Moving-magnet type precision miniature platform for fine positioning and compliant motion

This paper presents a unique precision miniature platform for fine position ing and compliant motion. This platform is implemented by using magnetic le vitation forces of permanent magnets and air-core solenoids in pairs. In ad dition, this platform has a moving-magnet type configuration that is advant ageous in small magnetic systems. Since magnetic levitation systems are inh erently unstable, the mechanical structure of the platform is designed to a ssure dynamic stability and to have simple dynamics. For positioning of the platform, a combined robust controller consisting of a model reference con trol and a H-infinity control is proposed. Positioning experimental results show that the performances of this control system may well be applied to f ine manipulation and micro-assembly. A compliant motion, instead of a force control, is also implemented with a feedforward-proportional-derivative co ntrol, of which the performance is presented in terms of a force repeatabil ity and seems to be satisfactory. (C) 2001 Published by Elsevier Science Lt d.