Presence Of Wind Disturbances Research Articles

Path-Following Formation of Fixed-Wing UAVs under Communication Delay: A Vector Field Approach

In many applications, such as atmospheric observation or disaster monitoring, cooperative control of a fleet of UAVs is crucial because it is effective in repeated tasks. In this work, we provide a workable and useful cooperative guiding algorithm for several fixed-wing UAVs to construct a path-following formation with communication delays. The two primary components of our concept are path-following (lateral guidance) and path formation (longitudinal guidance). The former is in charge of ensuring that, in the presence of wind disturbance, the lateral distance between the UAV and its targeted path converges using a well-known vector field technique. In the event of a communication delay, the latter ensures that several fixed-wing UAVs will create a predetermined formation shape. Furthermore, we provide a maximum delay bound that is dependent on the topology and a controller’s gain. Lastly, in order to confirm the viability and advantages of our suggested approach, we construct an effective platform for a hardware-in-the-loop (HIL) test.

Control of quadrotor robot via optimized nonlinear type-2 fuzzy fractional PID with fractional filter: Theory and experiment

This paper presents a novel approach for controlling quadrotor robots. It introduces an optimized nonlinear fractional order type-2 fuzzy system integrated with a Fractional Order Proportional-Integral-Derivative controller, supplemented by a fractional filter in the derivative section. The input scaling factors, which represent the scaling coefficients associated with the input variables of the fuzzy system, are adjusted using nonlinear gains. The proposed controller combines type-2 fuzzy logic, fractional calculus, and nonlinear gains to enhance the control performance of the system. Its purpose is to provide superior control accuracy, robustness, and disturbance rejection capabilities. In order to enhance the performance of the quadrotor, the Bat Optimization Algorithm is utilized to finely adjust the controller parameters and membership function parameters of the fuzzy system. The fuzzy system incorporates Gaussian membership functions and applies the Mamdani min-max method for inference, utilizing the centroid method for defuzzification. The performance of the controller is evaluated in two scenarios: tracking aerial maneuvers in the presence of wind disturbance, and achieving angular stabilization by tracking a pulse function in the Hardware-In-The-Loop real-time test. The findings demonstrate significant improvements compared to traditional PID controllers. These improvements surpass 34 % without a filter and 53 % with a filter, in all directions and scenarios.

Precision Landing of Unmanned Aerial Vehicle under Wind Disturbance Using Derivative Sliding Mode Nonlinear Disturbance Observer-Based Control Method

Unmanned aerial vehicles (UAVs) are extensively employed in civilian and military applications because of their excellent maneuverability. Achieving fully autonomous quadrotor flight and precision landing on a wireless charging station in the presence of wind disturbance has become a crucial research topic. This paper presents a composite control technique for UAV altitude and attitude tracking in harsh environments, i.e., wind disturbance. A composite controller was developed based on nonlinear disturbance observer (NDOB) control theory to allow the UAV to land in the presence of random external wind disturbances and ground effects. The NDOB estimated the unknown wind disturbance, and the estimation was fed into the derivative sliding mode nonlinear disturbance observer-based control (DSMNDOBC), allowing the UAV to perform autonomous precision landing. Two loop designs were applied: the inner loop for stabilization and the outer loop for altitude tracking. The quadrotor model dynamics and the proposed controller, DSMNDOBC, were simulated employing MATLAB/Simulink®, and the results were compared with the one obtained by the proportional derivative (PD) controller and the sliding mode controller (SMC). The simulation results indicated that the DSMNDOBC has superior altitude and attitude control compared to the PD and SMC controllers and better disturbance estimation and attenuation performance.

