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In this article, a distributed time‐varying optimization problem for multirobot systems with collision avoidance is studied. A hierarchical control framework is employed to simplify the complex problem into two subproblems in two layers. One is the network layer where a novel distributed time‐varying finite‐time optimal control protocol as a signal generator is proposed for each robot. The signal generator ignores the model constraint and uncertainty. The other is the real‐time layer, which mainly contains a sampling module and a robust nonlinear model predictive control (NMPC) module. The former samples the optimal signal from the signal generator as a series of sampling tracking points with proper distance to improve tracking performance, and the latter searches for the optimal control protocol for the robot system to track these sampling tracking points in sequence with the model constraint and uncertainty. Furthermore, considering the collision between each robot, a give‐way strategy is designed that the robot with a low priority has to stop to wait for the other with a high priority to move first. And a primary‐secondary judgment technology determines the priorities of robots adaptively according to the current state of the robots. If the way forward of the moving robot is blocked by the stopping one, an auxiliary point is introduced as a temporary transfer station to avoid collision further. Finally, the effectiveness of the proposed methods is verified by a simulation example. [ABSTRACT FROM AUTHOR]

Convergence speed is an important indicator to evaluate the performance of state-of-charge (SOC) estimators. To improve the convergence speed, this article proposes an adaptive radial basis function neural network-based prescribed-time observer to estimate the battery SOC. First, an adaptive RBF NN is employed to approximate the nonlinear part of the battery equivalent circuit model, and the online learning process of network weight can adapt the variations in battery parameters. Then, a prescribed-time SOC observer is developed to ensure the state and weight estimation errors converge within the convergence time $T$ , which can be prescribed by users and is irrelevant on initial values. Thus, the network weight no longer needs to update when time exceeds $T$ , and the computational burden can be effectively saved. Furthermore, a switched-gain scheme with a naturally switched time $T$ is employed to simultaneously guarantee the convergence speed and estimation accuracy. An adaptive robust term is designed to compensate the approximation error and possible variations of the network weight in the steady state. Finally, the theoretical stability is proved by the Lyapunov theory, and the practical effectiveness is evaluated by experiments and simulations. [ABSTRACT FROM AUTHOR]

In this brief, an improved event-triggered mechanism (ETM) whose inter-event times (IETs) are designable for the linear quadratic regulator is proposed to solve the lateral motion control problem of intelligent vehicle under bounded disturbances. Based on the IETs-designable event-triggered control mechanism proposed by our previous work, we further introduce two new design parameters into the clock-like variable dynamics in the event condition, so as to derive larger IETs. Distinct from existing ETMs, the above control framework features a global robust event-separation property (RESP) that is extremely required for resisting diverse disturbances, and its IETs are designable to cater to different needs, meaning that the proposed ETM can be deployed on the practical vehicle more easily and effectively. Theoretical analysis proves the stability and robustness of the proposed event-based lateral motion control strategy with the adjustability of IETs and global RESP. Finally, simulation results verify the theoretical results and illustrate the advantages of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This article deals with the fully distributed dual-terminal dynamic event-triggered bipartite output containment control of heterogeneous linear multiagent systems (HLMASs) subject to actuator faults. First, a class of fully distributed dynamic event-triggered observers is proposed over the directed signed communication network for each follower to estimate the leaders’ system matrices and (symmetric) combination states, which are merely available to a small fraction of followers. Then, based on the estimations of leaders’ system matrices, adaptive algorithms are employed to solve the regulator equations. Furthermore, the fully distributed observer-based dynamic event-triggered controllers are proposed by integrating the adaptive gains to compensate for actuator faults. Dual-terminal dynamic event-triggered mechanisms (ETMs) are addressed to exclude not only continuous control updates but also continuous communication among agents. Correspondingly, some mild criteria and the rigorous proofs are established to ensure the implementation of bipartite output containment through the Lyapunov stability theory. Moreover, the strictly positive lower bounds of intervals between two adjacent event-triggered time instants are derived, which indicates that Zeno behavior is ruled out in the dual-terminal dynamic ETMs. Finally, numerical simulations are performed to demonstrate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Cooperation control of heterogeneous multi-agent systems (MASs) with different fractional order subject to intermittent sampled-data transmission is investigated in this brief. Existing works considering MASs with multiple fractional order mainly focus on continuous input with frequency domain analysis and their results are thus based on sophisticated characteristic equations. Instead, inspired by the memory retention property of Caputo fractional derivative, heterogeneous experience-based fusion controllers are devised to handle the hereditary effect based on time domain analysis. The devised fusion controllers are composed of intermittent sampled data, which not only incorporate current available samplings but also include earlier experience of agents. In addition, the fusion controllers can successfully transform MASs with different fractional order into general discrete-time plants at sampling instants, and at the same time, ensure the asymptotical stability of sampling errors as well as controllers besides those sampling instants. Thereby, the achievement of consensus only relates to the connectivity of communication graph. Effectiveness of theoretical results is substantiated finally by numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, the adaptive secure output consensus tracking (ASOCT) problem for general linear multi-agent systems (MASs) with denial-of-service (DoS) attacks via novel dynamic event-triggered impulsive control (DETIC) protocols is considered. An observer-based distributed impulsive control scheme is proposed, where the designed control protocols and event-triggered mechanisms (ETMs) use the estimated value of the observer instead of the sampled information. The DoS attack considered in this paper appears aperiodically with an unknown attack strategy, which interrupts all communication links between agents, and further damages the controllers of agents. To handle the ASOCT under the DoS attack, some sufficient conditions for attack duration and attack frequency are derived. Moreover, the ETM considered in this paper is pull-based dynamic event-triggered mechanism (DETM), that is, the controllers of each agent merely are updated at its own triggering time while its neighbors will not be affected, as well each agent dynamically regulates its event-triggering threshold with the help of auxiliary parameters, which can effectively reduce controllers updates and allow larger triggering intervals. Furthermore, rigorous mathematical proofs are given, and some sufficient conditions are obtained to guarantee ASOCT of the linear MASs. The Zeno behavior is also proved theoretically to be precluded. Finally, the validity of the proffered control schemes is demonstrated by provided simulations. [ABSTRACT FROM AUTHOR]

