Planar Inductive Angular Sensor PCB Design
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Solution Overview
Problem
Conventional inductive position sensors with planar coil assemblies fail to meet the requirements of small form factor, airgap, and accuracy needed in industries like automotive and aerospace, where reliability and noise immunity are critical.
Innovation Solution
A non-contact inductive angular position sensor design featuring two planar excitation coils and two planar sensing coils with a circular rotatable inductive coupling element, positioned within a minor sector of the excitation coils' interior, allowing for a reduced form factor while maintaining airgap and sensing accuracy through a multilayer PCB implementation and optimized winding layouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional planar coil assemblies are used in inductive position sensors, then the device complexity is reduced and manufacturing is simplified, but the airgap increases and sensing accuracy deteriorates
Solution Approach 1:
The patent transitions from conventional three-dimensional wound coils to two-dimensional planar coils fabricated on PCB substrates. This dimensional reduction enables precise control of coil geometry and positioning in the plane, allowing for optimized magnetic field distribution while maintaining a compact form factor. The planar configuration improves manufacturing precision through standard PCB fabrication processes while enabling better control of the airgap distance.
Solution Approach 2:
The patent modifies the physical parameters of the coil assembly by changing from traditional wound wire coils to planar trace coils on PCB. This parameter change allows for precise control of coil dimensions, spacing, and geometry through PCB design rules, thereby improving manufacturing precision and enabling consistent airgap maintenance while reducing device complexity through standardized fabrication processes.
2Volume of moving object
If the form factor is reduced to meet small size requirements, then the device compactness is improved, but the airgap decreases and sensing accuracy worsens
Solution Approach 1:
By adopting planar coils on PCB substrates, the patent achieves compact three-dimensional integration while maintaining controlled two-dimensional coil geometry. This allows the sensor to achieve small form factor requirements through vertical stacking and layered PCB construction, while the planar coil design ensures precise magnetic field distribution and consistent airgap maintenance, thereby preserving sensing accuracy in a compact package.
Solution Approach 2:
The patent implements a nested structure where planar coils are fabricated on multiple PCB layers, with excitation coils and sensing coils arranged in different planes. This nested arrangement allows for compact vertical integration, reducing the overall sensor volume while maintaining adequate horizontal spacing for the airgap, thus achieving small form factor without compromising sensing accuracy.
3Ease of manufacture
If planar coils on PCB are used to reduce cost and size, then the manufacturing cost is reduced and form factor is decreased, but noise immunity deteriorates
Solution Approach 1:
The patent employs multi-layer PCB construction with excitation coils and sensing coils positioned on different layers. This vertical nesting separates the high-current excitation signals from the low-level sensing signals in the vertical dimension, reducing electromagnetic coupling and crosstalk. The layered structure maintains compact footprint while improving noise immunity through spatial separation of signal types.
Solution Approach 2:
The patent implements differential sensing coil arrangements where sensing coils are positioned to receive differential signals that reject common-mode noise. The planar coil geometry and PCB trace routing are optimized locally to minimize interference from nearby excitation coils, with careful attention to ground plane placement and signal return paths to enhance noise immunity in critical areas.
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 design achieves a compact, reliable, and accurate angular position sensing system with improved noise immunity and increased airgap, addressing the limitations of existing sensors by utilizing a planar coil assembly on a multilayer PCB with symmetric winding patterns and a rotatable inductive coupling element with sector apertures.
Implementation Method 1
an alternating current (AC) is injected into the excitation coil(s) which results in the generation of a time varying magnetic field in the vicinity of the excitation coil. The time varying magnetic field is sufficient to induce a time varying voltage in the sensing coils as a result of the mutual magnetic coupling between the excitation coil and the sensing coils
Implementation Method 2
The presence of the rotatable target within the time varying magnetic field changes the mutual magnetic coupling between the excitation coil and the sensing coils, relative to the position of the rotatable target
Data Source
AI summary
An angular position sensor comprising two planar excitation coils forming a substantially circular interior area and two planar sensing coils positioned within a minor sector of the substantially circular interior area. Each of the two planar sensing coils comprises a clockwise winding portion and a counter-clockwise winding portion. The angular position sensor further comprises a substantially circular rotatable inductive coupling element positioned in overlying relation to the two planar sensing coils and separated from the two planar sensing coils by an airgap, wherein the substantially circular rotatable inductive coupling element comprises three, substantially evenly space, sector apertures.