Time-varying Formation Control Research Articles

Time-Varying Formation Control of Multiagent Systems Across Two Networks With Mixed Interactions

Time-Varying Formation Control of Multiagent Systems Across Two Networks With Mixed Interactions

Informative Cooperative Path Planning and Time-varying Formation Control of Heterogenous Mobile Robots

Informative Cooperative Path Planning and Time-varying Formation Control of Heterogenous Mobile Robots

Average consensus time-varying formation control of underactuated autonomous underwater vehicles based on event triggering decoupling mechanism

This paper focuses on the challenge of time-varying formation control for underactuated autonomous underwater vehicles (AUVs). To tackle this challenge, an average consensus time-varying formation control based on event triggering decoupling mechanism (ETDM-ACTVF) is proposed. Firstly, the average consensus time-varying formation (ACTVF) based on the affine transformation are introduced, and the control objective considering the dynamic characteristics of underactuated AUVs is proposed. The trajectory tracking controller is designed by the back stepping method. Secondly, an event triggering decoupling mechanism (ETDM) achieves the state decoupling to constrain the uncontrollable state. Moreover, a dynamic event triggering mechanism is employed to reduce the execution frequency of actuators. Finally, the excellent performance of the proposed algorithm in addressing both the underactuated AUV time-varying formation control and decoupling control problems is demonstrated through simulation results.

Fault detection and time-varying formation control for nonlinear multi-agent systems with Markov switching topology

Fault detection and time-varying formation control for nonlinear multi-agent systems with Markov switching topology

Reinforcement learning based time-varying formation control for quadrotor unmanned aerial vehicles system with input saturation

Reinforcement learning based time-varying formation control for quadrotor unmanned aerial vehicles system with input saturation

Null-Space-Based Time-Varying Formation Control of Uncertain Nonlinear Second-Order Multiagent Systems With Collision Avoidance

In this paper, the time-varying formation control problem with collision avoidance is addressed for uncertain nonlinear second-order multi-agent systems in a null-space-based behavioral control architecture. To guarantee the tracking and coordination performance simultaneously, a novel and flexible time-varying formation task strategy is designed where only neighborhood information is necessary. Moreover, the agent radius and a sine function are introduced such that the collision avoidance task function describes collision risk more accurately in contrast to existing results. Then, two fixed-time sliding mode controllers with constant and variable exponent coefficients, respectively, are proposed to track the desired trajectory generated by null space projection. Also, the theoretical results for the task design and trajectory tracking are obtained by using the Lyapunov stability theory. Numerical simulation and practical experiments are finally conducted to illustrate the effectiveness and superiority of the proposed method.

Distributed robust adaptive formation control of multi-agent systems with heterogeneous uncertainties and directed graphs

This paper studies distributed time-varying formation control problems for a class of linear systems with heterogeneous uncertainties and directed graphs. Both the cases without and with an active leader having unknown control inputs are considered. Two new robust adaptive formation protocols are designed in a totally distributed fashion, both of which incorporate two parts: a fully distributed nominal controller relying on the neighbors’ relative state information and an adaptive compensating signal to restrain the influences of uncertainties. An original adaptive compensating strategy is proposed herein to deal with uncertainties related to not only system states but also control inputs. On the basis of adaptive mechanism, the controller design requires neither global information about communication topologies nor the upper bounds of uncertainties and the leader’s control inputs. Based on Lyapunov arguments, sufficient conditions to achieve the desired formation are derived in terms of Riccati equations. The proposed protocols guarantee that the formation errors can converge to zero. Finally, the theoretical results are demonstrated by numerical simulations.

Robust Leaderless Time-Varying Formation Control for Nonlinear Unmanned Aerial Vehicle Swarm System With Communication Delays.

This article investigates the tracking-oriented robust leaderless time-varying formation (TVF) control problem for unmanned aerial vehicle swarm systems (UAVSSs) with Lipschitz nonlinear dynamics under directed topology, where external disturbances are random and bounded, and communication delays (CDs) are bounded. In this article, a state-feedback control approach is adopted to make sure that a UAVSS forms a desired TVF and follows a specified trajectory when CDs and external disturbances occur. First, a novel PD-like formation control protocol with several unknown parameters and CDs is designed. The protocol contains the information of the local neighborhood status and its differential quantities. Second, the tracking-oriented robust leaderless TVF control problem with Lipschitz dynamics, external disturbances, and CDs is transformed into a problem about asymptotic stability of a lower dimensional closed-loop control system through a special matrix decomposition. Third, a theorem is proposed to determine the unknown parameters of the control protocol and the upper bound of CDs. In the theorem, sufficient conditions for a UAVSS to attain the anticipated TVF and trajectory tracking are obtained. A Lyapunov-Krasovskii (LK) functional is constructed to verify that the error among the practical flight state of UAVs, the anticipant TVF configuration, and tracking trajectory can asymptotically converge to 0. Finally, with the presentation of a simulation case, the effectiveness of the theoretical results is illustrated.

