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 2004-01-3545 Driving the Traction Circle Wm. C. Mitchell Wm. C. Mitchell Software Roger Schroer and Dennis B. Grisez Transportation Research Center Reprinted From: Proceedings of the 2004 SAE Motorsports Engineering Conference and Exhibition Motorsports Engineering Conference and Exhibition Dearborn, Michigan November 30-December 3, 2004Downloaded from SAE International by University of British Columbia, Tuesday, July 31, 2018The 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. This 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 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 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 themanuscript or a 300 word abstract to Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by University of British Columbia, Tuesday, July 31, 20182004-01-3545 Driving the Traction Circle Wm. C. Mitchell Wm. C. Mitchell Software Roger Schroer and Dennis B. Grisez Transportation Research Center Copyright © 2004 SAE International ABSTRACT It is time to introduce a new component to motorsports engineering - the driver. SAE papers rarely deal with the cognitive control system wh ich fills the space between the steering wheel and the s eat. It seems that only the safety papers admit the presence of a driver, and they treat the driver as a passi ve object to be protected. It is the driver who controls the race car. It is the driver who utilizes, or misuses, the capabilities of the car. It is the driver who chooses a path for the vehicle. It is the driver who decides how to use the traction circle to negotiate a turn in hopes of optimizing lap time. The traction circle is a G-G diagram of longitudinal acceleration as a function of lateral acceleration. It defines the capability of a vehicle to combine acceleration with cornering while exiting a turn or deceleration with cornering while entering a turn. Combining acceleration with cornering is universal because it offers greater cont rol than driving a constant arc at maximum lateral acceleration. Combining deceleration or braking with cornering, often called trail braking, is much more difficult and controversial. The traction circle describes vehicle acceleration and thus determines the path a vehicle follows. This path is usually called a racing line. This paper will explore the s ubject of trail braking and test the concept on a simple oval. It will include a literature review of driv ing books. A mathematical simulation will suggest several lines. These lines will be evaluated on a test oval at the Transportation Research Center in Ohio. The results will show the effect of different lines and demonstrate effective ways to analyze driver data. The traction circle is a useful anal yti