Optimal guidance law design for three-dimensional trajectory tracking of missiles based on fixed-gain disturbance observer

To address the trajectory tracking problem of missiles, an optimal disturbance rejection guidance law (ODRGL) in three dimensions is proposed under the premise of uncontrollable speed. Error models of the actual and the reference trajectory are built in channels of pitch and yaw, respectively. In the yaw channel, a modeling error is introduced as the model cannot be built directly. According to the separation theorem, the controller and the observer are designed respectively. A fixed-gain disturbance observer (FGDO) is proposed to estimate the disturbance such as wind disturbances and modeling errors, and the disturbance is compensated for feed-forward. The nominal error models of pitch and yaw channels are linearized by the differential geometric linearization theory, and then linear quadratic regulator (LQR) controllers are designed for the linearized models. The simulation results show that in the presence of wind disturbances and modeling errors, the optimal guidance law proposed in this paper can stabilize the original nonlinear system and ensure energy optimization.

Experimental investigation on turbulence effects on unsteady aerodynamics performances of two horizontally placed small-size UAV rotors

Wind turbulent disturbance is one of the critical challenges to flying unmanned aerial vehicles (UAVs); especially when the size, weight, and power on board such aircraft are limited. Therefore, to shed light on such turbulent wind effects on UAVs' aerodynamic performances, wind tunnel experiments were conducted on the single- and multi-rotor configurations by varying the turbulence intensity up to 15%, while setting the wind velocity at 5 m/s. The turbulent disturbances were generated inside the wind tunnel using two different passive grids. One is with 29% blockage, and the other is 49%. As the single-rotor experimental tests were conducted, the onset turbulence was found to give rise to a significant change in thrust and the power coefficient in the presence of a lower revolution per minute (rpm). However, at higher rpm, only the wind effect is observed to be the dominant contributor to the aerodynamic performance. Additionally, three different rotor spacings are experimentally examined to measure the propeller wake interactions at the same velocity and different onset turbulence intensities. It was experimentally found that a significant wake interaction occurs between 0.5 D (diameter) and 1.25 D below the propellers, depending on the rotor spacing and the flow conditions. The present work opens up an experimental approach to examine the unsteady aerodynamic performance of multi-rotor UAVs in the presence of wind disturbances, i.e. at different turbulence intensities.

ℒ1 Adaptive Path-Following of Airships in Wind

This paper proposes an adaptive, three-dimensional (3D) path-following controller for airships in the presence of wind disturbances, which explicitly considers that wind speed is time-varying. The main idea is to formulate airship path-following as control design for systems in the presence of parametric uncertainties and external disturbances. Assuming that there is no prior information on wind, the proposed solution is based on the [Formula: see text] adaptive controller. This approach makes clear statements for performance specifications of the controller and relaxes the common assumption that wind speed is constant. This makes the design more realistic and the analysis more rigorous, because in practice, the wind speed may be time-varying. The results of the simulation indicate that the path following system has a good performance and is robust against wind disturbances.

Precision Post-Stall Landing Using NMPC With Learned Aerodynamics

In this paper, we present an approach for achieving precision post-stall landings with medium-sized Group 1 Unmanned Aerial Systems (UAS). To do this, we employ an aggressive dive-and-stall maneuver to significantly reduce maneuver distance, time, and touchdown speed. Our approach relies on a nonlinear model predictive control (NMPC) algorithm and learned aerodynamic coefficients to achieve accuracy and reliability in the presence of wind disturbances. We demonstrate our approach in hardware with a 60-inch wingspan, 4.2 kg fixed-wing UAS, and show the ability to land with low speed and high accuracy using minimal throttle.

Distributed Motion Planning for Multiple Quadrotors in Presence of Wind Gusts

This work demonstrates distributed motion planning for multi-rotor unmanned aerial vehicle in a windy outdoor environment. The motion planning is modeled as a receding horizon mixed integer nonlinear programming (RH-MINLP) problem. Each quadrotor solves an RH-MINLP to generate its time-optimal speed profile along a minimum snap spline path while satisfying constraints on kinematics, dynamics, communication connectivity, and collision avoidance. The presence of wind disturbances causes the motion planner to continuously regenerate new motion plans, thereby significantly increasing the computational time and possibly leading to safety violations. Control Barrier Functions (CBFs) are used for assist in collision avoidance in the face of wind disturbances while alleviating the need to recalculate the motion plans continually. The RH-MINLPs are solved using a novel combination of heuristic and optimal methods, namely Simulated Annealing and interior-point methods, respectively, to handle discrete variables and nonlinearities in real-time feasibly. The framework is validated in simulations featuring up to 50 quadrotors and Hardware-in-the-loop (HWIL) experiments, followed by outdoor field tests featuring up to 6 DJI M100 quadrotors. Results demonstrate (1) fast online motion planning for outdoor communication-centric multi-quadrotor operations and (2) the utility of CBFs in providing effective motion plans.

