Encoderless Electric Machine Control With Torque-Gated HF Injection
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Solution Overview
Problem
Existing encoderless control methods for electric machines face issues with high-frequency losses and noise generation due to high-frequency voltage excitation, particularly at lower speeds, which lead to unwanted heating and disturbance, and are inefficient in determining rotor position without sensors.
Innovation Solution
A method and device that apply a high-frequency test signal only when a predetermined target torque exceeds a threshold, using a field-programmable gate array (FPGA) for high-frequency signal processing and detection, and employ dead-time compensation to estimate rotor position, reducing high-frequency losses and noise by activating the signal only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency voltage excitation is applied to determine rotor position at lower speeds, then position estimation accuracy is improved, but high-frequency losses and heating increase
Solution Approach 1:
The patent applies high-frequency voltage excitation only periodically when the electric machine operates in the lower speed range, rather than continuously. The control device switches between first operating mode (using back EMF at higher speeds) and second operating mode (using high-frequency excitation at lower speeds), thereby achieving position estimation only when necessary and reducing overall energy losses.
2Difficulty of detecting and measuring
If high-frequency voltage excitation is applied to determine rotor position, then position detection capability is improved, but noise generation increases
Solution Approach 1:
The patent implements periodic action by activating high-frequency excitation only during lower speed operation when position detection is critical, and switching to back EMF-based detection at higher speeds. This temporal separation reduces continuous noise exposure while maintaining detection capability when needed.
3Measurement precision
If high-frequency test signal is continuously applied for rotor position estimation, then measurement precision is improved, but power loss increases
Solution Approach 1:
The control device implements periodic action by switching between two operating modes based on speed range. In the lower speed range, high-frequency excitation is applied for precise position estimation. In the higher speed range, the system switches to back EMF-based detection, eliminating the need for continuous high-frequency excitation and thereby reducing power loss.
4Difficulty of detecting and measuring
If high-frequency excitation is used for position estimation at lower speeds, then detection capability is improved, but heating of rotor increases
Solution Approach 1:
The patent applies periodic action by limiting high-frequency excitation to specific operating conditions (lower speed range) rather than continuous operation. This reduces cumulative heating effects on the rotor while maintaining position estimation capability when the machine operates in the lower speed range where back EMF is insufficient.
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
Reduces power loss and noise generation by applying high-frequency test signals only when needed, improving signal-to-noise ratio and enabling precise rotor position estimation through FPGA-based high-frequency signal processing and dead-time compensation.
Implementation Method 1
this high-frequency voltage excitation has the disadvantage of generating high-frequency losses in the electric machine, primarily characterized by eddy current losses in the rotor and stator
Implementation Method 2
At higher speeds, a back EMF generated by the rotation of the permanent magnets is evaluated
Data Source
Figure 1
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AI summary
The invention relates to a method for controlling an electric machine (20), wherein the electric machine (20) is supplied with energy via an inverter (10) and controlledby means of asynchronous control, wherein phase currents (i-x) are detected at high frequency, and wherein phase voltages are estimated at high frequency, wherein a high-frequency test signal (30) is applied in order to determine a rotor position (14) of the electric machine (20) required for the controlling and a system response (32) is evaluated, wherein a predefined target torque (40) is received and evaluated, and wherein the high-frequency test signal (30) is deactivated if the predefined target torque (40) reaches or falls below a predefined threshold value (41), and wherein the high-frequency test signal (30) is activated if the predefined target torque (40) exceeds the predefined threshold value (41). The invention also relates to a device (1).for controlling an electric machine (20).