Performance of a multi-dimensional vibration isolation system is evaluated in several different ways, one of which is to employ the concept of vibration power. It will be especially useful in the high frequency range where radiation of noise from the receiver structure is concerned. With development of instrumentation techniques, the attempts to measure power flow onto the receiver structure were made by previous researchers. However, some erroneous results were observed in power estimations possibly due to practical limitations in instrumentation. One is negative power flow in the receiver, which should have been obviously mal-estimation. The phenomenon of negative power flow is considered to result from assumptions made for simplicity in experimentation and unexpected or unavoidable errors induced in the measurement of dynamic properties of subsystems.
In this paper, two problems among many assumptions made in power estimation are studied, which can possibly result in negative power flow. Two problems for this purpose are as follows :
1) Neglect of power transmission by moment and rotational velocity
2) Singularity problem in treatment of impedance or mobility matrix
Numerical simulations are illustrated to show the effects of neglect of power transmission by moment and rotational velocity. In addition, singularity problems in computation of impedance or mobility matrix are investigated. In order to verify conditions for negative power flow, two-point connected isolation system for source and receiver of flexible beam structures is used
