(a)

(b)

(c)

(d)

Figure 2: Phase portraits and amplitude-time response curves for parameter values of , , , , , , , , , , , and initial conditions and . (a) Amplitude-time transient curves on ; (b) amplitude-time response curve on ; (c) transient response phase portrait; (d) steady-state system response phase portrait on . The solid lines represent the numerical solution, and the dashed lines represent the proposed EBM solution.