Prescribed performance distance-based formation control of Multi-Agent Systems

The current paper investigates the active disturbance rejection time-varying formation control for second-order multi-agent systems subjected to external disturbances. Firstly, a robust time-varying formation control protocol with the disturbance compensation is proposed. Then, an extended state observer is designed to estimate the disturbance compensation by the active disturbance rejection control method. Moreover, sufficient conditions for robust time-varying formation feasibility analysis and protocol design are shown, respectively. Finally, a numerical simulation is presented to verify the theoretical results.

This paper introduces a novel decentralized distance-based formation controller for multi-agent systems by imposing constraints on inter-agent distance errors. Using a Nonlinear Mapping Technique (NMT) for dealing with the distance errors constraints, the problems of connectivity maintenance and collision avoidance between neighboring agents are handled. Furthermore, the proposed control scheme increases formation robustness and prevents convergence of the formation to incorrect shapes when external effects such as disturbances exist. Using Lyapunov based analysis the results are proved for both single and double integrator agent models where the target formation is minimally and infinitesimally rigid in 2-D or 3-D space.

In this paper and its companion paper [1], a stable leader-following formation control for multi-agent systems with obstacle collision avoidance with orientation control is considered. We propose a cascaded distributed control law that uses information about the angle and distance between agents to achieve a cycle-free persistent formation. First, we provide a control scheme with collision avoidance for groups of agents with a single integrator model. We show the asymptotic stability of the formation under a gradient control law. Second, the proposed control law includes a distance-angle-based controller for shape stabilization and displacement-based formation control of certain leader agents to control the direction of the whole formation. Simulation results are presented to illustrate the proposed approach.

In this paper, we focus on a multiple objective control problem for unicycle robots. By utilizing the gradients of collision avoidance and connectivity potential fields in designing reference orientations, we derive control laws for unicycle robots and show that they can track reference trajectories with bounded errors, which can be made arbitrarily small, while avoiding inter-agent collisions and ensuring that the communication among the agents is maintained. Additionally, we present experimental results where we illustrate the effectiveness of our proposed control laws by implementing them on a testbed with mobile robots.

This paper addresses finite-time platoon formation control scheme for vessel train problem subject to modeling uncertainties and external disturbances. The line-of-sight range and angle constraints are proposed to satisfy the collision avoidance and connectivity maintenance. Barrier Lyapunov function is introduced in the kinematic design such that each vehicle follows its leader within the required distance. To compensate for the uncertain model dynamics, the adaptive scheme is incorporated into the decentralized design to estimate nonlinear functions. Furthermore, a disturbance observer is developed to handle time-varying external disturbances. All closed-loop states are guaranteed bounded by Lyapunov theory, and the errors can be regulated to the small neighborhood around zero in finite time. Finally, simulation results are presented to illustrate the effectiveness of the proposed approach with a group of marine surface vessels.

This article studies formation control for multiagent systems in the presence of denial-of-service (DoS) attacks. The challenge is to address secure formation tracking and communication bandwidth-saving issues simultaneously. To tackle this, we propose a switching-like event-triggered mechanism that reduces excessive bandwidth consumption during interactions among multiple followers under DoS attacks. The triggering condition is allowed to be switched during the intervals when attacks are activated, ensuring that triggering can normally occur throughout the overall time interval by introducing an auxiliary variable depending on the success of the latest trigger moment. Based on this approach, we construct an event-based time-varying formation control scheme. In addition, we establish sufficient conditions that reveal the relationship between exponential stability and the frequency/duration of the DoS attacks. Unlike other single-leader methods, a significant feature of the formation control scheme is its ability to achieve the desired formation tracking for multiagent systems with multiple leaders. Finally, the validity of the proposed method is demonstrated through simulation and experimental results.

This article focuses on formation control of multiagent systems composed of a team of quadrotors subject to switching topologies. The quadrotor model is underactuated and includes nonlinear dynamics, parameter uncertainties, and external disturbance. A robust control approach is proposed that consists of a position and an attitude controller, both consisting of two subsystems: the nominal controller that is designed to achieve desired tracking for the nominal system, and the disturbance estimating controller that restrains the influence of uncertainties on the real system. Theoretical foundations, detailed simulation studies, and experimental results validate the effectiveness of the proposed methodology.

