Electrostrictive actuators

Multilayer-type piezoelectric or electrostrictive actuators are used for several apphcations including the composite smart stmcture shown in Figure 9... 

When compared with piezoelectric/electrostrictive transducers, the electro-magnetically driven variety suffer shortcomings in backlash , in the relatively low forces that can be generated and in their relatively low response speeds. Piezoelectric/electrostrictive actuators are capable of producing displacements of 10 + 0.01 /nn in a time as short as 10 /is, even when the transducer is subjected to high ( 100 kgf) opposing forces. 

The attractive features of a piezoelectric/electrostrictive actuator are mentioned above, but a penalty is the small displacements generated. For a d33 value of 500 pCN-1 (or, more appropriately in the present context, pmV-1) a voltage of 1000 Y applied across a 1mm thick poled disc would produce a... 

The ferroelectric Pb(Mgy3Nb2/3)03 (PMN) ceramic has been the snbject of extensive investigations due to its high dielectric coefficient and high electrostrictive coefficient, which renders it suitable for use in capacitors and electrostrictive actuators. However, the successful exploitation of this material is limited by the difficulty of producing a single-phase material with the perovskite structnre. Conventional solid state synthesis techniques invariably resnlt in the formation of one or more pyrochlore phases, which exhibit poor dielectric properties. 

Beginning with the work by Ohno and Yonezawa on PFN-PFW systems in the late 1970s [8], many multicomponent dielectric systems have been evaluated and put into manufacture. Some of the patented compositions developed for multilayer capacitor (MLC) application were recently summarized by Shrout and Dougherty [9]. Other compositions were developed for piezoelectric sensors and electrostrictive actuator applications [10]. Most of the compositions used for capacitor dielectrics are based on PFN [8], PMN [11-14], or PZN [15]. 

Uchino, K., Electrostrictive actuators Materials and applications, Ceram. Bull., 65, 4 (1986). 

Winzer, S.R., Shankar, N., and Ritter, A.P. (1989) Designing cofired multilayer electrostrictive actuators for reliability. 

Piezoelectric/electrostrictive actuators may be classified into two categories, based on the type of driving voltage applied to the device and the nature... 

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. 

FIGURE 4.1.25 Hubble telescope using three PMN electrostrictive actuators for optical image correction. 

Figure 13.17 Schematic illustration of bending electrostrictive actuators biomorph (a) and unimorph (b) actuators.

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