Sensorless Brushless Motor Control via Back-EMF Signal Processing
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Solution Overview
Problem
Existing sensorless control methods for single-phase brushless permanent-magnet motors face challenges in determining rotor position without Hall-effect sensors, leading to reduced electrical power delivery and increased complexity due to susceptibility to electromagnetic noise and the need for suspended excitation.
Innovation Solution
A method involving the generation of signals proportional to voltage and current across a winding, differentiation, and comparison to determine rotor position through back EMF edges, allowing commutation without suspended excitation and enabling more efficient power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall-effect sensor is integrated within the motor to determine rotor position, then measurement precision is improved, but device complexity increases due to complicated design and manufacture
Solution Approach 1:
The patent extracts the rotor position detection function from a physical Hall-effect sensor and implements it through signal processing of existing back EMF measurements. By processing the voltage signal across the winding to detect zero-crossings and determine rotor position, the system eliminates the need for integrating a physical sensor within the motor structure, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent replaces the mechanical/electronic Hall-effect sensor system with an electronic signal processing system. Instead of using a physical sensor to detect rotor position, the system uses software-based processing of the back EMF voltage signal to determine rotor position, substituting a mechanical sensing approach with an electronic computation approach that simplifies motor design and manufacture
2Device complexity
If sensorless control is implemented by suspending excitation to determine rotor position, then device complexity is reduced, but power delivery decreases
Solution Approach 1:
The patent maintains continuous excitation of the winding during rotor position detection, eliminating the need to suspend excitation. By processing the back EMF signal that exists during normal excitation operation, the system achieves sensorless control without interrupting the useful action of power delivery to the motor, thereby maintaining full power capability while reducing device complexity
Solution Approach 2:
The patent makes the winding serve multiple functions simultaneously: it acts as both the power-delivering excitation element and the sensing element for rotor position detection. The same winding that delivers electrical power to the motor also generates the back EMF signal used for sensorless position detection, eliminating the need for separate sensing mechanisms and allowing continuous operation without sacrificing power delivery
3Measurement precision
If a Hall-effect sensor is used to detect rotor position, then measurement precision is improved, but the system becomes susceptible to electromagnetic noise
Solution Approach 1:
The patent replaces the Hall-effect sensor that is susceptible to electromagnetic noise with a digital signal processing approach. By detecting zero-crossings of the back EMF voltage signal and using digital logic to determine rotor position, the system achieves noise-resistant position detection that is not affected by electromagnetic interference in the same way physical sensors are
Solution Approach 2:
The patent introduces signal processing as an intermediary between the raw voltage measurement and the rotor position determination. By processing the voltage signal across the winding to detect zero-crossings and generate position information, the system creates a noise-filtered intermediate representation that is more resistant to electromagnetic noise than direct Hall-effect sensor output
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 determination and efficient power delivery in single-phase motors by eliminating the need for Hall-effect sensors and suspended excitation, improving motor control and power efficiency.
Implementation Method 1
The rotor of a permanent-magnet motor induces a back EMF in the winding. The magnitude of the back EMF depends on, among other things, the angular position of the rotor.
Implementation Method 2
differentiating the second signal to generate a third signal
Data Source
AI summary
A method of controlling a brushless permanent-magnet motor. The method includes generating a first signal having a voltage that is proportional to a voltage across a winding of the motor, and generating a second signal having a voltage that is proportional to a current in the winding. The second signal is then differentiated to generate a third signal, and the voltages of the first signal and the third signal are compared. An output signal is generated in response to the comparison, the output signal having an edge whenever the voltages of the first signal and the third signal correspond. The winding is then commutated at times relative to the edges in the output signal. Additionally, a control system that implements the method, and a motor system that incorporates the control system.