Electric Machine Rotor Angle Detection via Torque-Contour Test Signal
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Solution Overview
Problem
Conventional methods for determining the rotor angle of electric machines, especially at low speeds, face challenges due to low voltage magnitudes and result in torque ripple, acoustic disturbances, and strain on film capacitors, as they use sinusoidal or square-wave voltage test signals that influence the torque and current.
Innovation Solution
A method employing a torque-dependent high-frequency test signal, either sinusoidal or rectangular, is superimposed on the supply signal but directed in a way that minimizes its impact on the motor's torque, using a voltage vector coordinate system with components only in the k-axis, ensuring the motor current vector oscillation is tangential to the required torque contour line, thus reducing torque and current ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sinusoidal or square-wave voltage test signals are used for rotor angle determination, then the rotor position can be detected, but torque ripple and acoustic disturbances occur
Solution Approach 1:
The patent changes the parameter of the test signal from conventional sinusoidal or square-wave voltage signals to a high-frequency current test signal. This parameter change allows the test signal to be directed along the torque contour line, minimizing its impact on motor torque while still enabling accurate rotor position detection through the current response analysis.
2Measurement precision
If high-frequency test signals are used for rotor angle determination, then measurement accuracy is improved, but strain on film capacitors increases
Solution Approach 1:
The patent changes the test signal from voltage-based to current-based, which fundamentally alters how the test signal interacts with the motor system. The high-frequency current test signal flows in a direction that minimizes torque production, thereby reducing the stress on the DC link capacitors while maintaining the ability to detect rotor position through the resulting current response.
3Measurement precision
If test signals are fed into the estimated d-direction, then rotor position can be determined, but large torque ripple and current ripple occur
Solution Approach 1:
Instead of feeding the test signal into the conventional d-direction (which causes large torque ripple), the patent inverts the approach by directing the high-frequency current test signal along the torque contour line. This inverted direction minimizes the test signal's impact on motor torque while still producing a detectable current response for rotor position determination.
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 torque ripple, current ripple, and acoustic interference, providing accurate rotor angle determination with minimal disturbance, even at low speeds, by using a closed control loop and transformation angles to demodulate the motor current vector effectively.
Implementation Method 1
determining the rotor angle of the electric machine rotor based on the effects of the test signal on the phase currents
Data Source
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AI summary
The present invention discloses a method for determining a rotor angle of a rotor of an electric machine, having the steps of producing a torque-dependent test signal which depends on the torque of the electric machine and has a higher frequency than a supply signal for the electric machine, controlling the electric machine using the supply signal and the test signal which is superimposed on the supply signal, recording phase currents of the electric machine, and determining the rotor angle of the rotor of the electric machine on the basis of the effects of the test signal on the phase currents. The present invention also discloses an angle determination apparatus and a corresponding control apparatus.