Active Control of Bending Wave Propagation At Acoustic Frequencies

This paper investigates, analytically and experimentally, the possibility of actively blocking the propagation of bending waves along a uniform beam. The work takes the form of a case study; a thin brass plate-beam is used, it is excited with a short duration impulse, and the resulting disturbance spreads dispersively as it travels along the beam. A short portion of the beam is used as an active block. Strain gage sensors are used to drive thin piezoceramic bending moment actuators through a dynamic compensator. The compensation is designed in the frequency domain with reference to the beam equation, but independent of boundary conditions. This paper describes the analytical work, including the nominal design and its performance, the performance degradation due to modeling errors, and the performance degradation due to approximate implementation of the dynamic compensator. The laboratory implementation used analog electronics for the compensator and essentially verifies some of the sensitivity predictions.