A nonlinear control strategy for robust tracking under exogenous vibrations for in-line nano-metrology

Abstract

This paper proposes a novel, observer-based, nonlinear control strategy aimed at facilitating the pursuit of nanomechanical measurements within the noisy environments of industrial production lines. The investigation makes use of a laboratory-prototype emulating an architecture composed by a sample to be analyzed, and by a metrology platform whose task is to carry out in-line measurements, while the whole system is being affected by exogenous vibrations. The control objective is to lock the distance between the metrology platform and the sample, thereby allowing the pursuit of the measurement task. The proposed solution achieves robustness with respect to unknown plant parameters and exogenous disturbances by means of a combination of high-frequency and high-gain tools, and by relying on a novel “learning observer”. The proposed design is formally analyzed, and then experimentally validated by providing a comparative study with a PID-based control-strategy. The experimental results indicate, overall, a favorable performance of the proposed control algorithm over the PID counterpart.