CN-122008243-A - Correction method and correction system applied to mechanical arm and mechanical arm

Abstract

The application discloses a correction method, a correction system and a mechanical arm applied to the mechanical arm, and relates to the technical field of machinery, wherein the correction method comprises the steps of obtaining an image coordinate change relation of characteristic points on a workpiece before and after rotation; and calculating the physical coordinate compensation quantity under the current angle, and correcting the original physical coordinate by utilizing the physical coordinate compensation quantity to obtain a target correction coordinate. According to the application, the compensation quantity accurately corresponding to the current target angle can be calculated by calibrating the rotation center offset and establishing a dynamic compensation model based on geometric kinematics. The mechanical arm can automatically correct nonlinear geometric deviation caused by misalignment of rotation centers when processing target objects at any angle, so that the problem that laminating errors are uncontrollable in a disordered angle scene in the prior art is solved, and positioning accuracy is improved.

Inventors

• ZHENG XIAOYANG
• Pan Longgao

Assignees

• 深圳市正运动技术有限公司

Dates

Publication Date

20260512

Application Date

20260403

Claims (10)

1. 1. A correction method applied to a mechanical arm having a rotation axis and a camera, comprising: establishing an image coordinate system, a physical coordinate system and a conversion relation between the image coordinate system and the physical coordinate system; Controlling a workpiece to rotate at a target angle, and acquiring an image coordinate change relation of feature points on the workpiece before and after rotation; Determining an initial offset of a workpiece feature center relative to the rotation center of the rotation shaft under the physical coordinate system based on the image coordinate change relation and the target angle; And acquiring the current angle and the original physical coordinates of the workpiece to be calibrated, calculating a physical coordinate compensation quantity under the current angle by combining the initial offset, and correcting the original physical coordinates by utilizing the physical coordinate compensation quantity to obtain target correction coordinates.
2. 2. The method for calibrating a mechanical arm according to claim 1, wherein the specific step of controlling the workpiece to rotate at a target angle and acquiring the image coordinate change relation of the feature points on the workpiece before and after rotation comprises: setting a certain characteristic position of the workpiece as a target characteristic point; Recording first image coordinates of the target feature points before rotation; And driving the rotating shaft to drive the workpiece to rotate at a target angle, and recording second image coordinates of the rotated target feature points to construct an image coordinate change relation before and after the workpiece rotates.
3. 3. The method of claim 2, wherein the determining an initial offset of the center of the workpiece feature relative to the center of rotation of the axis of rotation in the physical coordinate system based on the image coordinate variation relationship and the target angle comprises: According to the first image coordinates, the second image coordinates and the target angle of the target feature points, and the conversion relation, calculating a first physical coordinate of the rotation center of the rotating shaft under the physical coordinate system based on a preset point-around rotation formula; and acquiring a second physical coordinate of the workpiece feature center, and calculating the relative displacement between the second physical coordinate of the workpiece and the first physical coordinate of the rotation shaft to obtain the initial offset.
4. 4. The method for calibrating a mechanical arm according to claim 3, wherein the calculating the first physical coordinate of the rotation center of the rotation axis in the physical coordinate system based on a preset rotation formula of the rotation around the point according to the first image coordinate, the second image coordinate, and the target angle of the target feature point by combining the conversion relation comprises: Converting the first image coordinate and the second image coordinate into a pre-rotation physical point and a post-rotation physical point in a physical coordinate system respectively based on a conversion relation between the image coordinate system and the physical coordinate system; substituting the physical point before rotation, the physical point after rotation and the target angle into the preset point-around rotation formula to obtain the first physical coordinate.
5. 5. The correction method applied to a robot arm according to claim 3, wherein the coordinates of the physical point before rotation are set to (X 0 , Y 0 ), the coordinates of the physical point after rotation are set to (X 1 , Y 1 ), the target angle is θ, and the first physical coordinates are set to (C x , C y ); The preset rotation formula of the surrounding points is as follows: X 1 = C x +（X 0 - C x ）cosθ-（Y 0 - C y )sinθ; Y 1 = C y +（X 0 - C x ）sinθ+（Y 0 - C y )cosθ。
6. 6. The method for calibrating a mechanical arm according to claim 3, wherein the specific steps of obtaining the current angle and the original physical coordinates of the workpiece to be calibrated, calculating the physical coordinate compensation amount under the current angle by combining the initial offset, and correcting the original physical coordinates by using the physical coordinate compensation amount, and obtaining the target calibration coordinates include: Acquiring a current angle and an original physical coordinate of a workpiece to be calibrated; calculating the current offset between the characteristic center of the workpiece and the center of the rotating shaft under the current angle through rotation transformation by utilizing the initial offset and the current angle; Calculating a difference value between the current offset and the initial offset, and determining the difference value as a physical coordinate compensation amount under the current angle; and correcting the original physical coordinates by using the physical coordinate compensation quantity to obtain target corrected coordinates.
7. 7. The method of claim 6, wherein the absolute value of the target angle is greater than 10 °.
8. 8. The correction method applied to a robot arm according to any one of claims 1 to 7, wherein the step of establishing an image coordinate system, a physical coordinate system, and a conversion relationship therebetween further includes, before: Judging whether the polarity of an image coordinate system of the camera and the physical rotation direction of the rotating shaft are in a mirror image relationship or not; And if the polarity of the image coordinate system of the camera is in a mirror image relationship with the physical rotation direction of the rotating shaft, reversing the target angle and the current angle so that the polarity of the image coordinate system is consistent with the physical rotation direction of the rotating shaft.
9. 9. A correction system for a robotic arm, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the computer program being configured to implement the steps of the correction method for a robotic arm as claimed in any one of claims 1 to 8.
10. 10. A robotic arm comprising a calibration system as defined in claim 9 applied to the robotic arm, and The mechanical arm body is provided with at least one rotating shaft; a camera for acquiring an image of a workpiece; the correction system calculates the target correction coordinates according to the image acquired by the camera, and controls the mechanical arm body to perform alignment action.

