A Novel Demodulation for Pulsating Carrier Voltage Injection-Based Encoderless Control
Zhenbin Zhang, Zhou Shichang, Haitao Li, Jilin Qiu
Abstract
High-frequency (HF) sinusoidal pulsating signal injection is an effective technique to achieve encoderless control for permanent magnet synchronous motor (PMSM) drive systems, particularly for low-speed regions. Classical methods usually use <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coherent demodulation</i> to extract the rotor position from the HF current envelope. However, its design requires specific low-pass filters (LPFs), which limits the bandwidth of the subsequent rotor speed estimation, hence severely restricts the overall control performance. In this work, a novel fast <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">time-domain demodulator</i> is proposed, which eliminates the underlying LPF and significantly improves demodulation speed and accuracy of the ac-modulated signal. The proposed solution is verified via experimental data at a lab-constructed test bench. Results confirm that the proposal achieves good control performances at low-speed ranges.