Eddy Current Sensor Assembly Orthogonal Movement Insensitivity
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Solution Overview
Problem
There is a need for an inexpensive, reliable, and accurate sensor to monitor the position of a component translated along a movement axis in environments with thermal extremes and metallic particles, where conventional sensors like Hall-effect sensors are not suitable due to magnetic interference.
Innovation Solution
A sensor assembly comprising two eddy current sensors and targets, with coils wound helically around orthogonal axes, generating signals that are insensitive to movement perpendicular to the movement axis, allowing for accurate position determination along the axis using a controller to process signals and isolate noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall-effect sensors are used to determine position, then position measurement is possible, but the sensor becomes sensitive to metallic particles and magnetic interference in driveline environments
Solution Approach 1:
The patent replaces magnetic field-based sensing (Hall-effect) with eddy current sensing, which uses electromagnetic induction to detect position through conductive targets rather than magnetic fields, eliminating sensitivity to metallic particles and magnetic interference in driveline environments
Solution Approach 2:
The patent changes the physical principle of operation from magnetic field detection to eddy current detection, fundamentally altering how position is measured to be insensitive to the harmful environmental factors present in driveline applications
2Measurement precision
If conventional position sensors are used, then position can be monitored, but the sensors are affected by thermal extremes and metallic particles in driveline environments
Solution Approach 1:
The patent substitutes conventional magnetic sensing with eddy current sensing that measures position through electrical conductivity changes in conductive targets, making the system immune to thermal extremes and metallic particle interference
Solution Approach 2:
The patent uses simple conductive targets made of inexpensive materials like aluminum or copper that can be easily replaced if needed, eliminating the need for complex magnetic sensors that are sensitive to environmental factors
3Measurement precision
If eddy current sensors with helical coils are used, then position determination becomes insensitive to orthogonal movement, but device complexity increases
Solution Approach 1:
The patent uses helical coils wound around orthogonal axes (X and Z axes), where the three-dimensional helical structure creates magnetic field patterns that are insensitive to movement along orthogonal directions, enabling selective measurement along the movement axis
Solution Approach 2:
The patent divides the sensing function into two separate eddy current sensors with helical coils oriented along different axes, where each sensor contributes to the overall position determination while filtering out orthogonal movement through their combined output
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 provides accurate position determination along the movement axis with less than 0.5% error, regardless of temperature changes, vibrations, or presence of metallic particles, and eliminates the need for calibration, making it suitable for driveline components.
Implementation Method 1
The first sensor includes a first coil that is wound helically around the first Z-axis. The second sensor includes a second coil that is wound helically around the second Z-axis. The first target is formed of an electrically conductive material and is configured to interact with the first sensor to produce a first sensor signal. The second target is formed of an electrically conductive material and is configured to interact with the second sensor to produce a second sensor signal.
Data Source
AI summary
A method that includes: providing a structure that is movable along a first axis; coupling a sensor assembly to the structure, the sensor assembly comprising first and second eddy current sensors and first and second targets that are mounted to the structure for movement along the first axis; sensing the first target with the first eddy current sensor and responsively generating a first sensor signal; sensing the second target with the second eddy current sensor and responsively generating a second sensor signal; and using the first and second sensor signals to determine a location of the structure along the first axis in a manner that is insensitive to coordinated movement of the first and second targets along a second axis that is perpendicular to the first axis and a third axis that is perpendicular to both the first and second axes.