Vibration Isolator using Hybrid Reluctance Actuator toward Quasi-zero Stiffness

Abstract

This paper proposes a sample-tracking vibration isolator that integrates a flexure-guided hybrid reluctance actuator (HRA) with a negative stiffness for quasi-zero stiffness (QZS). In a sample-tracking vibration isolator, for example, for inline metrology, an actuator carries and positions an instrument with respect to a sample. By maintaining the distance between the instrument and the sample by feedback control, the vibrations between them are rejected for measurements in vibrational environments. To achieve high vibration isolation and rejection, the proposed sample-tracking vibration isolator uses the negative stiffness that is magnetically realized and cancels a flexure stiffness for QZS. Due to the rigid magnetic components of the HRA such as a permanent magnet and ferromagnetic cores, a high second mechanical frequency of 2.1 kHz is realized. Consequently, a high closed-loop control bandwidth of 806 Hz is achieved with feedback control. In order to validate the effectiveness of the rigid negative stiffness of the HRA, the negative stiffness is tuned to cancel a flexure stiffness at experiments. Experimental results show that transmissibility at a low frequency of 10 Hz is significantly decreased from -34 dB to -60 dB by a factor of 20 and successfully demonstrate high vibration isolation performance of the sample-tracking vibration isolator using the negative stiffness of the HRA.