Systematic design of multivariable fuel injection controllers for advanced diesel combustion

With multiple fuel injections per combustion cycle, the advanced diesel combustion process depends on all injection pulses in a coupled way. This makes the control of the multipulse fuel injection profile challenging, and the currently employed decoupled design methods might fail to guarantee closed-loop stability. Without explicit consideration of disturbances, it is also difficult for current design methods to guarantee the robustness of a fuel injection controller. In this paper, we present a general framework that describes the cycle-to-cycle fuel injection control problem. A control-oriented model is introduced and locally validated with experimental data. It considers the disturbances and captures the coupled relation between the multipulse fuel injection profile and the combustion process. Based on the general framework and the control-oriented combustion model, we propose a systematic design approach to synthesize a multivariable fuel injection controller. With guaranteed robust stability and fast settling time (0.5 seconds/5 combustion cycles in experiments), the controller's reference tracking performance and disturbance rejection capability are demonstrated experimentally on a single-cylinder engine test bench.