Path Following Control of an Atomic Force Microscope Driven by a Piezoelectric Inertia Actuated Robot Inside a Scanning Electron Microscope

Path following control of micrometer-sized tools is the key to improve automation capabilities at the small scales. This paper addresses the issue of path following control for piezoelectric inertia actuated nano-robotic systems operating inside electron microscopes. The aim is to control the trajectory of an end effector driven by a stick and slip principle using both electron microscope images and velocity measurements from optical encoders. The path following control is divided into two layers. The high level layer considers a Frenet frame kinematic model to compute velocity references along two orthogonal axes. The low level layer is based on an average closed loop velocity control of the nano-robotic system along the two orthogonal axes. The path following performances are evaluated and analyzed experimentally using an inertia nano-robotic system operating inside a Scanning Electron Microscope and holding an Atomic Force Microscope (AFM) cantilever. Experimental results show the effectiveness of the AFM cantilever for various paths following with a mean tracking error less than 2 μm in the worst case. These tracking capabilities are of importance toward automated manipulation and assembly sequences inside electron microscopes.