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New technological advancements in the communication channel of time delay teleoperation systems have attracted a lot of attention, which have produced recently new control schemes, under a variety of conditions, including unknown (either constant or varying) time delay and parametric uncertainty. In this paper, a well-known model free, exact differentiator, is used to estimate the full state along with a chattering free second order sliding mode controller to guarantee robust impedance tracking under constant, but unknown, time delay of nonlinear multi-degree of freedom (n - DOF) robots. In addition, a new nominal reference is tailored in order to introduce a change of coordinates in the slave closed-loop dynamics. Experimental results, that validate the predicted behavior, are presented and discussed using the Phantom Premium 1.0 as the master robot and the Catalyst-5 virtual model as the slave robot, whose dynamics is solved online.

This paper presents a dual-user teleoperation scheme to perform a collaborative task using n-DOF nonlinear manipulators as masters and slave. Impedance controllers for the manipulators are implemented in order to achieve a desired dynamic behavior depending on the user's necessities. Furthermore, a sliding mode controller is introduced to cope with the time delay in the communication channels and the uncertainty in the slave. Since the slave teleoperator is in contact with a rigid environment, the slave controller requires a free of chattering control strategy, which makes first order sliding mode teleoperation control unsuitable. Then a higher order sliding mode based impedance controller is proposed to guarantee robust impedance tracking under constant, but unknown time delay. Therefore, a position scaling factor is incorporated to deal with the different workspaces among masters and slave. The validity of the proposed control scheme is demonstrated via experimentation on a 3-DOF dual-user teleoperation system. While the haptic devices Phantom Premium 1.0A and a Phantom Omni are used as masters, a virtual industrial manipulator Catalyst-5 is used as slave. The dual-user system is tested not only in presence of constant unknown time delay in each of the communication channels but also in free and constrained motion regime.

This paper presents a dual-user teleoperation scheme to perform a collaborative task using n-DOF nonlinear manipulators as masters and slave. It consists on impedance controllers for the manipulators in order to achieve a desired dynamic behavior depending on the user's necessities. Moreover, to cope with the uncertainty in the slave, a sliding mode controller is introduced and a desired impedance model for the salve is chosen as the sliding surface. Since the slave teleoperator is in contact with a rigid environment, the slave controller requires a free of chattering control strategy, which makes first order sliding mode teleoperation control unsuitable. Then a higher order sliding mode based impedance controller is proposed to guarantee robust impedance tracking under constant, but unknown time delay. Therefore, a position scaling factor is incorporated to deal with the different workspaces among masters and slave. The validity of the proposed control scheme is demonstrated via simulations performed on a 3-DOF dual-user teleoperation system. The simulation setup includes a Phantom Premium 1.0, a Phantom Omni, a Catalyst-5 and communication channels which suffer from constant unknown time delays.

Bilateral teleoperation systems have attracted significant attention in the last decade mainly because of technological advancements in both the communication channel and computers performance. In addition, non-linear multi-degree-of-freedom bilateral teleoperators along with state observers have become an open research area. In this article, a model-free exact differentiator is used to estimate the full state along with a chattering-free second-order sliding mode controller to guarantee a robust impedance tracking under both constant and an unknown time delay of non-linear multi-degree-of-freedom robots. The robustness of the proposed controller is improved by introducing a change of coordinates in terms of a new nominal reference similar to that used in adaptive control theory. Experimental results that validate the predicted behaviour are presented and discussed using a Phantom Premium 1.0 as the master robot and a Catalyst-5 virtual model as the slave robot. The dynamics of the Catalyst-5 system is solved online.