Subsea robots go to greater depths. They are typically connected to a ship via a group of cables so they can be operated by someone at the water surface. ROVs have been used by the oil and gas industry for many years for a variety of works that may be challenging or unsafe for humans to conduct – from underwater drilling, construction and installation as well as the inspection and maintenance of key assets.
The most basic ROVs are equipped with a video camera and lights. However, they may also feature non-destructive testing sensors (to check structural integrity), cleaning devices such as rotating wire, nylon brushes, water-jetting etc. (to clean offshore infrastructure) and multiple single-purpose or multi-mode work tools such simple bars, hooks and knives.
Autonomous underwater vehicles (AUVs), on the other hand, are programmable, unmanned and untethered robotic vehicles which, depending on their design, can drift, drive or glide through the ocean without real-time control by human operators. Some AUVs communicate with operators periodically or continuously through satellite signals or underwater acoustic beacons to enable some level of control.
A PROMISING OUTLOOK
As the number of infrastructure operations carried out in deep water continues to rise, it will likely mean an increased need for more powerful, efficient and reliable underwater robots that can construct, maintain and monitor the necessary infrastructure at great depths.
A report by OG Analysis outlines that the global AUV and ROV market is anticipated to reach a market value of USD2,788.7 million by 2025, with an annual growth rate of 5.94 per cent between 2019 and 2025. Rising offshore oil and gas production activities, increasing oil and gas decommissioning activities and the growing offshore wind power industry are expected to be among the key market drivers of this growth.
MARKET ADVANCEMENTS
Researchers in China recently designed an improved energy aware and self-adaptive deployment method for AUVs. The team of Chunlai Peng and Tao Wang of the Guangdong University of Technology in Guangzhou said while AUVs are essential for performing certain tasks that are considered too hazardous for people to carry out for various reasons, there are two critical issues when deploying AUVs. First of all, algorithms currently do not optimise the travelling distances of AUVs and hence leads to excessive energy depletion. Secondly, these deployment models also rarely consider the available energy variations among AUVs in the task execution process.
For this reason, an energy-aware and self-adaptive deployment method has been developed and tested by the researchers for a group of AUVs. The method initially considers the movement priority of the AUVs according to their positions during the deployment process. After this, an improved virtual force algorithm obtains the initial deployment scheme. In addition, a self-adaptive deployment strategy redeploys the AUVs when the available energy of some AUVs has fallen below a certain threshold.
This approach has already been tested with 10 AUVs and the results indicate that the method decreases energy consumption (evaluated by the movement distances of AUVs) by about 30 per cent compared to its traditional counterpart while being able to redeploy AUVs adaptively and rapidly.
This method could be a real boon for offshore oil and gas operations as well as marine environment monitoring and search missions after the loss of a craft at sea. The two researchers conclude their paper with a nod to the future direction of their research. “Future work will study an energy-supplying problem during the ocean rescue that generating trajectories for AUVs to rendezvous with energy-carrying robots, such as mobile charging stations, i.e., a rendezvous problem for AUVs and mobile charging stations,” they explain.
Sources: An improved energy-aware and self-adaptive deployment method for autonomous underwater vehicles, Chunlai Peng and Tao Wang; Platforms: Autonomous Underwater Vehicles, J.G. Bellingham; Underwater Vehicles, Woods Hole Oceanographic Institution