“…This conflicts with the sinusoidal excitation condition required [Slotine, & Weiping Li, 1991, Atherton, 1975, Nuij, Bosgra, & Steinbuch, 2006, Nuij, 2007. This harmonic input signal u(t) causes several non-linear phenomena in the output signal y(t) [Bussgan, Ehran, & Graham, 1974, Wiener, & Spina, 1980, Billings, & Tsang, 1989, Solomou, Evans, Rees, & Chiras, 2002, Yue, Billings, & Lang, 2005 …”