A differential game control problem with state constraints

<p style='text-indent:20px;'>We study the Hamilton-Jacobi (HJ) approach for a two-person zero-sum differential game with state constraints and where controls of the two players are coupled within the dynamics, the state constraints and the cost functions. It is known for such problems that the value function may be discontinuous and its characterization by means of an HJ equation requires some controllability assumptions involving the dynamics and the set of state constraints. In this work, we characterize this value function through an auxiliary differential game free of state constraints. Furthermore, we establish a link between the optimal strategies of the constrained problem and those of the auxiliary problem and we present a general approach allowing to construct approximated optimal feedbacks to the constrained differential game for both players. Finally, an aircraft landing problem in the presence of wind disturbances is given as an illustrative numerical example.</p>

Loitering Formation of Fixed-Wing UAV Swarm under Communication Delay and Switching Topology

In this paper, we design a cooperative loitering formation guidance algorithm for the path-following formation of multiple fixed-wing UAVs. We are interested in the case of communication delays and switching topology. Our proposal has two main parts: path-following (lateral guidance) and path formation (longitudinal guidance). In particular, using a vector field approach, the former guarantees that the lateral distance between a fixed-wing UAV and its desired path converges in presence of wind disturbance. In the meantime, the latter proposes a cooperative path-following framework. We prove the convergence of the proposed method in uniform communication delays and switching topology. In addition, we give an upper bound of delays, which depends on the communication graph and a gain of a formation controller. Finally, we develop a robust hardware-in-the-loop (HIL) platform flight test to verify the feasibility of our proposed approach.

$\mathcal {L}{}_{1}$ Adaptive Path-Following of Small Fixed-Wing Unmanned Aerial Vehicles in Wind

This article proposes an adaptive path-following controller of small fixed-wing unmanned aerial vehicles (UAVs) in the presence of wind disturbances, which explicitly considers that wind speed is time-varying. The main idea was to formulate UAVs path-following as control design for systems with parametric uncertainties and external disturbances. Assuming that there is no prior information on wind, the proposed solution is based on the $\mathcal {L}{}_{1}$ adaptive control, using linearized model dynamics. This approach makes clear statements for performance specifications of the controller and relaxes the common constant wind velocity assumption. This makes the design more realistic and the analysis more rigorous, because in practice wind is usually time varying (windshear, turbulence, and gusting). The path-following controller was demonstrated in flight under wind speed up to $10 \text{ m/s}$, representing 50% of the nominal UAV airspeed.

Hierarchical robust control for variable‐pitch wind turbine with actuator faults

AbstractIn this brief, we develop a fault tolerant control (FTC) using a hierarchical‐robust methodology with guaranteed stability for a wind turbine (WT), which is subject to an exogenous input and an actuator fault. The high‐level control is designed to robustly compensate for the nonlinearities, uncertainty, and disturbance in the system. The low‐level control is designed to robustly automatically allocate control authority among redundant actuators mitigating an actuator fault. At the low‐level, the robust control problem is transformed into an equivalent optimal control problem. Finally, the developed FTC is validated using a comprehensive simulation study on a 5 MW variable‐pitch WT model given in the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) simulator provided by the U.S. National Renewable Energy Laboratory (NREL). The results show that the developed FTC retains robust performance in the presence of wind disturbance and a time‐varying actuator fault.

