Output feedback controller for trajectory tracking of robot manipulators without velocity measurements nor observers

The main contribution of this study is the design of a trajectory tracking controller using output feedback applied to robot manipulators. The given controller does not need velocity measurements for its implementation and to achieve the tracking control objective. The structure of the proposed scheme consists of a proportional gain plus a dynamic gain resulting from a first-order system. The dynamic gain is not motivated by any observer nor estimator to approach the joint velocity. The dynamic linear controller has three tunable gain parameters for the one degrees-of-freedom (DOF) systems and two gain matrices for the nDOF lagrangian systems. These gains can be tuned following the conditions given in the stability analysis. An adaptive estimator of the viscous friction coefficient is added to robustify the closed-loop design; the analysis for the estimator is presented for one DOF systems and nDOF manipulators. The closed-loop stability analyses are developed by using Lyapunov's theory. The performance of the proposed control structure is illustrated and compared with other controllers such as the PID controller and the first-order sliding mode algorithm via numerical simulations. Moreover, real-time experiments are carried out in a two DOF SCARA robot manipulator.