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Performance Evaluation of an Electric Vehicle with Multiple Electric Machines for Increased Overall Drive Train Efficiency

University of Ljubljana-Mario Vukotić, Damijan Miljavec
University of Rome Niccolò Cusano-Laura Tribioli, Daniele Chiappini
Published 2019-10-07 by SAE International in United States
Proposed solutions for electric vehicles range from the simple single-motor drive coupled to one axle through a mechanical differential, to more complex solutions, such as four in-wheel motors, which ask for electronic torque vectoring. Main reasons for having more than one electric machine are: reduction of the rated power of each motor, which most likely leads to simplification and cost reduction of all the electric drive components; increased reliability of the overall traction system, enhancing fault tolerance ability; increase of the degrees of freedom which allows for control strategy optimization and efficiency improvement. In particular, electrical machines efficiency generally peaks at around 75% of load and this usually leads to machine downsizing to avoid operation in low efficiency regions. The same output performance can be achieved by using two or more electrical machines, rather than only one, of smaller size and running them at unequal load - one of the machines at higher load and the other(s) at lower load.In this paper, the performance of an electric vehicle with multiple electric machines is analyzed to…
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Torque Characteristic Optimization of a Brushless DC Motor Based Integrated Starter-Generator

Hidria AET-Primoz Bajec, Peter Ursic, Jure Golob
University of Ljubljana-Damijan Miljavec, Bostjan Pevec
Published 2009-04-20 by SAE International in United States
Paper outlines a case study on optimal control of a brushless direct-current (BLDC) motor, operating as an Integrated Starter Generator (ISG) in a micro hybrid propulsion system for motorcycles. Main research focus is optimization of BLDC machine torque characteristics, particularly in starter operation mode, in order to improve cranking of the internal combustion engine (ICE) at various operation conditions. Stringent cranking torque demands, limited physical dimensions of the electrical machine and a wide rotational speed range of prototype ICE are most challenging reasons for the exhaustive study of applicable control algorithms in the low rpm range. Two approaches for optimization of torque characteristics are discussed, common known flux-weakening method and the modification of power-switch conduction angle, respectively. The evaluation of most relevant control approaches is based on computer simulation and prototype set-up measurements. As a result a novel control principle is proposed which includes both of the above discussed approaches. Experimental results fully confirm improvements in the starting procedure of the hybrid propulsion.
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