Active balancing actuators are essential components of intelligent machine tool spindles to automatically reduce the unbalance vibration and promote machining accuracy and efficiency. In this study, a novel electromagnetic-ring actuator is introduced, which can be integrated into the hollow rotor of the spindle and compensate the initial mass imbalance through step rotation of two counterweight discs driven by the magnetic field. The working principle of the actuator is described in detail and its performance is analyzed, including balancing ability, balancing accuracy and self-lock capacity. To control the normal operation of the actuator, a phase detection and control program was developed. Finally, to verify the effectiveness of the novel actuator, function experiments and active balancing experiments were carried out. The experimental results show that the novel actuator could reduce the unbalance vibration of the machine tool spindle by 87.5% at 3600 rpm.

Imbalance vibration is a typical failure mode of rotational machines and has significant negative effects on the efficiency, accuracy, and service life of equipment. To automatically reduce the imbalance vibration during the operational process, different types of active balancing actuators have been designed and widely applied in actual production. However, the existing electromagnetic-ring active balancing actuator is designed based on an axial excitation structure which can cause structural instability and has low electromagnetic driving efficiency. In this paper, a novel radial excitation structure and the working principle of an electromagnetic-ring active balancing actuator with a combined driving strategy are presented in detail. Then, based on a finite element model, the performance parameters of the actuator are analyzed, and reasonable design parameters are obtained. Self-locking torque measurements and comparative static and dynamic experiments are performed to validate the self-locking torque and driving efficiency of the actuator. The results indicate that this novel active balancing actuator has sufficient self-locking torque, achieves normal step rotation at 2000 r/min, and reduces the driving voltage by 12.5%. The proposed novel balancing actuator using radial excitation and a combination of permanent magnets and soft-iron blocks has improved electromagnetic efficiency and a more stable and compact structure.