### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 2pSA1. Active control of flexural and extensional power flow in beams
using time domain wave vector sensors.

**Gary P. Gibbs
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Chris R. Fuller
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*Vib. and Acoust. Labs., Dept. of Mech. Eng., Virginia Polytech. Inst. and
State Univ., Blacksburg, VA 24061-0238
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Active control of beam vibration using power flow considerations has been
a topic of interest in recent years. Traveling waves in structures can be
considered ``carriers'' of energy. For thin beams the magnitude of the energy
carried by the wave is proportional to the square of the amplitude of the
traveling wave. Thus if traveling waves in structures can be sensed in the time
domain then the corresponding power flow will be estimated in the time domain.
In this paper, a time domain method for the estimation of flexural and
extensional waves in beams will be presented. The method uses a spatial array
of sensors in conjunction with digital filters to estimate the separate power
flow associated with positive and negative traveling flexural and extensional
waves. In an example, surface-mounted PVDF sensors were used in conjunction
with a digital filter network to estimate the traveling waves for bandlimited
spectra. Experiments where conducted in which the simultaneous flexural and
extensional power flow in semi-infinite and finite beams was controlled using
the wave vector sensors and surface mounted piezoceramic actuators. These
experiments demonstrate the control of beam vibration using power flow-based
methods requires fewer actuators and sensors then corresponding modal control
techniques. [Work supported by NASA Langley Research Center.]