INTERNATIONAL^ 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. The "Lexus" Traction Control (TRAC) System Kiyotaka Ise, K. Fujita, Y. Inoue, and S. Masutomi Toyota Motor Corp. MAR 11990 LIBRARY Reprinted from SP-815 - ABS Traction Control and Brake Components International Congress and Exposition Detroit, Michigan February 26 - March 2,1990 Downloaded from SAE International by University of Wisconsin - Madison , Sunday, September 09, 2018No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior writ- ten permission of the publisher. lSSN 0148-7191 Copyright 1990 Soclety of Automotlw Englnoorr, Inc. Positions and opinions advanced in this paper are those of the Persons wishing to submit papers to be ansidered for presen- author(s) and not necessarily thoseof SAE. The author is solely tation or publication through SAE should send the manuscript responsible for the content of the paper. A process is available or a 300 word abstract of a proposed manuscript to: Secretary, by which discussions will be printed with the paper if it is Engineering Activity Board, SAE. published in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Division. Printed In USA Downloaded from SAE International by University of Wisconsin - Madison , Sunday, September 09, 2018The "Lexus" Traction Control (TRAC) System Kiyotaka Ise, K. Fujita, Y. Inoue, and S. Masutomi Toyota Motor Corp. One of the innovations for the Lexus LS400 is the development of a traction control system (TRAC system). The TRAC system suppresses the spinning of the driven wheels, which occurs easily on slippery roads during excessive acceleration, and it improves the acceleration perf omnce and the stability of the car. The TRAC system controls the engine sub- throttle angle and the brake hydraulic pressure for the driven wheels in the same way as the traction control system for the 1 987 Toyota Crown. But, acceleration performance and stability of Lexus LS400 is better than Crown as a result of good wheel spinning control by additional improvements of the throttle and brake control methods. Especially as the TRAC system controls the brake hydrau 1 ic pressure individua 11 y for left and right wheel, the car acceleration performance on split-p surfaces is improved notably. In regard to the system ccmposition, low costs and simplicity have been targeted by using components of the ABS, while the TRAC system is designed according to redundancy concept using two-valve type throttle bdy which gives satisfactory result in the Cram TRAC systen The TRAC system has been evaluated in the northern part of the USA, in Alaska, Canada ,Sweden, Hokkaida (Japan), e tc., and excellent car operation performance and high reliability have been confirmed. AS A DEVICE FOR IMPROVED CAR PERFORMANCE during braking on slippery surfaces like ice and snow, the ABS presently is standard equipment for near1 y a1 1 luxury cars- On the other hand, in the case of front engine rear drive (FR) cars equipped with high-power engines, car instability like fish-tailing (swaying of the rear) etc. may occur on slippery surfaces during acceleration, and various improvement devices also have come into existence. These instahi 1 ities are caused by a reduction of the tire lateral force due to whee 1 spin shown in Fig.1 when the wheel slides sideways because of camber, tracks, irregularities, or other road surface disturbances. Especially for FR cars, the rolling front wheels have a large lateral force and there is no wheel side slip, but when the driven rear wheels spin, the wheels slide sideways. Fig.1 Traction and lateral force coefficients Tract~on force ccefticient ,P! \ "'f-. 1 Y '. ', \ TRAO referancs sraa '\ lateral force coefficient (P The &st improvement methad for this is to use four wheel drive (4WD) syste