2001-01-0595 A Model-Based Brake Pressure Estimation ... - Delphi

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The appearance of this ISSN code at the bottom of this page indicates SAE’s consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay a $7.00 per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Sales and Satisfaction Department. Quantity reprint rates can be obtained from the Customer Sales and Satisfaction Department. To request permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. ISSN 0148-7191 Copyright 2001 Society of Automotive Engineers, Inc. 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 paper if it is published in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USA All SAE papers, standards, and selected books are abstracted and indexed in the Global Mobility Database
2001-01-0595 A Model-Based Brake Pressure Estimation Strategy for Traction Control System Copyright © 2001 Society of Automotive Engineers, Inc. ABSTRACT This paper presents a brake pressure estimation algorithm for Delphi Traction Control Systems (TCS). A control oriented lumped parameter model of a brake control system is developed using Matlab/Simulink. The model is derived based on a typical brake system and is generic to other types of brake control hardware systems. For application purposes, the model is simplified to capture the dominant dynamic brake pressure response. Vehicle experimental data collected under various scenarios are used to validate the algorithm. Simulation results show that the algorithm gives accurate pressure estimation. In addition, the calibration procedure is greatly simplified INTRODUCTION Traction control plays an important role in improving vehicle stability during vehicle acceleration. This is achieved by controlling brake pressure and engine torque together to reduce the wheel spin. During TCS brake pressure information is used to determine the torque reduction required by the engine. It is also used to prevent over heating of the base brake system during controlled brake events. Thus, brake pressure is valuable information needed to improve the safety of the vehicle. However, few vehicles install brake pressure sensors since it increases the cost and requires additional diagnostic algorithms [1]. Therefore, an estimation algorithm is required to provide the brake pressure information. The current pressure estimation algorithm relies on numerous of vehicle tests to determine the calibration values. In an effort to improve the accuracy of brake pressure estimation, reduce complexity of calibration and save the calibration time, the model-based brake pressure estimation strategy was developed. In this paper, a control oriented lumped parameter model of a brake control system is developed based on one channel hydraulic brake system. For production implementation purposes, Qingyuan Li, Keith W. Beyer and Quan Zheng Delphi Automotive Systems the higher order dynamics of the algorithm are ignored in this physical model, and it is simplified to capture the dominant dynamic brake pressure response. In order to verify the simplified model, vehicle experimental data collected under various conditions was used. This paper outlines and describes the derivation of the algorithm and presents the simulation results to show that the algorithm gives accurate pressure estimation. MODEL FOR TCS BRAKE PRESSURE CONTROL SYSTEM There are two types of disc brake calipers in current base brake products. One is the fixed-caliper disc brake, where two pistons are used to press the brake pad against the disc from opposite directions, and the other is the floatingcaliper disc brake, where only a single piston is used to press the brake pads against the disc [2]. Figure 1 shows the model schematic of the brake pressure control system for one simplified channel when it is in traction control mode. The figure shows a motor, a pump, an accumulator, an orifice, a pressure relief valve, two solenoid valves labeled as a pressure apply valve and pressure release valve, brake caliper and pad. The pressure apply and release valves are represented by an orifice and the corresponding control command. The motor drives the pump. The accumulator and orifice smooth the pressure transients. A pressure relief valve provides safety to the system. In traction control mode, the pressure generated by the pump is always higher than the setting of the pressure relief valve, so the relief valve is at work all the time. Therefore, the pressure labeled as s P in Figure 1 can be assumed a constant, which is equal to the setting of the relief valve. The pressure apply valve is normally open, and the pressure release valve normally closed. When the control command is in “APPLY” mode, the fluid from the pump flows through the apply valve’s
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2001-01-0595 A Model-Based Brake Pressure Estimation ... - Delphi

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