2206ENV Introduction To Oceanography

Introduction

A remotely operated underwater vehicle (ROV) is a mobile device used for underwater operations such as military use, survey applications, and science. It is controlled by a crew on land or aboard a vessel and is linked to the ship by a load carrying the cable. The device often integrates a tether management systems (TMS) which work to shorten and lengthen the cable connecting the device and the ship. Accordingly, the cable hosts fiber optics and electrical conductors, which relay data signals, electric power, and video between the crew and the device.

The extensive adoption of ROVs has mainly brought significant developments through the technology has had certain limitations.   

The use of ROVs has greatly advantaged underwater applications. First, they have developed deep-sea scientific studies of the sea substructure and the surrounding ecosystems. This scientific research has aided led to the discovery of certain animal and plants. Pollock and Godfrey (2007) state that good video footage is a critical element of scientific research and hence, ROVs design integrates high-quality cameras and light output systems. The devices have facilitated archeological and experimental research whose findings have contributed immensely to the scholarly world. Moreover, ROVs have encouraged the study of deep seas in school institutions, and have attracted support from private and governmental organs. 

Secondly, ROV technology has vast military and survey applications, and their use has greatly reduced the casualties of human drivers and proven to be a superior research mechanism.

Currently, it is easier to conduct the survey of sea substructures for probable developments and maintenance of utility layouts, which was initially limited to onshore divers. Consequently, the military has greatly adopted the use of ROVs in its ship rescue missions as well as identifying national security threats and environmental hazards. According to Worlds Hole Oceanographic Institution (n.d), ROVs have been used severally to trace shipwrecks, and at times to transport vital components from the seabed to the surface.

Similarly, ROVs have their fair share of disadvantages due to their limitations. First, the control system of an underwater vehicle is a challenging task due to a combination of factors such as the absence of a defined model addressing dynamic underwater conditions, environmental influences and non-linear plant equations (Christ & Wernli, 2013). In-depth, automatic control of the ROV poses a difficult design challenge due to model uncertainty caused by inertial and hydrodynamic nonlinearities. Thus, its operation requires the extensive combination of different control techniques, and the overall integration requires a solid workforce as these mechanisms complement each other. 

Secondly, the propulsion mechanisms of the thrusters used to drive the ROV in deep seas are difficult to design. The main challenge is the cross flow and axial nonlinearities which not only affect the hydraulics but extends to the overall system behavior. Louis (2004) posits that the dynamics involved in the thruster limit the highest closed-loop bandwidth, thus creating a limiting cycle. Moreover, cross-flow impacts rely on the thruster’s position in the device, making them difficult to model. Failure to consider these inconsistencies will result in a decrease in the overall gain of the system.

Conclusion

Remotely operated underwater vehicles (ROVs) are mobile devices linked to a ship through an umbilical cord and is used for underwater applications. The load bearing cable contains electrical conductors and fiber optics which connect the crew to the device through a tether management system (TMS) which relays data signals, power, and video supply. The technology has several advantages such as the increased development of underwater scientific study and the reduced casualty in human divers, particularly for rescue missions by the military. However, it also has disadvantages such as difficult controls due to the dynamic nature of underwater conditions and thrust considerations which may lead to an overall decrease in the system’s gain.

References

Christ, R. D., & Wernli Sr, R. L. (2013). The ROV Manual: A User Guide for Remotely Operated Vehicles. Butterworth-Heinemann.

Louis, G. (2004). Design, Modelling and Control of an Autonomous Underwater Vehicle. (B.Eng. thesis). The University of Western Australia.

Pollock, W. & Godfrey, M. (2007). The Diving for Science. 2007. American Academy of Underwater Sciences (AAUS).

Worlds Hole Oceanographic Institution. Ships & Technology used during the Titanic Expeditions. Retrieved from https://www.whoi.edu/page.do?pid=83577&tid=3622&cid=130989