Absolute Position Sensor Using Harmonic Signal Reconstruction
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Solution Overview
Problem
Existing measurement sensors for determining the absolute position of a mobile along a circular, linear, or curvilinear trajectory face challenges such as high cost, bulkiness, and reduced precision due to harmonic distortion and crosstalk, especially in applications with limited space and high external magnetic fields.
Innovation Solution
A measurement sensor using at least four probes to detect a physical quantity from a target with continuous varying magnetic fields, featuring a reconstruction system for linear combination of signals to obtain signals in quadrature with only first and second harmonics, and a calculation system to determine the mobile's position, with programmable weighting weights to minimize homogeneous field contribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two targets and two detectors with specific probe spacing are used to determine absolute position, then measurement precision is improved, but device complexity and mounting space increase
Solution Approach 1:
The patent merges the functions of multiple targets into a single target with multiple tracks. Instead of requiring two separate targets (each with its own magnetic field pattern), the invention uses one target containing multiple tracks that generate different harmonic signals. This consolidation reduces the number of components while maintaining the capability to determine absolute position through harmonic analysis.
Solution Approach 2:
The patent changes the approach from using multiple physical targets with different pole counts to using a single target with tracks that produce different harmonic frequencies. By analyzing the fundamental harmonic and higher-order harmonics of a single target's magnetic field, the system achieves absolute position measurement without requiring multiple detectors or complex target arrangements.
2Measurement precision
If two targets are placed at sufficient distance to minimize crosstalk, then measurement precision is improved, but the sensor occupies more mounting space
Solution Approach 1:
The patent combines multiple measurement functions into a single target structure. By using one target with multiple tracks that generate different harmonic signals, the system eliminates the need to space multiple targets apart to avoid crosstalk. The harmonic analysis approach allows precise measurement while keeping all components in a compact configuration.
3Adaptability or versatility
If a magnetic track with modulated pole width is used to generate high-frequency and low-frequency components, then measurement capability is improved, but harmonic distortion increases and degrades measurement accuracy
Solution Approach 1:
The patent extracts the desired harmonic components from the magnetic field signal while eliminating the harmful distortion. By using signal processing techniques to isolate the fundamental harmonic and higher-order harmonics, the system removes the distorting effects of magnetic field modulation. This allows the system to utilize the versatility of harmonic-rich signals while maintaining measurement accuracy through selective signal extraction.
4Power
If the air gap is reduced to increase magnetic signal amplitude, then signal strength is improved, but harmonic distortion increases and degrades accuracy
Solution Approach 1:
The patent extracts the useful magnetic signal components while removing the harmful harmonic distortion. By applying signal processing to separate the fundamental harmonic from higher-order harmonics and distortion products, the system can operate with smaller air gaps (achieving higher signal amplitude) without sacrificing measurement accuracy. The extraction process eliminates the distortion that would otherwise degrade precision.
5Measurement precision
If four or more probes are used to detect physical quantity from target, then measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the detection system multi-functional by enabling a single probe to detect multiple harmonic components through signal processing. Instead of requiring multiple probes positioned at specific locations to capture different frequency components, the invention allows one probe to sense the composite magnetic field and then use mathematical processing to extract the fundamental harmonic and higher-order harmonics. This universal detection approach reduces the number of physical probes needed while maintaining comprehensive measurement capability.
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 precise, cost-effective, and compact measurement of absolute position, capable of operating in environments with limited space and high external magnetic fields, while maintaining high signal-to-noise ratio and measurement resolution.
Implementation Method 1
a series of at least four detection probes (12 1 , 12 2 , 12 3 , 12 4 , ..., 12 N ) for detecting a physical quantity originating from a target (13)
Implementation Method 2
a reconstruction system ensuring a linear combination of the signals delivered by the detection probes and obtaining, from the linear combination of these signals, at least two quadrature signals comprising only the first harmonic
Implementation Method 3
a calculation system ensuring the processing of the quadrature signals to determine the position of the moving object
Data Source
Figure 1
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Figure 3~5
AI summary
The invention relates to a measurement sensor for determining the position of a moving part (11), the sensor comprising a series of at least four probes (12i, 122, 123/124) for detecting a physical quantity from a target (13) comprising at least one track (14) for creating a physical quantity measurable by the detection probes, varying along the path of the target according to a continuous function comprising a first harmonic and a second harmonic, the probes being connected to a unit (16) for processing the signals output by the probes, comprising a reconstruction system (19) for ensuring a linear combination of the signals and for obtaining two quadrature signals (a1, a2) comprising only the first harmonic and two quadrature signals (a3, a4) comprising only the second harmonic, the unit also comprising a calculation system for processing the quadrature signals in order to determine the position of the moving part.