Magnetic Position Sensor Zero Crossing Detection
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Solution Overview
Problem
Existing magnetic position sensors face challenges in accurately detecting the zero crossing point in a short cycle due to limitations in scanning frequency and detection speed, leading to errors in magnetic flux density detection and requiring a large number of magnetic detection elements.
Innovation Solution
A magnetic position sensor with a straight-line array of detection elements that scans every k-th element to approximate the zero crossing point and uses a position detection unit to accurately determine the point, reducing scanning time and processing requirements, and includes a correction unit for offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of magnetic detection elements are arranged in an array to obtain the zero crossing point with accuracy, then measurement precision is improved, but processing time increases and productivity decreases
Solution Approach 1:
The patent divides the array of magnetic detection elements into multiple groups, where each group contains elements at specific intervals (e.g., every k-th element). The detection process is segmented into two stages: first, a coarse detection is performed by reading only selected groups to identify the approximate zero crossing point region; second, a fine detection is performed by reading elements in a smaller range around the identified region to precisely determine the zero crossing point. This segmentation reduces the total number of elements that need to be scanned while maintaining detection accuracy.
2Productivity
If the frequency of alternating current applied to the coil array is increased to detect position at high speed, then productivity is improved, but measurement precision deteriorates due to detection errors
Solution Approach 1:
The patent replaces the coil-based electromagnetic induction system with a direct magnetic detection element array that detects magnetic flux density without requiring alternating current excitation. This substitution eliminates the limitation of coil current frequency that restricted detection speed, allowing high-speed position detection while maintaining accuracy through direct magnetic field sensing.
3Measurement precision
If every magnetic detection element is scanned to obtain accurate position, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs a preliminary coarse detection by reading outputs of selected magnetic detection elements (e.g., every k-th element) to identify the approximate region where the zero crossing point is located. Based on this preliminary information, the system then performs a fine detection only in a limited range around the identified region. This preliminary action eliminates the need to scan all elements, significantly reducing scanning time while maintaining detection accuracy.
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
This approach allows for faster detection of the zero crossing point, reduces processing time, and minimizes errors by scanning fewer elements and using output ratios for precise positioning, unaffected by magnetic flux density shape or temperature coefficients.
Implementation Method 1
magnetic detection elements whose output changes in polarity when the direction of the magnetic flux density is inverted
Data Source
AI summary
The present invention enables to obtain an approximate position of a zero crossing point in a shorter time period. A magnetic position sensor detects, with an array in which multiple magnetic detection elements are arranged in a straight line, the zero crossing point at which the magnetic flux density from a pair of magnetic poles is zero in a plane perpendicular to the longitudinal direction of the array. The magnetic detection elements are elements whose output changes in polarity when the direction of the magnetic flux density is inverted, and detect an approximate position of the zero crossing point by reading an output of every k-th magnetic detection element of the array (where k is an integer of 2 or greater). Then, the position of the zero crossing point is detected according to outputs of at least two magnetic detection elements on both sides of the zero crossing point.