The control problem associated with brushless DC motors (BLDCMs) for direct-drive robotic applications is considered. In order to guarantee the high-performance operation of BLDCMs in such applications, the effects of reluctance variations and magnetic saturation are accounted for in the model. Such a BLDCM model constitutes a highly coupled and nonlinear dynamic system. Using the transformation theory of nonlinear systems, a feedback control law, which is shown to compensate for the system nonlinearities, is derived. Conditions under which such a control law is possible are presented. The need for the derivation of explicit commutation strategies is eliminated, resulting in reduction of the computations involved. To guarantee the high-performance operation of the system under substantial uncertainties, a robust control law is derived and appended to the overall control structure. The inclusion of the robust controller results in good tracking performance when there are modeling and measurement errors and payload uncertainties. The efficacy of the overall control law is investigated by considering a single-link direct-drive arm actuated by a BLDCM.


Mechanical and Aerospace Engineering

Keywords and Phrases

BLDCM; DC motors; brushless DC motors; direct-drive robotic applications; feedback control law; high-performance operation; machine control; magnetic saturation; measurement errors; nonlinear control systems; payload uncertainties; position control; reluctance variations; robots; robust nonlinear control; single-link direct-drive arm; tracking performance; transformation theory

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 1990 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jan 1990