where “L” indicates the Laplace transform. To obtain a small IE, Ki should be as large as possible, i.e., ζ should be as small as possible. However, it is well known that a small ζ implies oscillatory response and poor stability robustness. Oscillations will cancel in the integral in (20), making the IE a poor performance measure. To avoid this, we consider the phase margin φm [30], which is calculated by first finding the crossover frequency ωc for the open-loop transfer function Gk(s) = F(s)G(s) (i.e., where |Gk(jωc)| = 1)