Absolute Encoder Magnetic Flux Segmentation for Accuracy
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Solution Overview
Problem
Existing absolute encoders face challenges in maintaining detection accuracy and reliability, especially in high-temperature environments and when operating at increased motor rotation speeds, due to issues like thermal expansion, backlash, and gear attachment.
Innovation Solution
The proposed absolute encoder design includes a first drive gear with a magnet on its top end, a first angle sensor to detect the rotation angle based on magnetic flux changes, and a second drive gear with a magnet and a second angle sensor, optimizing the arrangement of polar portions on the magnets to minimize the impact of leak magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple magnets are arranged close to each other on drive gears, then the encoder can detect rotation at multiple positions simultaneously, but leak magnetic flux from one magnet interferes with the magnetic sensor detecting another magnet, reducing detection accuracy
Solution Approach 1:
The magnet is divided into multiple independent magnetic poles (first polar portion and second polar portion) with different polarities arranged in specific patterns. This segmentation allows each pole to generate distinct magnetic flux patterns that can be detected separately, enabling multi-position detection while maintaining accuracy by preventing flux interference between adjacent poles.
Solution Approach 2:
The magnetic pole arrangement uses asymmetric positioning where first polar portions and second polar portions are placed at different angular positions and distances from the magnetic sensor. This asymmetric configuration ensures that magnetic flux from one pole does not symmetrically interfere with the sensor's detection of another pole, allowing simultaneous multi-position detection with maintained precision.
2Measurement precision
If magnets are placed on drive gears to enable magnetic detection, then absolute position can be detected, but thermal expansion and stress changes cause displacement between members, affecting detection reliability
Solution Approach 1:
The patent replaces direct mechanical contact-based position detection with magnetic field-based detection. By using magnets mounted on drive gears and magnetic sensors on driven gears, the system detects rotational position through magnetic flux changes rather than mechanical coupling. This substitution reduces the impact of thermal expansion and stress-induced displacement on detection reliability, as the magnetic field detection is less sensitive to mechanical dimensional changes.
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 design effectively reduces the influence of leak magnetic flux, enhancing the detection accuracy and reliability of the absolute encoder across varying environmental conditions and motor speeds.
Implementation Method 1
a first angle sensor configured to detect a rotation angle of the first drive gear, in accordance with a change in magnetic flux generated from the first magnet
Implementation Method 2
a second angle sensor configured to detect a rotation angle of the second driven gear, in accordance with a change in magnetic flux generated from the second magnet
Data Source
AI summary
An absolute encoder includes a first drive gear, a first magnet, a first angle sensor, an intermediate gear, a second drive gear, a layshaft gear, a second magnet, and a second angle sensor. A first magnetization direction of the first magnet is parallel to a first axial direction of the first angle sensor, and a second magnetization direction of the second magnet is perpendicular to a second axial direction of the second angle sensor, and the layshaft gear is disposed on an opposite side of the intermediate gear from a main spindle.