Rotor Position Determination Using Incremental Inductance
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Solution Overview
Problem
Existing methods for determining the axis of magnetization in rotor-based machines are ineffective at low speeds and when stationary, as they rely on terminal voltage, which is unreliable in these conditions, and previous solutions are limited to specific speed conditions and shapes.
Innovation Solution
A system and method that uses a combination of terminal flux and line current to estimate the axis of magnetization by applying pulse width modulated signals to measure incremental inductance, which is then used in lookup array functions to accurately determine the rotor position across various operational conditions, including high and low speeds, and stationary states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If terminal voltage is used to determine rotor position, then the method is effective at high speeds, but it becomes ineffective at low speeds and stationary states
Solution Approach 1:
The patent transitions from using terminal voltage (which varies with speed) to using terminal flux and line current parameters that can be measured reliably across all speed conditions. By changing the measurement parameters from voltage-based to flux-and-current-based, the system maintains effectiveness from high speed through low speed to stationary states.
Solution Approach 2:
The patent introduces terminal flux as an intermediary parameter that bridges the gap between electrical measurements and mechanical position. Terminal flux serves as a mediator that can be derived from terminal voltage and line current, providing a reliable indicator for rotor position determination regardless of speed conditions.
2Measurement precision
If sensors are used to identify the axis of magnetization, then position determination is accurate, but system complexity increases
Solution Approach 1:
The patent enables the machine's own electrical parameters (terminal flux and line current) to serve the dual purpose of both operation control and position determination. Instead of adding external sensors, the system uses measurements already available from the machine's electrical system, making the machine self-sufficient for position sensing.
Solution Approach 2:
The patent makes the terminal voltage and line current measurements serve multiple functions: both controlling power flow and determining rotor position. These electrical parameters become multi-functional, simultaneously providing operational control and positional information without requiring dedicated sensing hardware.
3Measurement precision
If inductance measurement methods are used, then rotor position can be determined, but the method is limited to specific speed conditions and predefined waveforms
Solution Approach 1:
The patent creates a universal position determination method that works across all speed conditions (high speed, low speed, and stationary) and with various waveform types. The approach using terminal flux and line current is not restricted to specific operating conditions or predefined waveforms, making it broadly applicable to different operational scenarios.
Solution Approach 2:
The patent employs a dynamic approach that adapts to varying operating conditions. By using terminal flux and line current measurements that can be obtained under any operating condition, the system dynamically adjusts to different speed regimes and waveform types without requiring separate measurement methods for each condition.
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 the rotor position regardless of machine speed, improving control and operation by utilizing incremental inductance measurements and back electromagnetic flux, even when terminal voltage is low or absent, enhancing the system's reliability and effectiveness.
Implementation Method 1
a controller (108) sends a signal to the stator (102)... based on the applied voltage and the measured current, the controller (108) determines an incremental inductance
Implementation Method 2
Combining Terminal voltage and line current into an estimation of machine EFLUX allows for the identification of the axis of magnetization
Data Source
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AI summary
A method 200 for determining rotor position comprising sending a signal to a stator 102, receiving a first signal indicative of a first estimated stator inductance, and receiving a second signal indicative of a second estimated stator inductance. The method further includes, calculating a first rotor position angle using a function including the first estimated stator inductance and the second estimated stator inductance.