*6.6. Controller's Behavior under DC-DC Buck Converter Parameter Variations*

As is well known, the PI and IP controllers are sensitive to system parameter variations. Thus, in this case, only the behavior of FLC, IMC, and the proposed SMC algorithms are tested. The DC input voltage, the load resistor, and the target output voltage are all held constant. Only the DC-DC buck converter parameter variations are considered in this case. Figure 12a,b show the adopted trajectories for the DC-DC buck converter inductor and capacitor, respectively. The obtained simulation results in this case are given in Figure 12c,d. The comparison performances of the three control algorithms in this case are summarized in Table 3.

**Figure 12.** DC-DC buck converter parameters variations: (**a**) trajectory of the inductor, (**b**) trajectory of capacitor, (**c**) control voltage and (**d**) output voltage.

It can be easily noted from both the obtained simulation results for different cases and the comparative study shown in Table 3 that the highest performance is achieved by the conceived SMC control algorithm, compared to the others.
