Next-Cycle Optimal Fuel Control for Cycle-to-Cycle Variability Reduction in EGR-Diluted Combustion

• Published in: IEEE control systems letters Vol. 5; no. 6; pp. 2204 - 2209
• Main Authors: Maldonado, Bryan P., Kaul, Brian C., Schuman, Catherine D., Young, Steven R., Mitchell, J. Parker
• Format: Journal Article
• Language: English
• Published: IEEE 01-12-2021
• Subjects: Atmospheric modeling; Automotive control; Combustion; energy systems; Fuels; grey-box modeling; Kernel; Parametric statistics; Solid modeling; Sparks; stochastic optimal control
• ISSN: 2475-1456; 2475-1456
• DOI: 10.1109/LCSYS.2020.3046433

Dilute combustion using exhaust gas recirculation (EGR) is a cost-effective method for increasing engine efficiency. At high EGR levels, however, its efficiency benefits diminish as cycle-to-cycle variability (CCV) intensifies. In this simulation study, cycle-to-cycle fuel control was used to reduce CCV by injecting additional fuel in operating conditions with sporadic misfires and partial burns. An optimal control policy was proposed that utilizes 1) a physics-based model that tracks in-cylinder gas composition and 2) a one-step-ahead prediction of the combustion efficiency based on a kernel density estimator. The optimal solution, however, presents a tradeoff between the reduction in combustion CCV and the increase in fuel injection quantity required to stabilize the charge. Such a tradeoff can be adjusted by a single parameter embedded in the cost function. Simulation results indicated that combustion CCV can be reduced by as much as 65% by using at most 1% additional fuel. Although the control design presented here does not include fuel trim to maintain <inline-formula> <tex-math notation="LaTeX">\lambda = 1 </tex-math></inline-formula> for three-way catalyst compatibility, it is envisioned that this approach would be implemented alongside such an external controller, and the theoretical contribution presented here provides a first insight into the feasibility of CCV control using fuel injection.