Brushless Motor Rotor Position Detection at Zero Speed
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Solution Overview
Problem
Existing sensorless brushless motor control methods are limited by the need for motor motion to detect rotor position through back EMF, making them ineffective at low speeds, such as in fine-positioning applications.
Innovation Solution
A method and device that inject electrical signals into the stator of a brushless motor to measure scattering parameters, which are used to determine rotor position without relying on back EMF, utilizing a neural network to interpret the data and provide position information at various motor velocities, including zero velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control uses back EMF detection to determine rotor position, then position feedback can be obtained without explicit position sensing components, but the motor must be in motion with sufficient rapidity which makes it ineffective for low-speed operation
Solution Approach 1:
The patent replaces the back EMF detection method (which relies on motor motion) with an electrical impedance measurement method. By injecting test signals into the stator windings and measuring the resulting current responses, the system determines rotor position through electrical characteristics rather than mechanical motion, enabling position sensing at zero and low speeds without requiring explicit position sensors
Solution Approach 2:
The patent introduces test signal injection and impedance measurement as an intermediary method to indirectly determine rotor position. Instead of directly measuring back EMF from motor operation, the system uses injected test signals and measures the electrical impedance characteristics that are influenced by rotor position, providing a mediator pathway for position detection that works independently of motor speed
2Measurement precision
If explicit position sensing components are added to the motor, then accurate rotor position detection is possible at all speeds including low speeds, but the device complexity and cost increase
Solution Approach 1:
The patent makes the motor's stator windings serve dual purposes: they function as both the power delivery components and the sensing elements. By injecting test signals into the existing stator windings and measuring the electrical impedance responses, the system uses the motor's own components for position sensing, eliminating the need for separate position sensing hardware while maintaining accurate position detection capability
Solution Approach 2:
The patent enables the stator windings to perform multiple functions simultaneously: they serve as both the power delivery coils for motor operation and as the sensing elements for position detection. The same electrical connections and windings used for motor control are also used to inject test signals and measure impedance characteristics, providing a universal solution that eliminates dedicated position sensors
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 rotor position detection at low or zero speeds, eliminating the need for position sensors and allowing for condition monitoring of motors, with potential applications in harsh environments and low-cost, low-mechanical-footprint solutions.
Implementation Method 1
measuring scattering parameters reflected back from the stator, wherein the scattering parameters are influenced by the near-field dynamics impaired by the motor
Implementation Method 2
measuring scattering parameters reflected back from the stator
Data Source
AI summary
A method and device for determining the position of a rotor in a brushless motor is provided. The method generally includes: injecting electrical signals into a stator of the brushless motor; measuring scattering parameters reflected back from the stator, wherein the scattering parameters are influenced by the near-field dynamics impaired by the motor; and comparing the measured scattering parameters to a predetermined data set of scattering parameters for known rotor positions to determine the position of the rotor. The method and device is also suitable for determining a condition of a motor or a generator.