Combustion diagnosis for internal combustion engines with real-time acquisition and processing

The use of vibration signals for internal combustion engines diagnosis is now well established for several applications such as knock detection or valve mechanics behaviour assessment. If standard knock detection can be performed in real time, diagnoses are generally carried out off-line due to algorithm complexity. Our aim was to get some insights on the time-frequency properties of the vibration signal in order to improve off-line techniques and propose adapted real time algorithms for combustion diagnosis. This paper addresses the problem of the identification of combustion related vibrations among others noise sources. In order to help this identification, pressure traces from in-cylinder sensors are also recorded and processed. Thus, pressure forces that generate the “thermal noise” in the vibration signal can be analyzed separately. The “thermal noise” associated events can be more easily isolated from the mechanical noise in the vibration signal mixture.