Analysis and control of monolithic piezoelectric nano-actuator

This paper describes the analysis and control of a two degree-of-freedom (DOF) monolithic piezoelectric actuator. This actuator is part of a six-DOF manipulator capable of linear resolution to 2 nm and angular resolution to 1 arc-second. Design of this actuator differs from the existing ones in that it has a monolithic structure which enables a high bandwidth, low drift, and high force realization. A number of nonlinearities exist in the actuator, stemming from the geometry and material properties. For example, coupling of the actuator elements can be modeled as a soft spring which increases displacement/drive-voltage gain (scale factor) at high actuation levels. In this work, a combination of feedforward (amplitude-dependent command prefiltering/input shaping) and feedback control are applied to reduce the effects of 1) scale factor nonlinearities; 2) hysteresis; and 3) output oscillations