Brushless Motor Position Sensing via Induced Stator Currents
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Solution Overview
Problem
Conventional position sensors for rotor-stator measurement in brushless motors require mechanical parts, increasing complexity and weight, and necessitate synchronization of magnetic and mechanical positions.
Innovation Solution
A position sensor that measures rotor position using induced currents in a distributed sensor winding, eliminating the need for mechanical parts by leveraging the motor's own magnetic field and stator lamination stack design, with optional two-phase or three-phase windings and a band-rejection filter to reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional position sensors (resolvers or encoders) are used to measure rotor position, then high-resolution continuous position detection is achieved, but mechanical parts must be incorporated between rotor and stator, increasing device complexity and weight
Solution Approach 1:
The patent extracts the position sensing function from mechanical components and implements it through electromagnetic induction in the stator windings. The sensor stator portion with sensor windings detects rotor position through induced currents without requiring mechanical parts between rotor and stator, eliminating the complexity and weight of conventional encoders or resolvers while maintaining measurement capability
Solution Approach 2:
The patent replaces mechanical position sensing systems (encoders, resolvers) with an electromagnetic field-based sensing system. The sensor windings on the stator detect rotor position through electromagnetic induction from rotor magnets, substituting mechanical measurement with field-based measurement to reduce mechanical complexity
2Measurement precision
If conventional position sensors (resolvers or encoders) are used to measure rotor position, then accurate position measurement is achieved, but synchronization between magnetic position and mechanical position calibration is required
Solution Approach 1:
The sensor system automatically detects rotor position through electromagnetic induction without requiring external calibration procedures. The sensor stator windings directly measure the magnetic field position of rotating rotor magnets, providing self-calibrating position detection that eliminates the need for manual synchronization between magnetic and mechanical position references
Solution Approach 2:
The patent replaces mechanical calibration procedures with electromagnetic field-based detection. By using sensor windings that directly sense the magnetic field position rather than mechanical position, the system eliminates the need for calibration procedures to synchronize different reference frames
3Device complexity
If magnetic hall sensors are used to measure rotor position directly, then mechanical parts are eliminated, but multiple sensors (at least 3) are required to detect position variations, increasing sensor quantity and complexity
Solution Approach 1:
The patent combines multiple sensing functions into a single integrated sensor stator structure. The sensor windings are distributed around the sensor stator poles and work together as a unified electromagnetic sensing system, eliminating the need for multiple separate hall sensors while maintaining the capability to detect complete rotor position through trigonometric calculation from induced currents
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 continuous magnetic position measurement without mechanical synchronization, reducing motor and sensor complexity and weight, while maintaining high-resolution position detection.
Implementation Method 1
The position sensor is configured to measure the position of the rotor in relation to the stator by measuring currents induced in the sensor winding caused by the rotation of the rotor
Implementation Method 2
The position sensor of the present invention is used as a 'small generator' where back electromagnetic forces are induced by faraday law thanks to the magnetic flux rotation of rotor
Data Source
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AI summary
Position sensor for a permanent magnet brushless motor, the motor comprising a rotor (100) with permanent magnets (101) surrounding a stator (200) with stator salient poles (202) and with a motor winding (201) wound around the stator salient poles (202), wherein the position sensor comprises: a salient pole sensor stator portion (400) configured to be placed adjacent to a salient pole motor stator portion (205) of the motor, and; a sensor winding (401) wound in a distributed manner around sensor salient poles (402) of the salient pole sensor stator portion (400); wherein the position sensor is configured to measure the position of the rotor (100) in relation to the stator (200) by measuring currents induced in the sensor winding (401) caused by the rotation of the rotor (100).