Re-examining the Nicosia-Tomei robot observer-controller from a backstepping perspective

Many robot controllers require not only link position measurements but also link velocity measurements; however, most robotic systems are only equipped with link position measurement devices. To address this problem, the authors present an observer-based controller for the link position tracking, output feedback control of robot manipulators. The approach is based on an observed integrator backstepping procedure which allows the authors to obtain a semi-global exponential stability result for the link position-velocity tracking error. Implementation of the proposed controller on a two-link direct-drive manipulator produces results which indicate good link position tracking performance and robustness against payload variations.