Bounded output feedback tracking control of fully-actuated Euler-Lagrange systems

We deal with the problem of trajectory tracking control of fully actuated Euler-Lagrange systems with unmeasurable velocities and bounded control inputs. In order to avoid the use of velocity measurements we introduce a nonlinear dynamic extension for the plant which renders the closed loop system semi-globally asymptotically stable, hence we prove that by increasing some of the dynamic extension parameters it is possible to enlarge the domain of attraction and to maintain the control inputs bounded