Figure 15

System response under parameter uncertainty (35) with \(\alpha _1 = 2\), \(\alpha _2 = 0.5\) and \(\alpha _3 = {\textbf {0.25}}\): Control inputs u(t) using PI (36) (dash red), ESTA (23) (dot blue), and STA (9) (solid black). One can see that the PI method becomes unstable.