High-performance and high-precision servo control of a single-deck dual-axis PMLSM stage

The inertia of the stacked multi-degree-of-freedom platform imposes limitation on the achievable motion speed. To overcome this barrier, the unstable design becomes very attractive. This research presents a novel single-deck dual-axis linear motor platform that is capable of fast long-range motion. The platform is equipped with air-bearing design to achieve backlash-free operation. As a result, the positioning rigidity depends entirely on the performance of the servo system. A force distribution control is used to decouple the difference axis dynamics. This research also proposes a chain scattering description (CSD) setup to allow a pseudo-derivative feedback (PDF) control framework that is commonly used in industrial motion control for achieving high servo rigidity. An interesting finding is that our experiments show that without the help of complex piggyback piezoelectric stage, the single-deck platform design, with a stroke as large as 20 mm, can already reach a servo accuracy of ±60 and ±80 nm in the x- and y-axis and 600 μarcsec in the yaw axis.