Novel High-Stiffness Active Structure Actuators Built on Piezo-Based Principles

The limited travel capability of conventional piezoelectric actuators has prevented their adoption in many longer-travel applications where magnetic actuation remains dominant. But the subatomic resolution, high acceleration, cool operation, vacuum compatibility, fieldlessness, stability, reliability and inherent stiffness of piezoelectric mechanisms present many valuable benefits. Recent innovations in piezoelectric-based actuation break through the former travel constraints, bringing the benefits of piezoelectric actuation into applications requiring many millimeters of travel. The novel actuation concepts are proving to be enablers for next-generation applications in fields as diverse as aerospace, semiconductor microlithography, data storage, life sciences and photonics. This paper briefly reviews the fundamentals of piezo actuation, the origins of its characteristics, and the classical approaches employed to address its shortcomings. We then explore several recent advances which form the basis of entirely new piezo-based mechanisms, some with essentially unlimited travel but which retain the rest of piezo actuators' signature benefits. Several of these new mechanical approaches are of potential value for innovative active structures. In addition, significant progress has been made in further burnishing the reliability of conventional layered piezo actuators and reducing their susceptibility to humidity; these approaches are reviewed and the reliability benefits are presented quantitatively.