Magnetic Multi-Turn Position Sensor With Nested Secondary Magnet
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Solution Overview
Problem
Existing magnetic position sensors face challenges in achieving precise absolute position measurement over multiple turns with high accuracy and compactness, particularly in applications like steering columns, due to limitations in precision, bulkiness, and sensitivity to external disturbances.
Innovation Solution
A magnetic position detection device featuring a multipolar main magnet with an adaptive number of pole pairs and a secondary magnet, integrated within the main rotor, utilizing Hall effect or magnetoresistive probes with ferromagnetic concentrators to provide precise and absolute position measurements without the need for extensive correction electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multipolar main magnet with many pole pairs is used to increase measurement precision over multiple turns, then the measurement precision improves, but the device complexity and computational requirements increase
Solution Approach 1:
The patent optimizes the number of pole pairs of the multipolar main magnet to a specific range (4-16 pairs) based on the reduction ratio and secondary sensor accuracy. This parameter optimization achieves high measurement precision without requiring excessive computational correction, resolving the contradiction between precision and device complexity.
Solution Approach 2:
The patent implements a feedback mechanism where the secondary sensor monitors the actual position and provides correction signals to compensate for magnetic field non-linearities. This feedback system enables high precision measurement while managing the complexity through controlled correction algorithms.
2Reliability
If magnetoresistive probes are positioned close to the magnet surface to increase signal amplitude, then the signal strength improves, but angular errors increase due to non-linear magnetic field variations
Solution Approach 1:
The patent introduces ferromagnetic concentrators as intermediary elements between the multipolar main magnet and the magnetoresistive probes. These concentrators reshape the magnetic field distribution, providing stronger signal amplitude while maintaining more linear field variations, thus resolving the contradiction between signal strength and measurement precision.
Solution Approach 2:
The patent positions the magnetoresistive probes at specific radial distances from the magnet surface where the magnetic field characteristics are optimal. This localized positioning ensures both sufficient signal amplitude and acceptable linearity of magnetic field variations for accurate angular measurement.
3Volume of moving object
If the secondary sensor is positioned on the axis of revolution of the magnet to simplify the structure, then the device compactness improves, but the measurement accuracy decreases due to magnetic field distortions
Solution Approach 1:
The patent nests the secondary sensor within the volume occupied by the multipolar main magnet, positioning it at an optimized radial distance from the axis of revolution. This nested configuration achieves compact axial footprint while maintaining measurement accuracy through careful geometric optimization.
4Measurement precision
If a high number of pole pairs is used in the main magnet to increase resolution, then the measurement resolution improves, but the sensor becomes more sensitive to external magnetic disturbances
Solution Approach 1:
The patent optimizes the number of pole pairs to a moderate range (4-16 pairs) rather than using very high numbers. This parameter optimization provides sufficient measurement resolution while reducing sensitivity to external magnetic disturbances, resolving the contradiction between resolution and disturbance sensitivity.
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 enables a compact, precise, and robust multiturn position sensor capable of maintaining accurate absolute position measurements with reduced axial bulk and minimal magnetic disturbance, effectively addressing the limitations of previous technologies.
Implementation Method 1
utilizing Hall effect or magnetoresistive probes
Implementation Method 2
utilizing Hall effect or magnetoresistive probes
Implementation Method 3
ferromagnetic concentrators
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~4c
AI summary
The invention relates to a magnetic device for detecting the absolute position of an input shaft capable of rotating more than 360°, said device including a main magnetic sensor (2, 6), a motion reducer (1,4), and a secondary magnetic sensor (7, 9), wherein the main magnetic sensor (2, 6) is connected to a rotor (5), measures the rotation of the shaft for ranges of angles of less than 360°, and includes a main magnet (2), the motion reducer (1, 4) converts the rotation of the shaft into a reduced rotation, the maximum amplitude of which is equal to no more than 360°, and the secondary magnetic sensor (7, 9) measures the reduced rotation and includes a secondary magnet (9). According to the invention, the secondary magnet (9) is arranged between the upper and lower planes of the main rotor (5), and the main magnet (2) has P pairs of poles, where P is greater than 1.