A New Robust Control Framework for Robot Manipulators without Velocity Measurements: A Modified Dual-loop Control Scheme

This paper proposes a new framework for the computed torque method (CTM) of robot manipulators without velocity measurements. We first introduce the Luenberger-observer-based CTM with only position measurements. We then clarify that the external disturbance affects not only the tracking performances with respect to the plant but also the estimation accuracies relevant to the state observer. To address this problem, we establish a new architecture for the so-called dual-loop control scheme, by which both the tracking performances and estimation accuracies can be simultaneously improved, in contrast to its existing structure. A guideline for taking control parameters corresponding to the proposed control structure is also provided with respect to the stabilization of the overall closed-loop systems. Finally, simulation and experimental results are provided to demonstrate the validity and practical feasibility of the developed structure.