Rotary Encoder Signal Processing for Interference Compensation
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Solution Overview
Problem
Existing rotary encoders face challenges in achieving high resolution and accuracy due to interference between magnetic tracks, which distorts signal outputs and introduces errors in velocity and position measurements.
Innovation Solution
A method involving two detectors positioned to capture alternating signals from annular tracks of magnetic encoding regions, identifying usable pairs of transitions to calculate angular velocity while compensating for errors caused by track interference, and using a first-order filter to refine position measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two tracks of magnetic elements are provided to increase resolution, then measurement precision is improved, but track interference distorts detector signals and introduces errors
Solution Approach 1:
The encoder track is segmented into multiple independent tracks (first track and second track) with detectors positioned at different radial locations. Each track-detector combination operates independently to measure angular position, allowing the system to achieve high resolution through multiple measurements while avoiding interference between tracks by spatial segmentation.
Solution Approach 2:
The system measures angular position using multiple detector tracks and computes a weighted average of the readings. The weighting factors are determined based on the radial positions of the detectors relative to the magnet centers, providing feedback-based error compensation that eliminates the effects of magnetic interference and manufacturing tolerances.
2Measurement precision
If magnet length is reduced to increase resolution, then measurement precision is improved, but signal strength and reliability deteriorate
Solution Approach 1:
Instead of increasing resolution by reducing magnet length in the angular dimension, the invention adds a radial dimension by positioning detectors at different radial distances from the rotation axis. This dimensional transition allows multiple detectors to measure the same angular position with different signal strengths, maintaining reliability while achieving high resolution through computational averaging.
3Measurement precision
If two detectors are provided for one track to increase resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple detectors positioned at different radial locations serve dual functions: each detector independently measures angular position and collectively they provide error compensation. The same physical structure (magnetic track and detectors) performs both high-resolution measurement and interference rejection, eliminating the need for separate correction mechanisms.
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 resolution and accuracy of rotary encoder measurements by eliminating interference effects, providing robust and precise angular position and velocity data.
Implementation Method 1
a detector which produces an output signal having a first state when proximal to one of the north poles and a second state when proximal to one of the south poles
Data Source
AI summary
A method of processing signals in a rotary encoder of the kind which comprises at least one annular track of encoding regions arranged as an alternating pattern of first encoding regions and second encoding regions. The encoder including first and second detectors, each of which is arranged to produce a first alternating output signal as the track of encoding regions rotates about its axis past the detector. The detector identifying a usable pair of transitions and a rejectable pair of transitions and utilizing the pairs of transitions to produce a compensated position measurement for the rotary encoder.