Surface Sensor Offset Compensation in Coordinate Positioning
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Solution Overview
Problem
Coordinate positioning apparatuses with articulating probe heads face inaccuracies in measurement data due to offsets of the surface sensor from its expected position, which affect the accuracy of measurements, especially when the sensor is rotatable about multiple axes.
Innovation Solution
A method involving obtaining first and second measurements at different angular orientations to compensate for and establish the offset of the surface sensor, where the second measurement's orientation is configured to have an opposing effect on the measurement data, allowing for the determination and correction of the offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the surface sensor is positioned at an expected fixed location on the probe head, then the measurement system is simple to operate, but measurement inaccuracies occur due to offset from the actual sensor position
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements at multiple predetermined angular orientations before actual workpiece measurement. The surface sensor is rotated to specific angles (e.g., 0°, 180°) to capture offset effects in advance, allowing the offset to be determined and stored for later compensation during normal operation.
Solution Approach 2:
The patent implements feedback by using the calibration measurements to determine the actual sensor offset, then applying this offset information to correct subsequent measurements. The system continuously refines measurement accuracy by comparing expected versus actual sensor positions and adjusting measurements accordingly based on the determined offset values.
2Adaptability or versatility
If the surface sensor is made rotatable about multiple axes to increase measurement capability, then the adaptability improves, but the offset error becomes more significant and complex
Solution Approach 1:
The patent performs preliminary calibration at multiple predetermined angular orientations (including rotations about first and second axes) before actual measurement. This captures the offset effects in all rotational degrees of freedom, allowing the system to determine compensation values for each orientation combination.
Solution Approach 2:
The patent changes the angular orientation parameters of the surface sensor systematically during calibration, rotating the sensor about multiple axes to different predetermined angles. This varies the measurement parameters to expose offset effects in different directions, enabling comprehensive offset determination across all possible measurement orientations.
3Measurement precision
If multiple measurements are taken at different angular orientations to compensate for offset, then measurement accuracy improves, but the measurement time increases
Solution Approach 1:
The patent performs all necessary offset determination measurements in advance during a calibration phase, before actual workpiece measurement begins. By pre-determining the offset at multiple orientations and storing the compensation data, the system avoids repeating time-consuming calibration measurements during production, thereby minimizing time loss.
Solution Approach 2:
The patent creates a digital model (copy) of the offset error characteristics by measuring at multiple orientations and storing the deviation data. This digital representation allows rapid compensation without physically repeating the complex multi-angle measurement procedure for each individual measurement, significantly reducing measurement time while maintaining accuracy.
Data Source
AI summary
A method of operating a coordinate positioning apparatus having a surface sensor that is rotatable about at least a first axis. The method comprises obtaining a first measurement with the surface sensor at a first angular orientation and obtaining a at least a second measurement with the surface sensor at a second angular orientation. The first and second angular orientations are different to each other such that any offset of the surface sensor from an expected position will have at least a partially opposing affect on the first and second measurements. The method then compensates and/or establishes for the offset using the first and second measurements.