Magnetic Sensor System for High Precision Shaft Positioning
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Solution Overview
Problem
Existing magnetic sensor systems for monitoring the turn count and angular position of rotating shafts lack the necessary precision and resolution, especially in applications where the shaft end is not easily accessible, and existing solutions like optical encoders are expensive or impractical.
Innovation Solution
A magnetic sensing system that combines a magnetic multi-turn sensor and absolute angle sensor with a rotating magnet, along with an incremental sensor system using a rotating disk with Archimedean spiral shaped structures, to provide higher precision angle measurements by detecting changes in the magnetic field as the disk rotates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensor systems use conventional magnetoresistive elements for monitoring turn count and angular position, then the system can detect rotation, but the measurement precision and resolution are insufficient
Solution Approach 1:
The magnetic disk is divided into multiple segments with different magnetic properties arranged in a radial pattern. Each segment creates a distinct magnetic field signature that can be detected by the sensor array, enabling high-resolution angular position measurement. The segmentation allows the system to differentiate between multiple positions within a single rotation cycle.
Solution Approach 2:
The patent transitions from conventional single-dimension magnetic sensing to multi-dimensional magnetic field detection by using a radially arranged magnetic disk with multiple magnetic segments. This creates a two-dimensional magnetic field distribution that provides both angular position and turn count information simultaneously, enhancing measurement precision without sacrificing resolution.
2Measurement precision
If optical encoders are used to achieve high precision angle measurements, then measurement resolution improves, but the system becomes expensive and impractical when the shaft end is not accessible
Solution Approach 1:
The patent replaces optical encoder systems with a magnetic field-based sensing system. The magnetic disk with radially arranged segments creates a magnetic field pattern that can be detected by magnetic sensors, eliminating the need for complex optical components. This substitution maintains high measurement precision while significantly improving ease of manufacture and accessibility, as magnetic sensors can be positioned closer to the shaft end than optical components.
Solution Approach 2:
The magnetic disk acts as an intermediary between the rotating shaft and the sensor system. Instead of directly measuring the shaft position optically, the magnetic disk converts mechanical rotation into magnetic field variations, which then serve as the measurement medium. This intermediary approach enables non-contact sensing with high precision while allowing flexible installation configurations.
3Measurement precision
If the magnetic disk diameter is increased to improve measurement resolution, then angular position detection improves, but the device complexity and size increase
Solution Approach 1:
The magnetic disk employs local quality variations through radially arranged magnetic segments with different magnetic properties at different radial positions. This creates a magnetic field pattern where each segment contributes to the overall field signature in a localized manner. The local quality approach allows high measurement resolution through the magnetic field pattern rather than requiring a large disk diameter, as the field variations are generated by the segmented structure itself.
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 precise measurement of the number of turns and angular position with higher resolution, independent of the disk diameter, allowing for accurate positioning in various applications such as automotive and industrial control systems.
Implementation Method 1
a magnetic sensing device in a vicinity of the magnet, the magnetic sensing device comprising an angle sensor configured to detect an orientation of a magnetic field generated by the magnet as the rotatable shaft is rotated, a magnetic multi-turn sensor configured to detect a number of turns of a magnetic field generated by the magnet
Implementation Method 2
a first incremental sensor configured to detect changes in the magnetic field induced by the first track as the rotatable shaft is rotated
Data Source
AI summary
Example magnetic sensor system includes a magnet mounted on a rotatable shaft, and a magnetic sensing device in a vicinity of the magnet. The magnetic sensing device includes an angle sensor configured to detect an orientation of a magnetic field generated by the magnet as the rotatable shaft is rotated, a magnetic multi-turn sensor configured to detect a number of turns of the magnetic field generated by the magnet as the rotatable shaft is rotated, a magnetic disk mounted on the rotatable shaft, wherein the disk comprises at least a first track for inducing a change in a magnetic field generated by the magnetic disk, wherein the first track is formed from a plurality of curved segments distributed around the circumference of the magnetic disk, and a first incremental sensor configured to detect changes in the magnetic field induced by the first track as the rotatable shaft is rotated.