Smart panel with multiple decentralized units for the control of sound transmission. Part II: design of the decentralized control units

This is the second of three companion papers that summarize the theoretical and experimental work carried out to develop a prototype smart panel with 16 decentralized vibration control units for the reduction of sound radiation/transmission. In this paper the design and implementation of the 16 decentralized control units is discussed. Each control unit consists of a collocated accelerometer sensor and piezoceramic patch actuator with a single channel velocity feedback controller in order to generate active damping. The design and implementation of a single control unit has been discussed first. The frequency response function of the sensor-actuator pair has been measured and compared with the results of a computer simulation in order to investigate the effects of accelerometer dynamics, and actuator size. Since the system is only conditionally stable, a phase lag compensator has then been designed so that larger control gains that guarantee stability could be implemented. The single-channel controller has then been implemented on each of the 16 decentralized control loops in the final system. The stability of the final control system has been assessed by plotting the 16 eigenvalues loci matrix product between the open loop sensors-actuators frequency response matrix and the diagonal matrix of control functions (fixed control gains multiplied by the phase lag compensators). None of the loci encircle the Nyquist point (-1,0) as the frequencies varies from - infinity to + infinity at moderate gains, although part of the locus occupies the left hand side of the plot. Thus the complete control system is stable only for a limited range of control gains. The control effectiveness of both the single control unit and 16 decentralized control units has been assessed by plotting the velocity at one error sensor with reference to either an acoustic source in the cavity (loudspeaker) or a primary point force on the panel (shaker). (C) 2003 Elsevier Ltd. All rights reserved.