400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org 2005-01-1162 Comparative Analysis of Single and Combined Hybrid Electrically Variable Transmission Operating Modes Brendan Conlon General Motors Reprinted From: Advanced H ybrid Vehicle Powertrains 2005 (SP-1973) 2005 SAE World Congress Detroit, Michigan April 11-14, 2005 SAE TECHNICAL PAPER SERIES The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE’s peer review process under the supervision of the session organizer. Th is process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,without the prior written permission of SAE. For permission and licensing requests contact:SAE Permissions 400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: [email protected]: 724-772-4028Fax: 724-772-4891 For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: Customer [email protected] ISSN 0148-7191 Copyright © 2005 SAE International Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the pap er if it is publishe d in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send the manuscript or a 300 word abstract to Secretary, Engineering Meetings Board, SAE. Printed in USA 2005-01-1162 Comparative Analysis of Single and Combined Hybrid Electrically Variable Transmission Operating Modes Brendan Conlon General Motors Copyright © 200 5 SAE International ABSTRACT Electrically variable transmissions divide power between the electrical and mechanical paths using input, output, or compound split schemes. When combined with an electrical energy storage element such as a battery, these systems allow numerous fuel saving and performance benefits. This paper examines the design tradeoffs in each of the three topologies in order to balance fuel economy, system performance against requirements, and electrical component size. A general EVT analysis method is presented and used to study the fuel economy and performance sensitivity of the three configurations to motor, inverter, and battery constraints, and planetary gear ratios. To evaluate fuel economy, the three systems are assessed for each of the primary fuel economy mechanisms enabled by hybridization. To evaluate performance tradeoffs, system performance against typical vehicle performance design points is compared. The effects of combining two modes that are optimized for individual speed ranges vs. a single mode covering all ranges are also discussed. The use of 2 modes provides significant advantages over a single mode design including reduced motor power for a given vehicle performance. INTRODUCTION It is known that hybrid vehicles provide the potential for significant fuel economy improvement as compared to conventional automatic transmission vehicles. However, to satisfy the automotive customer, this fuel economy improvement should not come at the cost of vehicle drivability or performance. The refined state of development of conventional automatic transmissions provides a good benchmark against which potential hybrid systems must be compared. At a minimum, hybrid vehicles typically incorporate engine-off at idle, a moderate level of coast down or braking regeneration, and possibly acceleration assist. As the level of power available increases and becomes a larger percentage of total power, increases in regenerative braking and engine boost are possib