On-Machine Workpiece Measurement via Rotary Table Multi-View Imaging
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Solution Overview
Problem
Existing machine tool measurement methods using single-lens cameras lack depth data and require multiple cameras to accurately determine workpiece shape, leading to errors in position and posture calculations if optical axis intersections are not precise.
Innovation Solution
A machine tool on-machine measurement method using a single imaging device with a five-axis machining device, where the rotary feed axes orient the workpiece's upper and side surfaces in the camera's line-of-sight direction, allowing for accurate position calculation by capturing images from different angles and minimizing errors related to camera optical axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-lens camera is used to image the workpiece, then the device complexity is reduced, but the measurement precision deteriorates due to lack of depth data
Solution Approach 1:
The patent applies dimensionality change by rotating the workpiece table to present different spatial dimensions (upper surface, side surfaces) to the single-camera line of sight. This transforms a 3D measurement problem into a series of 2D measurements from different orientations, enabling depth information to be inferred through multiple viewing angles rather than requiring multiple cameras simultaneously.
Solution Approach 2:
The patent uses preliminary action by pre-calculating the optimal rotation angles and positions of the workpiece table before imaging. The controller determines the precise orientations needed to capture upper and side surfaces, then executes these predetermined positions to ensure accurate geometric relationships between captured images for subsequent 3D reconstruction.
2Ease of operation
If the workpiece is imaged from only one direction, then the ease of operation is improved, but the measurement precision deteriorates due to insufficient shape information
Solution Approach 1:
The patent applies dynamics by making the workpiece table rotatable to change its orientation dynamically. Instead of moving the camera to multiple fixed positions, the system rotates the workpiece itself to present different surfaces (upper, side) to the stationary camera, enabling multi-view imaging while maintaining operational simplicity through automated table rotation.
3Measurement precision
If multiple imaging devices are used to capture depth information, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent uses copying by capturing multiple 2D images of the workpiece from different orientations using a single camera, effectively creating multiple views that replicate the information gathering capability of multiple cameras. The rotated table presents different spatial copies of the workpiece surfaces to the same imaging device, enabling depth inference without additional hardware.
4Ease of operation
If the optical axis intersection is not accurately calculated, then the ease of operation is maintained, but the measurement precision deteriorates due to increased error in position and posture calculations
Solution Approach 1:
The patent extracts and eliminates the problematic optical axis intersection calculation by using a different measurement approach. Instead of relying on precise camera optical axis alignment and intersection mathematics, the system uses workpiece table rotation to create known geometric relationships between imaging positions, removing the need for complex optical axis calibration while maintaining high measurement precision.
Data Source
AI summary
When measuring the position of a workpiece fixed to a table of a machine tool: rotary feed axes of the machine tool are pivoted such that an upper surface of the table faces in the direction of a line of sight of a camera, and an image of the workpiece is captured; the rotary feed axes are pivoted such that a side surface of the table faces in the direction of the line of sight of an image capturing device, and an image of the workpiece is captured; and the position of the workpiece is measured on the machine tool on the basis of the captured images.