Sensorless Rotor Position Detection Using Current Subtraction
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Solution Overview
Problem
Conventional methods for sensorless rotor angle determination in electric machines face conflicts due to high-pass filtering limitations, particularly in selecting appropriate limit frequencies that interfere with test signals, leading to inaccurate rotor position assessment.
Innovation Solution
The approach involves using computation technology to eliminate the current component for desired torque from measured total currents at the electric machine's phase terminals by subtracting the known setpoint value, allowing for optimized signal processing and accurate rotor angle calculation using test pulses, with options for different methods based on machine operating states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-pass filtering is used to remove torque current components from measured currents, then the torque component can be separated from total current, but the limit frequency selection interferes with test signals and reduces measurement precision
Solution Approach 1:
The patent extracts the torque current component from the total measured current by subtracting the setpoint current (which represents the torque-producing current) from the actual measured current. This extraction method isolates the test signal response without requiring high-pass filtering, thereby avoiding interference with test signals and improving rotor position measurement precision.
2Reliability
If conventional high-pass filtering is used to isolate test signal response, then torque component can be removed, but test signal determination is interfered with due to limit frequency conflicts
Solution Approach 1:
The patent uses the setpoint current as an intermediary representation of the torque-producing current component. By subtracting this intermediary (setpoint current) from the total measured current, the method reliably isolates the test signal response without directly filtering the test signal itself, thus maintaining both reliability and precision.
3Adaptability or versatility
If test signals are injected for sensorless rotor position determination, then rotor position can be determined without sensors, but the presence of torque-generating currents interferes with the test signal response measurement
Solution Approach 1:
The patent extracts the pure test signal response from the total current by removing the torque component through subtraction of the setpoint current. This extraction enables accurate sensorless rotor position determination even when torque-generating currents are present, maintaining measurement precision while preserving the adaptability of sensorless operation.
Data Source
AI summary
Signal processing for determining a rotor position without the use of encoders. To this end, test signals are applied to the electrical currents in the phase connections of an electric machine, and the total currents in the phase connections of the electric machine are measured. The current responses to the test signals are determined by establishing the difference between the measured phase currents and the setpoint-value settings for the phase currents. On the basis of this difference, any method for calculating the rotor angle position can be performed.