Rotating Body Absolute Position Detection Using Multi-Row Magnet Arrays
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Solution Overview
Problem
Existing rotary encoder systems cannot accurately detect the absolute position of a rotating body, limiting their application in fields such as vehicle wheel bearings and anti-lock brake systems.
Innovation Solution
A detection device comprising multiple rows of magnets with varying pole pairs and Hall sensors to measure the primary harmonic of the signals output from these sensors, allowing for precise detection of the absolute position of a rotating body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single row of magnets with n pole pairs is used in the rotary encoder, then the device complexity is low, but the measurement precision of absolute position is insufficient
Solution Approach 1:
The magnet assembly is segmented into multiple rows (first row with n pole pairs, second row with n+1 pole pairs, third row with n+2 pole pairs) instead of using a single row. Each row is detected by a corresponding Hall sensor, and the controller processes signals from multiple rows to calculate absolute position through least squares estimation, thereby improving measurement precision while maintaining manageable device complexity through modular segmentation
Solution Approach 2:
The system transitions from single-dimensional detection (one row of magnets) to multi-dimensional detection (multiple rows with different pole pairs arranged in different dimensions). The first, second, and third rows of magnets are arranged in different spatial dimensions, and the controller processes signals from all dimensions simultaneously to achieve more accurate absolute position detection through multi-dimensional signal fusion
2Measurement precision
If multiple rows of magnets with different pole pairs are used to improve measurement precision, then the absolute position detection precision improves, but the device complexity increases
Solution Approach 1:
The detection system is segmented into three independent detection channels, each consisting of a row of magnets and a corresponding Hall sensor. The first Hall sensor detects the first row with n pole pairs, the second Hall sensor detects the second row with n+1 pole pairs, and the third Hall sensor detects the third row with n+2 pole pairs. This segmentation allows the system to process multiple signals in parallel and use least squares estimation to improve precision while keeping each individual channel relatively simple
Solution Approach 2:
Each row of magnets with different pole pairs serves a dual function: individually, each row can provide rotation speed information, and collectively, the multiple rows with different pole pairs work together to provide absolute position information. The Hall sensors similarly serve multiple functions by detecting both the rotation speed and contributing to absolute position calculation through their combined signals
3Measurement precision
If only rotation speed detection is implemented, then the device complexity is low, but the measurement precision of absolute position cannot be achieved
Solution Approach 1:
The controller implements a feedback mechanism where it continuously receives signals from multiple Hall sensors, calculates the absolute position using least squares estimation based on the ratio of fundamental wave components, and uses this calculated position information to improve the overall detection accuracy. The system processes the signals from all three rows of magnets through a unified algorithm that provides feedback on the absolute position state
Solution Approach 2:
The controller performs preliminary signal processing by extracting fundamental wave components from the signals received from multiple Hall sensors before calculating the absolute position. The system pre-processes the signals by analyzing the ratio of fundamental waves at different frequencies (n, n+1, n+2 pole pairs) and uses this preliminary analysis to determine the absolute position through least squares estimation, rather than processing raw signals directly
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
Enables accurate detection of the absolute position and speed of a rotating body, improving resolution and applicability to various fields, including vehicle wheel bearings, even when some magnets are damaged.
Implementation Method 1
a first Hall sensor installed adjacent to the first row magnets, detecting a change in magnetism according to rotation of the first row magnet, and outputting a signal
Data Source
AI summary
This application relates to an absolute position detection device and detection method of a rotating body. In one aspect, the device includes first row magnets coupled to a rotating body to rotate together and having n pole pairs, and second row magnets coupled to the rotating body to rotate together and having (n+1) pole pairs. The device also includes a first Hall sensor installed adjacent to the first row magnets and configured to detect a change in magnetism according to rotation of the first row magnets. The device further includes a second Hall sensor installed adjacent to the second row magnets and configured to detect a change in magnetism according to rotation of the second row magnets. The device further includes a controller configured to measure an absolute position of the rotating body using signals output from the first and second Hall sensors.