The fully distributed consensus tracking of stochastic nonlinear multiagent systems (MASs) is investigated with Markovian switching topologies and intermittent control strategy, where the dynamics of agents are depicted by Itô differential equations and the leader’s information is just known for a fraction of followers. The switching mechanism of interaction topologies is modeled as a Markov process. A novel class of fully distributed control protocols is proposed via intermittent control method, which is only associated with the relative state measurements of neighbors and does not involve any global information. Meanwhile, the control gains are designed to be intermittently adaptive, which can effectively reduce energy consumption and avoid the gains being larger than those needed in practice. Several sufficient conditions and corresponding proofs are provided by using the Lyapunov stability theory. Finally, numerical simulation is presented to state the feasibility of the theoretical results. [ABSTRACT FROM AUTHOR]

This brief studies the fully distributed consensus control problem for linear multiagent systems (MASs) with a novel dynamic double-event-triggered mechanism (DDETM). The proposed DDETM can not only reduce the resource consumption of communication, but also reduce the frequency of controller update. Meanwhile, larger triggering time intervals are obtained by introducing two sets of dynamic variables in DDETM compared with the static double-event-triggered mechanism (SDETM). Then a fully distributed DDETM-based control protocol is designed, which is independent of any global information. Next, rigorous proofs are given to assure the realization of consensus control and the exclusion of Zeno behavior. Finally, an illustrative example is presented to verify the proposed protocol. [ABSTRACT FROM AUTHOR]

In this article, the containment control problem of multiagent systems (MASs) with active leaders under a directed communication graph is addressed. A novel pull-based event-triggered protocol combined with aperiodic sampled-data mechanism is first presented, where each agent merely updates controller at its own triggering instants. Under the proposed control protocols, the information is only exchanged and calculated at the aperiodic sampling instants, therefore, it can reduce communication congestion and save computing resources. Furthermore, the Zeno behavior is naturally excluded because the trigger instants are in the set of aperiodic sampled instants. By virtue of the algebraic graph theory and Lyapunov stability analysis, it is shown that the active leaders can reach their desired states predefined arbitrarily and all followers are driven to the convex hull formed by the leaders. Finally, an illustrative example is given to validate the theoretical results and emphasize the advantages of the proposed protocols. [ABSTRACT FROM AUTHOR]

