We hope to improve engine emmissions and efficiency through control of auto-ignition (homogeneous charge compression ignition - Wikipedia Entry). Our control is driven by simple models derived from the physics of the engine.
This project is a tight collaboration between researchers at Stanford University, the Robert Bosch Corporation and the General Motors Corporation.
Robert Bosch Corporation Research and Technology Center
Dr. Jasim Ahmed
Dr. Aleksandar Kojic
Dr. Sungbae Park
General Motors Research and Development Center
Dr. Chen-Fang Chang
Dr. Jun-Mo Kang
Dr. Jason Chen
Dr. Man-Feng Chang
Experimental studies at Stanford University and elsewhere demonstrate that variable valve actuation (VVA) can be used to initiate homogeneous charge compression ignition (HCCI). This is achieved by reinducting combustion products from the previous cycle, thereby increasing the sensible energy of the reactant charge and allowing ignition to occur by compression alone at modest compression ratios. Since the reinducted products act as a thermal sink during combustion, this process lowers the peak combustion temperature, which in turn lowers NOx concentrations. This drop in NOx is one of the major benefits of HCCI.
Other methods besides VVA exist to initiate HCCI, such as heating or pre-compressing the intake air or varying the compression ratio. Regardless of the method chosen, however, HCCI combustion exhibits some fundamental control challenges concerning combustion phasing and load, two critical parameters for any IC engine combustion methodology. Unlike spark ignition (SI) or diesel engines, where the combustion is initiated via spark and fuel injection, respectively, HCCI has no specific event that initiates combustion. Therefore, ensuring that combustion occurs with acceptable timing, or at all, is more complicated than in the case of either SI or diesel combustion. Combustion phasing in HCCI is dominated by chemical kinetics, which depends on both in-cylinder species concentrations and temperature. Load is dependent on both the combustion phasing and the amount of reactant species present in the cylinder. Both load and combustion phasing are therefore coupled and dependent on both in-cylinder species concentrations and temperature.
These parameters are controlled in the system studied solely through the use of the fully flexible VVA system. The control problem then becomes how to vary the valve timings to achieve the desired combustion phasing and load on a cycle-to-cycle basis. As noted previously, this is complicated by the lack of a direct combustion initiator. Furthermore, since products are re-inducted from the previous cycle, the composition and temperature of the exhausted products from the previous cycle have a direct impact on the next cycle, introducing cycle-to-cycle dynamics. Understanding the effect of the previous cycles exhausted products and the implications for control of combustion phasing and load during the next cycle must then be clearly understood before a control methodology for HCCI combustion can be completed.
To synthesize a controller to stabilize HCCI and track desired load trajectories using the VVA system, a model of the system with special attention paid to combustion phasing and cycle to cycle interactions is necessary. This model should be as simple as possible, as it is often difficult to synthesize controllers from more complex models. In previous and ongoing work a relatively high order (10-state) model of HCCI combustion has been formulated, showing very good correlation with experimental combustion timing, in-cylinder pressure evolution, work output, maximum rate of pressure rise and exhaust temperature. As well as this model works, it has been noted that a simpler and lower order description of HCCI combustion would probably be needed to synthesis a controller. The formulation of a low-order model and its use to synthesize a load and combustion phasing controller, have been completed. Implementation in simulation and experiment result in the desired tracking of both combustion timing and work output.
Gregory M. Shaver, Physics-Based Modeling and Control of Residual-Affected HCCI Engines using Variable Valve Actuation, a dissertation submitted to the department of mechanical engineering and the committee on graduate studies of stanford university in partial fulfillment of the requirements for the degree of doctor of philosophy
Gregory M. Shaver, Matthew J. Roelle, J. Christian Gerdes, Modeling Cycle-to-Cycle Dynamics and Mode Transition in HCCI Engines with Variable Valve Actuation, IFAC Journal on Control Engineering Practice (CEP), vol. 14, no. 3, pp. 213-222, March 2006, Advances in Automotive Control (AAC'04), doi:10.1016/j.conengprac.2005.04.009
Gregory M. Shaver, Matthew J. Roelle, J. Christian Gerdes, Patrick A. Caton and Christopher F. Edwards, Dynamic Modeling of Residual-Affected Homogeneous Charge Compression Ignition Engines with Variable Valve Actuation, ASME Journal of Dynamic Systems, Measurement and Control, vol. 127, no. 3, pp. 374-381, September 2005, doi:10.1115/1.1979511
Gregory M. Shaver, Matthew J. Roelle, Patrick A. Caton, Nalu B. Kaahaaina, Nikhil Ravi, Jean-Pierre Hathout, Jasim Ahmed, Aleksander Kojic, Sungbae Park, Christopher F. Edwards and J. Christian Gerdes, A Physics-Based Approach to the Control of Homogeneous Charge Compression Ignition Engines with Variable Valve Actuation, International Journal of Engine Research, vol. 6, no. 4, pp. 361-375, July 2005, doi:10.1243/146808705X30512
Stephen Erlien, Adam Jungkunz, J. Christian Gerdes, Multi-Cylinder HCCI Control with Cam Phaser Variable Valve Actuation Using Model Predictive Control, Proceedings of the 2012 Dynamic Systems and Control Conference, Ft. Lauderdale, FL, October 17-19, DSCC12-8585
Adam Jungkunz, Stephen Erlien, J. Christian Gerdes, Late Phasing Homogeneous Charge Compression Ignition Cycle-to-Cycle Combustion Timing Control with Fuel Quantity Input, Proceedings of the 2012 American Control Conference, Fairmont Queen Elizabeth, Montreal, Canada, June 27-29, ACC12-1258.
