Aquatic robots are unmanned vehicles engineered to operate within or on water. These machines allow exploration and interaction with aquatic environments often too hazardous, deep, or remote for direct human access. They enable a wide array of tasks in diverse underwater and surface settings.
Classifications of Aquatic Robots
Aquatic robots are broadly categorized based on their operational mode, distinguishing how they receive power and control signals.
Remotely Operated Vehicles (ROVs)
Remotely Operated Vehicles, or ROVs, are tethered underwater robots controlled by an operator from a surface vessel. An umbilical cable connects the ROV to the ship, providing continuous power, real-time video feeds, and command signals. This direct connection allows for precise manipulation and continuous oversight. For example, ROVs provided detailed imagery and data during the exploration of the RMS Titanic shipwreck from extreme depths.
Autonomous Underwater Vehicles (AUVs)
Autonomous Underwater Vehicles, or AUVs, operate independently without a physical connection to a surface vessel. These robots are pre-programmed with mission parameters before deployment, allowing them to navigate and collect data. AUVs are suited for large-area surveys, such as mapping vast expanses of the seafloor or gathering oceanographic data over extended periods. They store collected data onboard and transmit it upon returning to the surface, making them efficient for wide-ranging missions.
Autonomous Surface Vehicles (ASVs)
Autonomous Surface Vehicles, or ASVs, operate on the water’s surface without human crew onboard. These robots can be remotely controlled or follow pre-programmed paths. ASVs are used for collecting surface-level data, acting as communication relays for submerged AUVs, or monitoring environmental conditions over long durations. They can utilize solar power for extended missions and maintain consistent communication with shore or other vessels.
Applications in Exploration and Industry
Aquatic robots perform a wide range of tasks across scientific, commercial, and public safety sectors, extending human reach into challenging aquatic environments. Their specialized capabilities allow for detailed data collection and intervention in diverse settings.
Scientific Research
In scientific research, aquatic robots explore ocean depths and study marine ecosystems. They conduct ocean floor mapping and collect water samples for environmental analysis, monitoring parameters like temperature, salinity, and chemical composition. Researchers deploy them to observe marine life in natural habitats, such as deep-sea hydrothermal vents, and to survey underwater archaeological sites like shipwrecks.
Commercial and Industrial Use
Commercial and industrial sectors employ aquatic robots for various operational needs. They perform inspections of underwater infrastructure, including pipelines, subsea cables, and dam structures. In offshore oil and gas operations, these robots support drilling, maintenance, and repair tasks, often working at depths unsafe for human divers. They also monitor aquaculture sites, such as fish farms, to assess fish health, inspect nets, and manage feeding systems.
Public Safety and Defense
Aquatic robots play a role in public safety and defense applications. They assist in search and rescue operations by locating sunken vessels, aircraft debris, or missing persons underwater, significantly reducing risks to human divers. In military contexts, these robots are used for mine countermeasures, identifying and neutralizing underwater explosive devices. They also conduct harbor surveillance, monitoring for unauthorized intrusions or suspicious objects.
Core Operational Technologies
The functionality of aquatic robots relies on several interconnected technologies that enable them to navigate, sense their surroundings, and move through water.
Navigation and Positioning
Underwater robots navigate without relying on Global Positioning System (GPS) signals, which do not penetrate water. Instead, they use Inertial Navigation Systems (INS), which track changes in position and orientation using accelerometers and gyroscopes. Acoustic positioning systems, such as Ultra-Short Baseline (USBL) or Long Baseline (LBL) systems, provide location references by transmitting and receiving sound waves from surface vessels or fixed transponders. Doppler Velocity Logs (DVLs) further refine navigation by measuring the robot’s speed relative to the seafloor using sound pulses.
Sensing and Data Collection
Aquatic robots are equipped with a variety of sensors to perceive their environment and gather data. High-definition cameras capture visual information, allowing for detailed observation and recording of underwater scenes, even in low-light conditions with powerful lights. Acoustic sensors, like side-scan sonar, create detailed images of the seafloor by emitting sound waves and interpreting the echoes, revealing geological features or submerged objects. Chemical and biological sensors measure water quality parameters such as pH, oxygen levels, and pollutant concentrations, providing insights into marine ecosystems.
Propulsion
Movement for aquatic robots is achieved through various propulsion methods designed for water’s dense medium. Conventional thrusters, which typically consist of electric motors driving propellers, are widely used for precise control and maneuverability. These thrusters can be configured to allow for movement in multiple directions, including forward, backward, side-to-side, vertical, and rotational movements. Some long-duration AUVs, known as gliders, utilize buoyancy engines that change the robot’s density to ascend or descend, generating forward motion through wings or hydrofoils, enabling energy-efficient, sawtooth-patterned travel over vast distances.
Bio-Inspired Robot Designs
Engineers often look to marine life for inspiration when designing aquatic robots, a field known as biomimicry. This approach aims to replicate the efficient, agile, and often stealthy movements observed in natural organisms. Mimicking biological designs can lead to robots that navigate complex environments with greater fluidity and energy efficiency than conventional propeller-driven systems.
Robotic fish are a prominent example, designed to mimic the undulating motion of real fish, which provides high maneuverability and low acoustic disturbance. These robots can navigate through intricate spaces like coral reefs, inspect ship hulls, or observe sensitive marine life without causing significant disruption. Their design allows for quiet operation and access to confined areas where traditional thrusters might be less effective or cause entanglement.
Larger bio-inspired robots, such as those resembling manta rays or sea turtles, leverage broad, flapping fins for propulsion. This design enables efficient gliding motions, making them suitable for long-range surveillance, oceanographic data collection, or mapping missions that require extended endurance. Their natural-looking movement can also minimize their impact on marine ecosystems, allowing for less intrusive observation of wildlife and habitats.