Surface Assisted Autopilot for Remotely Operated Vehicle

Abstract

The following thesis was done in collaboration with Water Linked AS and the Norwegian University of Science and Technology. The task at hand was to demon- strate wireless control of an ROV done with Water Linked s Underwater Modem. The demonstration took place during the final phase of the SWARMs (Smart and Networking Underwater Robots in Cooperation Meshes) research project 26. June 2018.

The Underwater Modem makes wireless underwater communication possible. The Downlink provides communication from a topside computer to a subsea ROV, while the Uplink provides a video stream subsea to topside. This thesis focus solely on the Downlink to demonstrate a safe and robust system for controlling a BlueRov2 from BlueRobotics wirelessly.

The BlueRov2 is an affordable, high performance ROV, which is highly customizable. The ROV is normally connected with a tether going to a topside computer, but but using the Underwater Modem system, the tether is omitted. The Downlink requires an additional waterproof payload on the ROV, a Subsea Master unit, which was mounted on the ROV.

To control the ROV, software on both the Raspberry Pi on board the ROV (OBC) and topside computer was be made. Two different devices was integrated to provide pilot input for the ROV, an Xbox controller and the Intuitive Input Device (IID) from Inventas AS. To be able to control the ROV with a limited amount of bandwidth, 4 bytes per second, the transmitted data is parsed and encoded. The control commands provides control of four degrees of freedom, as well as giving the opportunity to turn off and on light, change the control mode and adjust pilot gain. On the OBC, the control commands are received and decoded. To control the ROV, a variety of software is used. ArduSub runs on the Pixhawk Flight Controller Unit (FCU), and the ROS framework is used to interface with the FCU, through the MAVROS package. How the software on both the topside computer and the OBC is implemented is explained in detail in the thesis.

Before demonstration the system in SWARMs project, vigorous testing was performed. To find tool and methods for testing, Software Development Life Cycle methods was explored. This provided testing tools that ensured that the demonstration was a success.