Black-box model identification of a magnetically levitated microrobotic system

Abstract

Magnetically levitated microrobotic systems have shown a great deal of promise for micromanipulation and biomedical applications. This paper discusses the identification of the vertical and horizontal motion models for a large-gap magnetic suspension system developed by the authors. The suspension system consists of six electromagnets attached to a soft iron pole piece, which levitate a small microrobot prototype manufactured from a 10 mm × 10 mm cylindrical neodymium magnet. A modified least squares algorithm is used to identify ARMAX models describing the motion of the system. Due to the unstable nature of open loop vertical position control, the black-box open loop model is extracted from the identified closed loop model by examining the motion of the closed loop poles on a root locus diagram. The identified models are able to reasonably predict the system behaviour.