Magnetic Multi-Turn Sensor Initialization via Axial Magnet Movement
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Solution Overview
Problem
Magnetic multi-turn sensors require initialization into a known magnetic state to accurately monitor the number of turns in a rotating device, but existing solutions are difficult to implement once the sensor package is assembled and installed.
Innovation Solution
A magnetic sensor system that includes a magnet mounted on a rotating shaft, a magnetic multi-turn sensor, and an initialization mechanism. The mechanism moves the magnet and shaft axially towards the sensor, exceeding the operating window of the sensor to nucleate domain walls and initialize the magnetoresistive elements, then returns the magnet to its starting position for use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnet is positioned close to the magnetic sensing device during normal operation, then the magnetic field strength is sufficient for accurate sensing, but the sensor cannot be properly initialized
Solution Approach 1:
The magnet is mounted on a movable carrier that can dynamically change its axial position relative to the magnetic sensing device. During initialization, the carrier moves the magnet to a first axial position closer to the sensor to generate domain walls. During normal operation, the carrier positions the magnet at a second axial distance for accurate turn counting. This dynamic positioning resolves the contradiction between needing strong magnetic field for initialization and controlled magnetic field for measurement.
2Reliability
If the magnet is moved axially towards the sensor to initialize domain walls, then the sensor can be properly initialized, but the magnetic field exceeds the operating window
Solution Approach 1:
The system uses a movable carrier to dynamically adjust the axial distance between the magnet and sensor. At the first axial position (closer), the magnetic field exceeds Bmax to initialize domain walls. At the second axial position (farther), the magnetic field is within the operating window (Bmin < B < Bmax) for accurate turn counting. This dynamic distance adjustment allows the system to operate in different magnetic field regimes as needed.
3Device complexity
If a fixed magnet position is used, then the device structure is simple, but the sensor cannot be initialized and then used for measurement
Solution Approach 1:
Instead of a fixed magnet position, the patent implements a movable carrier that can axially translate the magnet between two positions. This dynamic structure adds complexity but enables both initialization (at first axial position) and measurement (at second axial position) functions, resolving the contradiction between structural simplicity and functional capability.
4Measurement precision
If the magnet remains at the starting position, then the sensor operates within the operating window, but domain walls cannot be generated for initialization
Solution Approach 1:
The movable carrier enables the magnet to dynamically shift from the starting position (second axial distance) to an initialization position (first axial distance closer to sensor). This movement temporarily increases the magnetic field strength above Bmax to nucleate domain walls, then returns to the starting position for normal operation within the operating window, resolving the contradiction between operating specifications and initialization 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 system effectively initializes the magnetic multi-turn sensor into a known state, ensuring accurate turn count measurement by magnetizing all magnetoresistive elements into the same state, thereby enhancing the reliability of the sensor system.
Implementation Method 1
the magnetic field experienced by the magnet sensing device exceeds the upper limit, Bmax, of the operating window. This causes domain wall nucleation, whereby the sensor spiral is filled with domain walls that magnetise all of the magnetoresistive elements into the same state
Implementation Method 2
Magnetic multi-turn sensors typically use magnetoresistive elements that are sensitive to an applied external magnetic field. The resistance of the magnetoresistive elements in multi-turn sensors can be changed by rotating a magnetic field within the vicinity of the sensor
Data Source
AI summary
The present disclosure provides magnetic sensor system that includes a magnet mounted on the end of a rotating shaft, a magnetic sensing device comprising a magnetic multi-turn sensor, and a mechanism for initializing the magnetic multi-turn sensor into a known state ready for use. Whilst the magnetic sensing device is being used to monitor the rotation of the shaft, the magnet is located in a starting position a first distance from the magnet sensing device such that the magnet field strength experienced by the magnet sensing device is within the operating window of the magnet multi-turn sensor, the operating window being defined by a minimum magnetic flux density, Bmin, and a maximum magnetic flux density, Bmax. The mechanism comprises a means for moving the magnet and the shaft in an axial direction towards the magnet sensing device such that the magnetic field experienced by the magnet sensing device exceeds the upper limit, Bmax, of the operating window. This causes domain wall nucleation, whereby the sensor spiral is filled with domain walls that magnetise all of the magnetoresistive elements into the same state. Once the initialization has taken place, the mechanism is configured to return the magnet to its starting position ready for use. In this respect, the mechanism may have a biasing means such as a spring that biases the magnet towards the starting position.