Misfire Fault Diagnosis Method for Diesel Engine Based on MEMD and Dispersion Entropy

Algorithm 1

The standard EMD algorithm.

(1)	Find all local extrema of the original signal ; fit the upper envelope and the lower envelope according to the cubic spline function, .
(2)	Calculate the local mean from the upper and lower envelopes , and then subtract it from x(t), h1(t) = m(t)−x(t).
(3)	Check whether h1(t) satisfies the two conditions. If satisfies, h1(t) is the first IMF component; otherwise, replace h1(t) with x(t) and repeat (1)-(2) until the termination criterion is satisfied. Then, set the first IMF as c1(t).
(4)	Repeat (1)–(3) until all the IMFs and the residual are extracted. Finally, the original signal x(t) can be decomposed as .