Formation Control Of Quadrotors Research Articles

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

Adaptive Robust Time-Varying Formation Control of Quadrotors under Switching Topologies: Theory and Experiment

This paper investigates a practical time-varying formation control method for quadrotors subjected to disturbances, uncertainties, and switching-directed topologies. A fully distributed formation control scheme is proposed using a linear-velocity independent position controller (LVIPC) and a nonsingular terminal sliding mode attitude controller (NTSMAC). A distributed observer is adopted to eliminate the measurement of linear-velocity states, and only local neighbor states are needed to realize formation flight. A time-varying nonsingular terminal sliding mode manifold is designed to suppress the reaching phase and ensure the finite-time convergence. Adaptive estimators are employed to remove the reliance on the prior knowledge of the upper bound of lumped uncertainties. It is then proven that all the closed-loop signals are bounded under the proposed method. Comparative experimental results based on a practical outdoor hardware solution are presented to confirm the effectiveness of the suggested control algorithm.

Differentiator‐based bearing‐only formation control of quadrotors

AbstractThis article addresses the leader‐follower formation control problem for a group of quadrotors using only relative bearing measurements. Most existing methods require full position or velocity information, which cis challenging to obtain in harsh environments. In contrast, the proposed control scheme is based on a hierarchical system that does not rely on relative position or velocity measurements. The bearing‐only control law is designed to stabilize the desired formation, and each quadrotor maintains predetermined bearings with its neighbors. The control design relies on a non‐singular extraction algorithm for separate design of translation and rotation control. The outer loop of the control scheme utilizes a filter‐like approach to overcome the lack of bearing rate measurements in the bearing‐only formation controller. Moreover, employing differentiators following the separation principle with properties of asymptotic high accuracy, a uniform differentiator is provided for each following quadrotor to overcome the absence of linear velocity and acceleration feedback in the inner‐loop controller. Ultimately, the efficacy of the proposed control strategy is validated through a combination of Lyapunov stability theory and extensive numerical simulations.

Distributed cooperative obstacle avoidance and formation reconfiguration for multiple quadrotors: Theory and experiment

With the increasing demand for the application of multiple quadrotors, improving their autonomous flight ability in unknown environments has become one of the research focuses in the robot field. In this paper, a distributed obstacle avoidance controller is proposed with three elaborate control terms: obstacle avoidance term, inter-robot collision avoidance term, and formation reconstruction. Firstly, an online local obstacle avoidance algorithm is designed based on the obstacle avoidance behavior of the pigeon flock and potential field theory. Then, inspired by the spring-damped system, an inter-robot collision avoidance algorithm is designed based on Hooke's law with damping. Furthermore, based on the consensus theory and local neighboring information, a distributed formation reconstruction controller is designed. Finally, the simulation and quantitative analysis are carried out in Gazebo simulation platform. For practical application, an outdoor experimental platform with six quadrotors is constructed to verify the practicability of the proposed method. The results show that the three control terms are compatible with each other to achieve obstacle avoidance and can achieve formation control for quadrotors.

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.

Dynamic surface control for formation control of quadrotors with input constraints and disturbances

In this paper, a novel formation control scheme is presented by integrating the dynamic surface control for multi-quadrotor subject with model uncertainties and external disturbances. First, according to requirements of formation control, the target trajectories of followers are obtained by the designed virtual quadrotors. Then, the formation control problem is transformed into the trajectory tracking control problem. Second, the saturation function and the auxiliary system are developed to make up for nonlinear terms arising from input saturation. A nonlinear extended state observer (ESO) is proposed to estimate and compensate for model uncertainties and external disturbances, and a dynamic surface controller based on the nonlinear ESO is constructed for the desired formation performance. In addition, the amount of communications between the quadrotors is decreased by the constructed distributed speed estimator. And the uniformly ultimately bounded is proved by using the Lyapunov method. Finally, the numerical example is used to demonstrate that the designed controller is effective.

