Underwater robots are game-changers in ocean exploration. From tethered ROVs to autonomous AUVs and versatile hybrids, these machines tackle diverse tasks in marine environments. They're revolutionizing how we study, work, and protect our oceans.

Each type of underwater robot has its strengths. ROVs excel at precise tasks, AUVs cover vast areas independently, and hybrids offer the best of both worlds. Understanding their unique features helps match the right robot to the job at hand.

Underwater Robot Types

Classification of Underwater Robots

• Underwater robots can be broadly classified into three main categories: Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs), and hybrid vehicles that combine features of both ROVs and AUVs
• ROVs are tethered underwater robots that are controlled remotely by a human operator on the surface, typically via a cable that provides power and communication
• AUVs are untethered, self-contained underwater robots that operate independently without real-time human control, relying on onboard power, sensors, and decision-making capabilities
• Hybrid underwater vehicles, such as Intervention AUVs (I-AUVs) and Hybrid ROVs (H-ROVs), incorporate features of both ROVs and AUVs to enable more versatile and adaptive operations
  • I-AUVs can perform autonomous surveys and switch to ROV mode for intervention tasks
  • H-ROVs can operate as untethered vehicles for extended periods while still allowing for real-time human control when needed

Features of Underwater Robots

Characteristics and Capabilities of ROVs

• ROVs are characterized by their tethered connection to a surface vessel, which allows for real-time control, high-bandwidth data transmission, and unlimited power supply, but limits their range and mobility
• ROVs are well-suited for tasks requiring precise manipulation, such as underwater construction, inspection, and sample collection (e.g., collecting geological samples or biological specimens)
• ROVs are vulnerable to tether entanglement and require a dedicated support vessel for operation
• ROVs can carry a wide range of sensors and tools, such as cameras, manipulators, and scientific instruments, enabling diverse applications

Characteristics and Capabilities of AUVs

• AUVs are distinguished by their autonomy, self-contained power supply, and ability to cover large areas without constant human supervision
• AUVs are ideal for wide-area surveys (e.g., seafloor mapping), long-duration missions, and operations in hazardous environments (e.g., under-ice exploration)
• AUVs face challenges related to limited onboard power, navigation accuracy, and decision-making capabilities
• AUVs require robust communication and data transfer methods when surfacing or docking to transmit collected data and receive mission updates

Characteristics and Capabilities of Hybrid Vehicles

• Hybrid vehicles aim to combine the benefits of ROVs and AUVs, offering flexibility for diverse mission requirements
• I-AUVs can perform autonomous surveys and switch to ROV mode for intervention tasks, combining the efficiency of AUVs with the precision of ROVs
• H-ROVs can operate as untethered vehicles for extended periods while still allowing for real-time human control when needed, extending the range and duration of ROV operations
• Hybrid vehicles can adapt to changing mission demands and environmental conditions, enabling more versatile and efficient operations

Applications of Underwater Robots

Oceanography and Marine Biology

• In oceanography, underwater robots are used for seafloor mapping, water column sampling, and monitoring of physical, chemical, and biological parameters to study ocean circulation, climate change, and marine ecosystems
  • Examples include using AUVs for high-resolution bathymetric surveys and ROVs for collecting water samples at specific depths
• Marine biologists employ underwater robots to observe and collect data on marine life, including benthic communities, fish populations, and marine mammals, as well as to monitor the health of coral reefs and other sensitive habitats
  • Examples include using ROVs equipped with cameras and sampling tools to study deep-sea ecosystems and AUVs for large-scale marine mammal surveys

Offshore Oil and Gas and Maritime Archaeology

• The offshore oil and gas industry relies on underwater robots for tasks such as pipeline inspection, subsea infrastructure maintenance, and intervention in deep-water environments, enhancing safety and efficiency of operations
  • Examples include using ROVs for valve operations and equipment repair at deep-sea oil wells and AUVs for pipeline leak detection surveys
• Maritime archaeologists use underwater robots to locate, document, and study shipwrecks and submerged cultural sites, allowing for non-invasive exploration and preservation of underwater cultural heritage
  • Examples include using ROVs to visually inspect and create 3D models of shipwrecks and AUVs for large-area surveys to identify potential archaeological sites

Other Applications

• Underwater robots are used in military and security operations, such as mine countermeasures and port security, to detect and neutralize underwater threats
• In the renewable energy sector, underwater robots are employed for offshore wind farm inspection and maintenance, ensuring the integrity and performance of submerged structures
• Underwater robots also play a role in aquaculture, assisting in monitoring fish health, maintaining underwater cages, and inspecting mooring lines

Suitability of Underwater Robots

Factors Influencing Robot Selection

• When selecting an underwater robot for a specific mission, factors such as the required depth, range, and duration of the operation, as well as the need for real-time control, manipulation capabilities, or autonomous decision-making, must be considered
• Environmental conditions, including water depth, currents, temperature, and visibility, can impact the performance and suitability of different underwater robot types
  • For example, strong currents may favor the use of AUVs over ROVs to minimize tether drag, while low visibility conditions may require the use of acoustic sensors instead of optical cameras
• The choice of underwater robot type should also consider logistical factors, such as the availability of support vessels, launch and recovery systems, and data processing and storage infrastructure, as well as cost-effectiveness and regulatory compliance

Matching Robot Types to Mission Requirements

• ROVs are well-suited for missions requiring real-time control, precise manipulation, and high-bandwidth data transmission, such as complex intervention tasks or scientific sampling in deep-water environments
  • Examples include using work-class ROVs for subsea equipment repair and maintenance and observation-class ROVs for delicate biological sampling
• AUVs are preferred for wide-area surveys, long-duration missions, and operations in hazardous or inaccessible environments where tether management and human intervention are challenging, such as under-ice exploration or deep-sea mineral prospecting
  • Examples include using gliders for long-term oceanographic monitoring and multi-vehicle AUV fleets for efficient seafloor mapping
• Hybrid vehicles offer flexibility for missions that require a combination of autonomous operation and real-time human control, such as adaptive sampling based on in-situ data analysis or intervention tasks that benefit from both autonomy and operator input
  • Examples include using I-AUVs for autonomous pipeline inspection followed by targeted ROV-mode intervention for repair tasks