Consider a differential system of the form x′=F0(t,x)+i=1∑kεiFi(t,x)+εk+1R(t,x,ε), where
Fi:S1×D→Rm and R:S1×D×(−ε0,ε0)→Rm are piecewise Ck+1
functions and T-periodic in the variable t. Assuming that the unperturbed
system x′=F0(t,x) has a d-dimensional submanifold of periodic solutions
with d<m, we use the Lyapunov-Schmidt reduction and the averaging theory to
study the existence of isolated T-periodic solutions of the above
differential system