  Precision motion stages play a critical role in various manufacturing and
inspection equipment, for example, the wafer/reticle scanning in
photolithography scanners and positioning stages in wafer inspection systems.
To meet the growing demand for higher throughput in chip manufacturing and
inspection, it is critical to create new precision motion stages with higher
acceleration capability with high control bandwidth, which calls for the
development of lightweight precision stages. However, in today's precision
motion systems, only the rigid body motion of the system are under control, and
the flexible dynamic systems are in open loop. For these systems, the motion
control bandwidth is limited by the first structural resonance frequency of the
stage, which enforces a fundamental trade-off between the stage's bandwidth and
acceleration capability. Aiming to overcome this trade-off, we have introduced
a sequential structure and control design framework for lightweight stages with
the low-frequency flexible modes of the stage are under active control. To
facilitate the controller design, we further propose to minimize the resonance
frequency of the stage's mode being controlled and to maximize the resonance
frequency of the uncontrolled mode. The system's control bandwidth is placed in
between the resonance frequencies. This paper presents the design,
optimization, building, and experimental evaluations for a lightweight
magnetically levitated planar stage, which we call FleXstage, with first
flexible mode actively controlled via over-actuation. Simulations show the
proposed design is highly promising in enabling stages with lightweight without
sacrificing control bandwidth. We have some preliminary results now and are
still working on the experimental evaluations for the closed-loop system, and
will present the results in the oral presentation.

Systems and Control;Systems and Control