Brushless PM Motor Rotor Position Sensing via Back-EMF Phase
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Solution Overview
Problem
Brushless permanent magnet motors require accurate rotor position measurement, but existing methods often rely on sensors that complicate design, are costly, and susceptible to electromagnetic noise.
Innovation Solution
A method that calculates the phase of back EMF induced in the phase winding using measured current and reference voltage values, determines the zero-crossing point of the back EMF, and generates a rotor position signal based on this information, eliminating the need for physical sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors (e.g., Hall sensors) are integrated within the motor to measure rotor position, then rotor position measurement capability is provided, but device complexity and manufacturing complexity increase
Solution Approach 1:
The invention extracts the rotor position measurement function from physical sensors and implements it through software calculation using back EMF analysis. The controller determines rotor position by calculating the phase of back EMF induced in phase windings using measured current and reference voltage values, eliminating the need for integrated Hall sensors or other position sensors within the motor structure
Solution Approach 2:
The invention replaces the mechanical/electrical sensor system with a computational approach. Instead of using physical sensors to detect rotor position, the system uses software algorithms to calculate position based on electrical measurements (current and voltage) and back EMF phase analysis, substituting a mechanical sensing system with an electrical-computational system
2Measurement precision
If sensors are integrated within the motor to output rotor position signals, then rotor position information is obtained, but manufacturing complexity increases
Solution Approach 1:
The invention removes the sensor integration step from the manufacturing process. By using back EMF-based software calculation instead of physical sensors, the motor can be manufactured without the complex integration of Hall sensors or other position sensing components, simplifying the manufacturing workflow and reducing assembly steps
Solution Approach 2:
The invention replaces expensive, complex sensor components with a software-based solution that uses existing motor components (phase windings, controller) already present in the system. This substitution with a computationally-based approach reduces component costs and simplifies manufacturing
3Measurement precision
If physical sensors are used to measure rotor position, then position signals are obtained, but susceptibility to electromagnetic noise increases
Solution Approach 1:
The invention replaces physical sensors that are vulnerable to electromagnetic interference with a software-based calculation system. By computing rotor position from back EMF phase using measured current and reference voltage, the system avoids the electromagnetic noise susceptibility inherent in physical sensors operating within the motor's electromagnetic environment
Solution Approach 2:
The invention introduces back EMF phase calculation as an intermediary process between electrical measurements and rotor position determination. This computational intermediary filters out electromagnetic noise by using mathematical relationships (phase calculation from current and voltage) rather than direct electrical sensing, providing a noise-resistant measurement approach
4Device complexity
If software-based back EMF phase calculation is used instead of sensors, then component cost and device complexity are reduced, but measurement accuracy must be maintained
Solution Approach 1:
The invention successfully maintains measurement precision by using sophisticated software algorithms that calculate back EMF phase from measured current and reference voltage. The computational approach uses mathematical relationships to accurately determine rotor position without the hardware complexity of sensors, achieving high precision through algorithmic processing rather than physical sensing
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 method provides a cost-effective and design-simplified solution for determining rotor position in brushless permanent magnet motors, reducing component count and susceptibility to noise, while maintaining accuracy.
Implementation Method 1
calculating a phase of back EMF induced in the phase winding using the measured current value and the reference voltage value
Data Source
AI summary
A method of determining a position of a rotor of a brushless permanent magnet motor includes measuring a current value indicative of current flowing through a phase winding of the motor and providing a reference voltage value indicative of a voltage applied to the phase winding of the motor. The method includes calculating a phase of back EMF induced in the phase winding using the measured current value and the reference voltage value, and determining a zero-crossing point of the back EMF induced in the phase winding using the calculated phase of back EMF induced in the phase winding. The method includes generating a rotor position signal based on the determined zero-crossing point.