Event-Triggered Bipartite Time-Varying Formation Control for Multiagent Systems With Unknown Inputs.

This article addresses the issues of the bipartite time-varying formation (BTVF) control for multiagent systems (MASs) on signed digraphs. All the designs are performed under the assumptions that the leader and followers suffer from external disturbances, the control input signal of the leader is unreachable to any follower, and the state variables of the followers are unmeasurable. To begin with, an unknown input observer (UIO) is designed for each follower using a traditional interval observer to obtain the state estimates. To realize the BTVF tracking, a distributed consensus error dynamic system is constructed. Furthermore, a distributed unknown input reconstruction method is developed to estimate the multiple disturbances in the consensus error system. Then, an event-triggered BTVF control protocol is proposed which allows two antagonistic time-varying formations to be formed, while excluding Zeno behavior. A simulation of a group of wheeled robots is used to demonstrate the performance of the proposed methods.

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.

Fully distributed dynamic event-triggering formation control for multi-agent systems under DoS attacks: Theory and experiment

The fully distributed time-varying formation (TVF) control problem is investigated for multi-agent systems (MASs) subject to Denial-of-Service (DoS) attacks. An asynchronous dynamic event-triggering (DET) mechanism is introduced to alleviate agents’ communication burden suitably, and a fully distributed DET-TVF control protocol is designed. Sufficient conditions and theoretical analysis prove that this protocol can achieve the desired TVF configuration under DoS attacks, and Zeno behavior is excluded. Finally, experimental examples using six quadrotors demonstrate and fully showcase the efficacy of the proposed methods.

Distributed Robust Prescribed Performance 3-D Time-Varying Formation Control of Underactuated AUVs Under Input Saturations and Communication Delays

Distributed Robust Prescribed Performance 3-D Time-Varying Formation Control of Underactuated AUVs Under Input Saturations and Communication Delays

Security Time-Varying Formation Control for Multi-Agent Systems Under Denial-of-Service Attacks via Unknown Input Observer

The paper investigates the security time-varying formation control problem when the communication network of multi-agent systems (MASs) suffers from Denial-of-Service (DoS) attacks based on switched controller, state observers and unknown input reconstruction (UIR). To begin with, for the follower agents with unknown inputs, through an interval observer, the estimations of unknown input (UI) and system state can be obtained asymptotically and simultaneously by a Luenberger-like state observer (LLSO) combining with a UIR. After this, a distributed control protocol (DCP) on formation tracking is proposed based on the UIR and the state estimation, which can compensate the UI successfully. Moreover, the time space is divided into three parts utilizing the transmission interruption caused by DoS attacks, and the gain of the controller is designed corresponding to three different DoS attack duration, respectively. With the help of some concept in switched system, it is demonstrated that the given formation pattern can be reached under the proposed DCP. Finally, to verify the effectiveness of the proposed methods, a vehicle cruise control system used as the simulation example is given.

Fully Distributed Event-Triggered Bipartite Output Formation Control for Heterogeneous MASs With Directed Graphs

This brief considers the bipartite output time-varying formation control problem for heterogeneous multi-agent systems over signed directed graphs under an adaptive event-triggered mechanism. A fully distributed bipartite controller is designed to estimate the state of the leader and form the desired antagonistic formation shape only using the relative output information. With the help of the event-triggered mechanism, the proposed protocol prevents continuous communication among neighbor agents under the directed topology. Also, Zeno behavior is verified to be ruled out. Furthermore, the proposed protocol not only avoids using the eigenvalues of the Laplacian matrix but also does not need to continuously monitor the information of neighbor agents. Finally, the effectiveness of the designed protocol is illustrated by a numerical simulation.

Fuzzy Adaptive Fault Tolerant Time-Varying Formation Control for Nonholonomic Multirobot Systems With Range Constraints

This article studies the fault tolerant tracking problem of time-varying formation for nonholonomic multirobot systems. Uncertain nonlinear dynamics are approximated by employing fuzzy logic systems (FLSs), and based on the adaptive backstepping recursive procedure and dynamic surface technology, a fuzzy adaptive formation tracking control scheme is developed. It is notable for formation to achieve collision avoidance and connectivity maintenance, so the prescribed performance methodology is introduced to solve the constrained range problem of distance and angle. Meanwhile, in order to compensate the effect from the infinite number of uncertain actuator failures, the robots can maintain interacting with their leader at the moment of actuator faults, and also uninterruptedly track the time-varying referenced trajectory from the leader, a novel decentralized adaptive fault tolerant control (AFTC) strategy is further proposed for time-varying formation and guarantees all signals are semi-global uniformly ultimately bounded (SGUUB). Finally, the effectiveness of AFTC strategy is illustrated perfectly for nonholonomic multirobot systems.

