The Advance of Marine Micro-ROVs

A Versatile Tool for Marine Operations, and a Portable Undersea Platform for Small Sensors

Micro-ROVs (Remotely Operated Vehicles) are becoming increasingly capable even as their size and cost drop, opening up new possibilities for the application of undersea inspection, imaging, and measurement.

In this article, I’ll discuss four reasons why Micro-ROVs should be a routinely used part of a marine and water-side operations toolkit, and review some stand-out choices in the Micro-ROV category.


Micro-ROVs: A Versatile Tool for Marine Operations

Micro-ROVs (Remotely Operated Vehicles) are becoming increasingly capable even as their size and cost drop, opening up new possibilities for the application of undersea inspection, imaging, and measurement.

Members of this relatively new class of ROVs are distinguished by their ultra-small size (typically 3-10kg / 7-20lbs) and comparatively low cost (from $6000 to $15,000 to buy and from $600/day to lease). But of course, as compared to their larger, more pricey cousins, they offer less thrust, are typically rated for shallower depths, have correspondingly shorter tether lengths, and can accomodate fewer add-ons and accessories.

As in most technology applications, cost and capability are the common trade-off variables. The goal for each application is to find the right mix of the two.

Reasons to Consider Adding a Micro-ROV to your Marine Technology Toolkit

In my experience, the following are four reasons why Micro-ROVs should be a routinely used part of a marine and water-side operations toolkit:

    Reason 1. In certain situations it can be quicker and safer to use an ROV than a dive team. With a dive team, you have to observe strict safety procedures, current conditions, daylight hours, water temperature, the possibility of debris strikes, hazardous materials, and time in the water. In faster flowing waters, operational problems can mean overrunning a tide window of opportunity and delays of 6 to 8 hours. With crews on standby and big rigs in the water, the loss of a working day can hit the budget hard. If the required work involves multiple up and down trips, this can be exhausting on divers and require diver rotations or rest time. Where visibility is limited, temperatures are low, or otherwise hazardous, an inspection Micro-ROV is a useful tool to consider. In all of these situations, being able to go in with a Micro-ROV either in addition to, or instead of, a diver, can save valuable project time.

    Reason 2. Even when a dive team is necessary, and it often is, Micro-ROVs can be a useful supplement to the dive team, providing initial first-review of a situation and allowing the diver response mission to be adjusted after reviewing footage from the Micro-ROV. The additional advantage is that the customer’s technical staff can be viewing the footage alongside project staff and dive staff. This reduces the chance of misunderstanding or errors in judgment that can occur when all sub-surface information is being relayed back to the customer based solely on the visual observation and memory of a single diver.

    Reason 3. Where routine inspection would be advisable but is neglected due to the cost or availability of dive teams, having a rapidly deployable, pier-side Micro-ROV can substantially improve a waterside operation. There is no longer a reason not to start off with an inspection while the rest of the operation is gearing up. Frequently, problems can be caught early, before they become worse, or before testing or installation operations begin.

    Reason 4. Getting live footage while an expensive equipment trial is underway is often considered as an after-thought. For important trials or prototype evaluations, footage is very helpful. If the test run goes well or an installation goes as planned, then comes the celebration and preparation for presentations — but where’s the compelling footage? Or, in the opposite case, if there were problems with the test, the equipment, or the operational procedures, and if a costly failure occurred, a detailed post-mortem would be helpful — but no one actually witnessed the underwater failure, and there’s no footage. In both of these cases, having a Micro-ROV unobtrusively taking underwater high-definition color video footage of the action can be a boon, be it for customer presentation, business development, engineering analysis of problems, or project documentation.

Costs, Benefits, and Ease of Use

Micro-ROVs are coming down in cost. Capable systems can now be obtained from $6,000 – $15,000, depending on options and accesories. Systems can be leased from $600/day, $1500/week to $5000/month (USD).

In the right situation, this cost is small compared to the total cost of recovering from mistakes, delays, or testing failures.

How often have expensive crews waited while technical staff wrestled with equipment and deployment challenges and discussed alternatives in the absence of a way to see the problem underwater? Throw in a Micro-ROV, take a careful look, and then decide what exactly needs to be done.

The ability to setup and deploy within minutes — in many cases literally “drop it in” — is one of the most appealing aspects of the Micro-ROV platform.

Traditional work ROVs have a steep learning curve, are expensive, require lifting equipment to deploy, and are typically driven by a trained ROV operator. The Micro-ROVs now available have simpler control interfaces, can be deployed off the side of a pier or rubber boat simply by lowering the Micro-ROV into the water from its cable, and a first-time operator can be trained up comparatively quickly.

