How to solve or avoid the problem of “{log-affine} .* {concave}”?

(Tianze Wang) #1

Hi,I would like to achieve the following expression in CVX,where C_Rate and Ah are vectors(1400×1),R and Tbat are constants.We know exp() is convex,but x.^0.824 is concave.Therefore,It will prompt for errors in Matlab:
%Cannot perform the operation:
% {log-affine} .
So is there any ways to solve or avoid this error in Matlab?Thanks to everyone for their help.

(Tianze Wang) #2

I mean how to implement this expression in CVX fitting DCP rule?

(Michael C. Grant) #3

The FAQ adequately addresses your question. If you feel otherwise, do present your proof of convexity and we can help you show how that leads you to a DCP formulation.

(Tianze Wang) #4

All right,replace C_Rate with Ib/180 and Ah=Ib/3600.Bring two constant values R and Tbat.

make the second derivative of Ib,

ddQloss is negative at Ib belongs to[0,285], and [285,Inf] in positive.So does this prove that Qloss is a nonconvex problem when Ib belongs to[0,285]?Whatever it takes,thanks for your kind assistance.

(Tianze Wang) #5

:sweat:Can you give me a reply?Thank you~:sweat: