Design of six-parameter isolator using internal mass effect for improving vibration isolation

Abstract

Isolators designed based on a three-parameter model (or its equivalent five-parameter model) are used for vibration isolation of sensitive payloads. The three-parameter model consists of a spring arranged in parallel with an elastically supported damper. The three-parameter isolator performs better than conventional isolators, which are primarily based on a parallel spring–damper structure. However, it tends to sacrifice the resonance suppression at low frequencies when enhancing damping at high frequencies. Previous studies have shown that the internal moving mass of a three-parameter isolator, which had been neglected, can be beneficial for improving high-frequency vibration isolation; however, few design methods have been presented. Hence, we propose a six-parameter model based on the five-parameter model by considering the internal mass. This model combines the advantages of the internal mass effect and offers more designable parameters than the three-parameter model. In this study, the optimum damping of a six-parameter model was determined. An optimization method for the six-parameter model was proposed to maximize high-frequency isolation. Subsequently, an optimal six-parameter isolator was designed and tested. The results showed that the optimal six-parameter isolator can provide greater isolation by 30 dB than the three-parameter isolator at frequencies above 200 Hz, thereby validating the design method. This study provides new ideas for utilizing internal mass to improve vibration isolation.