Invalid operation: 1 / {positive convex}

where vm is a vector, other parameters are constants.
I want to represent this function in cvx, but when I add the second item the program gives me follow error,

Looking forward to your reply, thank you!

The function 1/\|x\| is non-convex on \mathbb{R}^n. It remains so after adding any polynomial of \|x\|. Your P approximation may become convex on some convex subsets of \mathbb{R}^n away from 0 (your text mentions “velocity larger than”…) but it is unlikely something like that is DCP. Maybe more context would be needed.

“velocity larger than v0” means , and v0 is a constants which is setted as 4.03 in this paper.
Your reply is helpful, thank you very much.