A Flexure-Based Parallel Actuation Dual-Stage System for Large-Stroke Nanopositioning

This paper presents a novel parallel actuation dual-stage system that delivers nanometric positioning over a large displacement. Unlike those traditional dual-stage designs, the translator of fine actuator in the proposed design is mechanically connected to the coarse translator via the flexure mechanism, while the actuation coils of both the coarse and fine actuators lay underneath the translators in parallel. The merits of the proposed parallel actuation dual-stage design are mainly twofold. First, both the coarse and fine actuators utilize the moving-magnet configuration, hence the translators do not need to carry any cables for power supply. Second, the coarse motion can exhibit better dynamics and energy efficiency due to the minimized moving size and weight. In this work, an analytical current-force model is established for the coarse actuator considering higher order harmonic magnetic field, and based on the proposed model, the force ripple of coarse actuator is quantitatively analyzed both in theory and in practical. Furthermore, a disturbance observer is employed in the dual-feedback configuration to deal with the uncertainties with the proved asymptotic stability. The experimental results show that the proposed dual-stage positioning system is capable to achieve 20 nm step resolution with a root mean square error of 13.15 nm, and the 5 mm point-to-point positioning error can achieve less than 40 nm.