Shape Measuring Apparatus Error Correction via Frequency Transfer Filtering
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Solution Overview
Problem
Existing shape measuring apparatuses, such as coordinate measuring devices, face challenges in accurately correcting measurement errors when scanning probes measure objects placed on displacement tables, particularly due to quadrant projection errors caused by mechanical backlash.
Innovation Solution
A shape measuring apparatus and method that utilize a displacement table, a scanning probe with a ball tip, a ball tip displacement detector, and a scale, where the calculator performs corrections based on estimated frequency transfer characteristics to accurately calculate and correct measurement values, accounting for displacement in multiple coordinate axes and eliminating errors like quadrant projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a scanning probe is used to measure a manufactured item, then shape measurement capability is provided, but measurement errors occur due to mechanical backlash and quadrant projection effects
Solution Approach 1:
The patent replaces mechanical error correction methods with signal processing and filtering techniques. A correction filter based on frequency transfer characteristics is applied to the scale output signal to eliminate quadrant projection errors and mechanical backlash effects, substituting mechanical compensation with electronic/signal-based correction.
Solution Approach 2:
The patent implements feedback by continuously monitoring the scale output signal and applying real-time correction based on predetermined frequency transfer characteristics. The correction filter processes the scale signal feedback to compensate for mechanical errors, creating a closed-loop error correction system that improves measurement reliability.
2Measurement precision
If correction is performed based on scale output signal, then quadrant projection errors can be corrected, but adequate correction cannot be performed when the measured object is placed on a displacement table
Solution Approach 1:
The patent creates a universal correction method that works for both fixed stage configurations and displacement table configurations. The correction filter is designed to process scale output signals regardless of whether the measured object is stationary or moving on a displacement table, making the error correction applicable to multiple measurement system configurations.
Solution Approach 2:
The patent adapts the correction approach to handle dynamic conditions where the measured object may be moving on a displacement table. The correction filter accounts for the dynamic relationship between scale displacement and measured object position, enabling accurate error correction in both static and dynamic measurement scenarios.
Data Source
AI summary
A calculator includes a first filter, a second filter, and an adding device. The first filter outputs, as a first corrected value, a value in which displacement of a displacement table detected by a scale has been corrected based on first frequency transfer characteristics from a scale to a measured object station. The second filter outputs, as a second corrected value, a value in which the first corrected value is corrected based on second frequency transfer characteristics from a ball tip to a ball tip displacement detector. The adding device adds the second corrected value and displacement of the ball tip detected by the ball tip displacement detector to calculate a measured value.