Date of Award

Summer 1990

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Electrical and Computer Engineering

First Advisor

Brown, Ronald H.

Second Advisor

Ruchti, Tim

Third Advisor

Heinen, James A.


This thesis on step motors is prepared with the objectives of finding the time-optimal controls, which include the free end-velocity time-optimal control and the zero end-velocity time-optimal control, for the bifilar-wound hybrid step motor. The necessary conditions for the optimal controls are derived from a motor, load, and driver circuit model using Pontryagin's Minimum Principle. A new reduced-order relaxation method, involving forward/backward integrations, for finding the solution to the nonlinear two-point boundary value problem specified by the necessary conditions, including generation of an initial control, is presented. A drive circuit model for the inverse-diode-clamped drive circuit is introduced and the time-optimal controls for the hybrid step motor with drive circuit are found. Example solutions are presented and comparisons to lead-angle controls are made. The major contribution of this work is the development of reduced-order time-optimal control problems for the hybrid step motor with the drive circuit model and a numerical method for solving these problems. In addition, initial guess solutions for the relaxation method have been found so that the method converges and converges quickly for arbitrary bifilar-wound hybrid step motors and load models, and for different length moves.



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