Peak Pressure Position Estimation from Structure-Borne Sound

Combustion control strategies based on the peak pressure position (PPP) can be used to optimize the engine efficiency in a torque producing sense. Though the methods are easy to implement, the direct acquisition of the in-cylinder pressure requires sensors that are expensive and have a reduced lifetime. This paper addresses the problem of obtaining reliable PPP estimates with structure-borne sound signals from accelerometers mounted on the engine's surface. Measurement data collected from a four cylinder SI test bed engine are used to validate the proposed approach. It is observed that, compared to the amplitude, the position of the pressure maximum can be robustly estimated with moderate sampling rates. The results are improved by combining several accelerometers into a multichannel signal.