Angle Detection Device Harmonic Cancellation
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Solution Overview
Problem
Existing angle detection devices with sensors arranged around a rotary shaft experience high spatial distortion of the magnetic field, leading to low angle detection precision.
Innovation Solution
The first and second sensors are positioned on different radial lines, each dividing the circumference into six equal parts, with calculations to cancel odd-order harmonic components of the sine and cosine signals to reduce spatial distortion and enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensors are arranged around a rotary shaft, then the angle detection device can be configured compactly, but the spatial distortion of the magnetic field becomes high resulting in low angle detection precision
Solution Approach 1:
The patent divides the sensor arrangement into specific radial line positions (0°, 120°, 240°) and uses selective combination of sensor outputs through harmonic cancellation calculations. This segmentation approach allows the system to maintain compact circular arrangement while achieving low spatial distortion by processing signals from specific segmented positions.
Solution Approach 2:
The patent introduces asymmetric processing in the signal calculation by selectively canceling odd-order harmonic components (3rd, 5th, 7th, etc.) while preserving even-order components. This asymmetric filtering approach compensates for the symmetric spatial distortion caused by circular sensor arrangement, thereby improving angle detection precision.
2Device complexity
If sensors are arranged on the same radial line, then the device structure is simplified, but the spatial distortion of the magnetic field increases leading to harmonic components in output signals
Solution Approach 1:
The patent transitions from one-dimensional radial arrangement to two-dimensional angular distribution by placing sensors on multiple radial lines separated by 120 degrees. This dimensional expansion allows the system to capture magnetic field information from different spatial perspectives, enabling harmonic cancellation and reducing spatial distortion effects.
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 configuration significantly increases angle detection precision by minimizing harmonic components and their associated errors, resulting in more accurate rotation angle calculations.
Implementation Method 1
a semiconductor sensor of a magnetic resistance type is arranged so as to be opposed to the sensor magnet in an axial direction of the rotary shaft
Data Source
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AI summary
There are arranged a sensor magnet fixed to a rotary shaft and configured to generate a magnetic field for detecting a rotation angle, and a plurality of sensors arranged so as to be opposed to the sensor magnet and each configured to output a sine signal and a cosine signal in accordance with the magnetic field. First and second sensors are arranged on two radial lines different from each other, respectively, out of three radial lines dividing a circumference about the rotary shaft of the sensor magnet into six equal parts. An angle calculation unit is configured to carry out calculation so that 3n-th (n is a natural number) order harmonic components out of odd-order harmonic components of each of the sine signal and the cosine signal output by the first and second sensors cancel one another, to thereby calculate the rotation angle.