RETRACTED: Fractional order adaptive robust formation control of multiple quad-rotor UAVs with parametric uncertainties and wind disturbances

In recent times, multiple Unmanned Aerial Vehicles (UAVs) are being widely utilized in several areas of applications such as agriculture, surveillance, disaster management, search and rescue operations. Degree of robustness of applied control schemes determines how accurate a swarm of UAVs accomplish group tasks. Formation and trajectory tracking controllers are required for the swarm of multiple UAVs. Factors like external environmental effects, parametric uncertainties and wind gusts make the controller design process as a challenging task. This article proposes fractional order formation and trajectory tacking controllers for multiple quad-rotors using Super Twisting Sliding Mode Control (STSMC) technique. To compensate the effects of the disturbances due to parametric uncertainties and wind gusts, Lyapunov function based adaptive controllers are formulated. Moreover, Lyapunov theorem is used to guarantee the stability of the proposed controllers. Three types of controllers, namely fixed gain STSMC and fractional order Adaptive Super Twisting Sliding Mode Control (ASTSMC) methods are tested for the swarm of UAVs by performing the numerical simulations in MATLAB/Simulink environment. From the presented results, it is verified that in presence of wind disturbances and parametric uncertainties, the proposed fractional order ASTSMC technique showed improved robustness as compared to the fixed gain STSMC and integer order ASTSMC.

Three-dimensional guidance and control for ground moving target tracking by a quadrotor

Abstract This paper develops a three-dimensional guidance and control algorithm to ensure that a manoeuverable target is preserved by a quadrotor in a long-term tracking scenario. The proposed guidance approach determines the desired altitude of the quadrotor to adjust the field of view (FOV) to the union of two desired trusted and critical regions. The dimensions of the desired trusted region depend on the controller performance that is evaluated by the distance of the target from the center of the FOV. The critical region is a predefined margin around the trusted region that is defined by the operator based on the upper bounds of the quadrotor and target localisation errors. It also depends on the duration and magnitude of the temporal increase in the target velocity compared to the quadrotor velocity. A sufficient condition is provided for the minimum desired altitude of the quadrotor to ensure that the target is maintained in the FOV. Furthermore, a model predictive control (MPC) is employed to preserve the target at the center of the aerial image and the desired altitude determined by the guidance law. Also, the integrals of the position errors are used to achieve null steady-state errors in the presence of wind disturbances. The simulation results show the effectiveness of the proposed approach in preserving the manoeuverable target in the FOV in the presence of the wind, the uncertainty of the target and quadrotor localisation, accelerations estimation errors, and terrain altitude variation.

Disturbance-Rejection-Based Optimized Robust Adaptive Controllers for UAVs

Most applications for small unmanned aerial vehicles (sUAVs) have a critical need for appropriate position and attitude control in environments with extreme external dynamic disturbances such as wind gusts. Moreover, to maximize flight time, UAVs have to operate within strict constraints on payload and under computational efficiency. This article presents an optimized robust adaptive controller for a UAV in the presence of realistic wind gusts that are flying in an urban environment at an altitude lower than 400 ft. The position controller is based on two degree-of-freedom proportional-integral-derivative controller tuned with particle swarm optimization, while the attitude controll is based on a robust adaptive integral backstepping controller. By assuming the knowledge of the predetermined limits of the external and unstructured disruptions (for example, wind gusts) at low altitude, a guaranteed quality of transient and steady-state tracking performance were attained. The aerodynamics, wind gust model, and control modules are integrated into a six-degree-of-freedom UAV with a fully nonlinear robust adaptive controller. Optimal power is obtained for UAVs using the radial inflow model in the presence of wind gusts that are compared with the simplified model. Two case studies were performed systematically for two representative flight paths, namely, up-cruise-down and circular paths. The simulation results demonstrate the robustness and adaptive property of controllers against wind gusts. These results are useful for a variety of UAV applications, e.g. accurate trajectory tracking and autonomous waypoint navigation without loss of performance in the presence of wind disturbances under computational efficacy.

