400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2004-01-2681 Design Optimization of Permanent Magnet Motors for Direct-Drive, In-Wheel Electric Propulsion Systems Z. Rahman Principal Engineer, Wave Crest Laboratories, LLC SAE Commercial Vehicle Engineering Congress and Exhibition Chicago, Illinois October 26-28, 2004Downloaded from SAE International by Big Ten Academic Alliance, Wednesday, August 01, 2018All 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]: 724-772-4891Tel: 724-772-4028 For multiple print copies contact: SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: Customer [email protected] ISSN 0148-7191Copyright © 2004 SAE InternationalPositions 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 themanuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by Big Ten Academic Alliance, Wednesday, August 01, 20182004-01-2681 Design Optimization of Permanent Magnet Motors for Direct-Drive, In-Wheel Electric Propulsion Systems Z. Rahman Principal Engineer, WaveCrest Laboratories, LLC Copyright © 2004 SAE International ABSTRACT A complete analytical design and analysis procedure of permanent magnet motors for ‘in-wheel’ traction application system is dev eloped. Method to obtain minimum power requirement and optimal torque-speed profile to meet acceleration performance is explained. Analytical design procedure to optimize electric motor parameters, such as, back emf and torque constants, inductance and magnet thick ness is developed that are based on the torque-speed requi rement of the system. The optimization technique focuses on minimizing the power and volt-ampere rating of the entire electrical system. The design process is validated through experiment and field-testing. Although the paper is focused on electric bicycle system, the approach is also applicable to electric and hy brid electric vehicles. INTRODUCTION Vehicle dynamics requires extended-speed, constant- power operation from the propulsion system in order to meet the vehicle’s operating constraints (e.g., initial acceleration and grade-ability) with minimum power. Initial acceleration and grade condition can be met with minimum power rating if the power train can be operated mostly in the constant pow er region. Generating the optimal torque-speed profile for the vehicle’s propulsion system is extremely import ant, because it reduces the cost by reducing the system power rating. In an electric bicycle syst em the propulsion unit is the electric motor. To calculate the total traction power of a bicycle, the constraint commonly imposed on the propulsion unit is the initial acceleration. The basic objective is to meet the acceleration performance with minimum power. Theoretically, minimum power is achieved when stall torque is infinity. However, with power limited to 750W by US regulation [1], it is observed that after a certain torque there is little improvement in acceleration time with further torque increment. This implies that there exists one optimal solution of torque-speed profile for an electric bicycle that