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The paper presents the development of a methodology for detecting the misfire event using the time-frequency analysis of the instantaneous engine speed signal. The diagnosis of this type of malfunctioning operating condition is enforced by OBD requirements over the whole operating range of the engine, and many different approaches have been developed in the past in order to solve this problem. The novel approach presented here is based on the observation that the misfire causes an impulsive lack of torque acting on the engine crankshaft, and thus it causes the excitation of damped torsional vibrations at frequencies characteristic of the system under study. In order to enlighten the presence of this torsional vibration (and therefore detect the misfire event), information contained in the instantaneous crankshaft speed fluctuations have been processed in the time-frequency domain.

Combustion control is one of the keys to obtain better performance and pollutants emission, both for diesel, spark ignition and HCCI engines. This paper presents a low-cost and high performance system based on commercially available hardware and software, which allows the implementation of control and diagnostic strategies based on combustions analysis, with the typical Rapid Control Prototyping (RCP) advantages (user friendly development tools, real time calibration, etc.). Information on the combustion process can be accessed by means of an indicating sensor such as an in-cylinder pressure transducer, or a ionization current measurement system, depending on the application. The signal must be sampled with a fast sampling system within a given crank angle window. It is then possible to process the input signal, in order to evaluate diagnostic or control indexes which can be calculated before the end of the same engine cycle, and finally used to correct the engine control parameters.