Reducing the uncertainty in a switched amplifier-driven positioning system to the sub-nanometer level

This paper presents a comprehensive position uncertainty analysis in a switched current amplifier-driven precision positioning system with an integrated full-state control structure. A mathematical system model is used combining the mechanical, electrical, and magnetical subsystem and their dynamic couplings. Further an internal quantization error feedback in the state-observer of the control is proposed, that reduces the unwanted effect of PWM-quantization on the positioning uncertainty of the system. The presented error budgeting analysis and practical experiments on a built prototype system demonstrate fast reference position tracking and a steady-state positioning uncertainty of 0.6 nm (rms), which is an improvement by a factor of 65 as compared to conventional control implementations.