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The Fifth International Conference on VIBRATION ENGINEERING AND TECHNOLOGY OF MACHINERY Huazhong University of Science and Technology, Wuhan, P.R. CHINA. 27-28 , August, 2009 © 2009 Huazhong Universiti of Science and Technology Press

ACTIVE CONTROL OF FLEXIBLE VIBRATION SYSTEMS WITH INCLINED COMBINED MOUNTS

Niu Junchuan a, b , Lim C W c Zhu Jiqing a, b

a School of Mechanical Engineering, Shandong University, Jinan, P R China

b Key Laboratory of High Efficiency and Clean Mechanical Manufacture (Shandong University), Ministry of

Education, P R China

c Department of Building and Construction, City university of Hong Kong, Hong Kong, P R China

(*Email: niujc@http://www.77cn.com.cn)

*

ABSTRACT In order to reduce the vibration and noise of flexible systems subjected to

multi-dimensional excitations efficiently, the paper presents a general model of isolation systems with passive-active inclined mounts by subsystem mobility technique and transfer matrix approach. In the model, the passive mounts are fixed to the seats to react against axial force, transverse force and couples, and inside actuators which are parallel with the passive mount and pined-pined at the seats produce axial active forces. The power flow transmitted into the foundation is considered as a cost function for optimal control and investigating the transfer characteristics of vibration. Some numerical examples are presented to show the effectiveness and the feasibility of the model, and also some useful conclusions are obtained. KEYWORDS active control, flexible system, inclined mount

I. INTRODUCTION

In mechanical engineering, some vibrating machines such as engines and compressors need to be supported by various mounts to isolate imposed vibration and keep silence. In order to achieve excellent isolation performance, numerous researches on the passive and active mounts have been investigated. As a kind of widely used passive mounts, rubber isolators, which have low damping, show efficient vibration isolation performance in the non-resonant and high frequency excitation [1, 2]. The traditional installation of the rubber mounts is always that the principle elastic axes of the rubber isolators run parallel to the principle inertia axis of the supported machine. In these cases, the dominated vibration is along vertical inertia axis of the machine when only a vertical force is applied to the center of gravity of the machine, and the mounts are subject to axial compression loadings [3]. But, in other cases of the complex excitations which are combined by vertical and horizontal forces and couples, the vertically installed mounts can not isolate the corresponding vibration efficiently, even result in the failure of isolation. Otherwise, inclined mounts can react against the compression, bending even buckling loadings, which is especially meaningful for the vibration isolation of machines subjected to combined excitations.

Though the advantages of the inclined mounts are found earlier, they are only discussed in condition of rigid foundations [3]. As far as flexible bases which mounts installed on are concerned, inclined mounts do not obtain enough attention until now [4, 5]. Moreover, due to more strict requirements of isolation of some high speed and high precision instruments which are installed on the flexible

foundations, increasing numbers of novel active control techniques are introduced to depress the vibration and noise [6-9], and once inclined passive mounts and parallel active mounts or actuators are combined to install on the flexible foundations, the characteristics of the isolation systems must be explored and discussed for achieving substantial vibration attenuation.

In order to reduce the vibration and noise of flexible systems subjected to multi-dimensional excitation efficiently, the paper presents a novel model of the flexible isolation system with inclined passive-active mounts. The hollow rubber cylinders and parallel actuators are combined to support the rigid machine and isolate the vibration transmitted into the foundation. The subsystem mobility technique and transfer matrix approach are employed to formulate the power flow. The power flow transmitted into the foundation is considered as cost function for optimal vibration control. At last, some simulations are performed to investigate the transfer characteristics of vibration and show the effectiveness of the presented model.

II. DYNAMIC ANALYSIS OF ISOLATION SYSTEM

In order to simulate the isolation system in practical engineering, the dynamic model of the system is given as shown in Fig. 1(a). In the model, the foundation is considered as a rectangular flexible plate, simply supported at the four edges. The machine is rigid and supported by two inclined combined mounts. The passive-active mounts are composed of passive isolators and inside actuators, as shown in Fig. 1(b). The passive mounts are generally hollow rubber cylinders which are fixed to the rigid seats so as to react against axial and transverse forces and couples, and the active mounts can be hydraulic servo or other electromagnetic actuators which are pined-pined at the joints with the seats and produce axial active forces.

passive-active mount combined by passive fixed-fixed isolator and pined-pined active actuator

2.1 Dynamics Analysis of Subsystems

The machine’s dynamic characteristics were studied using mobility technique. According to the dynamics of the rigid body, the governing equation of the machine is given by

Vo A11A12 Fo

= F (1) VAA22 ob ob 21

TT ] are the general multi-dimensional force acting on the where, F=[F,F,M],V=[V,V,θ

o

ox

oz

oy

o

ox

oz

oy

center of gravity of the machine and corresponding velocity, and also Fob,Vob are the general …… 此处隐藏：14238字，全部文档内容请下载后查看。喜欢就下载吧 ……