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 6 DOF manipulator [1] capable of linear resolution to 2 nanometer 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 materials properties. For example, coupling of the actuator elements can be modeled as a soft spring which increases scale factor at high actuation levels. In this work, a combination of feedforward (amplitude-dependent input shaping) and feedback control are applied to reduce the effects of 1) scale factor nonlinearities, 2) hysteresis, and 3) output oscillations. Application of this actuator include: optoelectronics assembly, optical fiber alignment, and semiconductor processing.