• UFRJ Nautilus

Flying Robots and Swimming Robots: drones and AUVs

Updated: May 20

One of the new goals of the Nautilus team is to diversify our areas of operation. To this end, we have recently started to develop autonomous aerial vehicles, and in the course of this article we will explain how this new class of vehicle differs and how it resembles the AUVs that are the focus of the team.


Very briefly, let's recap the definition of an AUV.


An Autonomous Underwater Vehicle is simply an autonomous vehicle, which operates in a specific medium, below the surface of the water. Essentially it would not be wrong to think of an AUV as a "submarine drone", but it is against the common use of the terms.


As a technical term for drone, we have a very similar acronym that can cause confusion, UAV, which means Unmanned Aerial Vehicle, or in Portuguese VANT (Unmanned Aerial Vehicle).


Many other acronyms such as ROV, UAS, VAS and RPA are related to this subject, but we will only use the terms drone and AUV to avoid confusion.


History


The drone has grown tremendously in the past decade, it is hard to have never seen one flying at any sporting event, or just flying as a hobby. These most common drones are a specific type called a multicopter, so called because they have multiple engines, which are their only form of propulsion and flight control.


The cheapening of electronic control technologies, accelerometers and pressure sensors has allowed quadcopters to take off as seen from 2010 until now. Today it is possible to find several relatively inexpensive models on the internet and even in malls. But how exactly do they work?





Feature


Just like the AUV, the drone is usually an electric vehicle and therefore relies on a battery as a source of energy. This battery is usually of the Lipo type (Polymer of lithium) and for the need to be of high capacity, it consists of much of the weight of the drone. This is the main factor that limits the flight range of a drone.


Multicopters can not glide like airplanes or float like AUVs, so every flight time and every maneuver depends on the constant action of the engines. The result of this is a huge expenditure of energy that strongly limits the flight time and the maximum weight of the cargo.


Worse still, it is not possible to just place larger batteries, as any additional weight is more energy used to lift and maintain flight. So for a drone it is very important to use lightweight materials in its construction. It is very common to see the use of plastics, carbon fiber, and when it is necessary to use metal, aluminum.


This made it impossible for many years to develop flying electric vehicles, however, when high density batteries arrived on the market, the drone established itself as an extremely valuable tool for professionals in the most diverse areas, as will be seen below.


AUVs and drones have very similar control systems, but they operate quite differently.


Both have some type of controller that will receive information from the sensors, make decisions and send commands to start the motors. In addition, this controller may or may not transmit data to an external station. In the case of AUVs and Nautilus drones, this external communication always occurs.


Because of the difference in the environment, the activation of the engines is quite different between these two. The AUV has motors associated with axes of movement, and when driving one of these, the AUV moves on that axis. Meanwhile, the drone increases or decreases the speed of groups of engines to move. It is easier to understand by looking at the diagram below: