and go to step 3. This step is different from Ge or ge et al. [30] as they use O/F rati of or checking conver- gence.As _ mf ðtÞ is in the denominator of O/F ratio using that could lead to non-conver gence.Also,Georgeetal. [30] as sumes an arbitrary value of ϕðtÞ, which could again leadtonon-conver genceano scillatory solution