${\xi }_i^{\mathit{up}+}$	Upper bound of${\xi }_i^{+}$
${\xi }_i^{\mathit{low}+}$	Lower bound of${\xi }_i^{+}$
${\mu }_i$	Membership function of${\xi }_i^{+}$
$w_i$	Weight of${\mu }_i$