Active control of the structural intensity in beams using a frequency-domain adaptive method

This paper presents an active control method which consists of minimizing the active part of the structural intensity aiming at reducing the overall vibration level in beams. The basic idea behind this strategy is that the control forces dissipate the input power due to the perturbing forces, thus preventing the structure from having to vibrate in order to dissipate the incoming energy. A frequency-domain adaptive structural intensity control method (ASIC) is used. The method is investigated using a simple example consisting of an aluminum beam which is fitted at one end with a quasi-anechoic termination (sandbox) and has the other end free. Numerically simulated and experimental results are presented. The numerical simulation uses a state-space model which was identified using experimental data. Results are compared with those obtained minimizing measured vibration directly, and with results using the instantaneous wave amplitudes as error signals in time-domain LMS control schemes. In the preliminary experimental results, the ASIC method and the method that controls the wave amplitudes outperformed one another at different frequencies. At frequencies where the power-flow-based methods performed well, their performance was equivalent to that of the direct control of vibrations. The relative advantages and disadvantages of the different control methods are discussed.