Robotics and Autonomous Systems 55 (2007) 205–215 www.elsevier.com/locate/robot Bilateral teleoperation through the Internet Emanuel Slawi˜ nski ∗ , Jos´ e F. Postigo, Vicente Mut Instituto de Autom´ atica (INAUT), Universidad Nacional de San Juan, Av. Libertador San Mart´ ın 1109 (oeste), J5400ARL, San Juan, Argentina Received 14 April 2005; received in revised form 19 September 2006; accepted 19 September 2006 Available online 1 November 2006 Abstract This paper proposes a stable control structure for the bilateral teleoperation of robots through Internet. The problem is motivated by the increasing use of the Internet as a communication channel. Internet has a time-varying delay which depends on factors such as congestion, bandwidth and distance. In this work, we propose a control structure for the teleoperation of a manipulator robot with force feedback. Such a control structure includes state controllers (placed on the local and remote sites) and a time-delay compensation, which modifies the delayed position command generated by the human operator using the force that he feels in such a delayed moment and the current force between the slave and the remote environment. In addition, the proposed control scheme is designed considering a model of the communication channel. Finally, experiments of bilateral teleoperation of robots through Intranet and Internet are shown to test the performance and stability of the designed teleoperation system. c  2006 Elsevier B.V. All rights reserved. Keywords: Asymptotic stability; Force reflecting; Internet; Teleoperation; Time varying delay 1. Introduction During the last decades, different teleoperation systems have been developed to allow human operators to execute tasks in remote or hazardous environments, with a variety of applications ranging from space to underwater, nuclear plants, and so on [26]. In general, the teleoperation systems with force reflecting are composed by a local site, where a human operator drives a hand-controller named master; a remote site, where a manipulator robot named slave follows the motion of the master to execute a given task in interaction with the environment; and a communication channel that links both sites [24]. The master is used to generate velocity or position commands to the remote manipulator, while the force due to the interaction between the slave and the environment is back-fed to the human operator through the actuators of the master. Perhaps, the most interesting case is the use of Internet as a communication channel between the local and remote sites of a teleoperation system. The possibility of interchange data on tactile and motion information could allow a real sense of ∗ Corresponding author. E-mail addresses: slawinski@inaut.unsj.edu.ar (E. Slawi˜ nski), jpostigo@inaut.unsj.edu.ar (J.F. Postigo), vmut@inaut.unsj.edu.ar (V. Mut). telepresence, with capability of touching objects and people at distance [22]. Thus, a wide range of applications could be opened, including telemedicine, exploration, entertainment, telemanufacture, and many more [9]. However, this technol- ogy (Internet) presents problems for the development of ap- plications to control at distance, such as haptic interfaces and telerobotics, because it introduces time varying delays as well as stochastic components [4,5], which add distortion in the ref- erence commands and feedback signals. Moreover, due to the time-varying characteristics of Internet (for example, the am- plitude of the time delay) it is useful to identify – in line – a model of the communication channel using it in the design of the control system [11]. The presence of time delay may induce instability or poor performance of a delayed system [10,18,23,25]. In general, in the design of teleoperation systems there is a trade-off between high transparency and sufficient stability margins [17]. The main control strategies proposed for bilateral teleoperation of systems with constant delay include the delay compensation proposed by Anderson and Spong [1], which assures the asymptotic stability of the manipulator velocities; the strategy proposed by Niemeyer and Slotine [19], where wave transformations are used to keep the passivity of the communication channel; remote compliance control proposed 0921-8890/$ - see front matter c  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.robot.2006.09.002