Sunday, November 19, 2017
Published: Jul 2015
Authors
  • Arnar Steingrimsson
    • Arnar Steingrimsson
    • Company: Teledyne Marine Systems

LOW-LOGISITICS MARINE SYSTEMS ENABLE NEW APPROACHES TO SURVEY

Unmanned maritime vehicles (UMVs) have been under development for decades. Since the late 1990s, several systems have evolved beyond research labs and have become commercial realities. These tools are now in routine use for scientific, commercial and military applications.

  • Fig_1_Gavia_OffShore_Surveyor_Two_Batteries.jpg
  • Figure_3_The_Gavia.jpg
  • Figure_4_the_Gavia_Modules.jpg
  • Fig_2_Gavia_OffShore_Surveyor_Sections_no_Perspective.jpg
  • Figure_5_Teledeyne_SeaBotix_Containerized_Delivery_System.jpg
  • Figure_7_AUV_Payload.jpg
  • Figure_6_The_SeaROVER_Illustration.jpg
  • Figure_6_SeaROVER_ROV_Photo.jpg
  • Fig_1_Gavia_OffShore_Surveyor_Two_Batteries.jpg Figure 1: The Gavia AUV
  • Figure_3_The_Gavia.jpg Figure 3: The Gavia is easy to deploy (image courtesy NCS Survey and BP)
  • Figure_4_the_Gavia_Modules.jpg Figure 4: The Gavia modules are easily transportable
  • Fig_2_Gavia_OffShore_Surveyor_Sections_no_Perspective.jpg Figure 2: The Gavia modules are fully independent and interchangeable
  • Figure_5_Teledeyne_SeaBotix_Containerized_Delivery_System.jpg Figure 5: Teledyne SeaBotix Containerized Delivery System
  • Figure_7_AUV_Payload.jpg Figure 7: AUV payload modules pole mounted from a vessel of opportunity
  • Figure_6_The_SeaROVER_Illustration.jpg Figure 6b: outfitted with AUV payload modules
  • Figure_6_SeaROVER_ROV_Photo.jpg Figure 6a: The SeaRover ROV

RAPIDLY EVOVLING TECHNOLOGIES

Unmanned maritime vehicles (UMVs) have been under development for decades. Since the late 1990s, several systems have evolved beyond research labs and have become commercial realities. These tools are now in routine use for scientific, commercial and military applications.

With robust vehicles available, logistics concepts are becoming a key element of UMV operations. All operators deploy UMVs for a purpose. Achieving that purpose safely at the lowest overall cost, or in the shortest time possible, is usually a key goal. The increased productivity of data collection in survey applications is enabled by new technology developments, especially modular and payload centric unmanned vehicles.

LOW LOGISTICS: MODULAR AUVS AND PAYLOAD CENTRIC ROVS

Low Logistics AUVS

Modular, low logistics autonomous underwater vehicles (AUVs) now provide a level of operational flexibility that was impossible to achieve with earlier monolithic systems. Fully modular, low-logistics AUVs with offshore survey capability were first deployed in the energy sector mid to late 2000s. The Teledyne Gavia AUV (Figure 1) is the primary example of a fully modular AUV that truly separates into independent modules (Figure 2). The Gavia is comprised of 20cm diameter cylindrical modules. A complete system can range from 1.85m long (60kg in air) to 3.2m (100kg), depending on the modules deployed.

Several fleets of Gavia vehicles now operate in locations around the globe, in depths up to 1000 meters. These AUVs are in service with navies worldwide and are used for a range of applications including search and salvage, mine counter measures (MCM), sonar training, and platform/sensor development. Commercial firms also employ them for applications such as pipeline route survey and inspection, a variety of pre and post construction support applications, and dredge monitoring. Universities engaged in robotics research and development and oceanographic and geophysical research are another user community. Each of these Gavia AUVs can be changed from one role to another in the field by swapping the survey, environmental sensing, battery, and navigation modules. In fact, there are examples of the commercial users renting academic payload modules to support critical mission requirements.

