Autonomous Underwater Vehicle
You may have heard about underwater vehicles. But do you know what an autonomous underwater vehicle is? It is also referred to as unmanned underwater vehicles, are often used to perform underwater survey missions like detecting and mapping submerged rocks, wrecks, and obstructions that create a hazard to navigation for commercial and recreational vessels.
The demand for a more sophisticated underwater robotic technology that reduces the cost and eliminates the requirement for human operator and is thus capable of operating autonomously becomes apparent. Moreover these needs lead to the development of Autonomous Underwater Vehicles (AUVs). A key drawback with autonomous underwater vehicles is being able to navigate in a typically unknown environment.
The available underwater sensor suites have a restricted capability to deal with such a navigation issue. In practice, no single sensor in the underwater environment will provide the level of accuracy, reliability and the coverage of data necessary to perform underwater navigation to cent percent safety.
The AUV conducts its survey mission without the intervention of the operator. When a mission is completed, the AUV can return to a pre-programmed location and the information collected are often downloaded and processed in the same way as information collected by shipboard systems.
In order to navigate accurately an AUV has to use a navigation sensing element with a high level of accuracy and reliability. It’s thus necessary to use a number of sensors and combine their information to provide the necessary navigation capability. As a matter of fact to attain this, a multisensor data fusion (MSDF) approach, which combines information from multiple sensors and related information from associated databases, can be used.
There are different kinds of underwater vehicles. One way of categorizing these vehicles is to identify them as members one of two categories of vehicles; manned and unmanned systems. We are familiar with the manned systems. Furthermore they can be represented simply as falling into two sub-classes; military submarines and non-military submersibles like those operated to support underwater investigations and assessment.
The second category of Autonomous Underwater Vehicle, the unmanned systems, falls into a number of different sub-classes. In fact the simplest and most easily described one is those that are towed behind a ship. The second category is Remotely Operated Vehicle (ROV). The third category of unmanned underwater vehicle is an Unmanned Untethered Vehicle (UUV).
Also some AUVs communicate with operators continuously or periodically through satellite signals or underwater acoustic beacons to allow some level of control. AUVs enable scientists to conduct other experiments from a surface ship while the vehicle is off collecting information elsewhere on the surface or in the deep ocean. Some AUVs also can create their own decisions, changing their mission profile based on environmental information they receive through sensors while under way.
Now let us see some of the benefits of this underwater vehicle:
- Control of survey
- Most sensors use adequate power
- Adequate power to continuously sample
There are certain benefits for AUV’s water column measurements. They are:
- Stop and float- requires ballast control
- Constant altitude above the bottom
- Constant pressure or layer of interest
- Actively loiter
- Sea saw or saw tooth pattern
- Acoustic or optical seafloor surveys