Hsien-Hsin Liao, Matthew J. Roelle, J. Christian Gerdes, Repetitive Control of an Electro-Hydraulic Engine Valve Actuation System, Proceedings of the 2008 American Control Conference, Seattle, Washington, June 11-13, ACC08331
Matthew J. Roelle, Nikhil Ravi, J. Christian Gerdes, Estimating Thermodynamic State and Ignition in HCCI with Variable Fuel Injection Timing, Proceedings of the 2007 ASME International Mechanical Engineering Congress and Exposition, Seattle, Washington, November 11-15, 2007, IMECE2007-42450
Nikhil Ravi, Matthew J. Roelle, J. Christian Gerdes, Controller-Observer Implementation for Cycle-by-Cycle Control of an HCCI Engine, Proceedings of the 2007 ASME International Mechanical Engineering Congress and Exposition, Seattle, Washington, November 11-15, 2007, IMECE2007-42371
Nikhil Ravi, Matthew J. Roelle, Adam F. Jungkunz, J. Christian Gerdes, Model Based Control of Exhaust Recompression HCCI, Proceedings of the Fifth IFAC Symposium on Advances in Automotive Control, pp. 295-310, Aptos, California, August 20-22, 2007, AAC07-084
Matthew J. Roelle, Nikhil Ravi, Adam F. Jungkunz, J. Christian Gerdes, A Dynamic Model of Recompression HCCI Combustion Including Cylinder Wall Temperature, Proceedings of the 2006 ASME International Mechanical Engineering Congress and Exposition, Chicago, Illinois, November 5-10, 2006, IMECE2006-15125
Nikhil Ravi, Matthew J. Roelle, Adam F. Jungkunz, J. Christian Gerdes, A Physically Based Two-State Model for Controlling Exhaust Recompression HCCI in Gasoline Engines, Proceedings of the 2006 ASME International Mechanical Engineering Congress and Exposition, Chicago, Illinois, November 5-10, 2006, IMECE2006-15331
Gregory M. Shaver, Matthew J. Roelle, J. Christian Gerdes, A Two-Input Two-Output Control Model of HCCI Engines,
Proceedings of the 2006 American Control Conference, pp. 472-477,
Minneapolis Minnesota, June 14-16, 2006, doi:10.1109/ACC.2006.1655401
Gregory M. Shaver, Matthew J. Roelle, J. Christian Gerdes, Decoupled Control of Combustion Timing and Work Output in Residual-Affected HCCI Engines, Proceedings of the 2005 American Control Conference, vol. 6, pp. 3871-3876, Portland, Oregon, June, 8-10 2005, doi:10.1109/ACC.2005.1470578
Matthew J. Roelle, Gregory M. Shaver, and J. Christian Gerdes, Tackling the Transition: A Multi-mode Combustion Model of SI and HCCI for Mode Transition Control, Proceedings of the 2004 ASME International Mechanical Engineering Congress and Exposition, Anaheim, California, November 13-19, 2004, IMECE2004-62188
Gregory M. Shaver, Aleksandar Kojic, J. Christian Gerdes, Jean-Pierre Hathout, and Jasim Ahmed, Contraction and Sum of Squares Analysis of HCCI Engines, In the Proceedings of the 2004 IFAC Symposium on Nonlinear Control Systems, Stuttgart, Germany
Gregory M. Shaver, Matthew J. Roelle, J. Christian Gerdes, Physics-Based Closed-Loop Control of Phasing, Peak Pressure and Work Output in HCCI Engines Utilizing Variable Valve Actuation, Proceedings of the 2004 American Control Conference, vol. 1, pp. 150-155, Denver, Colorado, June 30-July 2, 2004
Gregory M. Shaver, Matthew Roelle and J. Christian Gerdes, Modeling Cycle-to-Cycle Coupling in HCCI Engines Utilizing Variable Valve Actuation, Proceedings of the Fourth IFAC Symposium on Advances in Automotive Control, 2004, pp. 244-249, Salerno, Italy, April 19-23, 2004
Jean-Pierre Hathout, Jasim Ahmed and Aleksandar Kojic, Reduced Order Modeling and Control of an Electrohydraulic Valve System, In the Proceedings of the 1st IFAC Symposium on Advances in Automotive Control, 2004, Pages 182-187, Salerno, Italy
Gregory M. Shaver and J. Christian Gerdes, Cycle-to-cycle control of HCCI Engines, In the Proceeding of the 2003 ASME International Mechanical Engineering Congress and Exposition, IMECE2003-41966, Washington D.C.
Gregory M. Shaver, J. Christian Gerdes, Parag Jain and P.A. Caton and C.F. Edwards, Modeling for Control of HCCI Engines, In the Proceedings of the American Control Conference, 2003, Pages 749-754, Denver