 axis, Z1 axis, Y axis, B axis and C axis to 0. At this time, the position of the mechanism is the zero point position of station 1. Step 5: Set the zero point of station 2, keep the worktable horizontal, and adjust the joint values ​​of the X2 axis, Z2 axis, Y axis, B axis, and C axis to 0. At this time, the position of the mechanism is the zero point position of station 2. Step 6: Sensor installation. A 2D camera is fixedly installed on the Z1 axis of station 1 as a vision tool. The 2D camera is used to acquire image information of the calibration reference on the workbench and establish a visual coordinate system; Step 7: Tool head installation. The working tool head is fixedly installed on the Z2 axis of station 2. The working tool head can be selected according to process requirements, such as a dispensing tool head, laser tool head, or inspection tool head. A tool coordinate system is established. ; Step 8: Calibration reference setting. Fix a mark point at any position on the workbench as the calibration reference. The mark point must have clear outline features to ensure that the 2D camera can accurately identify it and the working tool head can be accurately aligned. Step 9: Establish the base coordinate system. Set workstation 1 and workstation 2 to share the same base coordinate system Base. The base coordinate system Base is a unified reference datum for the collaborative work of the two workstations and is used to associate the coordinate systems of the two workstations. Step 10: Vision tool calibration. Perform 9-point calibration on the 2D camera using conventional calibration methods. At the same time, complete the vision tool calibration. This step is used to obtain the positional relationship parameters of the vision coordinate system relative to the flange coordinate system of workstation 1. Step 11: Data Acquisition at Station 1. By controlling the movement of each axis at Station 1, move the 2D camera so that the mark point on the worktable enters the field of view of the 2D camera, and adjust it to a clear imaging state. At this time, record the flange position of Station 1. The parameters are obtained by simultaneously acquiring images of the mark points using a 2D camera and calculating the position of the mark points in the visual coordinate system. coordinate; Step 12: Calculate the base coordinates of the mark point. Based on the positional relationship parameters between the visual coordinate system and the workstation 1 flange coordinate system obtained in Step 10, the workstation 1 flange position parameters recorded in Step 11, and the position coordinates of the mark point in the visual coordinate system, the following formula ① is used: The position coordinates of the mark point in the base coordinate system are calculated as follows: Step 13: Data Acquisition at Station 2. By controlling the movement of each axis at Station 2, move the working tool head until its end is precisely aligned with the same mark point on the worktable. Record the flange position at Station 2 at this time. parameter; Step Fourteen: Dual-station association calculation. Based on the principle that the position coordinates of the mark point in the base coordinate system remain unchanged, the vision tool and the operation tool are associated using the following formula ②: Establish the relationship between the two workstations to enable the vision tool to guide and collaboratively control the work tools. The simultaneous formulas are as follows: .

[0020] Furthermore, the method of the present invention can be extended to multi-station five-axis mechanisms, that is, by adding linear axis groups (Xn axis, Zn axis), and combining them with common Y axis, B axis, and C axis to form multiple five-axis stations, using the same calibration logic, with a unified base coordinate system and mark point as the reference, the association calibration of each station with the reference station is completed in sequence, thereby realizing the collaborative work of multiple stations.

[0021] Example: The dual-station five-axis mechanism used in this embodiment is a seven-axis structure, whose axis system includes X1 axis, Z1 axis, X2 axis, Z2 axis, Y axis, B axis, and C axis. The functional definitions of each axis are as follows: X1 axis and X2 axis: Horizontal (left and right) linear motion axes used to adjust the lateral position of the tool head on the horizontal plane; Z1 axis and Z2 axis: Vertical (up and down) linear motion axes, used to adjust the height of the tool head, and are used to mount vision tools and work tools respectively; Y-axis: Longitudinal (front and back direction) linear motion axis, shared by two workstations, used to adjust the longitudinal position of the worktable or tool head; B-axis: The rotation axis around the Y-axis, used to adjust the tilt angle of the worktable, thereby adjusting the angle between the tool head and the workpiece; C-axis: The rotation axis around the Z-axis, used to realize the rotational movement of the worktable, enabling the workpiece to rotate around the vertical axis and meet the needs of multi-directional operation.

[0022] Before calibration, the motion status of each axis must be checked to ensure that the axis moves smoothly without jamming or offset, and that the positioning accuracy of the axis meets the equipment design requirements.

[0023] Workstation allocation: According to the model allocation scheme of the present invention, the X1 axis, Z1 axis and Y axis, B axis and C axis are combined to form workstation 1. This workstation is mainly used for workpiece positioning and guidance and is equipped with 2D vision tools; the X2 axis, Z2 axis and Y axis, B axis and C axis are combined to form workstation 2. This workstation is mainly used for specific operation execution and is equipped with dispensing tool head.

