Huber loss function [47]
$c({\lambda }_g)=\left\{\begin{array}{cc}\frac{{\lambda }_g^2}{2},& if{\lambda }_g\le \epsilon \\ \epsilon \left|{\lambda }_g\right|-\frac{{\epsilon }_{}^2}{2},& \mathit{otherwise}\end{array}\right)where\epsilon ={\epsilon }_1^{\ast }$ where ${\epsilon }_1^{\ast },{\epsilon }_2^{\ast }$ are input parameters.	$c({\zeta }_g)=\left\{\begin{array}{cc}\frac{{\zeta }_g^2}{2},& if{\zeta }_g\le \epsilon \\ \epsilon \left|{\zeta }_g\right|-\frac{{\epsilon }_{}^2}{2},& \mathit{otherwise}\end{array}\right)where\epsilon ={\epsilon }_2^{\ast }$