Practical control method for ultra-precision positioning using a ballscrew mechanism

This paper describes a practical control method for nanometer level point-to-point positioning (PTP) using a conventional ballscrew mechanism. nominal characteristic trajectory following controller (NCTF controller) is used for the ultra-precision positioning. The controller design, which s comprised of a nominal characteristic trajectory (NCT) and a PI compensator, is free from exact modeling and parameter identification. The NCT s determined from an open-loop experiment and the PI compensator is used to make the mechanism motion to follow the NCT. The compensator ain values are restricted by the practical stability limit of the control system, which is easy to determine. Using a high integral gain causes excessive vershoot, so an antiwindup integrator is used to improve the system performance. The NCTF control system achieves a positioning resolution of nm and is robust against friction variations. 2007 Elsevier Inc. All rights reserved.