A novel microwave-based dynamic measurement method for blade tip clearance through nonlinear I/Q imbalance correction

Blade is the core working components of an aero-engine, and its blade tip clearance (BTC) exerts a direct influence on the efficiency and safety of the engine. Aiming to extract the BTC region from the echo signal, a novel microwave-based dynamic measurement system through nonlinear I/Q imbalance correction is proposed. Firstly, to achieve accurately correction of the sensor under non-linear amplitude attenuation, a new correction method is proposed to map the amplitude decay attenuation into the imbalance parameters distribution. Secondly, to effectively localize the extraction BTC region, the Amplitude-phase Half Wave Extraction (APH) is proposed, which utilizes squared I/Q amplitude information to determine the BTC position and extract clearance information. Finally, in comparison to existing methods, the proposed algorithm exhibits excellent performance in signal correction under non-linear amplitude attenuation and achieves high-accurate BTC extraction. Experimental studies show a mean absolute error below 2 μm and a repeatability mean error of 0.154 μm for a BTC variation of 0.17 mm.