An Overview on Aquatic Unmanned Aerial Vehicles

Abstract

Since Wright Brothers’ first flight, aerial vehicles have been improved rapidly. Because manned vehicles are usually difficult to design due to complex layout, high cost, and low efficiency, unmanned vehicles like unmanned aerial vehicles (UAVs) and unmanned underwater vehicles (UUVs) developed rapidly and separately in the past several decades. There are two main types of UUVs, i.e., AUVs and remotely operated vehicles (ROVs). UAVs and AUVs comprise a large part of unmanned vehicles. In order to expand working domains of unmanned vehicles, aquatic UAVs have been developed. Easy transitions between air and water make them flexible and latent. There are many problems in the design of aquatic UAVs. For instance, in the air, the power demand of an aquatic UAV is usually large because it has to overcome its gravity, so diesel engines are suitable for UAVs; while in the water, the gravity can be offset by the buoyancy so the electric engine can satisfy the needed power; then using which type of engines becomes a problem. A partially functional aquatic UAV is usually hard to design, and more problems like the communication problems, fuselage shape problems, and design of the switching algorithms will occur if it is a fully functional aquatic UAV. There are some other names like amphibious UAV [1] and unmanned aerial-aquatic vehicle [2], but we use aquatic UAV in this paper to define those unmanned vehicles which can fly in the air and in the water. Many innovations to solve design problems of aquatic UAVs are bio-inspired, because many animals are able to dive and fly, like gannets, flying fish and cormorants [3-7]. But how to maintain a long time travelling in both domains is still an unsolved problem. Before reviewing the developments of aquatic UAVs, this paper first briefly introduces the developments of UAVs and AUVs separately. Then this paper discusses problems in the design of aquatic UAVs and give some bio-inspired solutions. In the end, this paper discusses some promising conceptual prototypes. The rest of this paper is arranged as follows. Section 2 is the introduction to potential applications of aquatic UAVs. Section 3 introduces developments and main types of AUVs, and Section 4 describes developments and main types of UAVs. Section 5 introduces two categorizing methods for aquatic UAVs. Section 6 discusses some designing problems including control problems, take-off and landing problems, and communication problems. Section 7 shows some promising conceptual designs and Section 8 makes a summary on the key problems of designing an aquatic UAV.