Leakage Flux Angle Sensing With Three 120° Hall Elements
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Solution Overview
Problem
Existing rotation angle calculation methods using two Hall elements to generate orthogonal components suffer from errors and noise due to signal deviations from a first-order SIN wave, leading to inaccuracies in calculating the rotation angle.
Innovation Solution
A rotation angle calculation system and method utilizing three detection elements arranged at 120-degree electrical offsets to generate orthogonal component signals from leakage flux, with the permanent magnet's axial length M constrained by S+2A≤M≤1.3S, allowing accurate calculation of the rotation angle by suppressing errors and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two Hall elements are used to generate orthogonal components, then the device complexity is reduced, but the measurement precision of rotation angle deteriorates due to signal deviations from first-order SIN wave
Solution Approach 1:
The patent divides the detection function into three separate detection elements arranged at 120-degree intervals, with each element detecting leakage flux at its specific position. This segmentation allows the system to capture more comprehensive magnetic field information compared to using only two elements, thereby improving rotation angle measurement precision while maintaining reasonable device complexity
Solution Approach 2:
The patent transitions from a two-element detection system to a three-element system, adding an additional detection dimension. By arranging three detection elements at 120-degree electrical offsets rather than the conventional 90-degree arrangement, the system captures leakage flux information from multiple spatial dimensions, enabling more accurate orthogonal component generation and rotation angle calculation
2Measurement precision
If three detection elements arranged at 120 degrees are used, then the measurement precision of rotation angle is improved, but the device complexity increases
Solution Approach 1:
The three detection elements serve multiple functions: each element detects leakage flux for rotation angle calculation, and collectively they provide the information needed to generate both orthogonal components (sin and cos signals). This multi-functionality reduces the need for separate sensing elements, making the three-element configuration more efficient than it initially appears
Solution Approach 2:
The patent changes the detection element arrangement from the conventional two-element 90-degree configuration to a three-element 120-degree configuration. This parameter change in the detection system's geometric arrangement fundamentally alters how orthogonal components are generated, allowing for improved measurement precision through better signal characteristics and reduced distortion
3Measurement precision
If permanent magnet axial length M is within S+2A≤M≤1.3S, then the measurement precision is improved by reducing magnetic flux distortion, but the manufacturing constraints are increased
Solution Approach 1:
The patent establishes a specific parameter range for the permanent magnet axial length M (S+2A≤M≤1.3S, where S is stator axial length and A is air gap length). By optimizing this dimensional parameter, the system achieves better leakage flux detection accuracy and reduced magnetic flux distortion, while providing clear manufacturing guidelines
4Measurement precision
If orthogonal components are generated from leakage flux detection, then the rotation angle calculation accuracy is improved, but the device complexity increases due to additional signal processing
Solution Approach 1:
The system uses the leakage flux detected by the three elements to self-generate the orthogonal components (sin and cos signals) needed for rotation angle calculation. The detection elements and signal processing work together in an integrated manner where the raw detection signals are directly transformed into the required orthogonal components through mathematical processing, eliminating the need for separate excitation windings and associated control circuitry
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 effectively suppresses errors and noise in rotation angle calculations by deriving orthogonal components from leakage flux, improving accuracy and reducing magnetic flux distortion from stator windings.
Implementation Method 1
acquires detection results of a leakage flux generated by a permanent magnet (4)
Data Source
AI summary
The rotation angle calculation device includes: an acquisition unit that acquires detection results of a leakage flux generated by a permanent magnet, from each of three detection elements, the permanent magnet being included in a detection target of the rotation angle, the three detection elements being arranged at positions offset by 120 degrees from each other in electrical angle relative to the permanent magnet, a generation unit that generates orthogonal component signals, each of the orthogonal component signals representing one of two orthogonal components representing the strength of the leakage flux, based on the three detection results, and a calculation unit that calculates the rotation angle of the detection target based on the orthogonal component signals.