Vibration suppression actuators

ABSTRACT Smart structures usually incorporate some control schemes that allow them to react against disturbances. In mechanics we have in mind suppression of mechanical vibrations with possible applications on noise and vibration isolation. A model problem of a smart beam with embedded piezoelectric sensors and actuators is used in this paper. Vibration suppression is realized by using active control. Classical mathematical control usually gives good results for linear feedback laws under given assumptions. The design of nonlinear controllers based on fuzzy inference rules is proposed and tested in this chapter. 

In this study, adaptive control algorithms have been utilized for designing active controllers for smart structure test articles. Adaptive control schemes require only a limited a priori knowledge about the system in order to be controlled. The availability of limited control force and inherent deadband and saturation effects of shape memory actuators are incorporated in the selection of the reference model. The vibration suppression properties of smart structures were successfully demonstrated by implementing the conventional model reference adaptive controllers on the smart structure test articles. The controller parameters converged to steady state values within 8 s for both direct and indirect MRACs. 

A typical example is found in a space truss structure proposed by the Jet Propulsion Laboratory [46]. A stacked PMN actuator was installed at each truss nodal point and operated so that unnecessary mechanical vibration was suppressed immediately. A Hubble telescope has also been proposed using multilayer PMN electrostrictive actuators to control the phase of the incident light wave in the held of optical information processing (Fig. 4.1.25) [47]. The PMN electrostrictor provided superior adjustment of the telescope image because of negligible strain hysteresis. 

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