Description

Correction method and correction system applied to mechanical arm and mechanical arm Technical Field The present application relates to the field of mechanical technologies, and in particular, to a calibration method and calibration system applied to a mechanical arm, and a mechanical arm. Background In the field of industrial automation, alignment lamination, precise assembly or disordered loading and unloading by adopting a vision-guided manipulator has become a mainstream technology. Such systems typically recognize the position and angle of the target object by a camera and direct the manipulator end effector to move to the corresponding pose to perform the operation. However, the prior art has a core pain which is not solved effectively for a long time, when the target rotates relative to the initial template established by the vision system, systematic errors related to the rotation angle are generated by the grasping or placing coordinates calculated by the system, and the attachment or grasping is inaccurate. The root cause is that there is a mismatch between the kinematic model of the manipulator and the coordinate calculation model of the vision system. Specifically, the manipulator end effector typically performs a rotational motion about its own fixed point, while the vision system, when calculating the coordinates of the target, defaults to the manipulator aligning the target by a purely translational motion. When there is a rotation motion, the actual motion track is an arc with the center of rotation as the center of circle, which has geometric deviation from the straight line translation path assumed by the vision system, and the deviation value varies non-linearly with the rotation angle. Disclosure of Invention The application mainly aims to provide a correction method, a correction system and a mechanical arm applied to the mechanical arm, and aims to solve the problem of nonlinear positioning error along with the angle change of a target object caused by the fact that the rotation center of the mechanical arm is not coincident with a theoretical operation point of a visual system in the existing visual guiding technology. In order to achieve the above object, the present application provides a calibration method applied to a mechanical arm, the mechanical arm having a rotation axis and a camera, comprising: establishing an image coordinate system, a physical coordinate system and a conversion relation between the image coordinate system and the physical coordinate system; Controlling a workpiece to rotate at a target angle, and acquiring an image coordinate change relation of feature points on the workpiece before and after rotation; Determining an initial offset of a workpiece feature center relative to the rotation center of the rotation shaft under the physical coordinate system based on the image coordinate change relation and the target angle; And acquiring the current angle and the original physical coordinates of the workpiece to be calibrated, calculating a physical coordinate compensation quantity under the current angle by combining the initial offset, and correcting the original physical coordinates by utilizing the physical coordinate compensation quantity to obtain target correction coordinates. In an embodiment, the specific step of controlling the workpiece to rotate at the target angle and obtaining the image coordinate change relationship of the feature points on the workpiece before and after rotation includes: setting a certain characteristic position of the workpiece as a target characteristic point; Recording first image coordinates of the target feature points before rotation; And driving the rotating shaft to drive the workpiece to rotate at a target angle, and recording second image coordinates of the rotated target feature points to construct an image coordinate change relation before and after the workpiece rotates. In one embodiment, the determining the initial offset of the center of the workpiece feature relative to the center of rotation of the rotation axis in the physical coordinate system based on the image coordinate variation relationship and the target angle comprises: According to the first image coordinates, the second image coordinates and the target angle of the target feature points, and the conversion relation, calculating a first physical coordinate of the rotation center of the rotating shaft under the physical coordinate system based on a preset point-around rotation formula; and acquiring a second physical coordinate of the workpiece feature center, and calculating the relative displacement between the second physical coordinate of the workpiece and the first physical coordinate of the rotation shaft to obtain the initial offset. In an embodiment, the calculating, according to the first image coordinate, the second image coordinate, and the target angle of the target feature point, the first physical coordinate of the rotation center of the r