Method, robot and storage medium for aligning robot end with target object

Patent metadata

Field	Value
Publication number	US-12564949-B2
Application number	US-202318576557-A
Country	US
Kind code	B2
Filing date	Jun 8, 2023
Priority date	Jun 8, 2023
Publication date	Mar 3, 2026
Grant date	Mar 3, 2026

Abstract

A method for aligning a robot end with a target object includes: acquiring a target direction for a surface to be aligned; selecting a control point, and establishing a coordinate system of the control point; controlling the surface to move along a direction such that the z-axis points in the target direction; rotating, when the surface is determined to be in contact with the target object, the surface with respect to the target object actively and keeping the surface in contact with the target object, and acquiring a first displacement of the control point; determining a relationship between the first displacement and the z-axis; determining, based on the relationship between the first displacement and the z-axis, whether a current rotation direction is a correct alignment direction; and controlling, based on the determination, the surface to be rotated.

First claim

What is claimed is:

1 . A method for aligning a robot end with a target object, the method being used to adjust a posture of the robot end when the robot end is in contact with the target object, and the method comprising:
acquiring a target direction for a surface to be aligned of the robot end; selecting a point having a known position with respect to the surface to be aligned as a control point, and establishing a coordinate system of the control point having an x-axis, a y-axis and a z-axis; controlling the surface to be aligned to move along a direction such that the z-axis of the coordinate system points in the target direction; acquiring force information of the robot end, and determining whether the surface to be aligned is in contact with the target object; rotating, when the surface to be aligned is determined to be in contact with the target object based on the force information, the surface to be aligned with respect to the target object actively and keeping the surface to be aligned in contact with the target object, and acquiring a first displacement of the control point during this process; determining a relationship between the first displacement of the control point and the z-axis; determining, based on the relationship between the first displacement and the z-axis, whether a current rotation direction is a correct alignment direction to obtain a first determination result; and controlling, based on the first determination result, the surface to be aligned to be rotated.

2 . The method of claim 1 , wherein, after the controlling, based on the first determination result, the surface to be aligned to be rotated, the method further comprises:
acquiring, during the surface to be aligned being rotated based on the first determination result, a second displacement of the control point; determining a relationship between the second displacement of the control point and the z-axis; determining, based on the relationship between the second displacement of the control point and the z-axis, whether the current rotation direction is the correct alignment direction to obtain a second determination result; determining, when the second determination result indicates that the current rotation direction is a wrong alignment direction, whether the surface to be aligned is aligned with the target object to obtain a third determination result; and controlling, based on the third determination result, the surface to be aligned to be rotated.

3 . The method of claim 2 , wherein the controlling, based on the first determination result, the surface to be aligned to be rotated, comprises:
rotating, if the alignment is not achieved, the surface to be aligned reversely until the surface to be aligned is aligned with the target object; and stopping rotating, if the alignment is achieved, the surface to be aligned.

4 . The method of claim 2 , wherein the determining the relationship between the first displacement of the control point and the z-axis comprises:
calculating a first vector projection of the first displacement of the control point on the z-axis; and determining, based on the first vector projection, the relationship between the first displacement of the control point and the z-axis, wherein: if the first vector projection is positive, it is determined that the first displacement points in a same direction as the z-axis; and if the first vector projection is negative, it is determined that the first displacement points in a direction opposite to the z-axis.

5 . The method of claim 2 , wherein the determining the relationship between the second displacement of the control point and the z-axis comprises:
calculating a second vector projection of the second displacement of the control point on the z-axis; and determining, based on the second vector projection, the relationship between the second displacement of the control point and the z-axis, wherein: if the second vector projection is positive, it is determined that the second displacement points in a same direction as the z-axis; and if the second vector projection is negative, it is determined that the second displacement points in direction opposite to the z-axis.

6 . The method of claim 4 , wherein the calculating the first vector projection of the first displacement of the control point on the z-axis comprises:
calculating the first displacement of the control point before and after the rotation in a base coordinate system; acquiring a vector expression of the z-axis in the base coordinate system; and acquiring a dot product of the first displacement and the vector expression of the z-axis to obtain the first vector projection of the first displacement in the z-axis.

7 . The method of claim 5 , wherein, the calculating the second vector projection of the second displacement of the control point on the z-axis comprises:
calculating the second displacement of the control point before and after the rotation in the base coordinate system; acquiring a vector expression of the z-axis in the base coordinate system; and acquiring a dot product of the second displacement and the vector expression of the z-axis to obtain the second vector projection of the second displacement in the z-axis.

8 . The method of claim 1 , wherein when the control point is located within the surface to be aligned, the determining, based on the relationship between the first displacement and the z-axis, whether the current rotation direction is the correct alignment direction to obtain the first determination result comprises:
determining, if the first displacement points in a same direction as the z-axis point, the current rotation direction as the correct alignment direction; and determining, if the first displacement points in a direction opposite to the z-axis, the current rotation direction as a wrong alignment direction.

9 . The method of claim 2 , wherein when the control point is located within the surface to be aligned, the determining, based on the relationship between the second displacement and the z-axis, whether the current rotation direction is the correct alignment direction to obtain the second determination result comprises:
determining, if the second displacement points in a same direction as the z-axis point, the current rotation direction as the correct alignment direction; and determining, if the second displacement points in a direction opposite to the z-axis point, the current rotation direction as a wrong alignment direction.

10 . The method of claim 2 , wherein the determining whether the surface to be aligned is aligned with the target object comprises:
presetting a distance threshold related to a size of the surface to be aligned and a position where the control point is selected; acquiring, during the rotation, a lowest point of the control point having a lowest projection in the z-axis; and comparing current coordinates of the control point with the lowest point, and wherein when a position deviation between the control point and the lowest point is less than or equal to the distance threshold, the surface to be aligned is aligned with the target object.

11 . The method of claim 1 , wherein the acquiring the first displacement of the control point comprises:
presetting a first threshold related to a size of the surface to be aligned and a position where the control point is selected; and acquiring, when a position deviation of the control point before and after the rotation is greater than or equal to the first threshold, the first displacement during the rotation.

12 . The method of claim 2 , wherein the acquiring, based on the first determination

Assignees

• Shanghai Flexiv Robotics Tech Co Ltd
• Flexiv Ltd

Inventors

• Ni Feijian

Classifications

• B25J13/085

  Force or torque sensors (B25J13/082, B25J13/084 take precedence) · CPC title

• B25J9/1687

  Assembly, peg and hole, palletising, straight line, weaving pattern movement · CPC title

• G05B2219/40087

  Align hand on workpiece to pick up workpiece, peg and hole · CPC title

• B25J9/1633 Primary

  compliant, force, torque control, e.g. combined with position control · CPC title