Written by Ken Thursday, 07 August 2008 23:49

ROV Chronicles: Part 1

 What is an ROV?

DinkyKitty labs has decided to branch out into robotics, and attempt to construct an ROV. We’ll document our efforts in a series of articles, of which this is the first. In this article: What is an ROV?

What is an ROV?

ROV stands for Remotely Operated Vehicle, but you can think of them as robot submarines. ROVs are used extensively in the oil and gas industry, mineral prospecting, salvage, and increasingly in the renewable energy industry.

ROVs can dive deeper than a human diver, stay down longer, and in some cases work harder. They are used where it would be too dangerous or too expensive to send a human to do a job. 

There are two basic types of ROV: observation class, and work class. An observation ROV is basically a camera that can be steered around underwater, and they are used for surveying underwater structures, supervising divers and other subsea work and exploration.

Commercial observation class ROVs start from around £5,000 for something basic like the VideoRay, which is small enough to fit in a suitcase, or around £70,000 for something like the SeaEye Falcon, a common and more capable observation ROV.

Work class ROVs are normally larger, and are able to carry out work as well as observe (hence the name). They are often equipped with manipulators (robot arms) or specialised tools for cutting, cleaning, welding, testing, bolting and a host of other jobs. Work class ROVs can cost several million pounds, weigh several tonnes and need a large team of people to maintain and operate them.

The vast majority of commercial ROVs are connected to the surface by a tether – an armoured cable that the ROV tows behind it. This is for two main reasons – firstly, it provides the ROV with power, which means no need to carry batteries, and gives the ROV unlimited endurance (it can stay underwater indefinitely).

Secondly, the tether transmits control signals down from the surface, and sends sensor data up to the operators. The main reason for this is that there is no easy way of communicating long distances underwater. Radio waves penetrate a few metres of water if you are lucky. There are technologies such as acoustic modems (which use high frequency sound to send digital data) and deep-blue lasers (which can penetrate several hundred metres of water), but these are not mature and ready for widespread use.

When investigating ROVs, I’ve been somewhat surprised by how low-tech they tend to be. For the most part, the design doesn’t appear to have changed significantly in the last 20 years. The electronics are fairly simple, the data signals are largely transmitted in analogue format (requiring the use of signal boosters) and there is generally no intelligence on the ROV itself, it is purely a remote controlled submarine, unable to carry out any tasks without its operator.

ROVs are also limited by how deep they can go. Typically, they include one or more air-filled compartments to protect their electronics. In my opinion this is a hold-over from when ROVs were built by the same people who built manned submarines – they were used to thinking in terms of protecting their contents from the outside pressure.

We are hoping to make a few improvements on the traditional ROV design, and build something with more intelligence, greater flexibility, and less limitations… and we hope to do it all on a VERY limited budget!

Next time: Our design philosophy and how our ROV will be built.

Below: a ROV observing diver operations

 

 

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