I set tau = 0.1*(B-steady_state(B)） to make sure tau equals 0 at steady state. But in this way, tau’s percentage chage “(tau-steady_state(tau))/steady_state(tau)” will be a missing vaule. I do not know how to solve this problem. Can someone help me?

For a value that is 0 in steady state, it does not make sense to compute percentage deviations. It seems you are asking the wrong question.

Yes! I understand now. Thank you~