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CN-122007733-A - Method for calibrating coordinate system of circular tube intersecting line weld joint

CN122007733ACN 122007733 ACN122007733 ACN 122007733ACN-122007733-A

Abstract

The invention relates to the technical field of intersecting line track calibration, in particular to a round tube intersecting line weld coordinate system calibration method which comprises the steps of establishing an intersecting line track mathematical model, determining the coordinate relation of intersecting lines under a main pipe coordinate system and a branch pipe coordinate system, adopting an antisymmetric matrix to express a gesture matrix based on the transformation relation of a robot base coordinate system and the main pipe coordinate system, establishing a calibration constraint equation for eliminating translation vectors, randomly selecting 3 teaching points on an intersecting line track, substituting coordinates of the teaching points under the two coordinate systems into the constraint equation, solving to obtain the gesture matrix and the translation vectors, completing the solving of a conversion matrix, and realizing the calibration of the main pipe coordinate system. The invention can complete calibration by only 3 arbitrary teaching points without auxiliary equipment, is suitable for the full-class intersecting line model, has the advantages of simple operation, high efficiency, high precision and wide application range, and can provide accurate coordinate system conversion basis for track planning and interpolation calculation of scenes such as robot intersecting line welding, cutting and the like.

Inventors

  • Su Fangyin
  • FENG LIANGYOU
  • YUAN YE

Assignees

  • 无锡信捷电气股份有限公司

Dates

Publication Date
20260512
Application Date
20260213

Claims (10)

  1. 1. The method for calibrating the coordinate system of the intersecting line weld joint of the circular tube is characterized by comprising the following steps of: Establishing an intersecting line track mathematical model in a fixed coordinate system mode, wherein the coordinate system comprises a main pipe coordinate system { U } and a branch pipe coordinate system { W }, a main pipe is a pipe which is penetrated, and a branch pipe is a pipe which is penetrated; step (2), establishing a calibration constraint equation according to the transformation relation between a robot base coordinate system { B } and the main pipe coordinate system { U }, wherein the transformation relation meets the following formula; , Wherein, the Is the point location under the base mark system, Is the point location under the dominant coordinate system, In order to transform the matrix, In the form of a matrix of gestures, For translation vector, the gesture matrix is expressed by adopting an antisymmetric matrix S ; Randomly selecting at least 3 points on the intersecting line track for teaching, substituting coordinate values of the obtained points into the calibration constraint equation, and solving to obtain a posture matrix Then the gesture matrix is used Substituting back into the transformation relation formula to obtain translation vector Completing the conversion matrix And (3) the calibration of the main pipe coordinate system { U } is realized.
  2. 2. The method for calibrating a coordinate system of an intersecting line weld of a round tube according to claim 1, wherein in the step (1), any point on the intersecting line is identified Coordinates in the branch coordinate system { W } are: , Wherein, the For the radius of the branch pipe, Is an intersecting line at Projection point and origin point on plane Is a connecting line segment of (a) The included angle formed by the coordinate axes is, Is that Point-in-branch coordinate system Coordinate values on the axis.
  3. 3. The method for calibrating a coordinate system of a circular tube intersecting line weld according to claim 2, wherein in the step (1), The coordinates of the point in the main pipe coordinate system { U } are: , Wherein: , Is the radius of the main pipe, Is offset distance.
  4. 4. A method of calibrating a coordinate system of a tubular intersecting line weld according to claim 3, wherein in step (1), the transformation matrix between the main coordinate system { U } and the branch coordinate system { W } is: , wherein beta is the deflection angle.
  5. 5. The method of calibrating a coordinate system of a weld joint on an intersecting line of a round tube according to claim 4, wherein in the step (1), a parameter equation of the intersecting line under the main tube coordinate system { U } is: , The parameter equation is calculated by Solving to obtain Substituting into coordinate system transformation matrix and branch pipe coordinate system The product expression of the point coordinates is deduced.
  6. 6. The method for calibrating a coordinate system of a tubular intersecting line weld according to claim 1, wherein in step (2), the antisymmetric matrix is The expression of (2) is: , Gesture matrix By passing through Calculated, wherein Is a matrix of units which is a matrix of units, 、 、 Is a gesture matrix Is a function of the number of parameters.
  7. 7. The method of claim 6, wherein in step (2), the calibration constraint equation cancels the translation vector by adding point pairs and making differences The post-derivation results are specifically: , Wherein, the Is the point location coordinate under the robot base standard system, Is the point location coordinates in the master coordinate system, =1,2。
  8. 8. The method for calibrating a coordinate system of a circular tube intersecting line weld according to claim 1, wherein in the step (3), the selected 3 teaching points are distributed on the intersecting line trajectory in a dispersed manner, and the positions of the teaching points are not particularly limited.
  9. 9. The method of claim 1, wherein the intersecting line comprises four models of orthogonal, diagonal, orthogonal offset and diagonal offset.
  10. 10. The method for calibrating a coordinate system of a circular tube intersecting line weld according to any one of claims 1-9, wherein the calibrating method is used in a robot intersecting line welding or cutting scene to provide a coordinate system conversion basis for track planning and interpolation calculation.