[0024] Zero point setting for station 1: Start the mechanism control system, control the rotation of the B axis, check the level of the worktable with a level instrument, and adjust the B axis until the worktable is completely level; then control the movement of the X1 axis, Z1 axis, Y axis, B axis, and C axis respectively, and adjust the joint value of each axis to 0. The position of the mechanism at this time is the zero point of station 1. Record the parameters of the zero point position and store them in the control system.

[0025] Zero point setting for station 2: Keep the worktable horizontal and control the movement of the X2, Z2, Y, B, and C axes. Adjust the joint values ​​of each axis to 0. The position of the mechanism at this time is the zero point of station 2. Record the parameters of the zero point position and store them in the control system.

[0026] Vision tool installation: Secure the 2D camera to the flange at the end of the Z1 axis at workstation 1 using bolts, ensuring that the camera lens faces the worktable and is firmly installed without any looseness; connect the camera to the control system, and test the camera's power supply and image transmission functions to ensure that the camera can acquire images normally.

[0027] Installation of the dispensing tool: Fix the dispensing tool head on the flange at the end of the Z2 axis of station 2. Adjust the installation angle of the tool head so that the dispensing port of the tool head faces the worktable surface and is consistent with the lens orientation of the 2D camera. Connect the dispensing tool head to the glue supply system and control system, and test the movement and dispensing functions of the tool head.

[0028] Mark point setting: Select any position in the center area of ​​the workbench and set a circular mark point by laser marking or pasting a calibration sticker. Ensure that the edge of the mark point is clear and burr-free, and that it is firmly fixed on the workbench and not easy to fall off. Adjust the position of the mark point to ensure that it can be fully captured by the 2D camera and can be accurately aligned with the dispensing nozzle of the dispensing tool head.

[0029] Base coordinate system establishment: Create a new coordinate system in the control system, define it as the base coordinate system Base, and set this coordinate system as the unified reference datum for workstation 1 and workstation 2; set the origin of the base coordinate system Base at the geometric center of the worktable, the X-axis is parallel to the X1 and X2 axes, the Y-axis coincides with the Y-axis, and the Z-axis is parallel to the Z1 and Z2 axes. Store the parameters of this coordinate system in the control system.

[0030] Vision tool calibration: Using conventional machine vision calibration methods, a standard 9-point calibration board is placed on the worktable. The X1 and Z1 axes of station 1 are controlled to move, so that the 2D camera sequentially captures the 9 calibration points on the calibration board and collects the image coordinates of each point. The intrinsic and extrinsic parameters of the camera are calculated through the calibration algorithm built into the control system to complete the 9-point calibration. At the same time, based on the calibration results, the positional relationship parameters of the vision coordinate system relative to the flange coordinate system of station 1 are further calculated to complete the vision tool calibration. The calibration parameters are then stored in the control system.

[0031] Data acquisition at station 1: The control system controls the movement of the X1, Z1, and Y axes of station 1 to move the 2D camera so that the mark point enters the camera's field of view; the camera's focal length and exposure parameters are adjusted to make the image of the mark point clear and the edges sharp; at this time, the flange position parameters (X1f, Z1f, Yf, Bf, Cf) of station 1 are recorded, where Bf and Cf are both 0; simultaneously, the image of the mark point is acquired by the camera, and the center coordinates of the mark point are extracted using an image processing algorithm to obtain the position coordinates (Uv, Vv, Wv) of the mark point in the visual coordinate system, where Wv is the distance from the camera lens to the worktable surface, which can be calculated from the position parameters of the Z1 axis.

[0032] Mark point base coordinate calculation: Based on the positional relationship parameters (Tx, Ty, Tz, Rx, Ry, Rz) of the visual coordinate system relative to the workstation 1 flange coordinate system obtained in step four, combined with the workstation 1 flange position parameters (X1f, Z1f, Yf, Bf, Cf) recorded in step five and the mark point's position coordinates (Uv, Vv, Wv) in the visual coordinate system, using formula ①: Perform coordinate transformation to calculate the position coordinates (Xb, Yb, Zb) of the mark point in the base coordinate system Base. Formula ①: Through rigid body transformation, the point coordinates in the visual coordinate system are transformed to the workstation 1 flange coordinate system, and then to the base coordinate system, finally obtaining the absolute position coordinates of the mark point. These coordinates remain unchanged throughout the calibration process.

