Magnetic Anisotropy Identification Using Orthogonal Voltage Vectors
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Solution Overview
Problem
Current sensorless control methods for induction machines, particularly anisotropy-based methods, are computationally intensive and not widely adopted due to high complexity and time requirements, limiting their industrial application and efficiency, especially at low speeds and in space-constrained environments.
Innovation Solution
A method that sets at least four voltage vectors during an injection interval, which are orthogonal or antiparallel to each other, allowing for reduced computational effort in identifying magnetic anisotropy by determining changes in current vectors, thereby inferring rotor position with minimal arithmetic operations, such as additions and subtractions, and enabling efficient encoderless control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anisotropy-based sensorless control methods are used to determine rotor position without encoders, then encoder-related costs and failure risks are reduced, but the computational complexity and time requirements increase significantly
Solution Approach 1:
The patent segments the inductance matrix identification into separate component measurements (Lαα, Lββ, Lαβ) performed at specific rotor positions (0°, 90°, 180°, 270°). This segmentation allows the complex anisotropy calculation to be broken down into simpler, sequential measurements that can be executed during normal motor operation, reducing the overall computational burden while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary measurements of the inductance matrix components at predetermined rotor positions during normal operation. These preliminary actions capture the necessary data for anisotropy calculation without requiring additional computational resources during critical control moments, enabling efficient real-time rotor position estimation.
2Measurement precision
If traditional encoder-based control is used to achieve precise rotor angle measurement, then control precision is improved, but system costs and installation space requirements increase
Solution Approach 1:
The patent enables the motor system to determine its own rotor position using built-in current sensors and inductance measurements, without requiring external encoder components. The system uses its own operational data (phase currents, voltages) to self-determine rotor angle and speed, eliminating the need for separate measurement devices and reducing system costs.
Solution Approach 2:
The patent replaces the mechanical encoder system with an electrical field-based measurement approach. Instead of using mechanical sensors to detect rotor position, the system uses electrical measurements of inductance anisotropy to determine rotor angle, substituting a mechanical measurement system with an electrical field-based solution.
3Adaptability or versatility
If anisotropy-based methods are used to enable sensorless control at low speeds, then operational range is extended, but computational time requirements increase
Solution Approach 1:
The patent merges the inductance measurement process with the normal motor control operations. The same current sensors used for torque control are utilized to measure inductance components, and the same processor used for current control executes the anisotropy calculations. This merging eliminates duplicate measurement systems and reduces overall computational time by using existing operational data.
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 significantly reduces computational burden, allowing for efficient encoderless control of induction machines across various speeds, including low speeds, and minimizes noise development, enhancing signal quality and reducing acoustic noise, while maintaining high signal-to-noise ratios.
Implementation Method 1
the voltage induced by motion disappears at low speeds
Implementation Method 2
evaluate the positional or angular dependence of the machine's inductance
Data Source
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Figure 5
AI summary
The invention relates to a method for identifying the magnetic anisotropy of an electric rotary field machine comprising a rotor and a stator. The rotary field machine is actuated by clocked terminal voltages according to a pulse width modulation method. At least four voltage vectors are set during one injection interval, wherein all of the voltage vectors have the same value in a space vector representation after a respective subtraction of the common average value, and the voltage vectors are orthogonal or anti-parallel to one another in pairs. In response to the four voltage vectors, a respective corresponding change of the current vector is ascertained, and the inputs of the anisotropy are inferred from each change of the current vectors while taking into consideration the voltage vectors. Such a method is easy to implement and offers the advantage of a very low computational complexity.