Study Of Data Transportation For Internet-based Teleoperation System

There are wide application areas for Internet-based teleoperation systems. However, Internet transmission time delays, delay jitter and bandwidth limitation and variation are unfavorable to the teleoperation system. To deal with these problems, the majority of current endeavours are devoted to developing various remote compensation control algorithms and interface techniques, without actively studying the effects and characteristics of Internet data transmission. Therefore, in this thesis, we study the main problems during data transportation between the operator and the remote device in the teleoperation system.Based on the constraints on new transport protocol and requirements of data transmission of teleoperation systems, we first present a novel congestion control algorithm. Based on this algorithm, an end-to-end rate-based transport protocol named the trinomial protocol is developed, In terms of individual performance and capacities, the trinomial protocol provides much better transmission service than current TCP or UDP protocols: it minimizes transmission delays and delay jitter by omitting re-transmission; in the steady state, its transmission rate is smooth; and when available network bandwidth increases/decreases, it adapts to the change quickly. Regarding social behaviors, it is responsive, inter-protocol fair (TCP-compatible), intra-protocol fairness convergent, and efficiency convergent. All these theoretical characteristics are conducted with extensive simulation studies. The simulation results validate the theories and conclusions.Next, the thesis analysis the characterization of Roundtrip time delay (RTT). The RTT time series collected from the Internet are studied statistically by using both linear and nonlinear methods. It is revealed that the RTT distribution is best fitted by a constant plus a "skewed right" gamma distribution. The adjacent and near-adjacent delays in the time series are linearly dependent rather than random. It is also indicated that there are only weak or no nonlinear correlations among RTT observations. Based on these findings, it is concluded that RTT time series can be characterized by linear models in estimating next RTT from past and current observations.Thirdly, a novel parameter-varying adaptive algorithm for RTT and RTO estimations based on the information theory and the maximum entropy principle (MEP) is presented. It is used in the implementation of trinomial protocol to detect packet losses and to adjust the sending rate. Compared to the traditional parameter-fixed autoregressive moving average (ARMA) method, the MEP algorithm is adaptive and capable of tracking RTT dynamics rapidly.Finally, a new modular platform for e-service mobile robotic systems is developed and implemented. This platform adopts a client-server architecture for robot control and feedback information display. The greatest benefit of this client-server architecture is that the applications are insulated from the lowest level details of the robot system. As a result, it is very easy to implement and test new advanced teleoperation control algorithms, interface designs and applications on this platform without large programming work. This platform is tested via experimental studies on the Internet. In the experiments, by using any Java-enabled web browsers, the users successfully navigated a mobile robot through a typical laboratory environment on a regular PC.