A method for mounting and calibrating a lower camera of a five-axis mechanism

Abstract

This invention discloses a method for installing and calibrating a lower camera in a five-axis mechanism, comprising the following steps: installation, lower camera calibration, and real-time tool head error correction. The method provided by this invention solves the installation adaptation problem of adding a new lower camera by rationally designing the installation method, and this installation method ensures a fixed positional relationship between the lower camera and the base coordinate system, providing a foundation for subsequent calibration. Through multi-coordinate system position association and matrix operations based on the same mark point, accurate calibration of the lower camera is achieved. The calibration process is logically rigorous and the steps are clear, ensuring the accuracy of the calibration results.

Description

Technical Field

[0001] This invention relates to the field of industrial automation control technology, specifically to a method for mounting and calibrating a lower camera in a 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 in 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 the five axes, the tool head can perform machining relative to the workpiece from any direction.

[0003] The tool head is fixedly mounted on the Z-axis and used for machining workpieces, such as dispensing tool heads or laser tool heads. In 3C applications, a 2D camera is mounted on the Z-axis for product positioning or auxiliary error compensation functions.

[0004] Based on the above structure, in certain special application scenarios, the tool head may be affected by external forces and other factors, which may cause deformation. Therefore, it is necessary to perform real-time error correction on the tool head. Thus, a new 2D camera will be added to the design to take pictures of the tool head from bottom to top for recognition.

[0005] Based on the above structure, how to install the lower camera, how to calibrate the lower camera, and how to perform real-time error correction of the tool head through the lower camera are the difficult problems that need to be solved in the control. Summary of the Invention

[0006] The purpose of this invention is to provide a method for mounting and calibrating a lower camera in a 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 mounting and calibrating a lower camera in a five-axis mechanism, comprising the following steps: (1) Mounting the upper camera: Fix the upper camera to the Z-axis. The upper camera is vertically downward and can move with the Z-axis; (2) Tool head installation: The tool head is fixed to the Z-axis and can move with the Z-axis; (3) Lower camera installation: Fix the lower camera to the Y-axis. The lower camera is vertically upward and can move with the Y-axis; (4) Based on the five-axis kinematic model, complete the calibration of the upper camera visual center and the tool head Tcp calibration; (5) Calibration plate installation: Select a calibration plate made of transparent material. A mark point is set on the calibration plate. After the calibration plate is installed, the mark point can be clearly imaged in the field of view of the lower camera. (6) Move the X-axis, Y-axis, and Z-axis to make the same mark point from step (5) clearly imaged within the field of view of the upper camera, and obtain the position of the mark point in the upper camera coordinate system. ; (7) Based on the calibration results of step (4), obtain the position of the upper camera coordinate system in the base coordinate system at the current position. ; (8) Assume the relationship between the camera coordinate system and the base coordinate system is as follows: ; (9) Based on the principle of the same mark point, establish the following equation: * = * ; (10) Based on the equation relationship in step (9), calculate the formula = * * ( ) -1 The relationship between the camera coordinate system and the base coordinate system is calculated during calibration. (11) Move the X-axis, Y-axis, and Z-axis to make the tool head clearly imaged within the field of view of the lower camera, and obtain the position of the tool head in the lower camera coordinate system. ; (12) Obtain the current end value of the institution The end value is the Cartesian value for the kinematic control of a five-axis mechanism without any tools; (13) Assume the real-time tool coordinates of the current error-laden toolhead are as follows: ; (14) Establish the equation relationship: * = * ; (15) Based on the equation relationship in step (14), calculate the formula. = ( ) -1 * * The tool coordinates of the tool head are calculated in real time to achieve real-time correction of tool head errors.

[0008] Furthermore, in step (3), after the lower camera is fixed to the Y-axis, the tool head and the lower camera can generate relative motion in the XY direction, and the positional relationship between the origin of the lower camera coordinate system and the origin of the five-axis mechanism base coordinate system remains fixed.

[0009] Furthermore, in step (4), the calibration of the upper camera visual center and the calibration of the tool head Tcp are conventional calibrations in five-axis control and are well-known technologies in the industry.

[0010] Furthermore, in step (5), the transparent material of the calibration plate must meet the optical requirements for clear imaging of the mark points, and the shape and size of the mark points must be adapted to the resolution and field of view of the upper and lower cameras.

