Force-reflecting teleoperation over the Internet: the JBIT project

An ever-growing number of Internet-connected devices are now accessible to a multitude of users. Being an ubiquitous communication means, the Internet could enable 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 the Internet users can access and command a two-degrees-of-freedom robot in real time, receiving both visual and force feedback. When 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 reported analysis shows that the main Internet limits are unknown available throughput, variable delay, and 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 are implemented. Such strategies are concerned with on-line identification of the connection characteristics, adaptation of the data rate to the available throughput, recovery of the missing packet, and handling of the variable delay. Moreover, visual feedback dataflow shares the same Internet connection with the real-time control data. To prevent congestion, new tools for adaptive dataflow management have been developed. Finally, an improved coordinating force control scheme, aimed at enhancing the transparency of the teleoperator, is presented.