Description

Method for calibrating coordinate system of circular tube intersecting line weld joint Technical Field The invention relates to the technical field of intersecting line track calibration, in particular to a round tube intersecting line weld coordinate system calibration method which is suitable for scenes needing track planning, such as robot intersecting line welding, cutting and the like. Background The space curve formed by intersecting two circular tubes is called intersecting line, and according to the relative position relationship of the two circular tubes, the intersecting line is mainly divided into four models of orthogonality, skew, orthogonal offset and skew offset, as shown in fig. 1. In the robot intersecting line trajectory motion scenario, the robot tip or the clamping tool needs to move along the intersecting line trajectory to complete the welding or cutting operation. In the process of performing the trajectory planning and interpolation calculation of the trajectory, in view of modeling characteristics of the intersecting line, the bottom layer algorithm of the controller is usually required to be performed under a main pipe (circular pipe with a larger radius) coordinate system, and the robot programming teaching point is often located in a robot base frame or other coordinate systems, as shown in fig. 2, so that point coordinates under the robot base frame or other coordinate systems must be converted into the main pipe coordinate system, and then subsequent speed planning and trajectory interpolation calculation are performed. In the coordinate conversion process, a conversion matrix (i.e., a transformation relationship) between the robot base standard system and the main pipe coordinate system is of great importance, and how to accurately and efficiently obtain the conversion matrix is a key technical problem in the field. There are several schemes for obtaining the transformation matrix in the prior art, but all have obvious drawbacks: 1. Patent CN114260625A discloses a welding method, welding equipment and storage medium for intersecting line of round tube, in which the method scans the contour of workpiece by laser sensor to obtain contour feature point, and fits the common vertical line of round tube axis and two tube axes according to the feature point, and further calibrates the relationship between the intersecting line coordinate system and the user coordinate system of welding equipment. But this scheme adopts plane ellipse fitting mode, and at least 5 points are needed to fit an ellipse, and a pipe needs two ellipses, and four ellipses in total need fit calculation, and required teaching point is too many, and complex operation and inefficiency. 2. Patent CN102069267a discloses a general arc welding robot teaching method for cylindrical intersecting line weld, which can be applied to all kinds of intersecting lines, and establishes a pose matrix of a workpiece coordinate system relative to a robot base coordinate system by teaching four feature points on a workpiece on line. However, the teaching mode of four feature points is not specifically described in the scheme, and from the view of the drawing, the four feature points comprise two points which are symmetrical on the branch pipe and parallel to the main pipe axis and two points which are parallel to the axis on the branch pipe, and precise teaching of the four points is difficult to realize in practical operation. 3. The paper 'automatic welding model and simulation of a main pipe rotary intersecting curve' proposes that the relation between a world coordinate system and a main pipe coordinate system is determined by rotating a main pipe by a certain angle, but the scheme requires the main pipe equipment to rotate, the welding point is always at the highest point of an arc, the application scene is limited, and most of the operation demands in the prior art cannot be met. 4. The journal literature 'three-coordinate measuring method of cylinder basic parameters' discloses a method for solving the axial direction, the position and the radius of a cylinder according to any group of discrete measuring points on the cylinder, and the proposal adopts a least square method, and requires 5 measuring points at least, and for two circular pipes, the number of the required point positions is more, and the operation cost is higher. 5. The journal literature 'study of a cylindrical fitting algorithm of sparse point measurement aviation conduit' proposes that fewer points are used for projection, the roundness of the projection points is calculated, and a vector with the minimum roundness is selected as an initial value of a fitting cylinder, but the number of fitting points of the scheme is still 15-20, the number of points is more, and the efficiency is lower. 6. The journal document '6-dof industrial robot intersecting line welding motion planning' adopts a standard tool to determine the relation between a workpiece coordinate s