Sensorless Unbalance Diagnosis of Affiliated Rotating Chamber Based on Driving Current of Permanent Magnet Synchronous Motor

Unbalance exists widely in rotating electromechanical systems, resulting in vibrations, instability, and many other negative influences. In this article, a novel method for unbalance diagnosis of the affiliated rotating chamber in 2-DOF precision centrifuge is proposed. Unlike the widely applied sensor-based unbalance diagnosis methods, the proposed one in this article investigates the internal relationships between signals in the control loop, involving the driving current of the permanent magnet synchronous motor, the disturbance signal of the control loop as well as the unbalance signal of the rotating chamber. By using the unbalance kinematic analysis, two kinematic-mechanical-electric driving current models are established, which are based on the 2-DOF precision centrifuge with uniform motion and uniform acceleration, respectively. Based on the models, the valid information of the unbalance is included in the driving current. Furthermore, a signal analysis procedure, which includes domain conversion and ensemble empirical mode decomposition, is presented to calculate the unbalance mass and the phase of the unbalance. Finally, the effectiveness of methods is validated by experiments and simulations.