Harmonic Coil Layout for Accurate Moving-Member Position Detection
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Solution Overview
Problem
Existing position detection devices for moving members, such as rack shafts in steering devices, suffer from detection errors due to non-uniform magnetic flux density and vibrations, leading to inaccurate position measurement.
Innovation Solution
A position detection device with a detection coil shaped as a combination of symmetrical curved portions, each comprising a sinusoidal fundamental wave component superimposed with harmonic components of the third or higher order, and adjusted coefficients to mitigate the effects of non-uniform magnetic flux density, using a substrate with excitation and detection coils to calculate the position of the moving member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a simple sine wave-shaped detection coil is used, then the device complexity is reduced, but the detection accuracy deteriorates due to non-uniform magnetic flux density
Solution Approach 1:
The detection coil's geometric parameters are modified by superimposing harmonic components (third order and higher) onto the fundamental sine wave. This changes the coil's shape parameters to compensate for non-uniform magnetic flux density distribution, transforming the output voltage into a more accurate sinusoidal signal that reflects position more precisely.
Solution Approach 2:
The detection coil is designed as a composite structure combining a fundamental sine wave component with multiple harmonic components (third order and higher). This composite geometric configuration allows the coil to counteract the non-uniform magnetic flux density through the combined effect of different waveform components, achieving higher detection accuracy.
2Measurement precision
If the detection coil shape is simplified, then the manufacturing precision requirement is reduced, but the detection accuracy deteriorates due to vibrations and non-uniform magnetic flux density
Solution Approach 1:
By adjusting the parameters of harmonic components (third order and higher) superimposed on the fundamental sine wave, the detection coil compensates for manufacturing tolerances and non-uniform magnetic flux density. This parameter adjustment allows the system to maintain high detection accuracy even with standard manufacturing precision levels.
3Measurement precision
If a rectangular excitation coil is used, then the manufacturing ease is improved, but the detection accuracy deteriorates due to non-uniform magnetic flux density distribution
Solution Approach 1:
The excitation coil's rectangular geometry is modified by superimposing harmonic components onto the fundamental waveform. This parameter change in the coil's geometric profile allows compensation for the non-uniform magnetic flux density naturally produced by rectangular coils, maintaining detection accuracy while preserving manufacturing ease.
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 device significantly enhances detection accuracy by minimizing errors caused by non-uniform magnetic flux density, allowing precise position detection of moving members.
Implementation Method 1
a substrate provided with an excitation coil for generating a magnetic field in an area including the detection object, and a detection coil being interlinked with a magnetic flux of the magnetic field
Implementation Method 2
a detection coil being interlinked with a magnetic flux of the magnetic field... a calculation unit that calculates the position of the moving member based on an output voltage of the detection coil
Data Source
AI summary
A position detection device for detecting a position of a moving member moving forward and backward in a predetermined moving direction is provided with a detection object attached to the moving member, a substrate provided with an excitation coil for generating a magnetic field in an area including the detection object and a detection coil being interlinked with a magnetic flux of the magnetic field, a power supply unit for supplying an alternating current to the excitation coil, and a calculation unit that calculates the position of the moving member based on an output voltage of the detection coil. The detection coil is shaped as a combination of a pair of curved portions that are symmetrical across a symmetry axis parallel to the moving direction of the moving member. Each of the curved portions is shaped as a sinusoidal fundamental wave component superimposed with a harmonic component of a third or higher order multiplied by each of coefficients corresponding to the order. The coefficients are adjusted in such a manner that a peak value of a voltage induced in the detection coil changes sinusoidally when the detection object moves at a constant speed relative to the substrate while facing a part of the substrate.