Robot Vision Calibration Using End-Effector Marker Estimation
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Solution Overview
Problem
Accurate calibration between a robot vision system's coordinate system and a camera is challenging without a separate marker, especially for low-end cameras with severe distortion, which often results in incomplete camera coordinate systems and the need for overfitting in work areas without predefined positions or constraints.
Innovation Solution
An automatic calibration method using a nonlinear optimization algorithm to estimate camera intrinsic parameters and position offsets between the camera and robot, involving the calculation of camera-robot and robot-end marker offsets based on images and coordinate systems, allowing for precise calibration without predefined markers or constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate marker with fixed coordinates is used for calibration, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the calibration marker from being a separate physical device and integrates it into the robot end effector itself. The marker is attached to the end effector, allowing the end effector to serve dual purposes: both as a tool for manipulation and as a calibration reference, thereby eliminating the need for separate calibration devices.
Solution Approach 2:
The end effector is given multiple functions: it serves as both the manipulator tool and the calibration marker carrier. This multi-functionality reduces the number of separate components needed in the system, simplifying the overall device complexity while maintaining calibration precision.
2Manufacturing precision
If calibration is performed with predefined marker positions, then manufacturing precision is improved, but adaptability decreases
Solution Approach 1:
The calibration system transitions from static predefined marker positions to dynamic marker positions. The marker moves with the end effector to various positions within the work area, allowing calibration data to be collected from multiple dynamic positions rather than fixed predetermined locations, thereby improving adaptability while maintaining precision.
Solution Approach 2:
The system performs preliminary actions by moving the end effector to multiple predetermined positions within the work area to collect calibration images before actual robot operations begin. This preliminary data collection enables the system to adapt to different work areas without requiring predefined marker positions for each specific application.
3Ease of operation
If automatic calibration without separate devices is implemented, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The robot system performs calibration automatically using its own end effector as the marker carrier, without requiring external calibration devices or manual intervention. The system captures images at multiple positions, processes the coordinate transformations automatically, and completes calibration through self-service operations, improving ease of operation while maintaining precision through computational methods.
Data Source
AI summary
According to one aspect of the present invention, disclosed is an automatic calibration method for a calibration device connected to a camera that is disposed the end effector of a robot and to a robot controller for controlling the robot. The method comprises the steps of: acquiring, from the camera and the robot controller, a robot-based coordinate system and an image of a marker marked in the work area of the robot (wherein the acquired image and robot-based coordinate system are recorded while the end effector is moved to a plurality of sample coordinates); and estimating the position of a robot coordinate system-based marker by using the acquired image and robot-based coordinate system.