2009-01-0951 Closed Loop Pressure Control System Development for an Automatic Transmission Quan Zheng, Jeremy Kraenzlein and Eunjoo Hopkins Delphi Corporation Robert L. Moses and Bret Olson General Motors Corporation Copyright © 2009 SAE International ABSTRACT This paper presents the dev elopment of a transmission closed loop pressure control system. The objective of this system is to improve transmission pressure control accuracy by employing closed-loop technology. The control system design includes both feed forward and feedback control. The feed fo rward control algorithm continuously learns solenoid P-I characteristics. The closed loop feedback control has a conventional PID control with multi-level gain selections for each control channel, as well as different operating points. To further improve the system performanc e, Robust Optimization is carried out to determine the optimal set of control parameters and controller hardware design factors. The optimized design is verified via an L18 experiment on spin dynamometer. The design is also tested on vehicle. INTRODUCTION Current production transmission control utilizes open-loop control of solenoid pressure, which requires investment in hardware characterization and testing. This initial characterization provides good initial pressure control quality under normal conditions. However, after the product goes into market, there is no compensation for any variations of the desired pressure that may be caused by factors like part-to- part variation, temperature, transmission fluid quality, system interaction, or system degradation over time. The alternative to achieve better pressure control is to add pressure sensors to the system and employ closed loop control technology to improve overall pressure control accuracy. The objective of this project is to develop a more accurate and robust pressure control system by applying closed loop controls technology. The system includes a hydraulic module with pressure control solenoids, pressure sensors, and a production intent transmission control module. This contro l strategy uses both feed forward and feedback controls. The feed forward control algorithm does large and slow adjustments of the future baseline, based on past and current data. The closed loop feedback control algorithm does fast fine-tune control in real time. These two algorithms compliment each other to deliver accurate pressure controls over a wide range of operating conditions. The control algorithm is developed by using Matlab/Simulink/Stateflow and run in a dSPACE AutoBox. The algorithm is tested on actual transmission hardware on a spin dynamometer. To further improve the system performance, a R obust Optimization study is carried out. The optimized system is installed in a test vehicle. This paper describes the deta ils of the system setup, control strategy developmen t, dynamometer and vehicle testing results, as well as proposed future improvements for the control system. SYSTEM CONFIGURATION The configuration of closed pr essure control system is shown in Figure 1 , which consists of a Transmission Control Module (TCM), pressure control solenoids, and pressure sensors. In this development system, a dSPACE rapid algorithm development unit is used in conjunction with a TCM for the control system design. The Engineering Meetings Board has approved this paper for publication. It has su ccessfully 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 o r by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not nec essarily those of SAE. The a