Robust control strategies of stick-slip type actuators for fast and accurate nanopositioning operations in scanning mode

This paper deals with robust closed-loop control of a nano-robotic system dedicated to fast scanning probe microscopy. The nano-robotic system is actuated by piezoelectric stick-slip actuators able to produce a millimeter range displacement with a nanometer resolution. In order to meet the requirements of fast scanning in terms of closed-loop bandwidth and vibration damping, robust control strategies are studied. We first show that a commonly used one degree of freedom (1-DOF) H_∞ controller is limited to satisfy robust performances required for fast and accurate positioning of the actuators. As such, the control strategy is defined considering two closed-loops. Results show that the 2-DOF H_∞ control scheme allows robust performances for the positioning of nanorobotic systems and lead to new perspectives for fast scanning probe microscopy using stick-slip actuators.