Hysteresis Compensation in Single-Drive Coordinate Measuring Machines
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Solution Overview
Problem
Coordinate measuring machines face inaccuracies due to hysteresis error, which is not adequately addressed by existing error compensation techniques that do not account for direction-dependent friction-induced errors in single-scale, single-drive systems.
Innovation Solution
A method and system that obtain hysteresis error data using calibration blocks or slots, and apply compensation factors to scale readings to correct for hysteresis errors, allowing for accurate measurement of workpiece features without additional bridge scales or drives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-scale, single-drive system is used in a coordinate measuring machine, then device complexity and cost are reduced, but measurement precision deteriorates due to hysteresis error from friction in guideways
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual workpiece measurements to determine hysteresis error characteristics. The system pre-characterizes the guideway friction effects through calibration blocks or slots, storing this error data for subsequent compensation during measurement operations
Solution Approach 2:
The patent implements feedback by using the determined hysteresis error data to compensate scale readings during measurement. The system continuously applies correction factors based on the direction of bridge movement and position, feeding back the calibration information to improve measurement accuracy in real-time operation
2Measurement precision
If conventional error compensation techniques are applied, then static guideway errors are reduced, but hysteresis error from direction-dependent friction remains unaddressed
Solution Approach 1:
The patent applies dynamics by transitioning from static error compensation to dynamic compensation that accounts for direction-dependent hysteresis effects. The system determines separate hysteresis error characteristics for different movement directions (positive and negative) and applies appropriate compensation based on the actual direction of bridge movement, making the compensation adaptive rather than fixed
Solution Approach 2:
The patent implements parameter changes by measuring and compensating for hysteresis error at multiple bridge positions throughout the measurement range. The system determines position-specific hysteresis error parameters using calibration features, creating a detailed error map that varies with position and direction to accurately compensate for changing friction conditions
3Measurement precision
If additional bridge scales or drives are added to eliminate hysteresis error, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies copying by using calibration blocks or slots that replicate the guideway friction conditions without requiring additional measurement scales or drive systems. The calibration features serve as substitutes for actual measurement features, allowing the system to determine hysteresis error characteristics through repeated measurements of these copied geometric elements
Solution Approach 2:
The patent uses calibration blocks or slots as intermediary elements to indirectly determine hysteresis error characteristics. Rather than directly measuring or eliminating hysteresis through additional hardware, the system uses these intermediary calibration features to characterize the friction effects, which then serve as the basis for software-based compensation during actual measurements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of coordinate measuring machines by effectively compensating for hysteresis errors in single-scale systems, reducing positional measurement errors and maintaining cost and maintenance efficiency.
Implementation Method 1
a scale operative to permit scale readings indicating a position of a portion of the bridge along the first guideway
Implementation Method 2
a probe, such as one using a touch sensor, is movable in three dimensions within a measurement volume to contact the workpiece at various points on the workpiece
Data Source
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AI summary
A single-scale, single-drive coordinate measuring machine that compensates for hysteresis error caused by friction at the non-driven end of the bridge. The coordinate measuring machine is calibrated to estimate hysteresis effects at one or more distances from the scale. Measurements of workpieces are adjusted based on the calibration data and the distances of the carriage from the scale at the point of the measurements. The scale and the drive system may be positioned on opposite guideways.