Quadrotor Formation Research Articles

Adaptive Factor Fuzzy Controller for Keeping Multi-UAV Formation While Avoiding Dynamic Obstacles

The development of unmanned aerial vehicle (UAV) formation systems has brought significant advantages across various fields. However, formation change and obstacle avoidance control have long been fundamental challenges in formation flight research, with the majority of studies concentrating primarily on quadrotor formations. This paper introduces a novel approach, proposing a new method for designing a formation adaptive factor fuzzy controller (AFFC) and an artificial potential field (APF) method based on an enhanced repulsive potential function. These methods aim to ensure the smooth completion of fixed-wing formation flight tasks in three-dimensional (3D) dynamic environments. Compared to the traditional fuzzy controller (FC), this approach introduces a fuzzy adaptive factor and establishes fuzzy rules to address parameter-tuning uncertainties. Simultaneously, improvements to the obstacle avoidance algorithm mitigate the issue of local optimal values. Finally, multiple simulation experiments were conducted. The findings show that the suggested method outperforms the proportional–integral–derivative (PID) control and fuzzy control methods in achieving formation transformation tasks, resolving formation obstacle avoidance challenges, enabling formation reconstruction, and enhancing formation safety and robustness.

Prescribed-time fault-tolerant control for the formation of quadrotors based on fully-actuated system approaches

This paper investigates the problem of prescribed-time fault-tolerant control for the formation of quadrotors by utilising the fully-actuated system approach. Since not all quadrotors can directly access the virtual leader's state, a distributed prescribed-time observer is designed to estimate the state of a virtual leader. Leveraging this observer, a horizontal position controller that combines the fully-actuated system approach with the prescribed-time method, as well as altitude and attitude fault-tolerant controller, are proposed. In the design of control law, two distinct sets of controllers are designed: asymptotically stable controller and prescribed-time controller, each tailored to specific control objectives. The proposed distributed prescribed-time observer can ensure that the estimation error of the leader's state reaches zero within any specified time interval. Finally, the numerical simulation is conducted to demonstrate the effectiveness of the proposed fault-tolerant formation control algorithm.

Singularity Analysis of Rigid Directed Bearing Graphs for Quadrotor Formations

Singularity Analysis of Rigid Directed Bearing Graphs for Quadrotor Formations

Forced Multi-Agent Bipartite Consensus Control: Application to Quadrotor Formation Flying

Forced Multi-Agent Bipartite Consensus Control: Application to Quadrotor Formation Flying

Robust Linear-Velocity-Free Formation Tracking of Multiple Quadrotors With Unknown Disturbances

This article addresses the problem of quadrotor formation control with inaccessible linear velocity and the unknown disturbances under directed interaction topologies. Considering the unknown disturbances act in both the translational and rotational motions of each underactuated quadrotor, a hierarchical distributed disturbance rejection controller is developed for the quadrotor formation. In the outer loop, an observerbased translational controller is designed to achieve the desired formation over directed interaction topologies. To estimate the inaccessible linear velocity measurements, a uniform differentiator is designed for each quadrotor using only the position information. In the inner loop, a robust geometric attitude controller is developed based on a super-twisting algorithm (STA). The proposed controllers can reach disturbance rejections in the whole frequency domain as much as desired and achieve asymptotic formation tracking within the appointed time. The stability analysis is presented using Lyapunov stability theory on cascaded systems, and the effectiveness of the proposed control strategy is demonstrated through numerical simulations

Formation control as a classical decentralized multivariable problem: Performance, robustness, cross-coupling and perturbation rejection

Several control algorithms for vehicle-formation control have been proposed in recent years. Nonetheless, some aspects remain understudied in existing literature, such as the integration of the formation control with existing vehicle controllers, the formation cross-coupling and the distribution of single-agent perturbations across the formation. The main contribution of this article is the reformulation of the formation control problem as a decentralized control problem using classical multivariable theory. This novel reformulation enables the development of general theoretical results, which are also supported by numerical examples and extensive simulations. The following problems are studied: performance, robustness, cross-coupling and perturbation rejection. These general results are then used to analyze two issues: 1) the integration of the formation control with existing vehicle controllers and 2) the distribution of single-agent perturbations across the formation. The main concepts are first derived for a simple formation structure and later used to characterize more complex formations with ease. The results show that a naive formation control design can lead to troublesome cross-coupling issues, reducing performance, robustness and compromising the perturbation rejection capabilities of the formation. On the other hand, a better handling of the formation cross-coupling yields an improved formation behavior while maintaining the individual agent robustness and performance. Although the main objective of this article is to contribute to general formation theory (rather than presenting a vehicle-specific result), quad-rotor formations are used to illustrate the theoretical results with numerical examples.

