Design and simulation of robust controller for flexure stage based piezo-actuated nanopositioning device

The rapid growth and rise in applications of nanotechnology demand investigation and control of matters at nanometer or subnanometer scale. The fundamental component of nanotechnology is the nanopositioning device, which can be used to scan or position the sample precisely at nanometer or subnanometer scale. Besides fine resolution, high precision positioning and long travel range, many applications of nanotechnology require fast positioning system. To achieve these requirements, design of high precision and high bandwidth nanopositioning device is needed. To achieve nanoscale precision over nanoscale, nanopositioning stage driven by stack piezoelectric actuator is widely used in applications such as atomic force microscope (AFM) and scanning tunneling microscope (STM). This paper presents open loop time and frequency response characteristics of piezoelectric actuator based nanopositioner. The transient response characteristics and stability margins of this device can be improved by using feedback control law. This paper shows that substantial improvement in operating speed and position precision has been achieved using a feedback controller. The presence of hysteresis is the significant challenge in the use of piezoelectric actuator for nanopositioning applications. A successfully designed control system must be able to maintain stability margins and performance level, even in the presence of uncertainties/nonlinearities in system dynamics and/or in the working environment to a certain degree. To meet these requirements, this paper synthesizes robust and optimal H-infinity controllers for a system having hysteresis non-linearities. Simulation results using MATLAB are given to validate the proposed controller for nanopositioning device. Further, a comparative analysis of different types of proposed controllers is also described.