Inductive Position Sensor Tri-Phase Coil Harmonic Rejection
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Solution Overview
Problem
Angular inductive position sensors face errors due to harmonic components in the signals received from the coils, which are not perfectly sinusoidal, affecting the accuracy of angle calculation.
Innovation Solution
A position sensor design with at least three receive coils, each with a conductive strand configured to form a continuous coil and an integrated circuit to process signals, where the strands are connected to subtract common mode signals, implementing a tri-phase configuration to reject even harmonics and eliminate the third harmonic component, and using a sinusoidal primitive function scaled and shifted for polar coordinate conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional receive coils are used in angular inductive position sensors, then the sensor structure is simple, but the signals contain harmonic components that cause angular measurement errors
Solution Approach 1:
Each receive coil is divided into two separate conductive strands (first strand and second strand) that are spatially separated and independently wound. This segmentation allows the strands to be positioned at different locations relative to the target, enabling them to pick up different components of the magnetic field, including harmonic components. The separate strands can then be connected in a differential configuration to reject common-mode harmonic signals while preserving the fundamental measurement signal.
Solution Approach 2:
The first and second strands of each receive coil are designed with different local geometries and positions. The first strand is wound in a specific pattern while the second strand is wound in a complementary pattern, creating local quality differences. This allows each strand to respond differently to the magnetic field harmonics generated by the target, enabling harmonic rejection through differential measurement while maintaining the overall coil function.
2Measurement precision
If signals from multiple receive coils are processed to eliminate harmonics, then measurement accuracy improves, but signal processing complexity increases
Solution Approach 1:
The harmful harmonic components are extracted and identified as common-mode signals present in multiple receive coils. By recognizing that harmonics appear as common-mode components across the tri-phase signal set, the invention extracts and removes these unwanted components through differential processing, leaving only the useful fundamental measurement signals. This extraction approach simplifies the processing by focusing on removing a specific identified component rather than complex filtering.
Solution Approach 2:
The invention converts the harmful harmonic components into a useful feature by treating them as common-mode signals. The tri-phase configuration and differential processing transform the presence of harmonics into a detectable pattern that can be systematically removed. What was originally harmful (harmonic distortion) becomes a identifiable common-mode component that, when removed, benefits the measurement by eliminating angular errors.
3Measurement precision
If a tri-phase configuration with three receive coils is implemented, then third harmonic components can be removed, but the device complexity increases
Solution Approach 1:
The invention merges the functionality of multiple receive coils into a tri-phase configuration where three coils are spatially arranged and electrically connected in a specific pattern. This merging allows the system to process three-phase signals that inherently provide the capability to eliminate third harmonic components through mathematical relationships. The combined output of the three coils, when processed differentially, automatically rejects third harmonics without requiring additional complex filtering circuitry.
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 design significantly reduces angular errors by removing common mode signals and harmonic components, improving the accuracy of position detection in both angular and linear position sensors.
Implementation Method 1
a transmit coil, an integrated circuit which is configured for exciting the transmit coil, thus inducing signals on the receive coils
Implementation Method 2
a transmit coil exciting a metal target, which in turn generates an induced voltage in a set of receive coils
Data Source
AI summary
A position sensor is for determining the position of a conductive target using a transmit coil and a plurality of receive coils. The receive coils may each include two strands and a strand may be obtained from a conversion of a substantially sinusoidal primitive function. The position sensor may realize a reduction of harmonics in signals from the receive coils.