Machine Tool Camera Calibration Using Probe-Guided Pattern Alignment
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Solution Overview
Problem
Conventional camera calibration methods for machine tools require dedicated jigs and instruments, leading to high labor and cost, and are inflexible when the machine tool's degree of freedom is low, particularly in aligning the Z-axis and calibrating arbitrary positions and postures.
Innovation Solution
A camera calibration device that uses a touch probe and a camera to acquire known points and patterns, allowing linear movement of the table or spindle in orthogonal directions to calculate the positional posture relationship between the machine coordinate system and the camera coordinate system, enabling calibration without the need for dedicated calibration instruments or jigs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated jig and calibration instrument are used to install the calibration instrument in a predetermined place, then the calibration accuracy is improved, but the device complexity and labor cost increase
Solution Approach 1:
The patent extracts the calibration function from a dedicated jig and integrates it into the machine tool's existing table and spindle system. The calibration instrument is installed directly on the table without requiring separate mounting jigs, thereby simplifying the device while maintaining calibration accuracy through the use of the machine tool's own coordinate system and movement capabilities
Solution Approach 2:
The table and spindle of the machine tool serve dual purposes: both for normal machining operations and for calibration operations. By utilizing the existing multi-functional components of the machine tool for calibration, the patent eliminates the need for dedicated calibration jigs and instruments, reducing device complexity while maintaining calibration precision
2Measurement precision
If a dedicated jig and calibration instrument are used to install the calibration instrument in a predetermined place, then the calibration accuracy is improved, but the labor time and cost increase
Solution Approach 1:
The machine tool performs its own calibration using its existing components (table and spindle) without requiring external jigs or specialized installation procedures. The operator simply places the calibration instrument on the table and executes the calibration program, allowing the machine to self-calibrate using its own coordinate system and movement capabilities, thereby reducing labor time and complexity
3Device complexity
If the table can only be moved parallel to the directions of the X and Y axes or is fixed, then the machine structure is simplified, but the adaptability for calibration in arbitrary positions and postures deteriorates
Solution Approach 1:
The patent adds rotational movement capability to the table along the Z-axis, transforming it from a two-degree-of-freedom system (X and Y linear movements only) to a three-degree-of-freedom system. This additional rotational dimension enables the calibration instrument to be positioned and oriented in arbitrary positions and postures, significantly improving adaptability while maintaining relatively simple machine structure
Solution Approach 2:
The table is designed with dynamic movement capabilities, allowing it to rotate along the Z-axis in addition to linear movements along X and Y axes. This dynamic flexibility enables the calibration instrument to achieve arbitrary positions and postures during calibration, enhancing adaptability without substantially complicating the machine structure
4Ease of operation
If a calibration instrument is installed in a predetermined stationary place, then the calibration process is simplified, but the flexibility to calibrate arbitrary positions and postures deteriorates
Solution Approach 1:
The calibration instrument is mounted on the movable table rather than being fixed in a predetermined stationary location. The table's ability to move linearly along X and Y axes and rotate along the Z-axis enables the calibration instrument to dynamically achieve arbitrary positions and postures, maintaining calibration process simplicity while significantly improving flexibility and adaptability
Data Source
AI summary
To provide a camera calibration device and a camera calibration method which can easily calibrate a relationship between a machine coordinate system of a machine tool and a camera coordinate system of a camera. A camera calibration device calibrates an imaging means of a machine tool, the machine tool includes: a touch probe which acquires one point whose machine coordinates are known; a camera which images the one point and a pattern including a feature used for calibration; and a drive mechanism which moves a table or a spindle in two orthogonal directions and an image obtained by imaging the one point and the pattern and images obtained by imaging the pattern or/and the one point when the table or a machining machine is moved in the two directions are used to calculate an external parameter by calculating a positional posture relationship between the machine coordinate system and the pattern.