Bifurcation of Limit Cycles by Perturbing a Piecewise Linear Hamiltonian System

Figure 1

The possible phase portraits of system (7).  

(a) 𝑎=0,𝑏>0

(b) 𝑎=0,𝑏<0

(c) 𝑎>0

(d) 𝑎<0