Inverse Hysteresis Control of Stick-Slip SEM Integrated Nano-Robotic Systems

This paper presents a methodology to control a class of nano-robotic systems using piezoelectric stick-slip (PSS) actuators. Such actuators are of importance for multi-scale displacements, i.e. from the mm down to the nm, which is needed in the most of robotic tasks at the small scales. However, due to their working principle, these actuators have both friction and hysteresis nonlinearities that makes them difficult to control with precision. The studied nano-robotic system is made of a 3 XYZ axes Cartesian structures and operates inside a Scanning Electron Microscope (SEM). The methodology proposed in this paper is based on an inverse hysteresis control strategy using a deadzone-based Prandtl-Ishlinskii model. The main contribution of the paper is the design of an feedforward controller using the inverse of deadzone-based Prandtl-Ishlinskii model to compensate the friction and hysteresis nonlinearities. This controller is implemented on each axis of the nano-robotic system when operating in scanning mode. Experimental results show the effectiveness of the proposed feedforward control technique.