Redundant Angle Sensor With Inductive Harmonic Compensation
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Solution Overview
Problem
Existing magnetic field sensors face challenges in accurately determining the angle of rotation of ferromagnetic objects due to limitations in sensing magnetic fields parallel and perpendicular to the substrate surface, and existing technologies struggle with harmonics that affect accuracy.
Innovation Solution
A redundant sensing system using both magnetic and inductive field sensing, employing a main coil to induce eddy currents and receive coils with a butterfly configuration to detect asymmetric reflected fields, combined with magnetic field sensing elements, to determine angular position with enhanced accuracy through harmonic compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensing elements are used to detect angular position, then the sensing capability is provided, but harmonics affect the measurement accuracy
Solution Approach 1:
The patent converts the harmful effect of harmonics into a beneficial signal processing opportunity by using both sine and cosine coil outputs. The harmonics appear in both channels, allowing them to be identified and removed through signal processing techniques, thereby improving angle measurement accuracy.
Solution Approach 2:
The system uses feedback by continuously monitoring both sine and cosine outputs and using this information to calculate and remove harmonic components. The processed signals are then used to determine the accurate angular position, creating a closed-loop error correction mechanism.
2Measurement precision
If redundant sensing systems are implemented to improve accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the inductive sensing system with the magnetic field sensing system into a single integrated angle sensor device. Both sensing mechanisms share common components such as the target structure and signal processing circuitry, reducing overall system complexity while maintaining redundant measurement capabilities.
Solution Approach 2:
The target structure serves multiple functions: it is both the ferromagnetic target for magnetic field sensing and the conductive target for inductive sensing. This multi-functionality eliminates the need for separate target structures, reducing device complexity while providing redundant sensing paths.
3Measurement precision
If both sine and cosine coils are used for inductive sensing, then measurement accuracy improves through harmonic compensation, but manufacturing precision requirements increase
Solution Approach 1:
The system uses feedback by continuously monitoring both sine and cosine outputs and using this information to calculate and remove harmonic components. The processed signals are then used to determine the accurate angular position, creating a closed-loop error correction mechanism that compensates for manufacturing variations.
Solution Approach 2:
The patent changes the approach from relying on precise physical geometry to relying on signal processing parameters. By using mathematical processing of the sine and cosine signals, the system can compensate for manufacturing tolerances and achieve high accuracy without requiring extremely precise coil configurations.
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 system achieves significantly improved angle accuracy, reducing residual errors by up to 57 times without increasing PCB space, and ensures robustness against system variations and stray fields.
Implementation Method 1
a main coil to direct a magnetic field at the target for inducing eddy currents in the target
Implementation Method 2
a receive coil having a butterfly configuration, wherein the receive coil has sine and cosine coils for detecting a reflected field from the target
Implementation Method 3
a magnetic field sensing system to detect the angular position of the target using magnetic field sensing elements
Data Source
AI summary
Methods and apparatus for having heterogenous redundant angle sensing. In embodiments, an angle sensor has inductive sensing and magnetic sensing for a target having a magnetic portion and a metallic portion. In embodiments, the magnetic portion includes a ring magnet centered within the metallic portion, which can be referred to as a cap. In some embodiments, the target-facing side of the cap is sloped. In some embodiments, the target-facing side of the cap and the ring magnet are sloped.