Distributed 3-D Time-Varying Formation Control of Underactuated AUVs With Communication Delays Based on Data-Driven State Predictor

Communication delays are a crucial issue in autonomous underwater vehicle (AUV) formation control. To solve this issue, this article for the first time develops an active communication delay compensation (ACDC) mechanism with an innovatively developed data-driven state predictor (DDSP) of AUVs. The DDSP of each AUV can online estimate the current motion states of its neighbors solely depending on its received delayed motion state information of its neighbors. Incorporating the ACDC, prescribed performance control method and neural networks into the backstepping approach, this article proposes a distributed 3D time-varying formation prescribed performance control strategy, where a novel auxiliary dynamic system is created to alleviate the adverse effect of input saturations. The proposed formation control strategy ensures AUVs maintain the desired 3D time-varying formation, while achieving the asymptotic stability with respect to formation errors and satisfying the performance constraints simultaneously. Simulations are performed to validate our proposed formation control strategy.

Adaptive Fuzzy Fixed Time Time-Varying Formation Control for Heterogeneous Multiagent Systems With Full State Constraints

This article presents an adaptive fuzzy fixed time time-varying formation control (TVFC) method for uncertain heterogeneous nonlinear multi-agent systems (HNMASs) with full state constraints. Meanwhile, both partial loss of effectiveness and bias fault are considered in HNMASs. The fuzzy logic systems (FLSs) are selected as an effective tool to approximate uncertain nonlinear functions. The original constrained states of the systems will be converted to unconstrained states by the nonlinear transformed function (NTF). Compared with previous papers, it is the first time to handle the TVFC problem of HNMASs with full state constraints. In addition, formation control based on an adaptive fuzzy fixed time strategy not only ensures fast convergence of the system, but also the convergence time doesn't depend on any initial conditions. The stability of HNMAs is proven by the fixed time stability theory. Finally, a simulation is given to testify the effectiveness of the control method.

Distributed finite-time performance-prescribed time-varying formation control of autonomous surface vehicles with saturated inputs

This paper studies a time-varying formation control problem of a swarm of autonomous surface vehicles (ASVs) with prescribed constraints. Every ASV suffers from unavailable velocities, saturated inputs, internal uncertainties, and external disturbances. A distributed finite-time performance-prescribed time-varying formation control method is proposed for ASVs. Specifically, an adaptive fuzzy state observer (AFSO) is firstly proposed to recover the unavailable velocity by using saturated inputs and estimated disturbances from the fuzzy logic system. Secondly, a tunnel prescribed performance (TPP) function is designed to limit tracking errors with a concise form and smaller overshoot. At the kinematic level, with TPP-based error transformation, a C1 finite-time time-varying guidance law is proposed by using the smooth switch functions and recovered velocities. Next, a finite-time command filter based on Levant differentiator is presented to smooth the guidance signals. At the kinetic level, a C1 finite-time saturated control law is developed with the estimated velocities and disturbances. Then, it proves that tracking errors of the proposed closed-loop system converge into a small neighborhood around the equilibrium within finite time while evolving under TPP constraints regardless of saturated inputs. Finally, comparison results are provided to demonstrate the effectiveness of the proposed distributed finite-time performance-prescribed time-varying formation control method.

Fully distributed adaptive time-varying formation control of singular multiagent systems

This paper addresses the fully distributed adaptive time-varying formation protocols design problem for singular multiagent systems with directed topology. The pinning control method is introduced into the design of the adaptive distributed protocols, which can effectively adjust the formation position among agents and greatly relax the constraints of the communication topology among agents. Then, the distributed algorithm that independent of the global information of the communication graph is designed to solve the proposed fully distributed protocols. Next, the sufficient conditions of time-varying formation control are provided by the feedback pulse elimination method and stability analysis. Finally, the time-varying formation simulation results are presented to verify the feasibility of the proposed theory.

Time-varying formation control for nonlinear multi-agent systems against actuator attacks

The formation control problem with time-varying characteristics is investigated for the time-delayed nonlinear multi-agent systems against actuator attacks. A neural-network-based adaptive control method is constructed to achieve the desired control objective, which is outputs of the followers can complete the desired transformation of formation configuration. To eliminate the influence of malicious attacks on the actuators, an actuator attacks defense strategy is proposed to resist false data injection attacks occurred in the actuator. The uncertainty of the dynamics caused by nonlinear functions is resolved by the neural-network approximate method. The problem of the time delay is handled by an improved Lyapunov-Krasovskii functional approach, which can also avoid the singularity problem that may occur during the construction of the control method. Based on the Lyapunov stability theory, it is proved that all signals of closed-loop systems are semi-globally stable and the formation error can converge to a small neighborhood of the origin. Finally, the results of simulations are provided to verify the feasibility of the theoretical analysis and the effectiveness of the proposed control method.