Contactless Magnetic Sensor with Compensation Induction for Position Detection
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Solution Overview
Problem
Existing non-contact magnetic sensors for detecting the position of moving objects along linear or rotating trajectories face challenges such as high manufacturing costs, bulkiness, non-monotonic output signals, sensitivity to air gap and temperature variations, and inability to accurately determine absolute position due to bulky magnetic systems.
Innovation Solution
A method and sensor design that utilizes a compensation magnetic induction with a fixed direction opposite to the main magnetic induction, allowing measurement of the resulting magnetic induction's components varying as cosine and sine functions of the angle, to determine relative position along a trajectory, while reducing the size and volume of the magnetic system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a more sensitive measurement system is used to lower the detection threshold, then the lower detection threshold is reduced, but the external field becomes more disturbing in relation to the signal to detect
Solution Approach 1:
The patent introduces a compensation magnet as an intermediary element that generates a compensation magnetic field to counterbalance external magnetic field disturbances. This mediator allows the measurement system to maintain high sensitivity while rejecting external interference through active compensation of the magnetic environment.
Solution Approach 2:
The patent dynamically adjusts the compensation magnetic field parameters (strength and direction) based on detected external field conditions. By changing the compensation field parameters in response to varying external disturbances, the system maintains optimal signal-to-noise ratio while preserving measurement precision.
2Measurement precision
If a bulky and relatively long magnet is used to meet the lower detection threshold, then the detection capability is improved, but the magnet size increases
Solution Approach 1:
The compensation magnet acts as a mediator that enables the use of a smaller main magnet while maintaining detection capability. The compensation field supplements the magnetic signal, allowing reduction of the main magnet volume without sacrificing measurement precision.
Solution Approach 2:
The patent employs an asymmetric magnetic system configuration where the compensation magnet is positioned and oriented differently from the main magnet. This asymmetric arrangement creates a combined magnetic field pattern that enhances detection capability while minimizing the volume of individual magnet components.
3Ease of operation
If a contactless magnetic sensor is used to detect position, then contactless detection is achieved, but the magnetic system becomes bulky and longer than the stroke to be detected
Solution Approach 1:
The patent implements a nested arrangement where the compensation magnet is positioned within or adjacent to the measurement system structure, and the main magnet is integrated with the moving component. This nesting allows the magnetic system length to be comparable to or shorter than the detection stroke while maintaining contactless operation.
Solution Approach 2:
The patent transitions from a linear extension of the magnetic system along the stroke direction to a compact three-dimensional arrangement. By utilizing spatial dimensions perpendicular to the stroke, the magnetic fields are generated without requiring the system length to exceed the detection stroke.
4Ease of operation
If a sensor design with three magnets is used to achieve contactless detection, then contactless detection is achieved, but the output signal becomes non-monotonic and sensitive to air gap variations
Solution Approach 1:
The compensation magnet serves as an intermediary that stabilizes the output signal by counterbalancing air gap variations. The compensation field is designed to compensate for signal fluctuations caused by positioning variations, ensuring monotonic and stable output throughout the detection range.
Solution Approach 2:
The patent implements a feedback mechanism where the compensation magnetic field is adjusted based on the detected signal characteristics. This feedback loop maintains signal monotonicity by dynamically compensating for air gap variations and other disturbances during operation.
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
This approach enables accurate, monotonic detection of relative movements with reduced sensor size, adaptability to detection thresholds, and insensitivity to external magnetic fields and temperature variations, maintaining conventional detection thresholds.
Implementation Method 1
a measurement system placed close to a moving magnet whose position is to be detected. This measurement system delivers an electrical signal relating to the direction of the magnetic induction
Implementation Method 2
document FR 2 452 716 describes a displacement measurement device using magneto-resistive technology, sensitive to the direction of the magnetic induction
Data Source
Figure 1~3C
Figure 4~5
AI summary
The invention relates to a measurement method for the contactless magnetic detection of relative movements along a path (T), between a system (3) for creating a main magnetic flux density (B) and a measurement system (4) that is sensitive to the direction of the magnetic flux density, the creating system (3) ensuring the creation of a main magnetic flux density (B) having a direction that is variable in at least one plane and detected by the measurement system (4) in order to determine the relative position along said path. According to the invention, the method comprises subjecting the measurement system (4) to a compensating magnetic flux density (Bi) with a fixed direction that is opposite to the direction of the maximum main magnetic flux density measured by the measurement system (4) and output only by the creating system (3), and determining the direction of a magnetic flux density resulting from combining the main (B) and compensation (Bi) magnetic flux densities by measuring the two components of the resulting magnetic flux density, which are normal to one another and vary respectively as substantially cosine and sine functions of the angle of the resulting magnetic flux density.