# Improvement of Hexacopter UAVs Attitude Parameters Employing Control and Decision Support Systems
## 2 Related Work
### Sensors Equipment  
In addition to the propulsion system, the sensors with which the drone is equipped play a critical role in terms of manoeuvrability, stability, command and control of the drone. The sensors also capture information from the surrounding environment (images, video, GPS location, photogrammetry, LIDAR), depending on the specific missions or activities that the drone is meant to perform. [PERSON] and [PERSON] [54] provide a source design pattern for building new drone systems, which includes blocks of the drones and relations between them that are distributed into four main groups: flight navigation, flight control, flight management and mission supervision. [PERSON] et al. [55] treat the examination of low power transmission lines using multicopter drones, in terms of making the right decision, cantered on data fusion acquired from a multisensor system. The information fused refers to the main aspects affecting the UAV parameters (flight speed), wind velocity, errors of the navigation positioning and size of the drone frame. A method called MFD-LPTL (multisensor fusion data analysis for low power transmission lines) is presented. This method's main purpose is to conceive a model for secure distance prediction between the drone and the power lines. Based on the multisensor data fusion, combining data from various sensors including radars, LIDAR and camera models, a statistical model which uses the autonomous avoidance navigation of the problems was applied. [PERSON] and [PERSON] [56] treat the problem of optimization of the sensors used for altitude estimation mounted on multicopter drones employed for spraying the vineyards. The study makes a comparison between a variety of low-cost sensors for measuring the distance between the drone and ground level, sensors which are most appropriate for vineyard-spraying drones. The signals were acquired from ultrasound, radar and Doppler sensors and were filtered using a Kalman filter. The study describes a variety of measures employed to improve the assessed altitude of the drone and to enhance the trustworthiness regarding the relative altitude approximation of the multicopter drone. In [PERSON] et al. 's [57] WILD HOPPER UAV study, a 600 \(L\) platform designed for forest firefighting is presented. The paper reveals a multilayer steadiness system for enhanced stability of the drone during the flight in severe conditions. WILD HOPPER is equipped with a range of sensors which include thermal cameras, geolocalization and navigation systems: satellite navigation and a new technology based on visual attitude estimation methods. The study presented by [PERSON] et al. [58] explains the extraction and analysis of GPS data from three different drone manufacturers, followed by analysis and representation of the positioning data as flight paths. GPS-related data from any drone's flight is of vital importance as it helps in establishing a legal framework for operating a drone in a country's airspace. In terms of sensors, all these data are obtained from the GPS antenna/antennae mounted on the drone. To be able to fly, a multicopter drone needs a flight controller, which is the brain of the drone. In terms of sensors, this flight controller consists of an AHRS (attitude and heading reference system) IMU (inertial measurement unit), which is a device that integrates multiaxes accelerometers, gyroscopes and magnetometers to provide estimation of the drone's orientation in space, providing measurements of pitch, roll and yaw. When the drone flies in an environment where GPS signal can be acquired, to ensure the reliability and highest performance, a sensor that includes an AHRS, as well as a GNSS receiver, which utilizes the GPS, GLONASS, BeiDou and Galileo satellite constellations, provide the best navigation system. If the drone needs to be flown BVLOS (beyond visual line-of-sight) without being reliant on GPS, it is mandatory to have mounted on the drone a fully calibrated and temperature compensated AHRS IMU sensor under all dynamic conditions.