[0033] Data acquisition at station 2: The X2, Z2, and Y axes of station 2 are controlled by the control system to move the dispensing tool head so that the dispensing nozzle of the tool head is aligned with the center of the mark point. Visual alignment is used, and the alignment can be observed through the 2D camera at station 1. The positions of the X2, Z2, and Y axes are finely adjusted to ensure that the deviation between the dispensing nozzle and the center of the mark point does not exceed 0.01mm. At this time, the flange position parameters (X2f, Z2f, Yf, Bf, Cf) of station 2 are recorded, where Bf and Cf are consistent with those during data acquisition at station 1 (both are 0).

[0034] Dual-station correlation calculation: Based on the principle that the position coordinates (Xb, Yb, Zb) of the mark point in the base coordinate system Base remain unchanged, the correlation relationship between the tool coordinate system of station 2 and the base coordinate system Base is established through formula ②: The relative positional relationship between the visual coordinate system and the tool coordinate system of workstation 2 is calculated to realize the association between the two workstations; Combining formulas ① and ②, we get the following formula: The positional correlation equation between the vision tool at station 1 and the work tool at station 2 can be obtained. This equation can convert the workpiece position information identified by the vision tool into motion commands for the work tool in real time, thereby achieving precise operation under vision guidance.

[0035] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calibrating a dual-station five-axis mechanism, characterized in that: Includes the following steps: Step 1: Model design, determine the axis system composition of the dual-station five-axis mechanism. The mechanism is a seven-axis structure, including X1 axis, Z1 axis, X2 axis, Z2 axis, Y axis, B axis, and C axis. Step 2: Model allocation, combining the X1 axis, Z1 axis with the Y axis, B axis, and C axis to form station 1; Step 3: Model allocation, combining the X2 axis, Z2 axis with the Y axis, B axis, and C axis to form station 2; Step 4: Set the zero point of station 1, adjust the B axis to make the worktable level, and set the joint values ​​of the X1 axis, Z1 axis, Y axis, B axis, and C axis to 0. Step 5: Set the zero point of station 2, keep the worktable level, and set the joint values ​​of X2 axis, Z2 axis, Y axis, B axis and C axis to 0; Step 6: Fix a 2D camera on the Z1 axis as a vision tool ; Step 7: Fix the tool head on the Z2 axis, tool coordinates ; Step 8: Set a mark point on the workbench; Step 9: Set workstation 1 and workstation 2 to share the same base coordinate system (Base); Step 10: Perform 9-point calibration of the 2D camera and vision tool calibration using conventional calibration methods to obtain the position parameters of the vision coordinate system relative to the workstation 1 flange coordinate system; Step 11: Move station 1 to ensure the mark point is clearly imaged within the 2D camera's field of view, and record the flange position of station 1. Parameters, to obtain the position of the mark point in the visual coordinate system. coordinate; Step 12: Using formula ①: Calculate the position coordinates of the mark point in the base coordinate system Base; Step 13: Move station 2 so that the tool head is aligned with the mark point, and record the flange position of station 2. parameter; Step Fourteen: Using Formula ②: To establish the association between the visual tool and the operational tool, formulas ① and ② are combined to achieve dual-station association calibration. The combined formulas are as follows: .

2. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: In step one, the X1 and X2 axes are horizontal linear axes, the Z1 and Z2 axes are vertical linear axes, the Y axis is a longitudinal linear axis, the B axis is a rotation axis about the Y axis, and the C axis is a rotation axis about the Z axis.

3. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: The 2D camera in step six is ​​used to acquire image information of the mark points and establish a visual coordinate system. The working tool head in step seven includes any one of a dispensing tool head, a laser tool head, or a detection tool head.

4. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: The mark points in step eight have clear outline features, can be accurately identified by a 2D camera, and can be precisely aligned by the tool head.

5. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: The visual tool calibration in step ten is performed simultaneously with the 9-point calibration. The calibration results are used to determine the relative positional relationship between the visual coordinate system and the workstation 1 flange coordinate system.

6. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: In step eleven, the position coordinates of the mark point in the visual coordinate system are calculated by an image processing algorithm based on the image captured by the 2D camera.

7. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: Formula ① in step 12 is derived based on the coordinate transformation relationship between the visual coordinate system, the workstation 1 flange coordinate system and the base coordinate system Base, and is used to calculate the absolute position of the mark point in the base coordinate system Base.

8. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: Formula ② in step fourteen is derived based on the principle that the position of the mark point remains unchanged in the base coordinate system Base, and is used to establish the positional association between the vision tool at workstation 1 and the operation tool at workstation 2.

9. The method for correlation calibration of a dual-station five-axis mechanism according to claim 1, characterized in that: The method can be extended to multi-station five-axis mechanisms. By adding Xn axis, Zn axis and Y axis, B axis and C axis to form multiple stations, the multi-station correlation calibration is completed with a unified base coordinate system Base and mark point as the reference.

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