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

Chris R. Fuller

Vib. and Acoust. Labs., Dept. of Mech. Eng., Virginia Polytech. Inst. and State Univ., Blacksburg, VA 24061-0238

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.]