Coordinate Positioning Apparatus Recalibration via Correction Factors
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Solution Overview
Problem
The existing calibration processes for coordinate measuring machines (CMMs) with reorientable probe heads are time-consuming and can introduce measurement inaccuracies, especially when recalibrating after disturbances like machine crashes or stylus breakage, leading to increased downtime and disruption in production processes.
Innovation Solution
A method for quickly recalibrating CMMs by calculating a correction factor from position measurements taken after a disturbance, which updates the calibration data for multiple orientations of the measurement probe, reducing the need for a full recalibration process and minimizing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a full calibration process is performed for each orientation of the measurement probe, then measurement accuracy is maintained, but calibration time increases significantly
Solution Approach 1:
The patent performs a full calibration process beforehand to establish accurate calibration data for multiple orientations. This preliminary calibration allows the system to store reference data that can be quickly adjusted later using correction factors, avoiding the need to repeat the entire calibration process for each orientation change.
Solution Approach 2:
The patent changes the calibration approach from recalibrating all parameters for each orientation to calculating only correction factors for the specific orientation change. This parameter change reduces the calibration process from a comprehensive multi-point measurement to a simpler correction calculation based on the difference between current and reference orientations.
2Measurement precision
If calibration data is collected for each orientation of the probe head, then accuracy for all orientations is ensured, but the calibration process becomes excessively time-consuming
Solution Approach 1:
The patent creates a reference calibration dataset for multiple orientations through a preliminary full calibration. This reference data acts as a template that can be quickly copied and adjusted using correction factors when the probe head is reoriented, rather than collecting entirely new calibration data for each orientation.
Solution Approach 2:
The patent develops a universal calibration approach where a single reference calibration dataset serves multiple orientations. The correction factor calculation method allows the same reference data to be adapted for different probe head orientations, making the calibration system universally applicable across multiple configurations without requiring separate calibration processes for each orientation.
3Measurement precision
If the coordinate positioning apparatus is taken offline for full recalibration after a disturbance, then measurement accuracy is restored, but production disruption increases
Solution Approach 1:
The patent applies partial recalibration by calculating correction factors for only the specific orientation affected by the disturbance, rather than performing a complete recalibration of all orientations. This partial action restores measurement accuracy for the current orientation while minimizing the time the apparatus needs to be taken offline.
Solution Approach 2:
The patent skips the time-consuming portions of the full calibration process by directly calculating correction factors from the disturbance characteristics and reference calibration data. This allows the system to rush through the essential correction step without performing the complete multi-point calibration sequence, significantly reducing downtime.
4Productivity
If stylus replacement is performed after breakage, then the measurement probe can continue to be used, but calibration accuracy may be compromised
Solution Approach 1:
The patent enables the measurement system to self-correct for stylus replacement by automatically calculating correction factors based on the new stylus characteristics and the existing reference calibration data. This self-service approach restores calibration accuracy without requiring manual intervention or a complete recalibration process.
Solution Approach 2:
The patent changes the calibration parameters to account for the new stylus by calculating correction factors that compensate for differences in stylus length, diameter, or tip geometry. This parameter adjustment allows the system to maintain measurement accuracy with the replacement stylus without requiring a complete recalibration.
Data Source
Figure 1
Figure 2~3
Figure 4a~4c
AI summary
A method is described for recalibrating coordinate positioning apparatus (2) after a disturbance, such as a stylus replacement. The coordinate positioning apparatus comprises a platform (8), a measurement probe (12) and a probe head (10) for reorienting the measurement probe (12) relative to the platform (8). A calibration data set is taken for the coordinate positioning apparatus (2) that comprises datum data for a plurality of orientations of the measurement probe. The datum data includes at least first datum data for a first nominal orientation of the measurement probe. After a disturbance to the coordinate positioning apparatus (2), the calibration data set is updated by acquiring one or more position measurements and calculating a first correction from the one or more position measurements. The first correction describes any change in the first datum data following the disturbance and is used to update the datum data for a plurality of different orientations of the measurement probe (12). Corresponding apparatus is also described.