Dual-Track Magnetic Position Sensor with Phase Shift
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Solution Overview
Problem
Existing magnetic position sensor systems are often sensitive to external disturbance fields, which can affect their accuracy and robustness, particularly in industrial, robotic, and automotive environments.
Innovation Solution
A position sensor system with a magnetic source featuring two tracks with alternating magnetic poles, where the magnetization of the tracks is substantially 180° phase shifted, and a sensor device with magnetic sensors configured to measure magnetic field components at specific locations above the tracks, deriving position from difference signals that are highly insensitive to external disturbance fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single track with alternating magnetic poles is used, then the sensor device can measure position, but the system is sensitive to external disturbance fields
Solution Approach 1:
The magnetic source is segmented into two separate tracks (first track and second track) with alternating magnetic poles. Each track independently generates magnetic field components that are measured by the sensor device. This segmentation allows the system to compute difference signals between the two tracks, which cancels out common-mode external disturbance fields while preserving the position-dependent magnetic field variations.
2Measurement precision
If magnetic sensors are spaced far apart to cover a large range, then the measurement range increases, but the accuracy decreases
Solution Approach 1:
The invention optimizes the spacing parameter between magnetic sensors to be less than 1.40 times the pole pitch. This specific parameter range maximizes the accuracy of position determination by ensuring that the sensors capture sufficient magnetic field variation while maintaining high sensitivity to position changes. The dual-track configuration further enhances accuracy by providing differential measurement that is less sensitive to absolute sensor positioning errors.
3Measurement precision
If complex arithmetic operations are used to improve measurement accuracy, then the precision increases, but the processing complexity and cost increase
Solution Approach 1:
The invention extracts the position information by computing simple difference signals between the magnetic field components measured at the two tracks. Instead of using complex arithmetic operations on multiple sensor signals, the system extracts the essential position-dependent information through straightforward subtraction: diff1 = BxA - BxB and diff2 = BzA - BzB. This extraction approach maintains high measurement precision while minimizing processing complexity.
4Reliability
If the sensor device is made more robust against positioning errors, then the reliability improves, but the mounting requirements become more stringent
Solution Approach 1:
The invention employs an asymmetric evaluation approach where difference signals are computed between two tracks rather than treating all sensors symmetrically. This asymmetric processing makes the system inherently more robust against positioning errors and mechanical tolerances, as the differential measurement cancels out common-mode errors. The relaxed mounting requirements are achieved because the system does not require perfectly symmetric sensor placement, only that the sensors be positioned within the specified distance less than 1.40 times the pole pitch.
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 system achieves high accuracy and robustness against external disturbance fields, aging effects, and mechanical wear, while also reducing the cost and complexity of the sensor device and relaxing mounting requirements.
Implementation Method 1
the sensor device comprises a plurality of magnetic sensors spanning a distance (or spaced apart over a distance) along the predefined path which is smaller than 1.40 times the pole pitch; wherein the plurality of magnetic sensors are configured for measuring a plurality of magnetic field components
Data Source
AI summary
A position sensor system includes a magnetic source and a sensor device movable relative to the magnetic source. The magnetic source has a first track of alternating magnetic poles, and a second track of an equal number of alternating poles, but 180° phase shifted relative to the first track. The sensor device is configured for measuring a plurality of magnetic field components, including a first magnetic field component at a first sensor location facing the first track, and a second magnetic field component oriented parallel to the first magnetic field component at a second sensor location facing the second track, and for deriving a first and a second difference signal from the plurality of magnetic field components, and for determining a position based on these difference signals.