Bilateral local-remote systems allow people to perform complex tasks in a remote or inaccessible environment. Main objectives are robustness, feeling of presence, task performance, and transparency. The capabilities of a bilateral robot system rely on the exchange of measured position and force data. However, the local and remote manipulators are connected via a communication channel that can result in substantial delays. Due to the delay nature, neither exact tracking position nor transparency in teleoperation can be achieved. For this reason, most control approaches are meant to guarantee only position regulation, to solve the consensus problem, with or without a leader, or to synchronize a set of robots by inducing periodic position trajectories. Furthermore, most algorithms are designed assuming that joint velocities are available. In this work, a new teleoperation control-observer scheme is introduced with the following properties. In free movement and without a human operator, the local and the remote manipulators tend either to a periodic trajectory or to a particular position, thus achieving either synchronization or position consensus. When a human operator moves the local robot in free motion, the remote one tends to track the commanded position with the corresponding delay. Additionally, in constrained motion the person will have the feeling of telepresence. Experimental results are provided to test the proposed algorithm.

This paper proposes a proportional plus damping injection (P + d) controller for bilateral teleoperators in the operational space. Unit quaternions are used to describe the end-effectors' orientation since they exhibit the well known property of being a singularity-free representation. The proposed controller does not need the measurement of the velocities, instead a passivity-based filter is used. Under the reasonable assumptions that the human operator and the environment define passive maps from force to velocity, it is proved that velocities and pose (position and orientation) errors between the local and the remote manipulators are bounded. Moreover, in the case that the human and the environment forces are zero, the velocities and pose errors converge asymptotically to zero. Finally, experimental validation using two robots of 6-Degrees-of-Freedom (DoF) shows the effectiveness of the proposed control scheme.

It is widely known that the problem of controlling a rigid bilateral teleoperator with time-delays has been effectively addressed since the late 80's. However, the control of flexible joint manipulators in a bilateral teleoperation scenario, with dynamic gravity compensation, remains an open problem. This work aims at filling this gap by presenting a new controller for bilateral teleoperators composed of a rigid local manipulator and a flexible-joint remote manipulator with dynamic gravity compensation and asymmetric variable time-delays in the communication channel. In order to dynamically compensate the gravity term, in the flexible joint manipulator, a change of coordinates which accounts for the joint and link gravity position drift is used. The rest of the controller is a simple PD scheme. Assuming that the human operator and the environment define passive maps from velocity to force, it is proved that velocities and local and remote position errors are bounded. Additionally, if the human operator and remote environment forces are zero then velocities asymptotically converge to zero and position tracking is established. Some simulations are presented in order to show the performance of the proposed controllers.

The present paper proposes two controllers for solving a consensus problem to a given desired position of networks composed of a class of under actuated mechanical systems: flexible joints robots. One of the controllers makes use of joint (motor) velocity signals while the other only uses joint positions. The only assumption on the directed and weighted interconnection graph is that it is connected. Further, the interconnection may induce variable time-delays. The paper presents some experiments, using three 3-Degrees of Freedom manipulators, which show the performance of the proposed approaches.

This paper presents a proportional plus damping controller that can asymptotically drive a network composed of N nonidentical Euler-Lagrange (EL) systems toward a consensus point. The agents can be fully actuated or can belong to a class of underactuated EL-systems. The network is modeled as a weighted and undirected static interconnection graph that can exhibit asymmetric variable time delays. Simulations, using a network with ten EL-systems, are reported to support the theoretical contributions of this study.

This paper presents an adaptive controller for the bilateral teleoperation of a system composed by a single local manipulator and multiple cooperative remote manipulators handling a common object. First, the nonlinear operational space dynamical behavior of the complete teleoperation system is derived. Then, under the assumptions that the remote manipulators are rigidly grasping a non-deformable object and that the communications may induce constant time-delays, it is proved that velocities and position-orientation error between the local manipulator end-effector and the object asymptotically converge to zero. Simulations results are included to show the effectiveness of the proposed approach.

