Enhanced piezoelectric voltage build-up for semi-active control of smart structures

Abstract

This paper presents a combination of the SSD (Synchronized Switch Damping) semi-active control and techniques developed for active control. The principle of modal SSDI is to synchronize the piezoelectric voltage inversion or switching with the extremum of the targeted mode modal displacement. This modal displacement is estimated even in the case of complex, broadband or noisy excitation with a modal observer. The switching process control induces a non linear processing of the piezoelectric voltage which results in a cumulative self generated control voltage in phase with the mode speed, thus generating an important damping of the targeted mode. This voltage self building is optimal if the piezoelectric voltage is maximum when the modal displacement of the targeted mode is extremum. But in the case of complex excitation or when the targeted mode amplitude is lower than higher modes, the performances are altered. The proposed method consists in implementing a decision algorithm allowing waiting for the next voltage extremum before to trig the voltage inversion, the whole process being globally synchronized with the targeted modal displacement. Indeed, the targeted mode amplitude is reduced by using part of the energy of the higher modes which enhances the build up of the self generated piezoelectric control voltage. Simulations carried out on a clamped free beam are presented. Results obtained first with a bimodal excitation then in the case of pulse excitation demonstrates a large increase of the damping on the targeted mode.