Off-Axis Magnetic Angular Sensing With Multi-Pole Arrays
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Solution Overview
Problem
Existing rotary encoders and resolvers for measuring angular position and displacement are costly, bulky, and prone to misalignment errors due to mechanical stack tolerance and aging, necessitating a more compact and reliable alternative.
Innovation Solution
A 2D surface magnet array with alternating north and south poles, configured to generate sine and cosine outputs with a 90-degree phase shift using magnetic field sensors, which can be tailored to match the electrical phase period of motors, providing a cost-effective and lightweight replacement for resolvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotary encoders or resolvers are used for measuring angular position, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical encoder systems with a magnetic field-based sensing system. A magnet array with alternating polarity patterns generates magnetic fields that are detected by magnetic sensors, eliminating the need for mechanical encoders or resolvers while maintaining angular position measurement precision.
Solution Approach 2:
The patent uses specific magnetic pole widths and spacing parameters in the magnet array to generate sinusoidal magnetic field variations. By carefully controlling these geometric parameters, the system achieves precise angular measurement through magnetic field detection rather than mechanical means.
2Reliability
If traditional resolvers are used for motor control, then reliability is improved, but weight and size increase
Solution Approach 1:
The patent substitutes heavy mechanical resolver components with lightweight magnetic sensors and magnet arrays. This substitution maintains the reliability needed for motor control applications while dramatically reducing the weight of the sensing system.
Solution Approach 2:
The patent employs inexpensive magnetic sensors and magnet arrays that can be easily replaced if needed, providing a cost-effective and lightweight alternative to expensive, heavy resolvers while maintaining adequate reliability for motor control.
3Ease of manufacture
If mechanical stack tolerance is present in resolver assemblies, then ease of manufacture is improved, but measurement precision deteriorates due to misalignment errors
Solution Approach 1:
The patent eliminates mechanical alignment requirements by using magnetic field interactions instead of mechanical contacts. The magnet array and magnetic sensors can be positioned with loose tolerances without affecting measurement precision, as magnetic fields are not sensitive to minor misalignments.
Solution Approach 2:
The patent designs the magnet array with specific pole widths and spacing that create robust magnetic field patterns tolerant to manufacturing variations. This allows easier manufacturing while maintaining measurement precision through the inherent tolerance of magnetic field sensing.
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 magnet array and magnetic field sensor system offers a compact, lightweight, and cost-effective solution that generates accurate sine and cosine outputs, compensates for misalignment errors, and is compatible with various motor types, enhancing motor control precision.
Implementation Method 1
A magnetic field sensor is an electronic component that measures a magnetic field
Data Source
AI summary
Apparatus and associated methods relate to measuring position and displacement of a 2D surface magnet array of at least three adjacent magnetic north and south tracks with an acute angle versus its motion displacement relative to a magnetic field sensor (e.g., magnetic sensing probe). In an illustrative example, the geometry of the 2D surface magnet array may be planar with adjacent and alternating north and south pole regions. In some embodiments, the 2D surface magnet array geometry may take the form of (1) an axial cylindrical helical multipole magnet array having individually magnetized layers that are oriented in helical shape, or (2) a radial disk spiral multipole magnet array with at least three adjacent north and south tracks oriented as a spiral shape.