PID Controller Modelling and Optimization in Cr Systems with Standard and Reduced Accumulators

The proportional-integrative-derivative (PID) controller and the pressure control valve of a Common Rail system are modelled by taking into account electronic, electrical, hydraulic and mechanical aspects. A fully predictive model of the injection apparatus is realized and validated by means of comparison with experimental data. The effects of the PID parameters on the injection system dynamics are illustrated and discussed on the basis of model results, which refer to steadystate and transient working conditions. The influence of the accumulator size on the rail pressure time history is investigated when the rail volume is dramatically reduced (up to 2.5 cm3). In particular, the effect of the large rail pressure drop that occurs at the end of the main injection for Minirail layout solutions is examined when after injections are implemented. An objective is to try to determine possible suitable values of the PID controller parameters and of the pressure-sensor sampling-frequency for rails of reduced size.