Superharmonic vibration and its reduction in SSD control by increase of voltage inversion time

The semi-active synchronized switch damping (SSD) approach has been widely used in vibration suppression owing to its many advantages compared with the active and passive approaches. The SSD method is realized by switching the voltage on the piezoelectric patch embedded in the structure, synchronically with the vibration of the mode to be controlled. Although good control performance can be obtained in the targeted mode, vibrations of high-order harmonic frequencies are usually excited due to the rectangular waveform of the switched actuator voltage because of infinitesimal inversion time, as observed in the previous experiments. This drawback of the SSD method has greatly hindered its application in practical engineering structures. In order to overcome this drawback, the authors propose a new method in this study to suppress the high-order harmonic components in the switched voltage by increasing the inversion time of the voltage. The theoretical expressions of the switched voltage and the dynamic response of the structure were formulated for the cases with finite voltage inversion time. The theoretical results show that increasing the inversion time may weaken the vibration control effect of the targeted mode, but it can significantly reduce the excitation force of the high-order harmonic components. When the inversion time is half of the period of the targeted mode, all the high-order harmonic components in the actuator voltage are completely erased and the control force of the targeted mode decreases by 21%. An experimental setup of a flexible beam was used to verify the theoretical results of the switched voltage and control performance under different inversion time.