How ROVs work?

ROVs is the abbreviation of Remotely Operated Vehicles, are submarine vehicles and this post’s subject.

Types of ROVs

Exist three classes of this submarine vehicle. The observation ROVs are smaller, lighter and don’t have arms.

The work or intervention ROVs are bigger, heavier and have manipulator arms.

And we have the medium size, which are used to make observations and light work.

Control and communication

The ROVs are controlled by a person in the surface using a command unit. Some units have a control which reminds a video game.

The operator controls direction and depth of ROV, the LED lamps, rotation and inclination of video cameras, manipulator arms and can set in autopilot. The submarine vehicle is linked to surface by a cable. Telemetry control, sensor signals, video signal and energy transmission pass through the cable.

Main components

The frame must carry the components, the material must have high strength and be as light as possible and resistent to corrosion. Some examples of used materials are plastic composites, acrylic, PVC or aluminum.

How ROVs float in water? According to Achimedes’ priciple, an object immersed in a fluid will receive a buoyant force equal to weight of displaced fluid, the mass of displaced fluid is:

$m_{f}=d_{f}V_{f}$

$d_{f}$ is the fluid’s density;
$V_{f}$ is the displaced volume when the body enters in the fluid.

This is the buoyant force (B) equation.

$B=m_{f}g$

$g$ is the gravity acceleration which is $9,81m/s^{2}$ .

The material to float must be as dense as the sea water to buoyancy be equal to the weigh. Usually is a resin or PVC foam with small spheres made of fibers or glass.

The ROVs move in water with brushless motors linked to a propeller and controlled by PWM.

Usually a ROV has two motors to propulsion and a motor in the vertical to go up or down.

Applications

These submarine vehicles are much used in extraction of minerals at deep sea and in oil and gas industry. Can reach depth where divers can’t, the later reach in maximum some hundred of meters. While some ROVs can reach thousands of meters.