# Improvement of Hexacopter UAVs Attitude Parameters Employing Control and Decision Support Systems
## 2 Related Work
### Experimental Procedures  
[PERSON] et al. [61] describe the mathematical modelling and implementation of a command-and-control system for a hexacopter employed to monitor radioactive-chemical-nuclear contamination using fuzzy logic. For accurate tracking of a trajectory, the hexacopter requires a high-performance altitude and attitude controller for its in-flight movement, since in conditions of external disturbances it introduces wind. In the first step, the dynamic equation of the hexacopter is developed using Newton-Euler equations, and in the second step, a solution consisting of a PID controller combined with fuzzy logic is proposed in order to include correction signals to eliminate positioning errors of the hexacopter when moving. Before implementation on the drone, the effectiveness of the proposed method was verified using a software-in-the-loop (SITL) robotic operating system (ROS) simulation environment together with the Matlab matrix calculation utility. Based on the numerical simulation and experimental results and using the fuzzy-PID intervention algorithm, the following parameters were improved: faster transient response hexacopter trajectory tracking performance, smaller errors in maintaining the steady state of the system, faster settling times to transient changes and better and more robust static and dynamic performance under disturbances introduced by different wind speeds. [PERSON] et al. [62] implemented a mathematical model of a hexacopter control system. Employing the Matlab/Simulink environment, it was possible to mathematically simulate the dynamics of the forces acting on the hexacopter rotors by inserting external disturbances: wind forces alongside one of the hexacopter axis. The block for estimating the model parameters is programmable and performs the computations using the theoretical formulae developed previously. Other aspects also treated in the paper were the problems associated with the selection of the optimal control for the hexacopter when flying along the path in the occurrence of wind. The attitude of the hexacopter in flight is adjusted using PID controllers because stabilization must be provided on all the axes of the drone during flight. Thus, four PID controllers must be implemented: one controller for roll motion stabilization, the second controller for pitch motion stabilization, the third controller for yaw motion stabilization and the fourth controller for hexacopter altitude stabilization. The stabilization of the hexacopter at a certain altitude was considered by [PERSON] et al. [63]. The Ziegler-Nichols method is employed to adjust the parameters of the PID controllers. [PERSON] et al. [64] present an analysis and management strategy for hexacopters during fixed-point hovering manoeuvres in the event of one or more engine failures. The study suggests keeping the deviation between input and output values unchanged by reallocating the thrust forces to the rotors. Simulations are performed on a hexacopter in different fixed-point flight modes [65]. Linear dynamics problems of the hexacopter are analysed and subsequently numerically validated for the unique nonlinear dynamics. If failure of one of the hexacopter motors occurs, the study proposes an allocation matrix to reallocate the lift forces to the functional motors. The study takes into account seven cases of engine failure; the conclusions derived from analytical analysis show that reduced control for emergency landing is achievable in four scenarios at the linear level, and for the other three scenarios, the drone is completely uncontrollable. To demonstrate the validity of the recommended algorithm, the paper also presents numerical simulations. [PERSON] et al. [66; 67], [PERSON] et al. [68] and [PERSON] et al. [69] present the mathematical modelling, estimation, attitude (drone position) control and altitude control of a hexacopter. Their works present the following contributions: First, mathematical modelling is performed, based on which the equations of the hexacopter model are obtained.