Impact factors on the rotor dynamic stability evaluation by the sine-sweep excitation with active magnetic bearing: Numerical and experimental investigation

It is of importance to obtain the stability margin of the industrial rotating machinery to avoid the instability risk by carrying out rotordynamic stability tests. To obtain accurate stability parameters results, it is essential to measure excitation forces accurately when using the frequency response functions (FRFs) to identify stability parameters. The commonly used actuator is the active magnetic bearing (AMB) for its easy controllability and convenience of non-contact. However, because of the difficulty of measuring force accurately, estimation errors inevitably exist. Hence, the factors affecting the identification accuracy are investigated, which include the bias currents in actuator coils, the locations of excitation and measurement, the force models of AMB, the magnitudes of excitation and the offset of shaft center at the actuator node. Groups of excitation experiments are also carried out. The results show that the tedious calibration of AMB force can be made omissible by choosing a small bias current, such that the negative stiffness can be neglected, and modal parameters analysis then performed easily for the rotor system. This guidance can be used for researchers to evaluate rotordynamic stability in the laboratory, shop test or fields.

Automated summary

This study focuses on investigating factors affecting the accuracy of stability parameter identification, including bias currents in actuator coils, excitation and measurement locations, force models of active magnetic bearings (AMBs), excitation magnitudes, and shaft center offsets at actuator nodes. Experimental results show that choosing a small bias current can eliminate the tedious calibration of AMB force, allowing for easier modal parameter analysis.