AC Motor Rotor Position Detection via Extended BEMF Model
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Solution Overview
Problem
Existing methods for determining rotor position and speed in AC electrical machines face challenges at low and high speeds due to unreliable fault-tolerances of rotor position sensors and unsuitability of current methods for separating rotor position information from high-frequency components.
Innovation Solution
A method that involves obtaining reference voltage signals and phase currents to determine orthogonal components of an extended back electromotive force (BEMF) model, calculating their product and squared-magnitude, and using these to generate an angular position error signal to estimate rotor speed and position, thereby eliminating the need for traditional rotor position and speed sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotor position sensors (encoder, electromagnetic resolver) are used to determine rotor position, then position data can be obtained for control routines, but the size of the AC electric machine increases and the complexity of controller logic increases
Solution Approach 1:
The patent extracts rotor position information from the back electromotive force (BEMF) signals generated by the motor itself, eliminating the need for external rotor position sensors. The controller processes the BEMF signals directly to determine rotor position, thereby removing the encoder or electromagnetic resolver components while maintaining position measurement capability
Solution Approach 2:
The patent creates a virtual model of rotor position by estimating it from electrical signals (BEMF) rather than directly measuring it with physical sensors. This virtual copy of position information is sufficient for control purposes and eliminates the need for complex sensor integration and processing logic
2Measurement precision
If rotor position sensors are used to determine rotor position, then position data can be obtained, but the fault-tolerance is low and position data may be unreliable
Solution Approach 1:
The motor system uses its own generated BEMF signals to determine rotor position, making the system self-sufficient and eliminating dependency on external sensors that can fail. The BEMF signals are inherently tied to the motor's operation, providing reliable position information without additional failure points
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors BEMF signals and adjusts position estimation in real-time. This feedback loop ensures accurate and reliable position data by constantly validating and updating the rotor position based on actual electrical signals from the motor
3Speed
If heterodyning routine is used to determine rotor position at low speeds, then rotor position can be extracted from current derivative response, but modeling errors and phase errors from digital filters make it unsuitable for higher speeds
Solution Approach 1:
The patent develops a universal BEMF-based position estimation method that functions across the entire speed range of the motor. Unlike speed-specific routines, this approach works consistently at low speeds, medium speeds, and high speeds, eliminating the need for different processing algorithms for different operating conditions
4Speed
If arctangent routine or quadrature PLL routine is used to determine rotor position at high speeds, then position can be determined from quadrature components of extended BEMF model, but these routines do not separate rotor position information from high-frequency current responses, making them unsuitable for lower or idle speeds
Solution Approach 1:
The patent creates a universal position estimation algorithm based on BEMF analysis that performs reliably across all speed ranges. The method appropriately handles high-frequency components at different speeds through consistent processing, eliminating the need for separate low-speed and high-speed routines
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 allows for accurate determination of rotor position and speed across various operating speeds without relying on traditional sensors, reducing the complexity and size of the AC electric machine's controller logic and enabling identification of faulty sensors.
Implementation Method 1
determining orthogonal components of an extended back electromotive force (BEMF) model of the AC electrical machine
Data Source
AI summary
A method for determining rotor characteristic of an alternating current (AC) electrical machine includes obtaining a reference voltage signal, one or more phase currents, and rotor data. The method includes determining orthogonal components of an extended back electromotive force (BEMF) model of the AC electrical machine based on the reference voltage signal, the one or more phase current characteristics, and the rotor data. The method includes determining a product of the orthogonal components of the extended BEMF model. The method includes determining a squared-magnitude of the orthogonal components of the extended BEMF mode. The method includes determining the rotor characteristic of the AC electrical machine based on the product of the orthogonal components and the squared-magnitude of the orthogonal components.