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Mathematical Problems in Engineering
Volume 2017 (2017), Article ID 1857186, 22 pages
Research Article

Energy Near-Optimal Control Strategies for Industrial and Traction Drives with a.c. Motors

1Faculty of Electrical Engineering, University of Žilina, Žilina, Slovakia
2Faculty of Mechanical Engineering, University of Žilina, Žilina, Slovakia

Correspondence should be addressed to Ján Vittek; ks.azinu.lef@kettiv.naj

Received 11 October 2016; Revised 18 November 2016; Accepted 24 November 2016; Published 24 January 2017

Academic Editor: Mohammed Nouari

Copyright © 2017 Ján Vittek et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The main contribution of this paper is a new rest-to-rest position control system for use with electric drives employing a.c. motors that is near-optimal with respect to combined electrical and frictional energy waste minimization. The friction has constant, linear, and quadratic components with respect to the rotor speed. The closeness to optimality is assessed by simulation, comparing the energy loss of the new control system with that predicted by computed optimal controls. The application of the near-optimal control system is rendered straightforward by using a symmetrical trapezoidal speed-time profile. This is provided by an energy saving reference position generator whose output is faithfully followed by means of a feedback control law based on forced dynamics control yielding prescribed closed loop dynamics, together with a matched zero dynamic lag precompensator. For load torque consisting of constant, linear, and quadratic components also maneuver time is optimized if it can be chosen arbitrary. Two case studies, one applied to position control of rotational drive and second one applied to train movement, confirm the possibilities of achieving energy savings.