Brushless Motor Position Detection Using Offset Hall Elements
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Solution Overview
Problem
Conventional brushless motor devices have limitations in detecting the rotational position of a rotor with sufficient resolution for applications like exhaust gas control actuators, where finer detection is desired.
Innovation Solution
A brushless motor device is designed with a stator and rotor configuration that includes a magnet with twice the number of poles for magnetic pole position detection, along with main and sub Hall elements arranged with specific offsets to enhance detection resolution, effectively creating a quadruple-precision system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet with twice the number of poles is used for magnetic pole position detection, then the resolution of rotational position detection is improved, but the device complexity increases
Solution Approach 1:
The detection system is segmented into two independent Hall element sets (main and sub) with different pole configurations. The main Hall elements detect positions using the magnet's twice-as-many poles, while sub Hall elements provide additional detection points, dividing the detection task into manageable segments that collectively achieve quadruple-precision resolution without overwhelming system complexity
Solution Approach 2:
The invention adds a spatial dimension to position detection by arranging Hall elements at different radial positions and angles around the rotor. This multi-dimensional arrangement of detection points allows the system to achieve higher resolution by detecting magnetic field variations from multiple spatial perspectives simultaneously
2Measurement precision
If multiple Hall elements are arranged with specific offsets to enhance detection resolution, then the measurement precision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention changes the detection parameters by using different pole numbers for the magnet (twice the rotor poles) and arranging Hall elements at specific angular offsets. These parameter changes enable high-resolution detection through mathematical relationships in the magnetic field patterns rather than requiring extremely tight mechanical tolerances on Hall element positioning
Solution Approach 2:
The control unit processes signals from multiple Hall elements with different offsets and uses feedback algorithms to calculate the precise rotor position. This computational feedback approach compensates for variations in Hall element positioning, allowing the system to achieve high measurement precision without proportionally high manufacturing precision requirements
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 improves the resolution of rotational position detection, doubling it compared to conventional double-precision systems, making it suitable for precise control in applications like exhaust gas control actuators.
Implementation Method 1
n main Hall elements arranged opposite to the magnet for magnetic pole position detection, for detecting a magnetic pole position of the rotor; n sub Hall elements arranged opposite to the magnet for magnetic pole position detection
Data Source
AI summary
An n-phase brushless motor device is provided. The device includes a magnet for magnetic pole position detection having a number of poles twice as many as that of a rotor and fixed to a face perpendicular to a rotation axis of the rotor; n main Hall elements arranged opposite to the magnet, for detecting a magnetic pole position of the rotor; n sub Hall elements arranged in such a way as to have an offset in a direction of a periphery with respect to the main Hall elements, for detecting the magnetic pole position; and a control unit for counting “2” according to a change in an output pattern of the main Hall elements, for counting “1” when the output pattern is the same as that of the sub Hall elements at a predetermined timing, and for controlling a rotation of the rotor according to these counted values.