A joint guidance and control framework for autonomous obstacle avoidance in quadrotor formations under model uncertainty

This paper presents a novel joint guidance and control framework for autonomous obstacle avoidance and swift maneuvering of quadrotor formations under model uncertainty. In this framework, the quadrotor formation uses a primary-secondary mode, where only the primary aircraft performs online planning of obstacle avoidance trajectory to form a safe flight corridor; the secondary aircraft follows the primary aircraft for safe flight through control algorithms. Firstly, based on a known and certain 3-DOF dynamics model, a successive convexification online guidance algorithm is proposed to compute a feasible and safe flight corridor through the nonconvex flight space. The planned trajectory contains velocity and attitude angle reference commands with temporal information, which can be used for the design of control algorithms for the 6-DOF dynamics mode. Subsequently, a global controller based on robust adaptive control of the RBF neural network is proposed for compensating external disturbances and model uncertainties. Finally, simulation experiments verify the effectiveness and superiority of this guidance and control framework for quadrotor formation autonomous obstacle avoidance applications under model uncertainty. This paper provides open-source ANSI-C code, which can be deployed directly to the embedded computer to carry out experimental verification. The code link is https://github.com/mazhenwei160/Uav-formation-obstacle-avoidance.git.

Data-driven time-varying formation-containment control for a heterogeneous air-ground vehicle team subject to active leaders and switching topologies

The optimal formation-containment control problem for a team of heterogeneous unmanned air-ground vehicles (UA-GVs), subject to active leaders and switching topologies, is addressed via reinforcement learning. The quadrotors are introduced to achieve predetermined time-varying formation and the ground vehicles are designed to move into the convex hull spanned by the quadrotor formation. The quadrotor dynamics is underactuated, and the UA-GV system involves nonlinear dynamics and uncertain dynamical parameters. Distributed observers are developed for each vehicle to provide the position reference under the effects of switching topologies and unpredictable maneuvers of the leaders. Optimal control laws are proposed without accurate information of the dynamical models of the UA-GVs using reinforcement learning. Simulation results of a heterogeneous UA-GV team are presented and the superiority of the proposed data-driven optimal control laws is validated.

Adaptive Predefined-Time Sliding Mode Control for QUADROTOR Formation with Obstacle and Inter-Quadrotor Avoidance

In this paper, aiming at the problem of control and obstacle avoidance in quadrotor formation when mathematical modeling is not accurate, the artificial potential field method with virtual force is used to plan the obstacle avoidance path of quadrotor formation to solve the problem that the artificial potential field method may fall into local optimal. The adaptive predefined-time sliding mode control algorithm based on RBF neural networks enables the quadrotor formation to track the planned trajectory in a predetermined time and also adaptively estimates the unknown interference in the mathematical model of the quadrotor to improve the control performance. Through theoretical derivation and simulation experiments, this study verified that the proposed algorithm can make the planned trajectory of the quadrotor formation avoid obstacles and make the error between the true trajectory and the planned trajectory converge within a predetermined time under the premise of adaptive estimation of unknown interference in the quadrotor model.

Robust adaptive control for formation-based cooperative transportation of a payload by multi quadrotors

This paper discusses the development of position control for a rigid body payload carried by a team of quadrotors in the presence of external disturbance and uncertainty in model parameters. The formation of quadrotors is controlled and maintained during payload transportation for uniform load distribution and collision avoidance. In the controller structure, an adaptive sliding mode hierarchical control with the constant plus proportional rate reaching law is designed to compensate for the uncertainties that have unknown bounds. The finite-time stability of the closed-loop system is performed using Lyapunov stability analysis and the multiple time scale principle. Finally, the simulation results are shown to confirm the performance of the proposed controller in payload trajectory tracking without knowing its mass while the formation of the quadrotors is maintained.

Adaptive prescribed time control for quadrotor formation with stochastic links failure

AbstractThe formation control for multiple quadrotors subject to maintaining the formation configuration and collision avoidance in the situation of stochastic links failure is investigated in this paper. First, the distributed formation controller is designed, the position controller is developed to manage the desired formation of position, and the attitude controller is developed to control the translation and rotation movements of the quadrotor. Then, in order to avoid the collisions between multiple quadrotors and the obstacles, a potential energy function method is introduced into the quadrotor formation control combined with the nest adaptive control. Inspired by the design of event trigger controller, a communication compensation controller is designed to ensure the stability of quadrotor formation under the condition of random communication interruption and recovery. Moreover, a prescribed time function is designed, which means the convergence time of the formation system can be set in advance. The prescribed time stability of the formation control system is proved by Lyapunov theory. Finally, the simulation results verify the effectiveness and superiority of this method.

