Performance of single-crystal $Pb(Mg1∕3Nb2∕3)-32%PbTiO3$ stacked actuators with application to adaptive structures

This article presents the performance of ultra-high-strain single-crystal piezoelectric stacked actuators using the composition $Pb(Mg1∕3Nb2∕3)-32%PbTiO3$ (PMN-32%PT)for adaptive structures (in particular for space-based applications). Generally, dimensionally adaptive or smart structures often utilize piezoelectric actuators [in particular lead zirconate titanate (PZT) elements] to provide high-frequency response motion. However, most commercial stacks are limited in range (often $<0.1%$ strain) and the motion is further reduced at low or cryogenic temperatures for satellite-based and many other applications. Comparatively, single-crystal actuators such as the ultra-high-strain PMN-32%PT provide greater than a factor of 4 displacement, factor of 2 strain energy density, and cryogenic displacements are comparable to room-temperature conditions for PZT actuators. Nonetheless, there are some technological and fundamental limitations, such as plate thickness, which is generally greater than $0.5mm$⁠, low elastic modulus, and low strain at each end of the stacks. Three stack configurations with 3, 5, and 40 active layers are tested and discussed. This report discusses each configuration type as a function of lost motion, obtainable strain rates, preload designs, applied stiffness, stress gradients, electric fields, and bandwidth performances. The results obtained in this study aim to show performance and discuss the relative merits and limitations of using this actuator material for adaptive structures. A case study is presented for a high bandwidth steering mirror using ultra-high-strain single crystals. Closed loop control results from the platform’s response are briefly discussed.