[0011] Furthermore, in step (6), by controlling the coordinated movement of the X-axis, Y-axis and Z-axis, the same mark point is clearly imaged in the fields of view of the upper camera and the lower camera respectively, ensuring the accuracy of the mark point position acquisition.

[0012] Furthermore, in step (12), the end value of the mechanism The kinematics data is obtained directly from the kinematic control system of the five-axis mechanism, without the need for additional calculations or measurements.

[0013] Furthermore, in step (11), the tool head is made fully within the clear imaging range of the lower camera through coordinated adjustment of the X-axis, Y-axis, and Z-axis, ensuring the tool head position. The accuracy of the data obtained.

[0014] Furthermore, the camera calibration results It is used to establish equations and calculate accurate tool head coordinates during real-time error correction of tool head.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a method for installing and calibrating the lower camera of a five-axis mechanism. By rationally designing the installation method, it solves the installation adaptation problem of adding a new lower camera, and this installation method ensures a fixed positional relationship between the lower camera and the base coordinate system, providing a foundation for subsequent calibration. Through multi-coordinate system position association and matrix operations based on the same mark point, precise calibration of the lower camera is achieved. The calibration process is logically rigorous and the steps are clear, ensuring the accuracy of the calibration results. Based on the calibration results, a real-time tool head error correction model can be established to quickly calculate the accurate coordinates of the tool head by real-time acquisition of the tool head position and the end effector value of the mechanism, achieving real-time correction of tool head errors. This effectively compensates for errors caused by external force deformation of the tool head, ensuring the machining accuracy and stability of the five-axis mechanism. Attached Figure Description

[0016] Figure 1 This is a simplified structural diagram of the five-axis mechanism of the present invention; Figure 2 This is a diagram showing the coordinate system relationship between the upper and lower cameras in this invention; Figure 3 This is the implementation flow of the lower camera calibration method of the present invention; Figure 4 This is a flowchart illustrating the calibration relationship of the base camera and the implementation of the tool value of the real-time correction tool head according to the present invention. Detailed Implementation

[0017] 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.

[0018] Please see Figures 1-4 This invention provides a method for mounting and calibrating a lower camera using a five-axis mechanism, comprising the following steps: Step 1: Install the upper camera: Select a mounting connector compatible with the Z-axis of the five-axis mechanism. Securely connect the upper camera to the Z-axis using this connector, ensuring the connection is secure. During installation, adjust the angle of the upper camera so that its lens faces vertically downwards. This ensures the upper camera moves synchronously with the Z-axis's lifting motion without shifting or wobbling, meeting subsequent requirements for product positioning and auxiliary error compensation.

[0019] Step 2, Tool Head Installation: Select the appropriate tool head according to the machining requirements. Use a dedicated fixing structure to secure the tool head to the Z-axis. The fixing structure must have sufficient strength and stability to prevent the tool head from shifting due to vibration or external forces during machining. The tool head installation position must maintain a reasonable distance from the upper camera to avoid mutual interference, while ensuring that the tool head can move smoothly with the Z-axis without affecting the normal linkage motion of the five-axis mechanism.

[0020] Step 3: Lower Camera Installation: Select a mounting component compatible with the Y-axis and securely connect the lower camera to the Y-axis. During connection, ensure the lower camera is firmly installed without any looseness. Adjust the mounting orientation of the lower camera so that its lens is vertically upward and that the lower camera moves synchronously with the horizontal movement of the Y-axis. This installation method has two key advantages: First, the tool head moves with the Z-axis, and the lower camera moves with the Y-axis, generating relative motion in the XY directions, facilitating subsequent nine-point calibration of the lower camera. Second, based on the kinematics of the five-axis mechanism, after the lower camera is fixed to the Y-axis, the kinematic relationship between the origin of the lower camera coordinate system and the origin of the five-axis mechanism's base coordinate system remains fixed, which is a crucial foundation for subsequent calibration methods.

