Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> A nonlinear dynamic model for a quadrotor unmanned aerial vehicle is presented with a new vision of state parameter control which is based on Euler angles and open loop positions state observer. This method emphasizes on the control of roll, pitch and yaw angle rather than the translational motions of the UAV. For this reason the system has been presented into two cascade partial parts, the first one relates the rotational motion whose the control law is applied in a closed loop form and the other one reflects the translational motion. A dynamic feedback controller is developed to transform the closed loop part of the system into linear, controllable and decoupled subsystem. The wind parameters estimation of the quadrotor is used to avoid more sensors. Hence an estimator of resulting aerodynamic moments via Lyapunov function is developed. Performance and robustness of the proposed controller are tested in simulation. <s> BIB001 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> ight control can be quite signicant, and can lead to dangerous situations when operating in close proximity to obstacles or other aerial vehicles. This work seeks to improve quadrotor positioning performance by formally modeling the wind eects on quadrotor dynamics in order to estimate wind velocities in ight and control the vehicle accordingly. Models for wind disturbances, quadrotor dynamics in wind and onboard measurements are presented and an estimation algorithm is developed for the current wind velocity experienced by the vehicle. This wind estimate is used to improve positioning accuracy by both eliminating the eect of wind on the feedback position control law and adding a wind compensator to mitigate the eect of the expected wind disturbance. Simulation results are presented for multiple scenarios, and work is ongoing for implementation on board a quadrotor testbed. <s> BIB002 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> This article deals with the problem of robust trajectory tracking for a scale model autonomous helicopter. A large class of uncertainties/disturbance is addressed, namely uncertain parameters and uniform time-varying tridimensional wind gusts occurring in the vicinity of the aircraft. Using an unknown input observer technique, it is shown that disturbances/uncertainties effects on the autonomous helicopter can be accurately reconstructed online. The analysis further extends to the design of a control law whose methodology takes the disturbance estimation procedure into account. Regarding passivity feature of the resulting model, a control law was designed using robust backstepping techniques. The approach proposed here significantly improves the performance of the control and the flight security by counteracting wind gusts in any flight phases. The framework proposed is applied to a non-linear six degree-of-freedom helicopter model. Consequently, a non-linear dynamic model of miniature helicopter is proposed, which focuses on the key effects in the dynamics of a miniature helicopter. Lyapunov stability analysis is then performed to keep the balance between robustness, short response time and large stability domain with a given security margin to guarantee obstacle avoidance during the tracking trajectory process. Simulations results are presented at the end of the article. <s> BIB003 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> Here, the attitude control of a quadrotor aircraft subject to a class of disturbances is studied. Unlike disturbances mentioned in most of the existing literature, the disturbance considered here is time varying and non-vanished. An extended observer is designed to estimate the disturbance by treating it as a new unknown state. Based on the estimation, a feedback controller with a sliding mode term is designed to stabilise the attitude of the quadrotor. Furthermore, to avoid the discontinuity of the control law caused by the sliding mode term, a modified sliding mode term is designed. The resulting continuous feedback controller makes the attitude error uniformly ultimate bounded. Theoretical results are confirmed by numerical simulations. <s> BIB004 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> An adaptive backstepping approach to obtain directional control of a fixed-wing UAV in presence of unknown crosswind is developed in this paper. The dynamics of the cross track error with respect to a desired trajectory is derived from the lateral airplane equations of motion. Adaptation laws are proposed to estimate the parameters of the unknown disturbances and are employed in closed-loop system. The stability analysis is proved using Lyapunov theory. In addition, several simulations taking into account unknown wind gusts are performed to analyze the behavior and the robustness of the control scheme. A test platform has been developed in order to validate the proposed control law. <s> BIB005 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> The paper addresses the flight control of a quad-rotor subject to two dimensional unknown static/varying wind disturbances. A model separation is proposed to simplify the control of the six-degrees-of-freedom (6DOF) nonlinear dynamics of the flying robot. Such approach allows to deal with quad-rotor’s 3D-motion via two subsystems: dynamic (altitude and MAV-relative forward velocity) and kinematic (nonholonomic-like navigation) subsystems. In terms of control, a hierarchical control is used as the overall control structure to stabilize the kinematic underactuaded subsystem. A control strategy based on sliding-mode and adaptive control techniques is proposed to deal with slow and fast time-varying wind conditions, respectively. This choice not only provides well tracking control but also improves the estimation of unknown disturbance. The backstepping technique is used to stabilize the inner-loop heading dynamics, such recursive design takes into account a constrained heading rate. Promising simulations results show the validity of the proposed control strategy while tracking a time-parameterized straight-line and sinusoidal trajectory. <s> BIB006 </s> Snake Aerial Manipulators: A Review <s> 2) ONLINE DISTURBANCE ESTIMATION <s> Nowadays, due to advantages of maneuverability, portability and low cost, the mini quadrotor unmanned aerial vehicle (UAV) catches much attention. In some special applications such as narrow space search, stealth detection and cooperative detection in huge region, the mini quadrotor UAV is more suitable than a big one. However, light weight and mini size lead to phenomenon that it is hard for mini quadrotor UAV to use complex control method. Besides, the performance of wind resistant is significant for practicability. In this paper, the under-actuated dynamics, strong nonlinear and coupling characteristics has been analyzed. After that, we propose a three-dimensional fuzzy PID control method for stabilizing attitude control and precise trajectory tracking control. The error, derivative of the error and the second order derivative of the error are the three-dimensional inputs of the controller. After using Simulink, the result shows that the proposed control method realizes precise trajectory tracking and robust attitude control. Furthermore, a kind of turbulent wind field, generated based on Dryden model, is added to disturb the control process. This study shows that three-dimensional fuzzy control method is better than the conventional fuzzy PID method under impact of wind disturbance. Finally, the results prove that our proposed control method has both excellent static and dynamic characteristics. <s> BIB007
Although the whole flight has disturbances, one of the critical parts is that of long duration movement or the aircraft mode, where it becomes necessary to estimate and counteract the effects of wind and pressure just to mention the most common perturbations. This is computationally complicated at open air because the wind represents a turbulent flow and its variations are modeled with partial differential equations that impacts over a beam (the aircraft is considered as a beam with multiple supports on their propellers). A more feasible option is to design robust flight control schemes BIB005 BIB006 BIB004 BIB002 BIB001 BIB007 BIB003 . 