Trajectory tracking and formation of quadrotors using a backstepping control and coupling with intermediary system

In this work, a trajectory-tracking scheme is proposed by using a backstepping control with a dynamic coupling used as an intermediary system of quadcopters in a master-salve configuration. The desired trajectories for the master quadcopter are conventional, concentric and chaotic trajectories. By means of a proper mathematical analysis and extensive numerical simulations, we show the correct performance of proposed scheme presented.

Target Enclosing and Coverage Control for Quadrotors with Constraints and Time-Varying Delays: A Neural Adaptive Fault-Tolerant Formation Control Approach.

This paper investigates the problem of formation fault-tolerant control of multiple quadrotors (QRs) for a mobile sensing oriented application. The QRs subject to faults, input saturation and time-varying delays can be controlled to perform a target-enclosing and covering task while guaranteeing the state constraints will not be exceeded. A distributed formation control scheme is proposed, using a radial basis function neural network (RBFNN)-based time-delay position controller and an adaptive fault-tolerant attitude controller. The Lyapunov–Krasovskii approach is used to analyze the time-varying delay. Barrier Lyapunov function is deployed to handle the prescribed constraints, and an auxiliary system combined with a command filter is designed to resolve the saturation problem. An RBFNN and adaptive estimators are deployed to provide estimates of disturbances, fault signals and uncertainties. It is proven that all the closed-loop signals are bounded under the proposed protocol, while the prescribed constraints will not be violated, which enhances the flight safety and QR formation’s applicability. Comparative simulations based on application scenarios further verify the effectiveness of the proposed method.

Design of multi-constraint robust formation controller based on error model

UAVs formation is a complex nonlinear system. Although quadrotor has many advantages, its dynamics model is nonlinear, coupled, and under driven. For model-based controller design, physical constraints, model uncertainties and external disturbances significantly deteriorate control performance. Therefore, a multi-constraints MPC strategy based on error model is proposed for the quadrotor formation. Firstly, a 3D model for quadrotor is established by using the Lagrange-Euler formulation, in which the model is divided into RS and TS. The corresponding multi-constraint MPC is designed for the two subsystems respectively. The tracking errors caused by external disturbances can be eliminated because of the integrator embedded in the augmented model. Comparing with RMPC, by making reasonable modifications to the cost function, the asymptotic stability of the open loop and the closed-loop subsystem can be ensured by MMPC. Moreover, the stability analysis of the above-mentioned algorithm is carried out. The simulation results show that the controller of the formation can not only achieve good path tracking, but also robustness to the multiple constraints and disturbances.

Distributed finite‐time formation of networked nonlinear systems via dynamic gain control

AbstractThis paper considers a finite‐time formation control problem of networked nonlinear systems with uncertain dynamics. A distributed control approach is developed based on the consensus theory and the finite‐time Lyapunov theorem along with the technique of dynamic gain control. Auxiliary dynamics are constructed to facilitate the design of finite‐time Lyapunov. It is shown that followers can form the desired geometric pattern within finite time and track a featured trajectory given by the leader via the proposed controller, and the potential controller singularity problem resulted from the introduction of the auxiliary dynamics can be circumvented. One of the key features of the proposed control approach is that fractional powers of system states, which are required in most existing finite‐time control approaches, are removed. Finally, the effectiveness of the proposed control approach is verified with a simulation example on quadrotor formation.

Effective Formation Tracking of Quadrotors with Intelligent Disturbance Observer-Based Control

This study addresses the design and analysis of distributed formation tracking control with disturbance rejection capability for a group of quadrotors that are perturbed by time-varying external disturbances. The proposed approach consists of two control loops: inner-loop and outer-loop control. In the inner-loop control, feedback linearization (FL) of the quadrotor system in the presence of disturbance yields linear equations with unknown disturbance parts. The unknown disturbance parts are estimated in the outer-loop control by using a disturbance observer (DO). Since the DO produces an estimation error or called residual error when estimating time-varying disturbance, this study introduces a radial basis function neural network (RBFNN) with adaptive weight to effectively approximate and eliminate the residual error. Then, to complete the formation mission, a consensus-based algorithm is implemented in the outer-loop control to enable the distributed formation tracking. The capabilities of formation tracking and online approximating are proved via the Lyapunov approach. Simulation of the quadrotor formation in the presence of time-varying wind disturbance was conducted to evaluate the effectiveness of the approach where the results obtained illustrate the robustness of the quadrotor formation towards the disturbances.