[0021] Step 4: Calibration of the upper camera's vision center and the tool head's Tcp: Based on the five-axis kinematic model, the upper camera's vision center and the tool head's Tcp are calibrated using industry-renowned standard calibration methods. This calibration process is a standard operation in five-axis mechanism control. Its purpose is to establish the initial correlation between the upper camera's vision center, the tool head's Tcp, and the base coordinate system, providing basic data support for subsequent lower camera calibration and tool head error correction. The calibration results must be accurately recorded and stored for use in subsequent steps.

[0022] Step 5: Calibration Plate Installation: Select a calibration plate made of transparent material with sufficient transparency. This calibration plate must possess good optical performance to ensure clear imaging of the mark point. Set a clearly visible mark point at the designated location on the calibration plate. The shape and size of the mark point should be designed according to the camera's resolution and field of view to ensure it can be accurately identified by both the upper and lower cameras. Install the calibration plate in a suitable position on the five-axis mechanism, adjusting its attitude and height to ensure the mark point is clearly imaged within the lower camera's field of view, facilitating subsequent acquisition of the mark point's position in the lower camera's coordinate system. .

[0023] Step 6: Imaging the mark point within the upper camera's field of view: Using the five-axis mechanism's control system, move the X, Y, and Z axes respectively to adjust the spatial position of the five-axis mechanism. During this movement, observe the upper camera's image in real time and gradually adjust the movement of each axis until the same mark point set in Step 5 can be clearly imaged within the upper camera's field of view. At this point, obtain the mark point's position coordinates in the upper camera's coordinate system using the upper camera's image acquisition system. And store the location coordinates in the system.

[0024] Step 7: Obtaining the position of the upper camera coordinate system in the base coordinate system: Based on the upper camera visual center calibration results completed in Step 4, directly retrieve the positional relationship of the upper camera coordinate system in the base coordinate system at the current position from the system. This positional relationship is the key correlation data between the upper camera and the base coordinate system, providing the necessary parameters for establishing subsequent equations.

[0025] Step 8, Assumption of the relationship between the lower camera coordinate system and the base coordinate system: Assume the relationship between the lower camera coordinate system and the base coordinate system is as follows. This relationship includes parameters such as translation and rotation, which are data that need to be calculated through calibration later.

[0026] Step 9: Establishing and Implementing Equations: Since the mark point is the same fixed point, its position in different coordinate systems satisfies the kinematic transformation relationship. Therefore, based on the principle of the same mark point, the following equation is established: * = * .

[0027] Step 10: Calculation of the relationship between the lower camera coordinate system and the base coordinate system: Based on the equation established in Step 9, the relationship between the lower camera coordinate system and the base coordinate system is calibrated and calculated. The calculation formula is derived through matrix operations: = * * ( ) -1 The data obtained in steps 6 and 7 , and the information obtained in step 5 Substituting the values ​​into the formula, the relationship between the lower camera coordinate system and the base coordinate system of the five-axis mechanism can be obtained by performing calculations using the control system of the five-axis mechanism or dedicated calculation software. Complete the calibration of the lower camera. The calibration results must be accurately stored for real-time correction of tool head errors in subsequent operations.

[0028] Step 11: Imaging of the tool head within the lower camera's field of view: Using a five-axis control system, the X, Y, and Z axes are moved in a coordinated manner to adjust the spatial position of the tool head. During this movement, the imaging status of the lower camera is monitored in real time, and the movement parameters of each axis are continuously fine-tuned until the tool head can achieve a clear image within the lower camera's field of view. At this point, the position coordinates of the tool head in the lower camera's coordinate system are obtained through the lower camera's image acquisition and processing system. The location coordinates are then transmitted to the control system in real time.

[0029] Step 12, Acquisition of Mechanism End-Point Values: The current mechanism end-point values ​​are directly acquired through the kinematic control system of the five-axis mechanism. This end value is a Cartesian value in the kinematic control of a five-axis mechanism without any tools. It is a direct reflection of the motion state of the five-axis mechanism itself and is a parameter that is known in the industry and can be obtained directly without additional calculation or measurement.

[0030] Step 13, Implement the assumption of tool coordinates with error tool head: Assume that the real-time tool coordinates of the current error tool head are as follows: This coordinate value is the actual coordinate that includes the tool head deformation error, and needs to be accurately calculated through subsequent steps.

