# Integrated Control Strategies for a Precision Long-Travel Stage: Applications in Micro-Lens Fabrication

## TL;DR

This paper presents control strategies for a high-precision stage used in fabricating micro-lenses, combining motor and piezoelectric systems for nanometer accuracy over long distances.

## Contribution

The novel integration of control switching, model estimation, gain scheduling, and feedforward mechanisms enables nm-level precision over long travels.

## Key findings

- Control switching and model estimation achieve nm-level precision in the PZT stage.
- Gain scheduling and feedforward control enable 0.1 μm resolution over 100 mm in the motor stage.
- The integrated system successfully fabricates micro-lenses with verified optical performance.

## Abstract

This paper develops multiple control strategies for a precision long-travel stage, which comprises motor and piezoelectric transducer (PZT) stages. First, the PZT stage is equipped with control switching and model estimation mechanisms to achieve nm-level precision within 100 μm distances. The control switching mechanism selects the optimal control sequences by predicting system responses, while the model estimation algorithm updates the system model to improve the prediction accuracy. Second, the motor stage is equipped with gain-scheduling and feedforward control mechanisms to achieve a maximum displacement of 100 mm with a resolution of 0.1 μm. The gain scheduling control modifies the control gain in accordance with tracking errors, while the feedforward control can mitigate phase lags. We integrate the stages to achieve nm-level precision over long travels and conduct simulations and experiments to show the advantages of the control mechanisms. Finally, we apply the long-travel precision stage to fabricate micro-lenses using two-photon polymerization and evaluate the fabricated micro-lenses’ optical characteristics to illustrate the merits of the control strategies.