Multi-turn Magnetic Encoder Using TMR Sensors and Ring Magnets
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Solution Overview
Problem
Existing magnetic absolute encoder technologies face limitations due to high power consumption, low resolution, and incompatibility with tunneling magnetoresistive sensors, primarily because they use Hall sensors and solid cylindrical permanent magnets, which are not compatible with the requirements of multiturn applications.
Innovation Solution
A multi-turn absolute magnetic encoder utilizing tunneling magnetoresistive angle sensors and a cylindrical ring permanent magnet structure with symmetrically aligned magnetization, integrated into a multi-stage gear set, allowing for high sensitivity, low power consumption, and precise position measurement, while being compatible with magnetoresistive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors are used for magnetic field detection, then the encoder can measure angular position, but the power consumption is high and resolution is low
Solution Approach 1:
The patent replaces Hall sensors with tunneling magnetoresistive (TMR) sensors to detect magnetic field changes. TMR sensors offer significantly higher resolution and lower power consumption compared to Hall sensors, directly resolving the contradiction between measurement precision and energy consumption.
Solution Approach 2:
The patent changes the detection parameter from Hall effect-based voltage output to TMR effect-based resistance output, enabling finer resolution measurement and lower power consumption. The TMR sensors detect magnetic field orientation through resistance changes, providing superior performance metrics.
2Adaptability or versatility
If solid cylindrical permanent magnets are used, then the structure is simple, but the design is not compatible with tunneling magnetoresistive sensors and increases space
Solution Approach 1:
The patent segments the permanent magnet into multiple magnetization units with different magnetization directions arranged in a cylindrical ring structure. This segmentation allows the magnetic field to be distributed in a pattern that is compatible with TMR sensor detection, enabling precise angular measurement while reducing the overall volume compared to solid cylindrical magnets.
Solution Approach 2:
The patent transitions from a solid cylindrical magnet (3D bulk structure) to a cylindrical ring magnet with segmented magnetization (2D surface distribution). This dimensional change concentrates the magnetic field in the plane of the TMR sensor, improving compatibility and reducing the axial height and radial footprint.
3Measurement precision
If multiple reduction gear stages are added to increase measurement range, then the number of turns can be measured accurately, but the device complexity increases
Solution Approach 1:
The patent implements a nested structure where multiple counting units with different resolution levels are integrated into a single compact assembly. Each counting unit corresponds to a reduction gear stage, and they are nested such that the overall device remains compact while achieving high measurement range through the combined capability of multiple stages.
Solution Approach 2:
The patent uses a dynamic signal processing approach where the system automatically selects and processes signals from different counting units based on the measurement range required. This allows the device to achieve high measurement accuracy without requiring all gear stages to be physically complex, as the processing unit dynamically adapts to the measurement task.
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 provides high precision, low power consumption, and compact design, enabling accurate measurement of absolute position and number of turns with improved resistance to environmental factors like dust and oil, and allows for a linear relationship between magnetic orientation and mechanical rotation angles.
Implementation Method 1
a tunneling magnetoresistive angular displacement sensor to detect the magnetic field component produced by the permanent magnet in the detection plane of the permanent magnet and output a signal
Implementation Method 2
tunneling magnetoresistive sensors have better magnetic field sensitivity
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A multi-turn absolute magnetic encoder, comprising (M+1) counting units, a single-turn signal processing unit (6), and a multi-turn signal processing unit (12). Each counting unit comprises counting wheels (4, 10) with a cylindrical ring permanent magnet (14) fixed thereon, and a tunneling magnetoresistive angular displacement sensor (11). The magnetoresistive angular displacement sensor (11) is located within a region in a detection plane of the permanent magnet (14) at within a specific radius range from the axis of the cylindrical ring permanent magnet (14), within the detection plane the angle of a component of a magnetic field generated by the permanent magnet (14) is linearly proportional to the rotation angle of the cylindrical ring permanent magnet. The single-turn signal processing unit (6) calculates and outputs a code characterizing the absolute angular position of the input shaft (3) based on the sensor signal of the first counting unit; and the multi-turn signal processing unit (12) calculates and outputs the integer number of turns of the input shaft based on the sensor signals of the second counting unit to (M+1) counting units.