Data Driven Model-Free Adaptive Control Method for Quadrotor Formation Trajectory Tracking Based on RISE and ISMC Algorithm.

In order to solve the problems of complex dynamic modeling and parameters identification of quadrotor formation cooperative trajectory tracking control, this paper proposes a data-driven model-free adaptive control method for quadrotor formation based on robust integral of the signum of the error (RISE) and improved sliding mode control (ISMC). The leader-follower strategy is adopted, and the leader realizes trajectory tracking control. A novel asymptotic tracking data-driven controller of quadrotor is used to control the system using the RISE method. It is divided into two parts: The inner loop is for attitude control and the outer loop for position control. Both use the RISE method in the loop to eliminate interference and this method only uses the input and output data of the unmanned aerial vehicle(UAV) system and does not rely on any dynamics and kinematics model of the UAV. The followers realize formation cooperative control, introducing adaptive update law and saturation function to improve sliding mode control (SMC), and it eliminates the general SMC algorithm controller design dependence on the mathematical model of the UAV and has the chattering problem. Then, the stability of the system is proved by the Lyapunov method, and the effectiveness of the algorithm and the feasibility of the scheme are verified by numerical simulation. The experimental results show that the designed data-driven model-free adaptive control method for the quadrotor formation is effective and can effectively realize the coordinated formation trajectory tracking control of the quadrotor. At the same time, the design of the controller does not depend on the UAV kinematics and dynamics model, and it has high control accuracy, stability, and robustness.

Adaptive Super-Twisting Distributed Formation Control of Multi-Quadrotor Under External Disturbance

In this paper, the adaptive super-twisting distributed formation control of multi-quadrotor in the presence of external disturbances and uncertainties is studied. First, the quadrotor formation system is separated into a position subsystem and an attitude subsystem which are represented by unit-quaternions. And then a composite adaptive super-twisting control method is proposed for the position subsystem and attitude subsystem respectively. For the position subsystem, an adaptive multivariable super-twisting controller is designed such that the positions of formation converge to the desired formation configuration and generate the desired attitude. And the adaptive fast super-twisting controller is designed for the attitude subsystem to track the desired attitude in finite time. Based on Lyapunov-based stability analysis, finite time convergence stability of the whole closed-loop system is proved. Finally, a numerical simulation result is provided to illustrate the effectiveness of the proposed formation control scheme.

Adaptive Fixed Time Nonsingular Terminal Sliding-Mode Control for Quadrotor Formation With Obstacle and Inter-Quadrotor Avoidance

In this paper, a robust and safety distributed formation control with unknown external disturbances is researched. For a multi-quadrotors system, a novel nonsingular terminal sliding mode control strategy is studied to realize the formation control with collision avoidance and inter-quadrotor avoidance. The formation controller is redesigned once the system reaches the small field of sliding surface to solve the existence of singular of quadrotor formation and realize the fixed time convergence of singularity region. Then, the position controller and attitude controller are designed to maintain formation configuration with collision avoidance and track the desired angular rate with disturbances, respectively. The global fixed time convergence of quadrotor formation is verified by Lyapunov theory with the fixed time convergence characteristic of singularity region and nonsingular region. At last, simulation results are presented to demonstrate the efficiency of the developed algorithm.

Quaternion-based nonlinear attitude control of quadrotor formations carrying a slung load

Control of a pair of quadrotors carrying a slung load is addressed. A hierarchical control algorithm is implemented on the leader quadrotor. The control system features a linear quadratic tracking controller on its outer loop for velocity command tracking and generates the thrust vector commands for the inner loop. The inner loop uses the to-go quaternion calculated from the thrust vector commands to control the attitude. The second quadrotor, designated as the follower quadrotor, has another hierarchical control structure on it. This control system features a Lyapunov function based nonlinear controller for formation guidance and thrust vector command generation in the outer loop. In the inner loop, the same nonlinear attitude controller is used. The dynamics of the two quadrotor slung load system is modelled and two simulation codes are developed utilizing first rigid, and then flexible load carrying rods. Simulation results are presented to show the efficacy of the control algorithm to keep the two quadrotors flying in a fixed geometrical formation in spite of the unmodelled disturbance dynamics of both the rigid bars, flexible bars and the load.