A study on pegging methods for noisy cylinder pressure signal

Cylinder pressure is one of the most valuable parameters for estimating the combustion process. Piezoelectric transducers are normally used for cylinder pressure measurements because of their high-frequency response capacity, small size, light weight, and low sensitivity to environmental conditions. However, inherent characteristics of piezoelectric transducers require referencing the output to absolute pressure (pegging). This study reviews several pegging methods, and proposes a modified least-squares method based on a variable polytropic coefficient. The feasibility of the proposed method is assessed using both the simulated and the experimental pressure data from common-rail direct injection (CRDI) diesel engine.