What Is Underwater Drone?

//What Is Underwater Drone?

What Is Underwater Drone?

The underwater drone is a device that can move underwater, has a visual and sensory system at the same time. We can use underwater drones to replace or assist a person to perform underwater tasks by remote control them.

In the 1970s, underwater drones were greatly developed, and a number of robots capable of working at various depths and performing various operations were produced.

underwater drone

underwater drone

They can be used for oil exploration, seabed mineral deposit investigation, salvage operations, Pipe laying, and inspection, cable laying and inspection, marine aquaculture and dam inspection of rivers and reservoirs.

Underwater drone classification

Underwater UUV(Unmanned Underwater Vehicle) can be divided into three categories: first, the submerged drones also can be called Towing Underwater Vehicle (TUV). Second, Remote Operated Vehicle (ROV). Third, the submarine-free drone, which is accustomed to being called the Autonomous Underwater Vehicle (AUV).

From the first generation of deep submersibles in the 1960s, the evolution of ROV (70s), AUVs (80s) and hybrid types of Hybrid Vehicles have been produced one by one.

The control of the underwater drone

The underwater drone is a rigid body with six degrees of freedom moving in the water. It is a strongly coupled nonlinear system; due to the movement in the water, the hydrodynamic (resistance) coefficient is proportional to the square of the moving speed.

underwater drone

underwater drone

Propulsion, the thrust is proportional to the square of the propeller speed. All of this makes the control problem very difficult, especially when it is required to perform the work at a fixed point.

The above-mentioned reason causes the phenomenon of “zero gain and zero dampings” at zero speed, which makes the rigidity of the dynamic positioning control system difficult to meet the requirements of the fixed point operation.

The communication of underwater drone

There are two systems directly related to communication: monitoring systems and control systems. The monitoring system mainly refers to equipment used for underwater search and underwater observation, generally including underwater cameras, pan/tilt, and illumination, imaging sonar, acoustic and magnetic positioning systems.

underwater drone

underwater drone

The control system mainly refers to the sensing equipment needed to intervene in the underwater drone motion control. And guarantee the normal operation of the system, generally including a depth gauge, altimeter, direction compass, temperature, pressure, voltage, and current, etc., which can be collected by sensors, and Information transmission via wire or wireless.

However, the only ways of underwater communication are underwater sound and fiber. At present, from the domestic and international situation, the reliable communication rate of underwater sound is 1200 baud rate.

underwater uav

underwater uav

The communication delay depends on the time it takes for the underwater sound to travel back and forth in the water. When the water depth is 6000 meters, the transmission time is 8 seconds.

The distance of transmission depends on the carrier frequency used and the power transmitted, which is very limited for underwater drones. Communication delay is a problem that cannot be overcome intrinsically.

Therefore, how to increase the communication distance in the case of power limitation will be a major problem. At present, the communication distance is only ten kilometers. As the communication distance increases, the operating range of the AUV can also increase.

The use of underwater acoustic information to achieve monitoring must overcome the difficulties caused by transmission delays.

The optical fiber is generally used for the underwater drones TUV and ROV with cables and is composed of an optical transceiver (water surface), an underwater optical transceiver, and an optical cable.

The advantage is the big data rate (100Mbit/s) and good anti-interference ability. Disadvantages limit the working distance and maneuverability of underwater drones.

Underwater laser communication uses the blue-green laser with the lowest absorption rate of seawater medium, which has reached the sea-air communication distance of 100 meters deep, but it is still in the experimental stage, with large power consumption and volume, low efficiency and practicality to be improved.

The energy of underwater drone

Energy issues have always been a major factor limiting the scope of AUV operations, research and development of energy sources with high energy rates is a long-term effort. In the foreseeable future, batteries are an option. It is possible to use batteries with variable half-life nuclear fuel in the future.

underwater drone

underwater drone

Before these problems are solved, the aforementioned recycling device can be used as a relay station to perform underwater charging, so that two AUVs can be alternately charged to realize indefinite underwater operation. Of course, this does not solve the wide range of work problems of AUV. The following are the different energy requirements for ROV and AUV.

The ROV underwater drone supply voltage is usually related to the power and the working depth of the underwater drone. As the depth increases, high-voltage power transmission and power equipment are required.

In order to reduce the size and weight of the umbilical cable, ROV will adopt a higher voltage level in the future.

These will provide AC power from the surface of the water. Generally, small and medium-sized underwater drones are powered by 220V, 50-60Hz single-phase AC power, and large-scale underwater drones use three-phase AC of 3000v or more to supply power to the underwater carrier.

The AUV itself carries a battery. In the early days, a sealed lead-acid battery was used. Now, a high-energy silver-zinc battery is used.

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By |2019-06-11T05:54:27+00:00June 5th, 2019|uav technology|0 Comments
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