Global output-feedback tracking for a benchmark nonlinear system

In this paper, the output-feedback global tracking problem is solved for th e well-known nonlinear benchmark RTAC system, in which one of the unmeasure d states appears quadratically in the state equations. Our novel observer/c ontroller backstepping design yields a nonlinear output-feedback controller that forces the translational displacement to globally asymptotically trac k an appropriate time-varying signal. The proposed solution is new even for the case of global output-feedback stabilization, namely when the referenc e signal is zero.