External Camera Calibration in Robot Cells Without Arm Repositioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for calibrating external cameras in robot systems require the installation of hand-end cameras at the tip of the robot arm, which limits their application and necessitates complex and time-consuming operations, especially when the camera is not installed at the tip end or when multiple positions and orientations are needed.
Innovation Solution
A robot system with a 3D robot camera and a 2D external camera, where the external camera is calibrated using a calibration pattern imaged by both cameras, allowing for efficient calibration without the need for multiple positions and orientations, utilizing a control device with processors to execute calibration processing and estimate coordinate transformation matrices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hand-end camera is installed at the tip end of the robot arm for calibration, then the external camera can be calibrated, but the method cannot be applied when the camera is installed at a place other than the tip end and the operation becomes time-consuming
Solution Approach 1:
A marker is introduced as an intermediary object that can be easily imaged by both the robot camera and external camera. The marker serves as a common reference that enables coordinate transformation without requiring complex hand-end camera operations, thus reducing calibration time while maintaining accuracy
Solution Approach 2:
The patent replaces the mechanical approach of moving the robot arm to multiple positions with an optical/computational approach. By using the marker and calculating coordinate transformations through image processing, the system eliminates the need for time-consuming mechanical positioning operations
2Measurement precision
If the robot arm is moved to a plurality of positions and orientations for calibration, then the external camera calibration can be executed, but the operation becomes indispensable and takes considerable time
Solution Approach 1:
The marker acts as a mediator that simplifies the calibration operation. Instead of requiring the robot arm to move to multiple positions, the marker can be imaged from various positions, and the coordinate transformation is calculated through image processing, making the operation simpler and faster
Solution Approach 2:
The patent changes the calibration approach from mechanical parameter adjustment (robot arm positioning) to computational parameter calculation (coordinate transformation through image processing). This allows calibration to be executed more easily without physical movement of the robot arm
3Measurement precision
If multiple positions and orientations are set for hand-end camera calibration, then the external camera can be calibrated accurately, but the robot arm operation is indispensable
Solution Approach 1:
The patent substitutes mechanical robot arm operations with computational image processing. The coordinate transformation is calculated by processing images of the marker captured by both cameras, eliminating the need for time-consuming mechanical positioning while maintaining calibration precision
Solution Approach 2:
The marker serves as a copy or representation of the reference frame that can be imaged easily. By capturing images of this simplified reference object and calculating transformations, the system achieves accurate calibration without requiring the complex mechanical operations of moving the robot arm to multiple positions
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A robot system includes a robot including a robot arm and a first camera, a second camera installed separately from the robot, and a control device which controls the robot and the second camera. The first camera has already been calibrated in advance, and first calibration data which is calibration data of the first camera is known. The control device (i) images a calibration pattern with the first camera to acquire a first pattern image and images a calibration pattern with the second camera to acquire a second pattern image, and (ii) executes calibration processing for obtaining second calibration data which is calibration data of the second camera using the first pattern image, the second pattern image, and first calibration data which is known calibration data for the first camera.