Smart cantilever beams for nanomanipulation

A smart micro cantilever beam, consisting of an atomic force microscope probe bonded with a piezoelectric actuator, is proposed to enhance the ability of mechanical nanomanipulation. A precise three-section Euler-Bernoulli beam model is developed to describe the dynamics of the beam. The forced vibration solution of this model with respect to two independent inputs from the piezoelectric actuator and the base excitation is derived. Through the solution and the geometry relationship, the trajectory of the end of the tip is obtained from the motion of the free end of the AFM probe. Based on the resonant response from two harmonic inputs, nano-scale elliptical and linear tip trajectories are predicted at the second dynamic mode. Analytical and numerical studies show that the characteristics of the resulting trajectories are influenced by the magnitudes of the two inputs. The potential applications of the elliptical and linear trajectories for nanomanipulation are proposed

Robust adaptive control of switched systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 141-149).In this thesis, robust adaptive controllers are developed for classes of switched nonlinear systems. Switched systems are those governed by differential equations, which undergo vector field switching due to sudden changes in model characteristics. Such systems arise in many applications such as mechanical systems with contacts, electrical systems with switches, and thermal-fluidic systems with valves and phase changes. The presented controllers guarantee system stability, under typical adaptive control assumptions, for systems with piecewise differentiable bounded parameters and piecewise continuous disturbances without requiring a priori knowledge on such parameters or disturbances. The effect of plant variation and switching is reduced to piecewise continuous and impulsive inputs acting on a Bounded Input Bounded State (BIBS) stable closed loop system. This, in turn, provides a separation between the robust stability and robust performance control problems. The developed methodology provides clear guidelines for steady-state and transient performance optimization and allows for parameter scheduling and multiple model controller adjustment techniques to be utilized with no stability concerns. The results are illustrated for various systems including contact-based robotic manipulation and Atomic Force Microscope (AFM) based nano-manipulation.by Khalid El Rifai.Ph.D