Magnetic Rotation Angle Sensor Pole Misalignment Correction
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Solution Overview
Problem
Rotation angle sensors using ring magnets and magnetic field sensors face accuracy issues due to misalignment of magnetic poles during manufacturing, leading to errors in detected rotation angles.
Innovation Solution
A rotation angle sensor system that includes a ring magnet with magnetized magnetic poles, a magnetic field sensor to detect radial and tangent magnetic field strengths, a correction value storage section, a facing magnetic pole detecting mechanism, and a rotation angle correcting section to calculate and correct the rotation angle using pre-set correction values for each magnetic pole or pair of poles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ring magnet is manufactured using a jig with electromagnets to magnetize the ring-shaped magnet raw material, then the manufacturing process can be automated and productivity is improved, but misalignment of magnetic poles occurs due to insufficient jig accuracy or misalignment between the magnet raw material and the jig, causing errors in detected rotation angle
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for each magnetic pole position before the actual rotation angle detection occurs. During manufacturing, the actual positions of magnetic poles are measured and correction values are computed in advance, which are then stored in memory. This allows the system to automatically compensate for manufacturing inaccuracies without requiring high-precision manufacturing processes, thus resolving the contradiction between automated manufacturing productivity and manufacturing precision.
2Manufacturing precision
If the accuracy of the jig used to magnetize the ring magnet is increased to improve magnetic pole position accuracy, then manufacturing precision is improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent applies parameter changes by transforming the physical parameter of magnetic pole position into a correctable data parameter. Instead of requiring the physical position to be perfectly accurate, the system measures the actual positions, calculates correction values, and stores them as data parameters. This allows the use of simpler, less expensive jigs while achieving high measurement accuracy through software-based parameter correction, resolving the contradiction between manufacturing precision and device complexity.
3Measurement precision
If correction values are stored for each magnetic pole or pair of magnetic poles, then the system can correct for misalignment and measurement precision is improved, but the memory storage requirements and data processing complexity increase
Solution Approach 1:
The patent applies segmentation by dividing the correction data into separate correction values for each magnetic pole or each pair of magnetic poles, rather than using a single global correction value. This segmentation allows the system to apply the appropriate correction value based on which magnetic pole is currently facing the magnetic field sensor, improving measurement precision. The segmented approach efficiently manages data volume by only storing correction values for discrete pole positions rather than continuous data.
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 enables high-accuracy detection of rotation angles even with misaligned magnetic poles, reducing errors and ensuring precise angle measurement.
Implementation Method 1
a magnetic field sensor that is provided so as to face the ring magnet in a radial direction of the rotating shaft and detects magnetic field strengths in radial and tangent directions of the rotating shaft
Data Source
AI summary
A rotation angle sensor includes a ring magnet that is provided around a rotating shaft, a magnetic field sensor that detects magnetic field strengths in radial and tangent directions of the rotating shaft, a rotation angle calculation section that calculates a rotation angle of the rotating shaft based on the magnetic field strengths detected by the magnetic field sensor, a correction value storage section that stores correction values preliminarily set for each magnetic pole or each pair of magnetic poles facing the magnetic field sensor, a facing magnetic pole detecting means that detects the magnetic pole or the pair of magnetic poles facing the magnetic field sensor, and a rotation angle correcting section that extracts correction values corresponding to the magnetic pole or the pair of magnetic poles detected, and corrects a rotation angle calculated in the rotation angle calculation section by using the extracted correction values.