Frequency-scanning interferometry for axial clearance of rotating machinery based on speed synchronization and extended Kalman filter

Rotor-stator axial clearance is a crucial design parameter affecting rotating machines' efficiency and safety. To realize accurate dynamic axial clearance measurement in high-speed rotating machinery with frequency-scanning interferometry (FSI), this paper proposes a novel algorithm of Doppler error suppression. By introducing rotor speed simultaneously as a Kalman filter parameter, the extended Kalman filter model is constructed by combining the a-priori information of rotating machinery. The feasibility is tested and verified by both simulation and experiment. This algorithm can suppress the Doppler error in FSI measurement and separate the axial movement and end face runout in real-time. Under laboratory conditions, a position measurement precision of ±3.5μm was achieved for rotation speed changing around 2400rpm.