Robotic Arm Coordinate Calibration Using 3D Alignment Imaging
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Solution Overview
Problem
Current calibration apparatuses for robotic arms can only measure relative deviations in the tool center point (TCP) and do not obtain the tool's dimension, limiting precision and failing to establish transforming relationships among multiple robotic arms, making it difficult for them to work together effectively.
Innovation Solution
A calibration apparatus and method that uses an alignment device to capture three-dimensional images, compute homogeneous matrices to determine transforming relationships between different coordinate systems, and perform a three-point fix procedure to establish precise relative positions of the TCP and alignment device coordinate systems, enabling high-precision tasks and coordination among multiple robotic arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current calibration apparatus uses infrared emitter to measure TCP deviation, then calibration can be performed, but the tool dimension cannot be obtained and measurement precision is limited
Solution Approach 1:
The patent replaces the traditional infrared emitter and mechanical blocking method with a vision-based system using a camera to capture images of the tool. This optical system allows for non-contact measurement of both TCP position and tool dimensions by detecting feature points in the captured images, thereby obtaining complete geometric information without physical interference.
Solution Approach 2:
The patent introduces a camera as an intermediary device between the operator and the tool. The camera captures images that serve as intermediate data, from which both TCP position and tool dimension information can be extracted through image processing and coordinate transformation, enabling comprehensive measurement without direct physical contact.
2Ease of operation
If calibration apparatus measures only relative deviation, then calibration procedure is simple, but multiple robotic arms cannot establish transforming relationships
Solution Approach 1:
The patent creates a universal coordinate system transformation framework that can handle both single-robot and multi-robot scenarios. By establishing transforming matrixes between the alignment device coordinate system and robot coordinate systems, the system provides a unified approach that works for individual robot calibration and multi-robot coordination, enhancing versatility while maintaining operational simplicity.
Solution Approach 2:
The patent segments the calibration process into distinct coordinate transformation steps: from alignment device coordinate system to robot coordinate system, and from robot coordinate system to tool coordinate system. This segmentation allows for systematic handling of multiple robotic arms by treating each robot's calibration as an independent transformation chain that can be composed together.
3Productivity
If traditional calibration method is used, then TCP calibration can be completed, but tool dimension and orientation information is lost
Solution Approach 1:
The patent implements a continuous measurement process where the camera captures images throughout the tool's movement through the workspace. By continuously capturing image data at multiple positions and orientations, the system extracts both TCP trajectory and tool geometric information (dimensions and orientation) in a single uninterrupted calibration process, maximizing productivity while preserving complete tool information.
Data Source
AI summary
A calibration apparatus includes a processor, an alignment device, and an arm. The alignment device captures images in a three-dimensional space, and a tool is arranged on a flange of the arm. The processor records a first matrix of transformation between an end-effector coordinate-system and a robot coordinate-system, and performs a tool calibration procedure according to the images captured by the alignment device for obtaining a second matrix of transformation between a tool coordinate-system and the end-effector coordinate-system. The processor calculates relative position of a tool center point of the tool in the robot coordinate-system based on the first and second matrixes, and controls the TCP to move in the three-dimensional space for performing a positioning procedure so as to regard points in an alignment device coordinate-system as points of the TCP, and calculates the relative positions of points in the alignment device coordinate-system and in the robot coordinate-system.