Integrated cycle-to-cycle control of exhaust gas temperature, load, and combustion phasing in an HCCI engine

Precise and integrated cycle-to-cycle control of exhaust gas temperature (T_exh), load, and combustion phasing is essential for realizing high efficiency Homogeneous Charge Compression Ignition (HCCI) engines with low exhaust emissions. In this paper a model-based control framework is developed for an integrated control of T_exh, Indicated Mean Effective Pressure (IMEP), and combustion phasing in an HCCI engine. A discrete Control Oriented Model (COM) is developed to predict the HCCI outputs on a cycle-to-cycle basis and validated against steady-state and transient experimental data from a single cylinder Ricardo engine. The COM provides sufficient accuracy with an average uncertainty of 7 °C, 0.3 bar, and 1.6 CAD for predicting T_exh, IMEP and combustion phasing, respectively. In addition, the COM is computationally efficient for real-time HCCI control. A three-input three-output controller is designed using a Discrete Sliding Mode Control (DSMC) method to control T_exh, IMEP, and combustion phasing by adjusting the intake manifold pressure, fuel mass flow rate, and ratio of two Primary Reference Fuels (PRFs), respectively. The results indicate the DSMC is capable of maintaining the stability of the engine operation and tracking the desirable HCCI engine outputs, while also rejecting internal disturbances.