The ease of use is due to the high degree of manoeuvrability of many of these Micro-ROVs. As an example, the AC-ROV (reviewed below) has full 5 degrees of freedom and 6 thrusters: 4 vectored horizontal thrusters and 2 vertical thrusters. This simplifies flying the Micro-ROV. Lateral movements can be made keeping the surface in view, and if the target is passed, the operator does not have to fly difficult manoeuvers to get back into position.

Recommendations

Given the foregoing discussion, I would recommend the following:

  • If you are a dive team, you may want to invest in a Micro-ROV as part of your infrastructure.
  • If you are involved in frequent waterside operations or equipment testing that involves coordinating groups of contractors or other “on-the-clock” resources, you should consider leasing a Micro-ROV as a contingency plan for when (not if!) things begin to go wrong. (And they always do). Think of it as an investment in giving your technical staff eyes below the surface to ensure that the operation goes smoothly.
  • If you are a marine consultant or ocean engineering company on a fixed-bid contract, you may wish to include the cost of such leases in your bids/proposals. It is part of your contigency planning to help reduce the likelihood of costly over-runs or re-work.

Micro-ROV Product Choices

There are now a number of choices for quality Micro-ROVs on the market. From among the half-dozen candidates that I have considered, the AC-ROV is particular impressive. Granted, there are always tradeoffs, and every application needs to consider the right mix of performance requirements and vehicle capabilities. But for an ultra-portable, rapidly deployable, shallow learning curve Micro-ROV that packs an impressive range of capabilities in a low price point, the AC-ROV is a head-turner. I’ll be scheduling a test drive soon.

Below, then, is a quick overview of the AC-ROV. More information is at the manufacturer’s site. Information on the best of the other half-dozen candidates that I considered is also below.

Useful white-papers and additional reference material is also given below.

AC-ROV (AC-CESS, UK)

Mar-17-2010 by Assad Ebrahim

The AC-ROV is an impressive 3kg (6.6lbs), ultra compact (LWH: 203mm x 152mm x 146mm / 8″ x 6″ x 5.75″), highly portable tethered micro-ROV outfitted with a digital CCD camera and optional additional sensors. The small size, portability, and rapid deployability make this piece of kit an attractive option for underwater inspection and flying-through large diameter pipes (8″ or more) or for work in tight spaces.
(Spec (AC-ROV 100) | Comparison | Images)

AC-ROV Appeal: the AC-ROV has full manoeuvrability (5 degrees of freedom), has automatically tracking camera lights, and can be flown with one hand, leaving the other free. It is depth-rated to 75msw (meters sea water), can fly out 120m from the operating unit (with tether deployment system), and can carry 0.5 lb (200g) payload.
It has 4 vectored horizontal thrusters and 2 vertical thrusters. The thrusters are designed to prevent catching and fouling — and in the event that one of the vertical thrusters gets jammed with kelp, you still have the redundancy to manoeuvre vertically.

  • Input: Power (300W – AC)
  • Basic Output: Composite Video from the on-board digital CCD camera
  • Additional Sensors: the AC-ROV can be outfitted with a USBL (ultra-short baseline) transponder for tracking or precise positioning, an optional rear-view camera and light, depth and pressure sensors, a laser scaling head for measurement of surface features, a thickness gauge for measurement of metal thickness
  • Operating Information: The six independent thrusters allow full range of motion and manoeuvrability. This, coupled with the ability to attach the cable at the rear, top or bottom, allow the AC-ROV to be used for forward-fly-through, drop-down, or up-rise inspection missions in close quarters (mininum opening 8″ diameter is required in forward flying mode, 9″ diameter in drop-down mode).
  • Clean Profile: The AC-ROV has a clean profile and is free of protrusions that are likely to snag the tether
  • Portability: The AC-ROV, together with all required parts and pieces, fits into a single storm case that weighs in under 20kg (40lbs) — light enough for checked baggage on most airlines.

Other Vendors with MicroROVs and some MiniROVs

VideoRay (US) | Seabotix (US) | Cetrax (UK) | Subsea Tech (France) | Albatros (Spain) | Gnom (Russia)


Related Reading, Further Interest

  1. Each of the vendor sites has useful information on applications, case studies, and success stories.
  2. (PDF)The Role of MicroROVs in Maritime Safety and Security, M. Molchan, H_2Ops, April/May 2006.
  3. (PDF) A Micro-ROV Simulator, Z. Fabekovic, Z. Eskinja, Z. Vukic; IEEE Proceedings Electronics in Marine; 2007; pp.97-101;
    Keywords: Mathematical Modeling, VRML platform, 3-D visualization

  4. Sensors and Systems: Integrating Sensors into the Ubiquitous Computing Stack

Stay tuned for the next article on Marine Technologies.

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