Data-driven fault-tolerant formation control for nonlinear quadrotors under multiple simultaneous actuator faults

This paper addresses the problem of data-driven fault-tolerant formation control for quadrotors with nonlinearities, unknown system parameters, and multiple actuator faults in the vehicle dynamics. A distributed fault-tolerant formation control law is developed including a distributed observer to generate the position reference for each vehicle, a fault-tolerant position control law to track the position reference, and a fault-tolerant attitude control law to regulate the attitude. Reinforcement learning approaches are implemented to update the optimal control weights in the fault-tolerant formation control law design. Stability of the proposed fault-tolerant formation control law is proven and simulation results of quadrotors under multiple actuator faults are provided to demonstrate the effectiveness of the proposed method.

Time-varying formation control of multiple quad-rotors based on ellipsoid

Time-varying formation control problem for a group of multiple quad-rotors has been considered in this article with the help of ellipsoid. Firstly, an elliptic equation with time-varying parameters has been firstly introduced to describe the desired formation patterns for multiple quad-rotors in three-dimensional space. Then position controller and attitude controller are constructed using the method of sliding model control, respectively. Through tuning parameters of the elliptic equation, time-varying formation control of multiple quad-rotors has been realized using the controllers proposed in this article where smoothing transition between rigid formations has been guaranteed. Simulation results for formation control of quad-rotors that perform translation, scaling, and rotating actions have illustrated effectiveness of the time-varying formation controller that proposed in this article.

Distance-Based Formation Control for Quadrotors with Collision Avoidance via Lyapunov Barrier Functions

In this paper, group formation control with collision avoidance is investigated for heterogeneous multiquadrotor vehicles. Specifically, the distance-based formation and tracking control problem are addressed in the framework of leader-follower architecture. In this scheme, the leader is assigned the task of intercepting a target whose velocity is unknown, while the follower quadrotors are arranged to set up a predefined rigid formation pattern, ensuring simultaneously interagent collision avoidance and relative localization. The adopted strategy for the control design consists in decoupling the quadrotor dynamics in a cascaded structure to handle its underactuated property. Furthermore, by imposing constraints on the orientation angles, the follower will never be overturned. Rigorous stability analysis is presented to prove the stability of the entire closed-loop system. Numerical simulation results are presented to validate the proposed control strategy.

Formation control of quadrotors via potential field and geometric techniques

Formation control of quadrotors via potential field and geometric techniques

Optimal Formation Control for Quadrotors with Collision Avoidance Based on Dynamic Constraints

This paper studied the optimal formation control of quadrotor UAV based on the dynamic model, and the collision avoidance between quadrotors is considered. By constructing the problem into a standard convex quadratic programming problem, we hope to improve the solving efficiency of the formation control problem. Firstly, the nonlinear dynamic model of quadrotor is linearized and the prediction model is established. Then, the safety zone constraints are transformed from a circular zone to a half-plane zone, making the optimization problem be a standard convex quadratic programming problem. Finally, the quadratic programming problem is solved using distributed receding horizon optimization. Numerical simulations in three-dimensional space show that this method can obtain the optimal formation trajectory with collision avoidance, and can improve the solving efficiency.

Distributed adaptive neural networks leader-following formation control for quadrotors with directed switching topologies

The leader-following formation problem is discussed for a team of quadrotors under directed switching topologies. To obtain a more general dynamic model, we describe the quadrotor system in a non-affine pure-feedback form with mismatched unknown nonlinearities. By employing an adaptive neural networks state observer to approximate the unknown nonlinear functions and to reconstruct the immeasurable inner states, we propose a novel distributed output feedback formation control protocol with the backstepping method combining with the dynamic surface control technique. From the Lyapunov stability theorem, all signals in the closed-loop formation system are proven to be cooperatively semiglobally uniformly ultimately bounded for any given bounded initial conditions. Finally, we proved that we verify the performance of the proposed formation control approach by a simulation study.

