| Fuel injection systems have become the primary fuel delivery systems in internal combustion engines. For better combustion performance, modern fuel injection systems require flexible fuel injection with complex injection rate profiles. Piezoelectric actuator-based injectors are capable of delivering a wide range of injection profiles including tightly-spaced multiple pulse profiles as well as continuously variable injection profiles, which is known as "rate shaping". The challenge of precisely controlling the fuel flow rate of an injector comes from its highly dynamic internal system. A further difficulty is out of the absence of a means to measure the fuel flow rate from the injector while on the engine, for use in diagnostic flow control algorithms. Therefore, closed-loop control with on-line estimation of the fuel flow rate turns out to be a solution.;This thesis summarizes an effort resulting in within-a-cycle estimation of injected fuel for "rate shaped" profiles. First a physically-based simulation model is introduced, which describes injector dynamics in detail. The derivation of the dynamic equations is illustrated briefly. Next, a reduced order model is introduced by simplifying the simulation model. The reduced order model captures the main components of the injector. Furthermore, from the reduced order model, an estimation algorithm is derived and implemented at a "loop time" of 6 micros on an FPGA based system with line pressure measurement as feedback. The resulting estimator is experimentally validated, and it is able to make an on-line prediction. The prediction error of the fueling amount per cycle is less than 10%. In summary, the work mainly focuses on the development of a physically-based, experimentally-validated estimator, for the purpose of designing a controller which provides ways to reduce the overall fuel consumption and harmful emissions of diesel engines. |
