In classic EMD

the envelopes fitted by cubic spline interpolation may often occur overshoots.In this paper

a new envelope fitting method based on the least-length constrained interpolation is proposed.Taking the length of the fitted envelope as the target function

Lagrange optimization method is used to optimize the derivatives of the interpolation nodes.With the optimized derivatives

piecewise Hermite interpolation method is used to fit the more smooth envelopes.The result of experiments proves that the new method can solve the overshoots caused by cubic spline interpolation and the artificial bends caused by piecewise parabola interpolation effectively and let the results of EMD more accurate.This method can overcome mode mixing well

which is one of the major drawbacks of the original EMD.