Closed-loop performance of a six degree-of-freedom precision magnetic actuator

Zhaohui Ren, Lyndon S. Stephens

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The slotless permanent-magnet self-bearing motor (SBM) technology is used to fully provide radial bearing and motoring functionality simultaneously in a six degree-of-freedom magnetic actuator for potential precision pointing and tracking applications in space such as intersatellite laser communications. This novel precision magnetic actuator incorporates two SBMs to produce both radial bearing forces and motoring torque, and one active magnetic bearing to provide axial support, and thus allows for a complete eleetromagnetic suspension and precision noncontact pointing. An analytical representation of the overall dynamic system is presented for controller design. Six decoupled proportional-integral-derivative controllers are designed, and a feedback control system is implemented. The closed-loop performance confirms experimentally that the precision magnetie actuator is capable of smooth angular slewing while maintaining good stabilization. The most encouraging result is that the actuator achieves a high angular resolution of 754 nrad over a large azimuth range of ±45°.

Original languageEnglish
Pages (from-to)666-674
Number of pages9
JournalIEEE/ASME Transactions on Mechatronics
Issue number6
StatePublished - Dec 2005

Bibliographical note

Funding Information:
Manuscript received May 30, 2005; revised August 16, 2005. This work was supported in part by Airex Corporation, Dover, NH. Z. Ren was with the Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506 USA. She is now with Mohawk Innovative Technology, Inc., Albany, NY 12205 USA (e-mail: zh L. S. Stephens is with the Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506 USA (e-mail: Digital Object Identifier 10.1109/TMECH.2005.859823


  • Active magnetic bearing (AMB)
  • Laser communication
  • Permanent-magnet (PM) self-bearing motor (SBM)
  • Precision pointing and tracking

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


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