[0031] Step 14, Establishing and Implementing the Error Correction Equation: Establish the following equation relationship: * = *

[0032] This equation accurately reflects the relationship between the end effector, the error-laden tool head, the lower camera, and the tool head's position in the camera coordinate system. It is the core equation for achieving tool head error correction.

[0033] Step 15, Implementation of Accurate Tool Head Coordinate Calculation: Based on the equation established in Step 4, and through mathematical methods such as matrix inversion, the formula for calculating the real-time accurate tool head coordinates is derived as follows: = ( ) -1 * * The information obtained in step 11 Step 12 obtained and the results of the lower camera calibration Substituting the values ​​into the formula, the control system performs real-time calculations to obtain the accurate tool coordinates of the tool head. These accurate coordinates are then fed back to the motion control unit of the five-axis mechanism, which corrects the tool head's motion trajectory in real time, thereby achieving real-time correction of tool head errors and ensuring the tool head's machining accuracy.

[0034] 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 mounting and calibrating a lower camera in a five-axis mechanism, characterized in that: Includes the following steps: (1) Mounting the upper camera: Fix the upper camera to the Z-axis. The upper camera is vertically downward and can move with the Z-axis; (2) Tool head installation: The tool head is fixed to the Z-axis and can move with the Z-axis; (3) Lower camera installation: Fix the lower camera to the Y-axis. The lower camera is vertically upward and can move with the Y-axis; (4) Based on the five-axis kinematic model, complete the calibration of the upper camera visual center and the tool head Tcp calibration; (5) Calibration plate installation: Select a calibration plate made of transparent material. A mark point is set on the calibration plate. After the calibration plate is installed, the mark point can be clearly imaged in the field of view of the lower camera. (6) Move the X-axis, Y-axis, and Z-axis to make the same mark point from step (5) clearly imaged within the field of view of the upper camera, and obtain the position of the mark point in the upper camera coordinate system. ; (7) Based on the calibration results of step (4), obtain the position of the upper camera coordinate system in the base coordinate system at the current position. ; (8) Assume the relationship between the camera coordinate system and the base coordinate system is as follows: ; (9) Based on the principle of the same mark point, establish the following equation: * = * ； (10) Based on the equation relationship in step (9), calculate the formula = * * ( ) -1 The relationship between the camera coordinate system and the base coordinate system is calculated during calibration. (11) Move the X-axis, Y-axis, and Z-axis to make the tool head clearly imaged within the field of view of the lower camera, and obtain the position of the tool head in the lower camera coordinate system. ; (12) Obtain the current end value of the institution The end value is the Cartesian value for the kinematic control of a five-axis mechanism without any tools; (13) Assume the real-time tool coordinates of the current error-laden toolhead are as follows: ; (14) Establish the equation relationship: * = * ； (15) Based on the equation relationship in step (14), calculate the formula. = ( ) -1 * * The tool coordinates of the tool head are calculated in real time to achieve real-time correction of tool head errors.

2. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (3), after the lower camera is fixed to the Y-axis, the tool head and the lower camera can generate relative motion in the XY direction, and the positional relationship between the origin of the lower camera coordinate system and the origin of the five-axis mechanism base coordinate system remains fixed.

3. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (4), the calibration of the upper camera visual center and the tool head Tcp calibration are routine calibrations in five-axis control and are well-known technologies in the industry.

4. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (5), the transparent material of the calibration plate must meet the optical requirements for clear imaging of the mark points, and the shape and size of the mark points must be adapted to the resolution and field of view of the upper and lower cameras.

5. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (6), by controlling the coordinated movement of the X-axis, Y-axis and Z-axis, the same mark point is clearly imaged in the fields of view of the upper camera and the lower camera respectively, ensuring the accuracy of the mark point position acquisition.

6. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (12), the end value of the mechanism The kinematics data is obtained directly from the kinematic control system of the five-axis mechanism, without the need for additional calculations or measurements.

7. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: In step (11), the tool head is made fully within the clear imaging range of the lower camera through coordinated adjustment of the X-axis, Y-axis, and Z-axis, ensuring the tool head position. The accuracy of the data obtained.

8. The method for mounting and calibrating a lower camera in a five-axis mechanism according to claim 1, characterized in that: Lower camera calibration results It is used to establish equations and calculate accurate tool head coordinates during real-time error correction of tool head.

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