Abstract :
An ever-growing number of Internet-connected devices is now accessible to a multitude of users. Being a ubiquitous communication means, the Internet could allow any user to reach and command any device connected to the network. This paper reports the successful application of real-time closed-loop control over the Internet in the Java Based Interface for Telerobotics (JBIT) system, in which Internet users can access and command a two-degrees-of-freedom robot in real time, receiving both visual and force feedback. When the closed-loop control of a remote system comes into play, careful evaluation of the performance and limits of the communication system in use is mandatory. The analysis reported shows that the main limits of the Internet are the unknown available throughput, the variable delay, and the loss of some data packets, in particular, when the network is congested. Once the limits of the communication system are known, it is shown that it is possible to use the Internet for the remote closed-loop control of a slave robot, provided that suitable strategies to guarantee operability and safety of the controlled system have been implemented. The strategies implemented in order to overcome the limits posed by the present Internet characteristics are described, along with an improved coordinating force control scheme, which enhances the transparency of the teleoperator.