The problem of controlling a rigid bilateral teleoperator with time-delays has been effectively addressed since the late 80's. However, the control of flexible joint manipulators in a bilateral teleoperation scenario is still an open problem. In the present paper we report two versions of a proportional plus damping injection controller that are capable of globally stabilizing a nonlinear bilateral teleoperator with joint flexibility and variable time-delays. The first version controls a teleoperator composed by a rigid local manipulator and a flexible joint remote manipulator and the second version deals with local and remote manipulators with joint flexibility. For both schemes, it is proved that the joint and motor velocities and the local and remote position error are bounded. Moreover, if the human operator and remote environment forces are zero then velocities asymptotically converge to zero and position tracking is established. Simulations are presented to show the performance of the proposed controllers.

This paper presents two versions of adaptive controllers for nonlinear bilateral teleoperators, each providing asymptotic convergence of velocity and position errors to zero, independent of constant time-delays. Moreover, the proposed schemes do not rely on the use of the scattering transformation. The paper also proves that the teleoperator is Input-to-State Stable from human operator and environment inputs to some synchronization signals. Simulations show the effectiveness of the proposed controllers.

Two controllers capable of achieving asymptotic convergence of position and velocity errors, of the ith-manipulator within a multiple robot network, are proposed. The controllers employ adaptive techniques to find an estimate of the physical parameters of the nonlinear dynamics of the robot network. Moreover, the controllers can deal with different connectivity topologies (ring and star) and and can handle time-delays in the communications. Simulations, using a ten robot manipulators network with different connectivity topologies, that confirm the theoretical results are presented.

This work presents a multimodal teleoperation framework that makes use of novel tools and techniques, such as: nonlinear teleoperators control, for ensuring position tracking in the presence of variable time-delays; relational positioning, for increasing operator performance on precise movement execution by visually and haptically displaying geometric constraints; and augmented reality, for visually combining real and virtual information in a compelling way. Experimental evidence is presented that validates the aptitude of the different components of the proposed framework.

This paper aims to take a first step towards the unification of the stability analysis for teleoperators with time-delays. It proposes a general Lyapunov-like function that, upon slight modification, allows to analyze the stability of different control schemes, ranging from constant to variable time delays, with or without the scattering transformation and with or without position tracking. It also presents design examples of the corresponding Lyapunov-like function for some schemes based on PD controllers and on the scattering transformation for variable time-delays.

This paper extends the previous results on position tracking for bilateral teleoperators with constant time-delays, reported in Nuno et al. IEEE Trans. Robot., vol. 24, no. 3, pp. 753-758, June 2008, to the case of variable time-delays in the teleoperator's communications. The key part is the extension of a previous Lemma that is used to prove that P+d or PD+d controllers can stabilize the teleoperator under variable timedelays, and moreover, they provide position tracking. The paper outlines the conditions under which velocities and position errors, of the nonlinear teleoperator, are bounded, and using Barbalat's Lemma, it is proved asymptotic converge to zero if the local manipulator stands still and the remote manipulator does not interact with the environment. Simulations and real experiments validate the proposed schemes. The experiments have been performed using the Internet as communication channel between Urbana-Champaign, USA and Barcelona, Spain.

In a recent scheme, with delayed derivative action [Lee and Spong,IEEE Trans. Robot., vol. 22, no. 2, pp. 269--281, Apr. 2006], it is claimed that a simple proportional derivative (PD) scheme yields a stable operation. Unfortunately, the stability proof hinges upon unverifiable assumptions on the human and contact environment operators, namely, that they define${\cal L}_\infty$--stable mapsfrom velocity to force. In this short paper, we prove that it is indeed possible to achieve stable behavior with simple PD-like schemes---even without the delayed derivative action---under the classical assumption of passivity of the terminal operators.

This paper addresses the problem of stable bilateral teleoperation, through a time-delayed communication channel, for a n-DOF system without position drift. The classical wave variables-based scheme encodes velocity and force whilst the proposed scheme encodes position and integral of force. The resulting passive communication scheme is used in an extended teleoperation framework, in which the human operator can define geometrical motion restrictions in order to increase his awareness and his feeling of immersion, hence improving his ability to perform complex tasks. The framework also provides the operator with video feedback and 3D rendering of the remote scene.