The Engineering Meetings Board has approved this paper for public ation. 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 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 necessarily those of SAE. The author is solely responsible for the content of the paper. SAE Customer Service: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: [email protected] SAE Web Address: http://www.sae.org Printed in USA 2009-01-1131 Concept and Implementation of a Robust HCCI Engine Controller Jun-Mo Kang, Chen-Fang Chang, Jyh-Shin Chen and Man-Feng Chang General Motors Corporation Copyright © 2009 SAE International ABSTRACT General Motors recently demonstrated two driveable test vehicles powered by a Homogeneous Charge Compression Ignition (HCCI) engine. HCCI combustion has the potential of a signifi cant fuel economy benefit with reduced after-treatment cost. However, the biggest challenge of realizing HCCI in vehicle applications is controlling the combustion process. Without a direct trigger mechanism for HCCI’s flameless combustion, the in-cylinder mixture composit ion and temperature must be tightly controlled in order to achieve robust HCCI combustion. The control architecture and strategy that was implemented in the demo vehicles is presented in this paper. Both demo vehicles, one with automatic transmission and the other one with manual transmission, are powered by a 2.2-liter HCCI engine that features a ce ntral direct-injection system, variable valve lift on both intake and exhaust valves, dual electric camshaft phasers and individual cylinder pressure transducers. The development of the HCCI engine controller starts with a stability analysis of the HCCI combustion process. Based on the stability analysis, operating set-points (e.g., EGR rate, air-fuel ratio, etc.) for robust HCCI combustion were determined. The engine controller was then designed to follow those set-points in HCCI combustion mode as well as manage transitions to and from SI combustion mode, which is necessary because conventional SI combustion is still currently required in high-load operations. The engine controller has been validated on both single-cylinder HCCI engine and multi-cylinder HCCI engine in the engine test cell. Finally, some test results from demo vehicles are included. INTRODUCTION Homogeneous Charge Compression Ignition (HCCI) combustion is flameless, and spontaneously occurs at the entire cylinder volume. The homogeneously mixed cylinder charge in the combustion chamber is auto- ignited as its increasing temperature reaches a certain threshold during the compressing stroke. The ignition timing strongly depends on t he initial conditions of the cylinder charge such as temperature, pressure, and composition. It has long been recognized that HCCI combustion has the great potential of a significant fuel economy benefit with near-zero NOx and particulate emissions. However, it has only recently been demonstrated in two HCCI-powered vehicles that HCCI combustion was succesfully realized in vehicle application through combination of modern engine hardware (e.g., variable valve actuation, central direct injection, cylinder-pressure sensing, etc.) and advanced controls [1]. The HCCI engine in the demo vehicles is managed by an internally-developed engine controller.