Adaptive neural network-based robust <i>H</i><SUB align="right">∞ tracking control of a quadrotor UAV under wind disturbances

The paper deals with the stabilisation and trajectory tracking control of an autonomous quadrotor helicopter system in the presence of wind disturbances. The proposed adaptive tracking controller uses radial basis function neural networks (RBF NNs) to approximate unknown nonlinear functions in the system. Two controllers are proposed in this paper to handle the modelling errors and external disturbances: H∞ adaptive neural controller H∞-ANC and H∞-based adaptive neural sliding mode controller H∞-ANSMC. The design approach combines the robustness of sliding mode control (SMC) with the ability of H∞ to deal with parameter uncertainties and bounded disturbances. Furthermore, the RBF models are derived using Lyapunov stability analysis. The simulation results show that H∞-ANSMC is able to eliminate the chattering phenomenon, reject perturbation mismatch and leads to a better performance than H∞-ANC. A comparative simulation study between the proposed controllers is presented and the results are discussed.

Tracking aircraft trajectories in the presence of wind disturbances

<p style='text-indent:20px;'>A method of path following, utilized in the theory of position differential games as a tool for establishing theoretical results, is adopted in this paper for tracking aircraft trajectories under windshear conditions. It is interesting to note that reference trajectories, obtained as solutions of optimal control problems with zero wind, can very often be tracked in the presence of rather severe wind disturbances. This is shown in the present paper for rather realistic and highly nonlinear models of aircraft dynamics.</p>

Adaptive neural network-based robust <i>H</i><SUB align="right">∞ tracking control of a quadrotor UAV under wind disturbances

The paper deals with the stabilisation and trajectory tracking control of an autonomous quadrotor helicopter system in the presence of wind disturbances. The proposed adaptive tracking controller uses radial basis function neural networks (RBF NNs) to approximate unknown nonlinear functions in the system. Two controllers are proposed in this paper to handle the modelling errors and external disturbances: H∞ adaptive neural controller H∞-ANC and H∞-based adaptive neural sliding mode controller H∞-ANSMC. The design approach combines the robustness of sliding mode control (SMC) with the ability of H∞ to deal with parameter uncertainties and bounded disturbances. Furthermore, the RBF models are derived using Lyapunov stability analysis. The simulation results show that H∞-ANSMC is able to eliminate the chattering phenomenon, reject perturbation mismatch and leads to a better performance than H∞-ANC. A comparative simulation study between the proposed controllers is presented and the results are discussed.

Formation of a director index to assist the pilot in conducting airborne geophysical survey

Airborne geophysical survey of the territory is performed by flying an aircraft along the trajectories covering the studied area of the surface. Naturally, the quality of manual piloting is subject to increased requirements. At the same time, a flight with terrain tracking and in the presence of wind disturbances is a difficult task for the pilot. The paper suggests informing the pilot about deviation from the specified trajectory and indicating in the field of view the director index for thrust control. The task of the pilot is to bring the index to zero by manipulating the power lever and thereby zeroing the piloting error. The solution of the task is achieved by using an original energy approach. The mathematical formulation of the approach is the energy balance equation. A variant of the structure of the energy control system and a prototype of a navigation indicator with a director index is proposed. The results of flights along the route using the director index are presented in the form of graphs and numerical estimates.

Multiple observers based anti-disturbance control for a quadrotor UAV against payload and wind disturbances

This paper presents a multiple observers based anti-disturbance control (MOBADC) scheme against multiple disturbances for a quadrotor unmanned aerial vehicle (UAV). The quadrotor UAV dynamics can be represented by the Newton’s second law and Lagrange–Euler formalism. The proposed control scheme consists of disturbance observer (DO) based controller and extended state observer (ESO) based controller, which are utilized in the position loop to mainly eliminate the cable suspended payload disturbance with partially known information and mitigate the wind disturbance with bounded variation. What is more, in order to reject the model uncertainty and disturbance moment, another ESO based controller is designed for the attitude loop. Using the proposed control scheme, the anti-disturbance performance can be significantly enhanced. Experimental results in the presence of wind disturbance, payload oscillating disturbance, and hybrid disturbances illustrate the robustness and effectiveness of the proposed method compared to the classical PID method.