The network and video latencies in marine remote-controlled applications

This thesis provides an overview of research work in the domains of marine sensing and underwater robotics. The main aim of the study is to investigate the challenges and requirements that are imposed on a communication channel in the application of permanently deployed underwater robots, i.e., in the growing field of underwater resident robots, with an emphasis on signal and video latency measurement in Remote Operating Vehicle (ROV) systems where short or minimum latency is necessary for pilot in the loop control of the ROVs based on camera feed. The work starts with the analysis of the ways to expand the role of conventional marine sensing platforms from tasks such as data logging and telemetry to the inspection, repair, and maintenance (IRM) of underwater structures. The proposed way of achieving this is by integrating an ROV into a marine sensing platform. However, in order to achieve the goal of having a permanently deployed robot that can reliably conduct remotely controlled operations, the low-latency, high bandwidth and secure communication channel between the remote deployment site, i.e., the robot, and a pilot is a must. Until recently, these requirements could be met only in operations where an ROV is deployed from a ship and is connected to the control site via umbilical cable. However, in the last decade, a considerable effort has been made by several companies to enable high-bandwidth global Internet coverage by launching constellations of mini-satellites. This would bring the high-bandwidth Internet connectivity to remote areas where, until recently, only low–bandwidth data connectivity was possible. Using the Internet as a communication channel in a system with real-time requirements poses a threat to control system stability due to the stochastic component of the Internet connection. Another challenge that arises is the exposure of the connected robot to various network attacks. This can be solved only by providing security for the data that is transmitted to and from the robot over the Internet. For these reasons, the focus of this work is on exploring the effects of latency of control signal and video stream on the controllability of the robot over the Internet. The software and hardware apparatus, with the purpose of data and video latency measurement, was developed and extensive testing, during which the latency measurements were acquired, was conducted. The work consists of two major parts. The first part of the thesis is in the marine sensing platforms domain. It presents the work conducted on the development of a novel ocean monitoring platform that could serve as a docking station for the ROV. Low power consumption of the platform is a requirement that was set to the design. For this reason, a solution called the event-triggering mechanism was integrated into the platform hardware and software. The possible ways of integrating the ROV onto the platform are presented and several use cases are stated. The second part deals with the control signal and video stream latency measurement results.. The goal of this work was to establish the maximum network latency that will not impair the remote control of the ROV. For this reason, the simulation of the robot was created and tested for different latencies. This was later compared to the results obtained from latency measurement experiments. The work continues with expanding the latency measurement to the video signal that is streamed from the robot. The video is generally the main feedback that the robot is transmitting to the pilot and having low latency is crucial for the control. The work ends with exploring the ways of introducing security to the system and testing the latency of the system with encryption introduced.