Automotive Electronics Handbook, Second Edition
Use this guide to become an instant expert on today's leading edge auto electronic technologies--stability control, object detection, collision warning, adaptive cruise control, and more.
TABLE OF CONTENTS Automotive Electronics Handbook, Second Edition
Chapter 16: Traction Control
Thomas Sauter
Development Engineer
Robert Bosch GmbH
16.1 Introduction
Traction control systems or ASRs designed to prevent the drive wheels from spinning in response to application of excess throttle have been on the market since 1987. Vehicles with powerful engines are particularly susceptible to drive-wheel slip under acceleration from standstill and/or on low-traction road surfaces. The results include attenuated steering response on front-wheel-drive (FWD) vehicles, diminished vehicle stability on rear-wheel-drive (RWD) cars, and both on four-wheel-drive (4WD) cars depending on their concept.
Large mutual discrepancies in left- and right-side traction levels engender early drive-wheel slip on slick surfaces. Under these conditions, the effective accelerative forces at both drive wheels are limited to a level corresponding to the adhesion available at the low-traction side. The traction control system inhibits wheelspin, allowing the wheel on the high-traction surface to apply maximum accelerative force to the road.
Figure 16.1 shows different kinds of interventions to reduce drive-wheel slip.
Figure 16.1: Stability and traction control system.
16.1.1 Optimizing Traction
The optimization of traction becomes a top priority when the motive force must be transmitted to surfaces on which the adhesion varies substantially between sides.
The typical passenger car features a differential unit at the drive axle. This unit allows virtually loss-free differences in wheel speed (for instance, in corners) in combination with uniform torque distribution to the drive wheels. This layout generally provides favorable dynamic vehicle response, as the equal distribution of drive torque inhibits vehicle yaw. However, a difference in the force-transmission potentials at the drive...
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