INVERSION-BASED ITERATIVE FEEDFORWARD-FEEDBACK CONTROL: APPLICATION TO NANOMECHANICAL MEASUREMENTS AND HIGH-SPEED NANOPOSITIONING

Abstract

OF THE THESIS Inversion-based Iterative Feedforward-Feedback Control: Application to Nanomechanical Measurements and High-speed Nanopositioning by Yan Zhang Thesis Director: Professor Qingze Zou This thesis presents the development of inversion-based iterative feedforward-feedback (II-FF/FB) approach and its application to achieve high-speed force load in nanomechanical property measurement of soft materials in liquid, and high-speed nanopositioning control using piezoelectric actuators. High-speed nanopositioning is needed in various applications. For example, high-speed precision tracking of the force load is needed to measure the rate-dependent viscoelasticity of a wide range of soft materials in liquid, including live cells. In these applications, however, various adverse effects exist that challenge the precision tracking of the desired trajectory. For instance, during the nanomechanical measurement in liquid, the tracking precision is limited by the thermal drift effect, the reduction of the signal to noise ratio, and the hysteresis and the vibrational dynamics effects of the piezoelectric actuators (used to position the probe relative to the sample), particularly during high-speed measurements. These adverse effects limit the positioning precision not only during quasi-static operation (i.e., lowspeed), but also in high-speed tracking. This research is focused on the development the II-FF/FB technique to tackle these critical issues in practical applications. Motivated by the challenges in high-speed nanomechanical measurement of soft materials in