Disturbance rejection for interconnected positive systems and its application to formation control of quadrotors

This study deals with disturbance rejection of interconnected positive (IP) systems by output feedback laws that are installed as an outer loop of the IP system. Since the IP system without disturbances has a first integral, which is a linear function of the state and takes a constant value along the trajectories, this study utilises this function as an index of detecting the disturbances. Then, dynamic and static disturbance rejection output feedback laws with the first integral are proposed, respectively. Although the pole assignment problem of the IP system with the static output feedback law is not solvable in general, this study reveals that the system matrix of the closed-loop system has a structure called rank-one updated matrices. This special structure implies that the simple eigenvalue zero of the original IP system moves to a stable one by the feedback law while the other stable eigenvalues never move. This study applies these feedback laws to formation control of quadrotors based on IP systems where the dynamics of a quadrotor are linearised to be positive and stable second-order subsystems by dual quaternion techniques. Numerical examples illustrate the quadrotors achieve a designed shape of formation against the disturbances.

Quadrotor Formation Control Method Based on Graph and Consistency Theory

Abstract This paper introduces graph and group system consistency theory and puts forward a quadrotor formation control method. The quadrotor is described as a second-order integrator dynamic system, and the relative position deviation of different quadrotors is used to describe formation. According to the communication topology relationship between quadrotors, the formation is modeled by graph theory. The fusion of the pilot-follow and graph theory method is analyzed, and a second-order coherence algorithm with a pilot is presented. With this algorithm, the quadrotors can complete behaviors just as formation rally and formation mobility etc. Finally the paper verifies the availability of the proposed method through simulation tests.

Backstepping Based Formation Control of Quadrotors with the State Transformation Technique

In this paper, a backstepping-based formation control of quadrotors with the state transformation technique is proposed. First, the dynamics of a quadrotor is derived by using the Newton–Euler formulation. Next, a backstepping-based formation control for quadrotors using a state transformation technique is presented. In the position control, which is the basis of formation control, it is possible to derive the reference attitude angles employing a state transformation technique without the small angle assumption or the simplified dynamics usually used. Stability analysis based on the Lyapunov theorem shows that the proposed formation controller can provide a quadrotor formation error system that is asymptotically stabilized. Finally, we verify the performance of the proposed formation control method through comparison simulations.

Formation Control of Quadrotors Based on Interconnected Positive Systems

This paper deals with formation control of quadrotors based on interconnected positive linear systems where the notion of interconnected positive systems has been known recently in the literature. One of the applications of interconnected positive linear systems has also been known as formation control where each subsystem, for example, each position dynamics of agents must be stable and positive SISO linear system. This paper considers that each agent has dynamics of a quadrotor and investigates formation control based on interconnected positive linear systems. A linearized feedback with a reference point and a local linear feedback are employed to transform each coordinate of the reference point into a stable and positive SISO system. As a result, formation with respect to the reference points of the quadrotors can be achieved. In particular, formation with respect to the real position of the quadrotors can be achieved in a choice of the reference points. The results are illustrated by numerical examples.

A leader-following trajectory generator with application to quadrotor formation flight

This paper presents a strategy for real-time generation of formation trajectories using a leader–follower approach. A trajectory generator prescribes the motion of a group of virtual vehicles, using a Lyapunov-based nonlinear controller that stabilizes the position of the leader in the reference frame of the virtual vehicles at a predefined distance vector. This strategy differs from the standard approach of defining the desired distance vector in an inertial frame and can be used to obtain rich formation trajectories with varying curvatures between vehicles. By imposing adequate constraints on the motion of the virtual vehicles, the generation of valid formation trajectories is naturally guaranteed, bypassing the demanding task of obtaining complete path descriptions. The trajectories are generated online and provided to a trajectory tracking controller specifically designed for quadrotor vehicles. Simulation and experimental flight tests are presented to evaluate the performance of the solution proposed, applied to formation control of quadrotors.