# A Robust Fixed-Time Sliding Mode Control for Quadrotor UAV
## 1 Introduction
Similarly, reference [17] presents a backstepping-sliding mode control using a closed-loop identification for Quadrotor aircraft trajectory tracking. However, the problem of finite-time tracking control has been considered in many types of research. In reference [18], the authors perform an altitude control for a Quadrotor aircraft using an integral slip control (ISM) approach which aims to improve the robustness and accuracy of the altitude controller. Something similar is used in reference [19], where a sliding mode control approach is also presented to improve the accuracy and robustness of attitude and altitude control for a Quadrotor aircraft, while in references [20; 21], the author focuses on trajectory tracking control for a Quadrotor aircraft using an approach combining a dynamic surface controller (DSC) and an extended state observer (ESO). Then, in reference [22], an adaptive sliding mode controller approach is proposed to improve the accuracy of the path tracking with rejection of external disturbances. Furthermore, in reference [23], the authors propose a robust adaptive non-singular fast terminal sliding mode tracking control for an uncertain Quadrotor UAV subject to disturbances. Similarly, an adaptive controller was used in reference [24] to adjust the parameters of the SMC in real time, further improving the system's ability to adapt to adverse environmental conditions. The SMC technique is used to improve the robustness and adaptability of flight control to external disturbances such as gusts of wind. In the same way, reference [25] deals with the characteristic chatter phenomenon of slider mode control. The characteristic oscillation of this type of control can affect the trajectory following tracking, so a sliding mode controller with integral action is proposed to minimize the vibration and improve the trajectory-tracking accuracy of the UAV. The approach proposed in reference [26] uses an improved sliding mode speed control that combines a smoothed switching function and a low-pass filter to attenuate noise and improve motor speed control accuracy, while in reference [27], a control method is proposed where the estimated angles converge to the desired value for the scope of the orientation and therefore execute the tracking of the vehicle position to the given reference. Then, in reference [28] also uses an observer based on a sliding mode controller to stabilize a Quadrotor aircraft in hover flight in outdoor environment, while reference [29] uses an observer to estimate disturbances and a finite-time tracking control law to achieve robust trajectory tracking in an aerial vehicle. In addition, in reference [30] a robust control based on fixed-time sliding modes is also used to control the attitude of a Quadrotor aircraft in the presence of external disturbances. The contribution of this article is the implementation of a control algorithm based on a fixed-time sliding mode controller (FTSMC) to improve trajectory-tracking errors to zero, providing robust results in the presence of external disturbances such as gusts of wind. FTSMC is a control technique used in nonlinear dynamic systems such as Quadrotor aircraft that allows for reaching a stable control state at a fixed time. This technique uses a sliding surface to maintain the system in a steady state, even in the presence of disturbances or uncertainties in the system [31]. The FTSMC is an advantageous control algorithm to apply in Quadrotor aircraft due to its ability to provide robust and fast real-time control performance. This algorithm uses a control law based on a sliding surface to reduce the error between the desired output and the actual system output. In addition, this strategy reduces external disturbances and considers the non-modeling dynamics. Therefore, FTSMC is a powerful control technique for Quadrotor aircraft that allows for achieving high precision and stability in the navigation and positioning of these unmanned aerial vehicles.