Magnetic Position Sensor Using Angled Field and Ferromagnetic Modulation
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Solution Overview
Problem
Existing position measurement systems for linear motors face challenges in achieving high-resolution, long-stroke, and cost-effective absolute position sensing, especially over a wide temperature range, with existing solutions often requiring additional magnets and complex calibration processes.
Innovation Solution
A low-cost non-contact position sensor system that uses a combination of magnetic field direction sensors and Hall effect sensors to determine the position of a linear motor armature, where the magnetic field orientation is angled with respect to the path, and a ferromagnetic element changes the magnetic field distribution as the armature moves, allowing for compensation of magnetic field strength variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional magnets and complex calibration processes are used to achieve high-resolution position sensing, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses the motor's own magnets to generate the magnetic field for position sensing, eliminating the need for additional sensing magnets. The ferromagnetic element modulates this existing field to provide position information, making the system self-sufficient and reducing overall complexity
Solution Approach 2:
The motor magnets serve dual purposes: generating force for motor operation and creating the magnetic field for position sensing. The ferromagnetic element also serves multiple functions by modulating the magnetic field and providing position information, reducing the need for separate components
2Measurement precision
If additional magnets are added to the system for position sensing, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses the motor's own magnets to generate the magnetic field for position sensing, eliminating the need for additional sensing magnets. The ferromagnetic element modulates this existing field to provide position information, making the system self-sufficient and reducing overall complexity
Solution Approach 2:
The force-generating magnets and position-sensing magnetic field source are merged into a single component (the motor magnets). The ferromagnetic element combines the functions of field modulation and position indication, reducing the total number of components
3Device complexity
If magnetic field strength variations are not compensated, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system measures the magnetic field strength and uses this information to compensate for variations in position measurements. The ferromagnetic element's modulation of the magnetic field provides feedback information that allows the system to correct for field strength changes and maintain measurement accuracy
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 provides high-resolution, absolute position measurement with reduced complexity and cost, capable of operating over a wide temperature range and maintaining accuracy across the entire stroke of the motor, suitable for applications like vehicle suspension systems.
Implementation Method 1
a sensor determines a position of the member along the path based on a measurement of a magnetic field generated by the elongated magnet
Implementation Method 2
The member can include a ferromagnetic element that changes the distribution of the magnetic field as the member moves along the path
Implementation Method 3
The sensors can be digital sensors (such as Hall effect switches)
Data Source
AI summary
A position sensing system includes a member movable along a path, the member having an elongated magnet extending along the path, the magnetic field orientation of the elongated magnet being at an angle with respect to the path. A sensor determines a position of the member along the path based on a measurement of a magnetic field generated by the elongated magnet.