Whale of the season: The secret of fish anatomy will make underwater drones super energy efficient

MIPT specialists described in a mathematical model the motion features of an underwater vehicle with a swim bladder that repeats the principles of fish anatomy. This will make the drones maneuverable and enable them to move with minimal energy expenditure. Calculations can already be used to design silent and economical underwater robots that can be used in environmental monitoring or covert surveillance. However, according to experts, the data still needs to be confirmed experimentally.

The principle of fish movement

MIPT specialists have developed a mathematical model of the movement of biosimilar underwater soft-body vehicles using an analog of a fish swim bladder. Reproducing this natural mechanism can make it possible to create maneuverable drones capable of moving in the water column with minimal energy consumption by changing the volume of a special organ. The developers plan to test the data obtained on existing prototypes of such devices.

Photo: Global Look Press/Klaus-Dietmar Gabbert/ZB

— We finally figured out how the fish uses the swim bladder. In fish-like robots with a soft body and variable volume, as in living organisms, the state of zero buoyancy is unstable. Therefore, depending on the position of the bubble, they either sink or float. However, if the fish is moving, then there is a lifting force. If you place a bubble in the tail section and lower it, the rear part of the device will begin to descend, but the fins will stabilize it. When inflating, the reverse process occurs — the tail begins to rise. Thus, balancing between these states, the robot can move," said Viktor Kazantsev, head of the Laboratory of Neurobiomorphic Technologies at MIPT.

This principle will allow the drone to stay at a given depth and maneuver with minimal energy consumption. At the same time, buoyancy control will not require sensors, electronics or pumps, the specialist added.

Calculations have shown that stabilization occurs after reaching the minimum critical velocity. When moving more slowly, the robot loses stability. It is also important that the bladder and fins are shifted back relative to the center of the apparatus. If the speed is too high or these proportions are violated, the system, on the contrary, may become unstable.

Photo: IZVESTIA

Fish robots are currently being developed in many countries. So, Swiss engineers together with colleagues from the USA have created a universal model that can be scaled to different sizes without changing the design. It mimics the movements of mackerel and Atlantic cod and has a solid body with a flexible tail. Chinese developers this spring introduced a robotic model of aravana, a fish native to the Amazon basin. The device is 69 cm long, 20 cm high and weighs 3.8 kg. It can reach speeds of up to 1.9 km/h and work for up to 12 hours on a single battery charge.

Technology from printing: how drones and ammunition are created using 3D printers on the front line

UAVs are assembled, repaired and upgraded around the clock in field workshops.

The use of robot fish

Such biosimilar underwater drones look promising due to their ability to maintain buoyancy and hover at a given depth with minimal energy consumption. The use of a soft body and an air bubble can make the devices more maneuverable, quieter and safer for the environment compared to traditional rigid devices. However, the technology has yet to be tested in real conditions: pressure at different depths, strength of materials, resistance to currents and control accuracy will affect efficiency, Oleg Kivokurtsev, co-founder of Promobot, a robot manufacturer, explained to Izvestia.

Photo: Global Look Press/Rodrigo Reyes Marin/AFLO

— The main areas of application are environmental monitoring of reservoirs, marine animal monitoring, underwater ecosystem research, pollution detection and monitoring of pipelines, hydraulic structures and underwater cables. Such drones can also be used for scientific expeditions and covert long-term surveillance, as low-noise movement reduces the likelihood of exposure to living organisms. With successful tests, the technology can lead to the creation of autonomous groups of robots capable of working underwater for a long time without frequent recharging," the specialist said.

Earth robots: NRTKS have become platforms for launching drones

The new tactic significantly expands the range of drones

The study provides a good theoretical basis for a promising area of underwater robotics — the creation of quiet and energy-efficient autonomous vehicles, says Artyom Bogatyrev, market expert at Aeronet Research Institute.

— So far, this is a calculated job, and its main value lies in the practical rules for designers. The authors showed where the analog of the swim bladder and fins should be positioned and at what speed the device should move so that it can maintain depth without pumps and constant operation of the control system. Today, most underwater drones change depth using ballast systems that pump water, waste energy, and create noise. Passive stabilization can significantly extend the autonomous operation of vehicles during long—term monitoring of water areas, underwater infrastructure and marine ecosystems," he said.

Photo: IZVESTIA

It is important to consider the limitations of the method. The model is based on a simplified formulation and does not yet take into account many situations that the device may encounter in practice. Now the technique will be tested on prototypes of fish robots. If the calculations are confirmed, Russian developers will receive a ready-made tool for designing economical underwater vehicles capable of performing long-term autonomous missions, the expert added.