Enabling large load transitions on multicylinder recompression HCCI engines using fuel governors

The fuel governor control design methodology presented in [1] is extended and experimentally validated on a multicylinder recompression homogeneous charge compression ignition (HCCI) engine. This strategy regulates desired combustion phasing during load transitions across the HCCI load range. A baseline controller tracks combustion phasing by manipulating valve and fuel injection timings. A reference governor is then added on to the compensated system to modify the fuel injection amount by enforcing actuator constraints. Experimental results show improved transient responses of combustion phasing and load during load transitions, when the possibility of constraint violations exists. The nonlinear fuel governor predicts future model trajectories in real-time, and enables larger load transitions than were possible with the baseline controller alone. The complexity and computational overhead of this strategy are reduced by developing a linearized fuel governor, which is shown to work well in the entire HCCI load range and for small variations in engine speed.