# Improvement of Hexacopter UAVs Attitude Parameters Employing Control and Decision Support Systems
## 1 Introduction
Likewise, current advances in microelectronics and proximity/optical sensors [25; 26], coupled with the availability of detailed geographic information systems mapping [27; 28; 29], contributed to the development of micro-UAVs [30] that can be operated autonomously at very low altitudes within dense urban locations and provide accurate intelligence data. This paper aims to treat the category of multicorers UAVs, specifically the category of hexacopter drones. Given the upward trend in the aviation industry in the field of unmanned aerial vehicles (UAVs), especially in the field of multirotor drones [31; 32; 33; 34], whose advantage over fixed-wing aircraft (airplanes) is that they can hover at a fixed point, which obviously allows their use in remote surveillance applications of different types of targets, the use of UAVs in the field of surveillance is also a key issue, and, at the same time, taking into account that the market for components for this type of vehicle is constantly growing and developing, with increasingly lower costs. Due to their cost efficiency and numerous possibilities for use in a wide range of civil, commercial and industrial applications (inspection of power lines, inspection of road infrastructure, bridges, inspection of oil pipelines, inspection of industrial facilities of strategic interest, e.g., oil refineries, nuclear power plants, inspection of disaster areas), multirotor UAVs have already been the subject of study for more than a decade. Since then, numerous research studies have been carried out on the modelling [33; 34; 35] and design of actuation, command and control systems [36] and the development of various design solutions [37; 38]. Despite the abundance of the scientific literature, the topicality of the subject remains high, due to the subtle balance between the sensor features and involved outlays. This paper is structured as follows: Section 2 encompasses a synthetic and critical overview of the latest developments in hexacopter drones design, sensors equipment and experimental procedures but also regarding numerical evaluation of the drone stability and reliability. Section 3 depicts a novel hexacopter platform architecture in two variants, equipped with avionic components and sensors. In Section 4, the results of the carried-out tests, both in the laboratory and in situ, during the start-stop manoeuvres of the hexacopterengines are described and discussed, and it also discusses the necessary corrective measures that were taken accordingly to check and assure the reliability of the hexacopter. Section 5 encompasses an extended FEM decision support study to investigate if resonances of the structural components interfere with the operational frequencies in order to avoid flight instabilities. The structural integrity of the hexacopter in case of a drop event was assessed, and the influence of the air pressure at different wind speeds was also investigated in respect to the hexacopter flight path accuracy. The accomplishments are summarized in Section 6, where conclusions are drawn and perspectives for the future work are highlighted. The novelty of the work consists of a new perspective of comparative analyses of the performance of the hexacopter drone in different equipment variants in terms of battery, propellers, avionics components and engines employed by carrying out simulations using devoted simulation platforms. These studies also allowed us to establish the appropriate criteria for choosing the best combination of the propulsion system, consisting of a battery, such as an electronic speed controller (ESC), or a brushless DC motor (BLDC)--propeller--depending on the size of the drone frame, in order to achieve maximum efficiency (range vs. maximum carried payload).