The advantages of a fully modular AUV system include: ease of deployment (Figure 3), ease of storage and transport to site (Figure 4), small deployment team, modular sensor platforms, ability to adapt the AUV capability in-theatre, and multiple swappable battery modules for tailoring endurance. Modular systems allow for fast mission-turn-around, ease of maintenance, and replacement of modules without losing operational capacity. In addition, future sensor solutions can be integrated into a module offline, and then added to the AUV in the field, enhancing capability. Modularity allows service life benefits of being able to replace individual modules due to obsolescence, technology advances, or changing capability requirements, without losing the operational AUV asset for an extended period for factory level overhauls or reconfigurations. Full AUV modularity answers the requirement for an asset that can be designated to a variety of tasks as they arise without being dedicated to one task, while allowing future upgrade paths.

REMOTELY OPERATED VEHICLES (ROVs): PAYLOAD CENTRIC “WORKSPECTION” SYSTEMS

Undersea inspection began with divers who were gradually replaced by Work Class ROVs. The ROV industry has a long history and has grown to significant size. While these ROVs are effective, they are certainly not seen as affordable. They are significant, yet necessary, investments that demand sophisticated vessels and trained operators. Offshore survey inspection has benefitted from work class ROVs with the new missions they can accomplish, but dramatic improvements in the economics of the application are still slightly over the horizon.

In contrast, small ROVs have advanced in capability and are significantly changing the economics of many missions. Available in many sizes and price ranges these ROVs enable rapid and effective inspection of the seafloor and structures. Though depth ratings of most small ROVs are not typically equal to work class ROVs, new technology has brought the deeper missions within reach of smaller systems improving economics as well as providing novel means of deployment. The Teledyne SeaBotix Containerized Delivery System (figure 5) allows for small ROVs to be employed for certain tasks which would typically require the much larger and costlier work class ROV.

An array of sensors support applications such as leak detection and pipeline imaging, and improved auto-pilots and subsea positioning reduce the burden on operators. The significant increase in the number of mini-ROVs deployed by police departments, universities, and other fiscally constrained operators is a testament to the economics of this class of UMV. While the user base is growing, the gap between the capabilities of work class ROVs and the mini-ROVs is closing. Select low-logistics ROVs now offer the high thrust to weight ratio required to support long tethers in high currents. Flexible architectures allow these ROVs to be adapted to powerful sensors without the high drag the “strap-on” approach imposes on micro-ROVs. Thus a low-logistics ROV can now support missions such as bridge piling inspections in extremely low visibility and high current environments. A previously slow, expensive, if not impossible task is now routine and economical.

ROVs have been adopting increased “autonomy” for many years. Improved station keeping and closed loop control, common in large work class ROVs, are now available features in miniROVs. Likewise, the evolution of modular payloads for AUVs will impact the future of ROVs. At Teledyne, the SeaRover class ROV (Figure 5a) is designed to provide both autonomy and an interface to high value sensors, such as imaging sonars, in a low-logistics high performance platform. The SeaRover can be adapted to carry the same payload modules as the Gavia AUV (Figure 5b). This would allow a customer to derive additional value from their investment in high cost sensors. For example, an AUV sub-bottom profile module could be moved from an AUV to an ROV to complete both broad area survey and detailed inspection for a client.

THE FUTURE: HETEROGENOUS MODULAR SYSTEMS

Today, modular AUVs are supporting commercial, defense, and scientific users, providing improved economics and operational flexibility. Sensors continue to evolve and adapt to enable increased modularity on UMVs. This versatility is already at work with fleet users of Gavia AUVs in survey missions. Thus far, we have not yet seen modular payload architectures cross lines between different platform types. But, that is the next logical step. The exchange of payload modules between AUVs and ROVs or even pole mounting of sensor modules from a vessel of opportunity (figure 6) is easily implemented and should come on scene very soon. This will require operators to carefully track and manage vehicle configurations. Failure to note a 300m rated payload module is installed on a 1000m rated AUV could prove problematic. But, manufacturers with diverse vehicle portfolios can assist users by building in “smart” features in payload modules. A 300m rated module could announce itself to the host vehicle, which could then reject a mission profile sending it deeper than the safe rating.

The added value of modular architectures is just beginning to impact operations. The technology will advance quickly and UMV operators should begin planning for the capability today. Robust feedback between users and developers of these systems will ensure technical and logistic issues can be resolved early. Thus a significant expansion of the business and operational value is anticipated from heterogeneous modular UMVs in the future. With a wide variety of payloads and vehicles to choose from, survey operators will be able to manage their capital expenditures and optimize their operations. New technologies will continue to shape the future of seafloor survey and unmanned vehicles will be a key element.

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