Optical Piston Rod Displacement Sensing with Speckle Calibration
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Solution Overview
Problem
Existing piston position sensors face challenges in accurately determining absolute position due to variable oil conductivity with temperature and pressure, limited memory storage for calibration images, high manufacturing costs from optically detectable code patterns, and low reliability of optical time of flight sensors, especially when dealing with wear and damage.
Innovation Solution
A self-calibrating and recalibrating optical sensor system that uses natural speckle patterns for calibration, reduces the need for marked calibration positions, and employs proximity sensors and time of flight sensors to estimate piston rod absolute displacement, allowing for closely spaced or continuous calibration positions and immunity to localized damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical position sensors store multiple calibration position images to improve measurement precision, then absolute position accuracy is improved, but memory storage capacity is exceeded
Solution Approach 1:
The patent extracts only the essential calibration information from full calibration images. Instead of storing complete calibration position images, the system identifies and stores only the unique features or parameters that define each calibration position. This extraction approach maintains absolute position accuracy while dramatically reducing memory storage requirements.
Solution Approach 2:
The patent creates simplified representations or copies of calibration position data. Rather than storing actual calibration images, the system stores condensed calibration position information that can be used to reconstruct or reference the original calibration data when needed, reducing storage while preserving measurement precision.
2Measurement precision
If marked encoded sequences are used as calibration positions to improve measurement precision, then absolute position determination is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent enables the piston rod surface to serve its own calibration function through naturally occurring speckle patterns. The roughness and optical properties of the metal surface create unique speckle patterns that act as self-generated calibration markers, eliminating the need for externally applied marked encoded sequences and reducing manufacturing costs.
Solution Approach 2:
The patent utilizes optical property changes of the metal surface under laser illumination to create distinguishable calibration positions. The speckle patterns created by laser light interacting with the metal surface roughness provide unique optical signatures that can be detected and used for calibration without requiring physical markings.
3Productivity
If optical time of flight sensors are used to determine absolute piston rod displacement to improve productivity, then measurement speed is improved, but reliability decreases due to vulnerability to obscuring objects
Solution Approach 1:
The patent introduces an intermediary optical measurement approach that uses speckle pattern correlation instead of direct time of flight measurement. By using the piston rod surface itself as the reference and measuring optical path differences through speckle pattern analysis, the system achieves both speed and reliability without being vulnerable to obscuring objects.
Solution Approach 2:
The patent replaces the mechanical/optical time of flight sensing approach with an optical correlation-based measurement system. Instead of measuring the time for light to travel to and from the piston rod, the system uses optical speckle pattern correlation to determine position, eliminating vulnerability to obscuring objects while maintaining measurement speed.
4Measurement precision
If closely spaced or continuous calibration positions are implemented to improve measurement precision, then absolute position accuracy is improved, but computational resources required increase
Solution Approach 1:
The patent applies partial action by using only the necessary computational effort for speckle pattern correlation. Instead of performing exhaustive calculations for continuous calibration positions, the system uses efficient correlation algorithms that provide sufficient accuracy with reduced computational resources, applying just enough processing power needed for the measurement task.
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 enables efficient field calibration and recalibration, reduces memory requirements, and enhances the reliability of piston rod displacement measurement by using multiple optical sensors and significant feature storage, effectively addressing the limitations of existing technologies.
Implementation Method 1
Optical position sensors measure the position by series electrical resonates
Implementation Method 2
EP patent no. EP2775268 A1 utilize coherent or nearly coherent light to gather speckle interference image for each position
Implementation Method 3
proximity sensors, time of flight sensors and cumulative relative displacement are used to estimate the piston rod absolute displacement
Data Source
AI summary
The present invention relates to using a self calibrating and recalibrating 230, 925 optical sensors piston rod displacement. Self calibration enables field calibration of uncalibrated 230, 925 optical sensors. During operation, recalibration enables detecting and correcting for wear and damage of the 200 piston rod and/or 230, 925 optical sensors. 210 Calibration positions on the surface of the 200 piston rod are imaged by 230 optical sensors using laser or darkfield lenses designed for optical computer mice. Natural surface patterns can be used in locations where 210 calibration positions are required, which reduces or eliminates the need for marked 210 calibration positions. Marked 210 calibration positions are spatially unique encoded sequences used to determine the piston rod absolute position. Storing only the significant features of 210 calibration positions saves significant memory. The reduced memory requirements of each 210 calibration position enables the use of closely spaced or continuous 210 calibration positions. Multiple 210 calibration position features and multiple 230, 925 optical sensors together collectively provide immunity to localized 208 surface damage. Proximity sensors, 925 time of flight sensors and 031 cumulative relative displacement are used to estimate the 200 piston rod absolute displacement and reduce the number of spatially unique 210 calibration positions needed to compare in order to determine the piston rod absolute displacement.