| A wonderful opportunity exists to capitalize on recent improvements in actuator and sensing technologies in the pursuit of cleaner and more efficient automobiles. While a considerable amount of attention has been given to hybrid and fuel cell approaches, significant improvements can be made in the area of advanced combustion strategies. One such strategy, Homogeneous Charge Compression Ignition (HCCI), combines benefits of both diesel and spark ignition (SI) methodologies to produce a strategy that is cleaner than either approach. Residual-affected HCCI uses variable valve actuation (VVA) to reinduct or trap hot combustion gases, enabling dilute, stable autoignition. As a result, residual-affected HCCI has an efficiency exceeding SI and matching diesel. While these characteristics of HCCI can address increasing environmental regulatory demands, there are some fundamental challenges. To practically implement residual-affected HCCI, closed-loop control must be used for two reasons: there is no direct combustion trigger and cycle-to-cycle dynamics exist through the residual gas temperature. Although HCCI is a complex physical process, this thesis shows that the aspects most relevant for control---in cylinder pressure evolution, combustion timing, work output and cycle-to-cycle dynamics---can be captured in relatively simple and intuitive physics-based simulation and control models.; From the control model, three different control strategies are outlined and implemented in experiment to control HCCI.; The first control strategy outlined is developed from the peak pressure dynamics in the control model and allows the modulation of work output via closed-loop control of peak in-cylinder pressure at constant combustion timing. The second control approach allows the simultaneous control of combustion timing and peak pressure (or work output) on different time scales through modulation of effective compression ratio and inducted gas composition, respectively. The final and most capable strategy allows the simultaneous, coordinated control of combustion timing and peak pressure within 4--5 engine cycles via an H2 controller synthesized from the complete control model, using effective compression ratio and inducted gas composition as inputs. The successful implementation of these control approaches demonstrate the utility of physics-based modeling and control, and represent a positive step toward the practical implementation of clean and efficient HCCI engines. |
