Autonomous underwater vehicle
Basically human is so keen in exploring things. With the gift of vision we have been exploring things since a very long time ago. We kept finding new secure caves, hunting locations, mountains, lands suitable for agriculture, rivers, seas islands and etc. The most of the findings were possible using the natural light. This doesn’t mean that without natural light, nothing is possible.
Why we are sending the machines to Mars instead of human? By sending human we can save a huge money, isn’t it? We can’t risk the human at all in navigation. Once upon a time, humans themselves engaged in navigation. Took risks and ended up in successes and failures. Now, the world has changed and more concerned over the security of the people and stuffs. Due to the development of the technology we are sending machines to do navigation that can ensure us whether we can lay the leg or not or even the required information are being gathered.
Have you ever been think about the ocean navigation? underwater navigation?
There are so many parts in this world which are remain as undiscovered or not reached yet by the human. The majority of them are in the oceans. So how can we proceed navigation below the sea level in the oceans without risking the human life?
You may ask we have already started building Submarines. We used them even in the World War I. Then how can we say that there were no underwater navigation? Yes, we are using submarines for a century. But, it is not autonomous. It is fully controlled by the humans, the crew. Typically the crew size changes from 40–80 depend on the class. With out the family contact, the entire crew has to work for a long time even during the transportation. They always maintain radio silence to avoid being detected by the enemy submarines. Operating submarines is one of the dangerous task because many submarines have been lost due to the accidents. And in submarines they can’t see, but can hear. They use sonar telephones in sending and receiving signals.
We can see the water up to some depth, that is why divers are going to some extents. But when we are going deeper in the ocean, we can’t even see. Also the pressure get increasing for every 10 meters depth. The picture below describe how the ocean light level is divided. If we reach aphotic zone, there won't be any light and that is the place the most possibly the things which we are going to search may exist.
To do navigation at that level, we need a machine. It can be guided or unguided (simply, Autonomous). So the usage of unmanned underwater vehicle begun. The vehicles belong to this category can be a guided vehicle or can travel without any guidance. Autonomous underwater vehicle (AUV) is a special robot that travels in the deep sea without the input from any operators, unguided. Military also uses this vehicle for their purposes. It plays major role in Air Crash Investigations if the crash has happened in the sea. Also using this illegal drug trafficking is also monitored and encountered.
Since the radio waves can’t be penetrated in water the GPS in AUV looses at the moment when it begins to dive. So these machines uses Dead Reckoning to navigate. Also with the usage of underwater acoustic positioning system the navigation of AUV is improved. They use acoustic distance and directions and triangulation of subsequent positions to locate and navigate these AUV. Since they always have the referencing ships which enables ultra-short baseline (USBL) or short-baseline (SBL) positioning, the AUV is able to update the relative GPS by means of GPS of the reference ship, acoustic range and bearing measurements from the ship to itself.
As an improvement, AUV can now also surface and takes its own GPS location. Between position fixes and for precise maneuvering, an Inertial Navigation System on board the AUV calculates through dead reckoning the AUV position, acceleration, and velocity. By adding Doppler Velocity Log (DVL) and readings from the pressure sensors, the final navigation solution is rendered. Using rechargeable battery, this robot dives in the deep seas and oceans to show us a different world which is being with us for a longer millenniums.
