Eddy Current Angle Sensor Coil Layout for Harmonic Compensation
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Solution Overview
Problem
Magnetic field sensors used for angular position detection suffer from harmonic errors due to mismatch in sine and cosine channels caused by harmonic effects, leading to angle inaccuracy in sensing systems.
Innovation Solution
The use of offset receive coils, specifically configured to compensate for third, fifth, and seventh order harmonic effects, along with a processing module to process the reflected magnetic field, ensures accurate angular position determination by minimizing residual angle errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional receive coils are used for angular position sensing, then the device structure is simple, but harmonic errors cause mismatch in sine and cosine channels resulting in angle inaccuracy
Solution Approach 1:
The receive coil is segmented into multiple constituent coils (first, second, third, and fourth coils) with specific offset arrangements. Each coil group targets specific harmonic orders (third, fifth, seventh), allowing selective compensation of harmonic errors while maintaining overall system functionality.
Solution Approach 2:
The constituent coils are positioned with asymmetric offsets relative to the main coil axis. The first and second coils are offset by sixty degrees, while the third and fourth coils have different offset angles, creating an asymmetric configuration that specifically compensates for odd-order harmonic effects in the angular position sensing.
2Measurement precision
If multiple harmonic compensation coils are added, then angle accuracy improves to 0.03 degrees, but the PCB space requirement increases
Solution Approach 1:
Multiple coil functions are merged into a compact receive coil assembly. The first, second, third, and fourth constituent coils are integrated together with the main coil, sharing common mounting space and electrical connections, thereby achieving harmonic compensation without proportionally increasing PCB area.
Solution Approach 2:
The coil offsets are implemented in angular dimensions rather than purely radial expansion. By arranging coils at specific angular offsets (sixty degrees, other specific angles) around the main coil axis, the design achieves harmonic compensation through spatial distribution in the angular domain, minimizing radial space requirements on the PCB.
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 solution significantly improves angle accuracy by reducing residual errors to 0.03 degrees, enhancing the precision of angular position sensing without increasing PCB space or requiring additional front-end processing.
Implementation Method 1
a main coil to direct a magnetic field at a rotatable target for inducing eddy currents in the target
Implementation Method 2
the reflected field is generated by eddy currents in the conductive surface of the target
Implementation Method 3
a receive coil having sine and cosine coils for detecting a reflected field from the target
Data Source
AI summary
Methods and apparatus for sensors having a main coil to direct a magnetic field at a rotatable target for inducing eddy currents in the target and a receive coil having sine and cosine coils for detecting a reflected field from the target wherein each of the sine and cosine coils is configured such that an asymmetric reflected field from the target seen by the sine and cosine coils corresponds to conductive properties of a surface of the target in relation to the main coil and the receive coil. The sine coil comprises first and second constituent coils offset from each other to compensate for third order harmonic effects and the cosine coil comprises first and second constituent coils to compensate for third order harmonic effects.