Absolute Position Encoder Using Variable Grating Diffraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional position encoders require multiple tracks for high resolution and are sensitive to contamination, making them inefficient for accurate absolute position detection on topographic surfaces with arbitrary curvature and multiple degrees of freedom.
Innovation Solution
A multi-spectral light source illuminates a variable grating on the surface, producing a diffraction pattern whose angular dispersion varies with position, detected by a chromatically responsive sensor, allowing for absolute position measurement without initialization and on surfaces with arbitrary curvature and multiple degrees of freedom, using a system transfer function for precise mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate encoder tracks are used for each bit of Grey code to achieve high resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple encoder tracks into a single track by encoding multiple bits of Grey code in different spatial locations along the same track. Instead of using separate tracks for each bit, the invention integrates all bit information into one continuous track, reducing the number of tracks from N (for N bits) to just one track while maintaining high resolution position detection capability.
Solution Approach 2:
The patent transitions from a multi-track two-dimensional arrangement to a single-track one-dimensional arrangement by utilizing the spatial dimension along the track. Different bits of the Grey code are positioned at different locations along the single track, allowing all bit information to be encoded and read from one linear track rather than requiring multiple parallel tracks.
2Measurement precision
If multiple separate encoder tracks are used for high resolution, then measurement precision is improved, but sensitivity to contamination worsens
Solution Approach 1:
By merging multiple encoder tracks into a single track, the invention reduces the total surface area that is exposed and vulnerable to contamination. Instead of having multiple separate tracks that each could be independently contaminated, the single integrated track presents a unified, minimized surface that is less susceptible to particulate contamination and other harmful factors.
3Adaptability or versatility
If conventional encoders are used on surfaces with arbitrary curvature, then adaptability is improved, but measurement precision worsens due to initialization requirements
Solution Approach 1:
The patent incorporates preliminary action by pre-encoding absolute position information directly into the single encoder track in a contamination-resistant format. The track is designed with specific features that allow immediate absolute position determination upon initialization, eliminating the need for complex calibration procedures and ensuring accurate measurements from the start of operation on curved surfaces.
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 solution enables accurate absolute position detection on complex surfaces with high sensitivity and robustness to contamination, maintaining geometric relationship with the surface normal, and supports multiple degrees of freedom without requiring initialization.
Implementation Method 1
A target on, and positionally-registered to, the topographic surface comprises a variable grating that diffracts the incident light to form a multi-special diffraction pattern in which the angular dispersion of the diffraction pattern varies with the absolute position of the incident light along the grating
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A light source illuminates a position on a topographic surface at an angle of incidence determined from a vector normal to the surface. A target on, and positionally-registered to, the topographic surface comprises a variable grating that diffracts the incident light to form a multi-spectral diffraction pattern in which the angular dispersion varies with the absolute position of the incident light along the grating. A chromatically responsive sensor detects a narrow band of the diffraction pattern and outputs a signal responsive to the change in the angular dispersion of the detected narrow band of the diffraction pattern. The source/sensor unit maintains its geometric relationship to the vector normal to the topographic surface at the position of illumination. A processing element uses a system transfer function to map the detected signal to an absolute-position on the topographic surface.