Rotary Encoder Axial Run-Out Error Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotary encoders face challenges in accurately measuring rotation angles due to axial run-out (dynamic eccentricity) in speed reducers, leading to insufficient error reduction and detection accuracy.
Innovation Solution
An encoder unit with a rotary unit, scale portion, and imaging elements that perform template matching to calculate rotation angles, using both first and second movement amounts from symmetrical imaging elements to offset measurement errors caused by axial run-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single imaging element is used to measure rotation angle, then the device complexity is reduced, but measurement precision deteriorates due to axial run-out errors
Solution Approach 1:
The encoder is divided into multiple imaging elements (first imaging element and second imaging element) positioned at different locations. Each imaging element independently measures the scale pattern, and their results are combined through averaging to eliminate axial run-out errors, thereby improving measurement precision without requiring complex correction mechanisms
Solution Approach 2:
Multiple measurement results from different imaging elements are merged through averaging calculation. The rotation angles measured by the first imaging element and second imaging element are combined to produce a final measurement that cancels out axial run-out errors, achieving high precision through simple arithmetic operations rather than complex mechanical structures
2Measurement precision
If eccentricity correction factors are stored and applied, then angle errors due to dial eccentricity are eliminated, but errors due to axial run-out cannot be sufficiently reduced
Solution Approach 1:
The solution transitions from single-point measurement to multi-point measurement by positioning imaging elements at different angular locations around the rotary shaft. This spatial dimensionality change allows the system to capture axial run-out variations and eliminate them through averaging, making the measurement reliable under dynamic rotation conditions where single-point correction fails
3Measurement precision
If multiple imaging elements and template matching are used, then detection accuracy is enhanced, but device complexity increases
Solution Approach 1:
The scale pattern is effectively copied and viewed from multiple angular positions by different imaging elements. This allows the system to capture the same rotational information from multiple perspectives, and through averaging, eliminate position-dependent errors while maintaining a relatively simple overall structure
Solution Approach 2:
Complex mechanical correction mechanisms are replaced with computational averaging of multiple simple optical measurements. Instead of using complex mechanical systems to physically correct axial run-out, the patent uses multiple simple imaging elements whose results are combined through calculation, achieving high precision with simpler components
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
Enhances detection accuracy by reducing measurement errors due to axial run-out, allowing for precise rotation angle measurement and improved drive control in robotic applications.
Implementation Method 1
a first imaging element that images the first mark, a second imaging element that is disposed at a position symmetrical with the first imaging element with respect to the rotary shaft and images the second mark
Data Source
AI summary
Template matching with an image captured by the first imaging element is performed to obtain a first movement amount in a circumferential direction of the first mark, template matching with an image captured by the second imaging element is performed to obtain a second movement amount in a circumferential direction of the second mark, and a rotation angle is calculated and output by using the first movement amount and the second movement amount.