Brushless Motor Controller Using Back-EMF Feedback for High-Speed Operation
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Solution Overview
Problem
Conventional brushless permanent magnet motors face challenges in controlling high-speed applications due to the need for high-frequency PWM controllers, which are impractical with current high-powered electronic circuitry, and design compromises that increase size, weight, and cost while reducing efficiency.
Innovation Solution
A control system that supplies excitation current independently to motor windings, using a commutation feedback loop to control current timing and duration based on back EMF signals, allowing for high-speed operation without the need for high inductance and high-frequency PWM, enabling efficient motor operation at high mechanical and electrical speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional PWM control methods are used for high-speed motor operation, then motor speed can be controlled, but the controller becomes overly complex and requires high-frequency PWM which is impractical with current high-powered electronic circuitry
Solution Approach 1:
The control system is segmented into two independent loops: a commutation feedback loop that handles timing and duration of excitation current based on back EMF signals, and a power supply that independently controls current amplitude. This segmentation eliminates the need for complex high-frequency PWM controllers while enabling high-speed operation.
Solution Approach 2:
The patent extracts the commutation control function from the power supply control, creating a separate commutation feedback loop that operates independently. This extraction allows each loop to be optimized for its specific function, reducing overall controller complexity while maintaining high-speed capability.
2Ease of operation
If design compromises are made to simplify motor control (such as field weakening, helical magnets, electromagnets), then control becomes easier, but motor size, weight, and cost increase while efficiency decreases
Solution Approach 1:
The patent employs a commutation feedback loop that uses back EMF signals to automatically control the timing and duration of excitation current. This feedback mechanism simplifies control by eliminating the need for complex control algorithms while maintaining optimal performance across varying speeds, without requiring additional heavy components.
3Speed
If high-frequency PWM controllers are used for high-speed motor operation, then motor speed control is achieved, but the electronic circuitry becomes impractical and efficiency is reduced
Solution Approach 1:
The control system dynamically adapts to motor speed by using back EMF signals to automatically adjust commutation timing and duration. This dynamic adaptation eliminates the need for fixed high-frequency PWM switching, reducing energy losses while maintaining high-speed operation capability.
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 approach simplifies the controller design, reduces motor inductance, and improves efficiency, enabling higher motor speeds without the need for complex high-power electronic controllers, thus overcoming the limitations of conventional PWM control methods.
Implementation Method 1
using a commutation feedback loop to control current timing and duration based on back EMF signals
Implementation Method 2
The stator windings must be excited by an oscillating or intermittent electrical current (i.e., AC or PWM) in order to exert an electromotive force upon the magnets as the magnets rotate or translate relative to the windings
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3~4
AI summary
An electrical controller for electric motors is provided. A control system for an electric motor comprises means for supplying excitation current to different windings of the motor at any given time. Furthermore, the amplitude of the excitation current is independently variable of the timing and duration of the application of the excitation current to the windings. This allows increased control of the motor and facilitates the operation of the motor at high mechanical and/or electrical speeds.