Fast Precision Positioning of a Ball Screw Mechanism Based on Practical NCTF Control

Abstract

We discuss improvements in a practical nominal characteristic trajectory-following (NCTF) controller for fast positioning. The NCTF controller consists of a nominal characteristic trajectory (NCT) as the movement reference and a PI compensator making object movement follow the NCT. It is easily designed without an exact model, known parameters, or much control theory knowledge. The step speed of NCTF control depends on the NCT. We introduce two ways to construct the NCT for high-speed step movement, - fast positioning is introduced and the performances by two NCTs thus constructed are compared to clarify a more suitable way using two ball screw mechanisms. Experiments in positioning with the NCT by the suitable way are evaluated, whose results show that the NCT increases step speed while preserving the robustness of feature step height and movable mass changes.