  In this work, we propose a passivity-based control approach that addresses
the trajectory tracking problem for a class of mechanical systems that
comprises a broad range of robotic arms. The resulting controllers can be
naturally saturated and do not require velocity measurements. Moreover, the
proposed methodology does not require the implementation of observers, and the
structure of the closed-loop system permits the identification of a Lyapunov
function, which eases the convergence analysis. To corroborate the
effectiveness of the methodology, we perform experiments with the Philips
Experimental Robot Arm.
