Adaptive Control of Acoustic Waves in Flexible Structure

An active cascading control method for suppressing acoustic waves propagating along a flexible structure is proposed, developed, and experimentally evaluated on a hanging steel beam. To ensure satisfactory performance, multiple control points are set up along the wave propagation path. A coupled feed forward control algorithm was developed to suppress both the head wave from the transmitter and the coupling waves from the wave-cancelling actuators. An equation error adaptive system identification approach was taken to extract system dynamics and avoid mode uncertainty/truncation under high frequencies. To determine the optimal controller weights and minimize wave energy, an NLMS adaptive algorithm was realized, based on the obtained models. An experimental setup, composed of a steel beam as the wave propagation medium and five cascading control stations, was developed. Experimental results have shown that, under both wide and narrow bandwidth conditions, wave energy suppression of over 98.7% has been achieved.