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Three-Dimensional Ruler for Robots

IP.com Disclosure Number: IPCOM000062331D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Tsai, RY: AUTHOR

Abstract

Carefully dimensioned truncated pyramids, at known positions on a three-dimensional (3D) ruler, provide reference dimensions with great accuracy at the actual location of the robot end effector, unaffected by dimensional tolerances of the robot arm. For most of the dimensions to be inspected in mechanical parts, the dimensions are defined as the spatial relationships between multiple features or surfaces, such as distances between two parallel planes, angle between two planes, distance or angle between two axes, etc. When vision is used to perform automatic inspection of general mechanical parts of any possible shapes, existing tools such as profile projector or a measuring microscope cannot be fully automated to perform such inspection.

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Three-Dimensional Ruler for Robots

Carefully dimensioned truncated pyramids, at known positions on a three- dimensional (3D) ruler, provide reference dimensions with great accuracy at the actual location of the robot end effector, unaffected by dimensional tolerances of the robot arm. For most of the dimensions to be inspected in mechanical parts, the dimensions are defined as the spatial relationships between multiple features or surfaces, such as distances between two parallel planes, angle between two planes, distance or angle between two axes, etc. When vision is used to perform automatic inspection of general mechanical parts of any possible shapes, existing tools such as profile projector or a measuring microscope cannot be fully automated to perform such inspection. Although there exist systems that use remote cameras to view the light-emitting diodes (LEDs) attached to the robot gripper, in order to determine the general 3D configuration of the robot gripper with optical triangulation, three problems exist: a. It is difficult to estimate general robot gripper motion with accuracy. b. It is necessary to rotate the camera with extremely high accuracy to keep the targets (LED) on the gripper within the field of view. c. To avoid occlusion, it is necessary to use many cameras. The 3D Ruler helps to perform mechanical part assembly with tolerances much smaller than the accuracy of the robot gripper. When one robot gripper attempts to carry a part (moving part) and insert it into a part (mating part) on the work table, a standard robot move command is first issued to move the moving part to the destination from a fixed known position. The 3D Ruler is then used to tell where exactly the robot gripper actually arrives by estimating the 3D movement of the robot gripper. Since the robot gripper moving accuracy usually is about...