J. Tsinias et I. Karafyllis, ISS property for time-varying systems and application to partial-static feedback stabilization and asymptotic tracking, IEEE AUTO C, 44(11), 1999, pp. 2179-2184
A concept of input-to-state stability for time-varying control systems is i
ntroduced that constitutes extension of the well-known notion concerning th
e autonomous case. We use this concept to derive sufficient conditions for
global stabilization of triangular systems by means of a time-varying smoot
h feedback and to achieve asymptotic tracking of unbounded signals.