Multi-Turn Magnetic Position Sensor with Bipolar Magnet
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Solution Overview
Problem
Existing multi-turn non-contact sensing systems face challenges in achieving high-resolution angular position measurement of rotating objects due to poor resolution and complex mechanisms, particularly when determining the linear motion of rotating objects over multiple turns.
Innovation Solution
A position sensing device comprising a first sensor assembly that counts the number of turns and a second sensor assembly that measures the angular position within each turn, utilizing a bipolar and diametrally magnetized magnet to provide orthogonal and parallel magnetic fluxes to a magnetic sensor, which operates in quadrature mode with Hall-effect, magneto-resistive, or GMR sensors, and an ASIC for signal processing, allowing for high-resolution angular displacement measurement over multiple turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex mechanical mechanisms are used to achieve multi-turn sensing, then the measurement range is improved, but the device complexity increases and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces complex mechanical multi-turn sensing mechanisms with a magnetic field-based sensing system. A single magnet mounted on the rotating shaft interacts with magnetic sensors to detect both angular position and number of turns through non-contact magnetic field measurements, eliminating the need for complex mechanical linkages, gears, or multiple sensors while achieving high-resolution multi-turn measurement
Solution Approach 2:
The patent makes a single magnet serve multiple functions: it simultaneously provides angular position information through its angular orientation and number of turns information through its radial displacement from the shaft center. This multi-functional approach allows one component to replace what would traditionally require separate mechanical mechanisms for each measurement function
2Measurement precision
If traditional mechanical mechanisms are used for multi-turn sensing, then the measurement range is improved, but the manufacturing precision deteriorates
Solution Approach 1:
The patent eliminates precision-critical mechanical assemblies by using magnetic field sensing. The magnet's position relative to the sensors is determined by magnetic field interactions rather than mechanical contacts, removing the need for precision mechanical alignment, bearing assemblies, and linkages that would require tight manufacturing tolerances
Solution Approach 2:
The patent introduces magnetic field as an intermediary between the rotating shaft and the sensing system. Instead of direct mechanical coupling that requires precision alignment, the magnetic field mediates the transmission of rotational information to the sensors, allowing for greater manufacturing tolerance and easier assembly
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-resolution angular position measurement with up to 18-bit effective resolution over multiple turns, maintaining accuracy and simplicity by transforming rotational motion into translational motion and using non-contact magnetic sensing, thereby avoiding mechanical complexities.
Implementation Method 1
a bipolar and diametrally magnetized magnet to provide variable orthogonal and parallel magnetic fluxes to the second magnetic sensor
Implementation Method 2
The second magnetic sensor can include four sensors positioned in quadrature and configured to operate as sine-cosine sensors. The second magnetic sensor can be configured to operate in quadrature mode. The second magnetic sensor include a plurality of Hall-effect sensors
Implementation Method 3
The second magnetic sensor include a plurality of magneto-resistive (MR) sensors
Implementation Method 4
The second magnetic sensor include a plurality of giant magnetic resistive (GMR) sensors
Data Source
Figure 1
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Figure 5A~5B
AI summary
Disclosed are systems and methods for measuring multi-turn position of a shaft with high resolution and in a non-contact manner. In some embodiments, a multi-turn sensing apparatus (600) can include a rotation counter (604) configured to determine a number of turns made by a shaft, and an angular position sensor (602) configured to measure an angular position of the shaft (102) within a given turn. The number of turns can be determined with an M-bit resolution, and the angular position per turn can be measured with an N-bit resolution. Selected appropriately, the rotation counter can be configured to operate as a relatively low resolution; and yet the multi-turn sensing apparatus can maintain the N-bit per-turn angular resolution throughout the full range. Accordingly, the multi-turn sensing apparatus can have an effective resolution of M+N bits.