Hybrid Position Encoder for Absolute Sensing in Limited Space
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Solution Overview
Problem
Existing position encoders face challenges in achieving high-resolution absolute position measurements with high reliability while requiring minimal space, particularly due to limitations in inductive sensing and interference issues with magnetic sensing.
Innovation Solution
A position encoder that combines inductive and magnetic sensing techniques, using an inductive sensor with a track of alternating conductive and non-conductive sections and a magnetic sensor with a track of alternating magnetic poles, allowing for both absolute and incremental position measurements to enhance overall resolution without significant space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inductive sensing is used for position measurement, then the sensor can be made on printed circuit boards at low cost, but the resolution is limited due to the fineness of engraving or etching of the PCB
Solution Approach 1:
The patent combines inductive sensing and magnetic sensing techniques in a single position encoder system. The inductive sensor reads a scale with conductive and non-conductive sections, while a magnetic sensor simultaneously reads a scale with magnetic poles. This merging allows the system to achieve high resolution through magnetic sensing while maintaining the cost-effectiveness and ease of manufacture of inductive sensing on PCBs.
2Measurement precision
If magnetic sensing is used for high-resolution position measurement, then higher resolution can be achieved, but interference issues arise when multiple magnetic elements are positioned in close proximity
Solution Approach 1:
The patent divides the position measurement function into two separate sensing systems: an inductive sensing system and a magnetic sensing system. Each system has its own sensor and scale, positioned adjacently but independently. This segmentation allows the magnetic sensor to achieve high resolution without interference from other magnetic elements, as the inductive system operates separately with its own conductive scale.
Solution Approach 2:
The patent introduces an inductive sensing system as an intermediary that can operate independently alongside the magnetic sensing system. The inductive sensor with its conductive scale serves as a separate measurement channel that does not interfere with the magnetic field-based measurements, allowing both high-resolution magnetic positioning and interference-free operation.
3Ease of manufacture
If the scale includes repetitive patterns to cover the entire track, then the encoding can be simplified, but only incremental position can be derived which is ambiguous as to which section it is
Solution Approach 1:
The patent merges two different sensing approaches: the inductive sensor reads a scale with repetitive conductive and non-conductive sections that provide absolute position information, while the magnetic sensor simultaneously reads a scale with magnetic poles that provides high-resolution incremental position information. This combination allows the system to recover both absolute and incremental position data, eliminating the ambiguity of repetitive patterns while maintaining ease of manufacture.
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
The combined inductive and magnetic sensing approach enables high-resolution absolute position measurements with improved reliability and minimal space usage, achieving resolutions of 20 bits or more in a rotary encoder with compact dimensions.
Implementation Method 1
one of them may be provided with a sensor and the other one with a reference track including some kind of scale which extends along the track and can be scanned by the sensor
Implementation Method 2
other measurement techniques, such as measurements based on inductive or magnetic sensing, can be preferred
Data Source
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AI summary
A position encoder comprises: a first member and a second member, with the first member being movable relative to the second member; a first sensor arranged at one of the first and second members, and a first track arranged at the other one of the first and second members such that the first sensor moves along the first track when the first member moves relative to the second member, with the first sensor being configured to capture its position and/or displacement along the first track; a second sensor arranged at one of the first and second members, and a second track arranged at the other one of the first and second members such that the second sensor moves along the second track when the first member moves relative to the second member, with the second sensor being configured to capture its position and/or displacement along the second track. The first sensor is an inductive sensor and the first track includes alternating conductive and non-conductive sections distributed along the first track, whereas the second sensor is a magnetic sensor and the second track includes a plurality of magnetic poles distributed along the second track with alternating magnetic polarity.