Multi-Layer Control with Disturbance Observers for a Long-Travel Dual-Stage Precision Positioning Platform

This paper investigates the effects of disturbance observers on a long-travel precision positioning platform. We propose a multi-layer control architecture, including a disturbance observer, a feedforward compensator, gain-scheduling, and control switching. The platform consists of motor and piezoelectric transducer (PZT) stages to enable nanometre-level accuracy within 10 cm travel ranges. We identified the dynamic models of the stages through experiments and applied them to develop control designs. The PZT stage was equipped with feedforward compensators, a disturbance observer and real-time switching control schemes to achieve robust and precise tracking. On the other hand, we applied gain-scheduling and feedforward compensation to the motor stages to track large displacements. The control effects of the integrated platform were validated through simulations and experiments and demonstrated significant improvements in accuracy and robustness. Finally, the platform was incorporated with two-photon polymerisation to fabricate micro-lenses. This work evaluates the lenses' optical properties to highlight the advantages provided by the multiple control structure for improving precision and microfabrication applications.