Design and Analysis of a Novel Quasi-Zero Stiffness Isolator under Variable Loads

Yingjiang Xie,Fu Niu,Jinggong Sun,Lingshuai Meng,Agathoklis Giaralis

doi:10.1155/2022/9082752

Abstract

The designed load of most quasi-zero stiffness (QZS) isolators is constant. The isolation performance will drop sharply once the load changes. A novel QZS isolator that can adapt to variable loads is proposed in this paper to improve the range of application of the isolator. The isolator is designed by paralleling the electromagnetic spring (ES), which provides negative stiffness, and the pneumatic spring (PS), which provides positive stiffness. The positive and negative stiffness can be adjusted by changing the pressure and coil current, which provides the possibility for the isolator to adapt to variable loads. This paper derived the conditions for the isolation system to obtain QZS characteristics, proposed the dynamic model of the isolation system, derived and verified the analytical expressions of the amplitude-frequency response and force transmissibility (FT), and discussed the change of FT and displacement transmissibility(DT) under different loads. Theoretical analysis shows that changing the pressure and coil current in the same proportion can maintain the superior low-frequency isolation performance when the load changes, thanks to the preservation of the QZS characteristics of the system after adjusting the pressure and coil current. Finally, the simulation results fg and isolation frequency band over the linear isolation system and PS isolation system. Furthermore, the proposed isolator can be adjusted online.

Highlights

Vibration is pervasive in the engineering field, and various instruments and equipment are constantly disturbed by vibration from the base or other dynamic loads
Howe√v er, the linear isolator only works in the range of more than 2 times the natural frequency of the system according to the vibration theory. e only way to broaden the isolation frequency band is to reduce the stiffness of the system, which will result in poor static supportability and system stability. erefore, some novel isolation systems have been continuously developed and upgraded to solve these inherent contradictions, such as the isolator with inerter-based damper and the quasi-zero stiffness (QZS) isolator. e inerter has a negative stiffness effect, which can be used to reduce the natural frequency of the system [1]
Nakamura et al [2] proposed an electromagnetic inertial mass damper (EIMD) composed of a ball screw and a generator, and the shaking table test results verified the vibration control performance of the structure. en, Wang et al [3] carried out simulation experiments on a five-story building using seismic records and the results show that the EIMD can significantly improve the seismic performance of the baseisolated structure

Summary

Introduction

Vibration is pervasive in the engineering field, and various instruments and equipment are constantly disturbed by vibration from the base or other dynamic loads. Wang et al [16, 17] combined the diamond-shaped negative stiffness structure and inertial dampers to design a new type of inertial-based QZS isolator, which has good nonlinear stiffness characteristics and mass amplification effects and can achieve superior vibration isolation performance. E ES element is the negative stiffness mechanism of the QZS isolation system, which comprises a pair of coil windings and a ring magnet arranged coaxially. E traditional QZS isolator is mainly composed of a linear spring and a nonlinear negative stiffness mechanism, and the stiffness is difficult to adjust

Statics Analysis of the QZS Isolator

Findings

Dynamic Response of the QZS Isolator