A New Approach to Achieve Variable Negative Stiffness by Using an Electromagnetic Asymmetric Tooth Structure

Chao Han,Muyun Wu,Weilong Liang,Xueguang Liu

doi:10.1155/2018/7476387

Abstract

Traditional passive nonlinear isolators have been paid much attention in recent literatures due to their excellent performance compared to linear vibration isolators. However, they are incapable of dealing with varying conditions such as changing excitation frequency due to the nonadjustable negative stiffness. To solve this drawback, a new approach to achieve variable negative stiffness is proposed in this paper. The negative stiffness is realized by an electromagnetic asymmetric magnetic tooth structure and can be changed by adjusting the magnitude of the input direct current. Analytical model of the electromagnetic force is built and simulations of magnetic field are conducted to validate the negative stiffness. Then the EATS is applied to vibration isolation and an electromagnetic vibration isolator is designed. Finally, a series of tests are conducted to measure the negative stiffness experimentally and confirm the effect of the EATS in vibration isolation.

Highlights

Nonlinear passive isolators with high-static-low-dynamic stiffness characteristic, generally achieved by combining a positive stiffness spring and a negative stiffness springs, have received considerable attention in the past twenty years due to their excellent performance compared to linear vibration isolators [1,2,3,4]
In an effort to capture the negative stiffness characteristic of the electromagnetic asymmetric tooth structure (EATS) in the following experimental tests, the EATS is applied to vibration isolation and an electromagnetic vibration isolator (EVI) is proposed
The negative stiffness of the EATS can be changed by adjusting the current which leads to the variation of the resonance frequency

Summary

Introduction

Nonlinear passive isolators with high-static-low-dynamic stiffness characteristic, generally achieved by combining a positive stiffness spring and a negative stiffness springs, have received considerable attention in the past twenty years due to their excellent performance compared to linear vibration isolators [1,2,3,4]. Zhou and Liu [18] and Francisco LedezmaRamirez et al [19, 20] have presented a series of papers in which the negative stiffness is obtained by using two electromagnets and one (or two) permanent magnet It works like the mechanism proposed by [13], but the negative stiffness can be changed by adjusting the input current. Unlike the way of using the electromagnets, Xu and Sun [21] proposed a theoretical model with adjustable negative stiffness by applying actuators to the traditional negative stiffness mechanism shown in [5, 6] to change the prestressed length of oblique springs. The system behaves like a mechanical spring and has a positive stiffness near the equilibrium position

Analytical Model of the Electromagnetic Force of the EAST

Application of the EATS

Experimental Studies

Conclusions