Controlling cyclic combustion timing variations using a symbol-statistics predictive approach in an HCCI engine

Cyclic variation of a Homogeneous Charge Compression Ignition (HCCI) engine near misfire is analyzed using chaotic theory methods and feedback control is used to stabilize high cyclic variations. Variation of consecutive cycles of theta(Pmax) (the crank angle of maximum cylinder pressure over an engine cycle) for a Primary Reference Fuel engine is analyzed near misfire operation for five test points with similar conditions but different octane numbers. The return map of the time series of theta(Pmax) at each combustion cycle reveals the deterministic and random portions of the dynamics near misfire for this HCCI engine. A symbol-statistic approach is used to predict theta(Pmax), one cycle-ahead. Predicted theta(Pmax) has similar dynamical behavior to the experimental measurements. Based on this cycle ahead prediction, and using fuel octane as the input, feedback control is used to stabilize the instability of theta(Pmax) variations at this engine condition near misfire. (C) 2011 Published by Elsevier Ltd.