Dual Magnetic Sensor Layout for Brushless Motor Position Control
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Solution Overview
Problem
The challenge in using magnetic sensors for controlling brushless motors, especially in liquid cooling pumps, is the difficulty in accurately detecting the rotor's position due to the immersion of the rotors in cooling liquids, leading to weaker signal detection and reduced control accuracy.
Innovation Solution
The implementation of a brushless motor design that incorporates two magnetic sensors statically arranged relative to the stator, with one sensor aligned with a first magnetic pole and the other with a second magnetic pole, allowing the combination of their signals to enhance control accuracy and robustness against variations in magnetic pole strength and external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are placed close to the magnetic poles of the rotor, then the signal detection accuracy is improved, but the device complexity and manufacturing difficulty increase due to the immersion of the rotor in cooling liquid
Solution Approach 1:
The patent divides the sensing function into two separate magnetic sensors instead of using one sensor close to the rotor. This segmentation allows each sensor to be positioned at a manageable distance from the magnetic poles, reducing the complexity of placement while maintaining adequate signal detection through signal combination.
Solution Approach 2:
The patent combines the outputs of two magnetic sensors to achieve the desired measurement precision. By merging the signals from two sensors positioned at different locations, the system attains accurate rotor position detection without requiring any single sensor to be placed in the complex environment immediately adjacent to the immersed rotor.
2Measurement precision
If multiple magnetic sensors are used to determine rotation direction, then the control accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The two magnetic sensors serve multiple functions: they determine rotation direction, measure rotor position, and provide redundant measurement for improved accuracy. This multi-functionality justifies the addition of sensors by extracting maximum utility from each component, reducing the overall system complexity compared to using specialized sensors for each function.
Solution Approach 2:
The patent uses the outputs from multiple magnetic sensors to provide feedback for motor control. The combined information from the sensors enables accurate determination of rotor position and rotation direction, creating a feedback loop that improves control accuracy while the systematic use of feedback principles keeps the control logic manageable.
3Temperature
If the rotor is immersed in cooling liquid, then the cooling efficiency is improved, but the signal strength detected by magnetic sensors decreases
Solution Approach 1:
The patent combines the signals from two magnetic sensors to compensate for the signal weakening caused by liquid immersion. The combined signal strength is sufficient for accurate control despite each individual sensor operating at a distance from the magnetic poles due to the cooling liquid barrier.
Solution Approach 2:
The patent introduces an intermediary signal processing stage that combines and processes the outputs from multiple sensors. This intermediary processing compensates for the signal attenuation caused by the cooling liquid, allowing the system to maintain measurement precision while preserving the cooling efficiency benefit of rotor immersion.
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 improves the motor's control accuracy and reliability by minimizing the effects of suboptimal component placement and variations in magnetic pole strength, while also reducing the impact of external magnetic fields, thereby ensuring stable operation even in harsh environments.
Implementation Method 1
Magnetic sensors are used in the art to detect the position of magnetic poles of rotor magnets. The magnets of the rotor yield a magnetic field which depends on how the rotor is positioned. The magnetic field is measured by the magnetic sensors.
Implementation Method 2
This force is provided by running current through wires acting as electromagnets. The electromagnets can be controlled such that the rotor will continuously be subjected to a force to maintain rotation
Data Source
AI summary
A brushless motor having a rotor arranged to rotate around a rotor axis and a stator. The rotor comprising a plurality of magnetic poles comprising at least a first magnetic pole, and a second magnetic pole. The motor further has a first magnetic sensor and a second magnetic sensor, where the first magnetic sensor and the second magnetic sensor are arranged statically relative to the stator. The first magnetic pole is arranged at a first angle and the second magnetic pole is arranged at a second angle while the first magnetic sensor and the second magnetic sensor are arranged with an angle difference corresponding to the angle difference between the first angle and the second angle. The first magnetic sensor and the second magnetic sensor are configured to combine the signals output by the first magnetic sensor and the second magnetic sensor such that the combined signal being used for the control of the brushless motor.