... -2. 692 0, -2.35 69, and 2.04 89, hence 0(,)fxt is unstable. The unmatched system matrix uncertainties and matched input matrix uncertainties and matched disturbance satisfy the assumption A3 and ... scientific papers available in literature (Porter and Power, 197 0)-(Sastry, 199 9), some of which also very recent (Paarmann, 2001)-(Siciliano and Khatib, 20 09) , the following practical limitations remain: ... KIEE, vol. 59, no.5, pp .95 0 -96 0. Lijun, L. & Chengkand, X., (2008). Robust Backstepping Design of a Nonlinear Output Feedback System, Proceeding of IEEE CDC 2008, pp.5 095 -5 099 . Lu, X. Y....