In-cylinder pressure measurement for control and diagnostics in spark ignition engines

There is an increasing interest on innovative controls based on in-cylinder pressure measurement. However, due to current capabilities of ECUs, only a small number of pressure cycles can be sampled. Therefore suitable algorithms are required to extract from few pressure points the information useful to implement the desired control strategies. In this paper a method for the interpolation of in-cylinder pressure cycle during the constant mass phase of S.I. engines is described. It is based on the estimation of Cumulative Heat Release (CHR) in selected crank angle positions and on a simple algorithm of pressure reconstruction. To test this method, peak pressure position and magnitude have been identified on the basis of a set of experimental pressure cycles measured on a gasoline direct injection engine. In addition, a control scheme for the closed-loop control of spark timing have been set up using a numerical engine (WAVE) and a numerical ECU build in the Matlab-Simulink environment. Finally, the modeled pressure cycle is used to obtain an accurate estimation of Indicated Mean Effective Pressure (IMEP).