The paper examines the time-varying formation control problem of multi-agent systems subject to external disturbances under switching topologies. The topologies considered are directed, and it is not required for each topology to have a globally reachable leader. Considering the unmeasurable states of agents, the present paper proposes formation control protocol that employ an observer and an event-triggered communication mechanism, along with sufficient conditions to guarantee the desired formation of the multi-agent systems. The introduced control protocol removes the requirement for agents to communicate continuously. Finally, a simulation example is furnished to substantiate the efficacy of the results.

This paper mainly studied the $H_{\infty}$ formation control of multi-agent system with external disturbances and time delays. For the second-order multi-agent system, the distributed formation control protocol is designed, and used the Lyapunov stability theory to analyze the sufficient conditions for the given system to achieve asymptotic stability by the method of linear matrix inequality, so that the multi-agent system can achieve the desired formation and speed of the agent, and also can meet the $H_{\infty}$ performance index. Finally, a simulation example is used to verify the validity of the conclusion.

This paper deals with the trajectory tracking of differential driven wheeled mobile robots (WMRs). It is widely known that parameter uncertainty and unknown external disturbances could bring adverse effects to WMRs. To achieve high-performance tracking, a control scheme is proposed in this paper, which integrates a kinematics controller and a dynamics controller. The kinematics controller is designed by the backstepping control and the dynamics controller is derived via adaptive sliding mode control. Moreover, dual radial basis function neural networks (RBFNNs) with adaptive adjust algorithms are adopted to approximate parameter alterations of system dynamics as well as external disturbances. To solve the uncertainty of wheel rolling radius, an adaptive control law is applied. In addition, a PI-type sliding mode control strategy with an exponential reaching law is designed to compensate for the approximation errors of the RBFNNs. Furthermore, the stability and global asymptotic convergence of the control system are proved by the Lyapunov stability theorem. Finally, simulations are provided to verify the effectiveness of the proposed control strategy. The results indicate that the proposed control law is effective in response to parameter uncertainty and external disturbances.

This paper proposes distance-based adaptive formation control laws for the leader-follower system. The developed controller makes all the agents maintain the formation group and move with a constant reference velocity in a plane. It is assumed that there are one leading and two following agents. The leading agent knows the reference velocity whereas the follower does not know the velocity of other agents. Thus, to move in a group, the controller for the follower estimates the reference velocity. An adaptive method is used in the estimation process. The stability and boundedness of the formation are proved by using Lyapunov stability analysis and Barbalat's lemma. Simulations results are included to illustrate the validity of the developed theories.

<strong>ABSTRACT: </strong>In this study, we develop a shape formation controller based on regular distance-based control law. As distance rigidity theory may not be successful in achieving desired shape when the control system defined under minimally rigid graph. As a matter of fact, the formation may converge to ambiguous framework when the group of mobile robots did not initialize in proper way. This is a well-known issue with distance-based formation control while there are multiple equilibrium points in the dynamics. We introduce a new controller by adding virtual constraints to the system. The performance of control system is exemplified through numerical simulations and the convergence to the desired formation for all initial conditions validated with stability analysis.

Adaptive robust fault-tolerant control for a two-slider synchronization system with a flexible beam

Design methods of adaptive H ∞ formation control of multi-agent systems composed of Euler-Lagrange systems are presented in this paper. The proposed control schemes are derived as solutions of certain H ∞ control problems, where estimation errors of tuning parameters and error terms in potential functions are regarded as external disturbances to the process. It is shown that the resulting control systems are robust to uncertain system parameters and that the desirable formations are achieved asymptotically via adaptation schemes.

In this paper, the problem of distributed rendezvous of a network of multiple unicycles with nonholonomic kinematics is investigated. In contrast to traditional artificial potential field (APF) based approaches, decentralized and bounded time-varying continuous control protocols are developed via devising a class of smooth and bounded navigation functions which is free of local minima and nicely integrates consensus requirement, connectivity maintenance and collision avoidance, simultaneously. It is shown that the proposed bounded controllers could enable the group to converge to the common position with a common orientation while preserving the network connectivity during the system evolution if the underlying network is initially connected. Finally, simulations are conducted to verify the effectiveness of the proposed control algorithms.