Closed-loop control of a multi-cylinder HCCI engine

This thesis focuses on closed-loop control of multi-cylinder HCCI engines. A single-cylinder Caterpillar 3401 HCCI engine is used to demonstrate closed-loop combustion timing control. An exhaust throttle adjusts the combustion timing by altering the amount of in-cylinder residual gases. However, when the strategy is applied to a four-cylinder Volkswagen 1.9L HCCI engine, cylinder-to-cylinder cross-talk is discovered. Because of cross-talk, multi-cylinder HCCI engine control is not a simple extension of single-cylinder HCCI engine control. A comprehensive 42-state dynamic HCCI engine model is created to capture cylinder-to-cylinder cross-talk and suggest possible control strategies. Simulations show the intake valve opening and intake valve closing events significantly affect cross-talk. Thus, managing cross-talk may be a significant aspect of multi-cylinder VVT HCCI engine control.; The 42-state HCCI engine model is useful for analysis but too complex for control synthesis. A more suitable low-order model is derived through subspace system identification and used to design an LQG controller. The LQG controller performs poorly due to engine and cylinder wall temperature fluctuations. The poor performance is remedied by adding integral action to the LQG controller. The resulting LQG-integral controller suppresses misfire and independently controls the combustion timing on each of the four cylinders. Though the LQG-integral controller performs well, a more robust controller is desired. In order to improve robustness, a nominal transfer function and uncertainty description are derived using spectral analysis and used to synthesize Hinfinity and mu-synthesis controllers.; While satisfactory for research, the piezoelectric pressure transducers used for feedback in these controllers are too expensive for commercial production. A procedure is derived for estimating combustion timing using low-cost microphones, knock sensors, and ion sensors. The procedure is experimentally validated with microphones and knock sensors, and used with a microphone for feedback in a closed-loop single-cylinder HCCI engine controller. Though only a single low-cost sensor is used in this controller, future HCCI engine control strategies may use a combination of low-cost sensors.