This paper investigates the cluster consensus of multi-agent systems (MASs) with general linear and nonlinear dynamics via intermittent adaptive pinning control, where each cluster has a virtual leader whose state can be sensed by only a small part of followers on some disconnected time intervals because of communication constraints. The communication topology is considered to be weakly connected, that is, it is not necessary to be in-degree balanced, strongly connected or contain a directed spanning tree. To realise the cluster consensus, a class of intermittent adaptive pinning control protocols is proposed according to difference that the agents receive information source. The pinning gains are designed to be intermittent adaptive and with an exponential convergence rate, which will effectively reduce communication costs, avoid the pinning gains being larger than those needed in practice. Meanwhile, it guarantees that the pinning gains quickly converge to steady value. Correspondingly, some sufficient consensus criteria are derived to guarantee that the agents in the same cluster asymptotically can reach consensus while the agents in different clusters can reach different consensus. Rigorous proofs are given by the aid of Lyapunov stability theory and matrix theory. Finally, a numerical simulation example is presented to validate the main results. [ABSTRACT FROM AUTHOR]

This brief studies the time-varying formation (TVF) control of linear multi-agent systems (MASs), where the communication topology switches from several different topologies and the switching signal is depicted by a right-continuous Markov process. The communication noises are taken into account simultaneously, which are described as independent white noises with noisy intensities. A class of stochastic-approximation type control protocols is given and certain sufficient conditions are derived for realizing the TVF stabilization in mean square sense. Moreover, the indicative function and infinitesimal generator are imported in Lyapunov functions to help proving that the MASs can be formed into stable TVF shapes with the proposed control protocols. In the end, an simulation example is performed to state the availability of the approach. [ABSTRACT FROM AUTHOR]

This paper addresses the time-varying formation-containment (FC) problem for general linear multi-agent systems based on an observer viewpoint under the directed communication graph which contains a spanning tree. A new format of time-varying formation shapes with the properties of translation, scalability and rotation is proposed. Then the time-varying formation tracking problem where the real leader's input is unknown to all other agents is solved independently. After that, the time-varying FC problem where the challenge is how to deal with the formation-achieving agents' unknown nonzero inputs for containment-achieving agents, is firstly addressed. All the designed controllers, which need no eigenvalue information of the whole graph, are fully distributed and so can be applied to large-scale systems. The influence of communication graph structure to the control convergence rate is further analysed. The above theoretical results are verified by multiple nonholonomic vehicles in simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the event-triggered consensus of linear multiagent systems with periodic data sampling mechanisms, where random packet losses are taken into account. The random packet losses occur in communication links based on a certain probability, and it is subject to the Bernoulli distribution. A novel distributed control protocol is designed based on the combined measurement to achieve the mean square consensus. By using the Riccati inequalities and linear matrix inequalities, an event-triggered condition with fewer parameters is also designed to reduce the information updating number. The interaction among the control gain matrix, sampling interval, and packet losses probability is used to describe the consensus conditions. The maximum sampling interval is presented explicitly. It is shown that the advantages of the proposed event-triggered strategy with the data sampling mechanism can avoid the Zeno behavior of the systems and continuous monitoring of the states. The simulations are provided to verify the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper investigates the distributed fixed-time consensus-based formation tracking problems for multiple nonholonomic wheeled mobile robots under a directed interaction topology. The distributed fixed-time consensus-based controllers under the directed interaction topology are proposed for the multiple wheeled mobile robots with nonholonomic constraints, which can guarantee the group of robots converge to a predefined formation pattern with its centroid moving along the predefined reference trajectory in a fixed time. The fixed-time formation tracking can be achieved within a fixed settling time, which is independent of the initial states of the whole system. Moreover, the conditions of formation stability control are analysed by utilising graph and Lyapunov stability theories. Finally, the feasibility of the proposed distributed controllers is verified by numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper, over fixed directed communication graph, the leader‐following consensus of heterogenous fractional‐order multi‐agent systems (HFOMASs) is investigated with respect to input delays, where the fractional orders between leader and followers are heterogenous, which is more general. Firstly, a control algorithm with a fractional‐order estimator is proposed to guarantee the leader‐following consensus of the HFOMASs. Then, the identical input delays are taken into account in the above control algorithm, and the leader‐following consensus of the HFOMASs can be achieved under the derived sufficient and necessary condition. Thirdly, the diverse input delays are further considered in the HFOMASs, and a sufficient condition is put forward under the designed control algorithm. Finally, simulations are conducted to make the results be convinced. [ABSTRACT FROM AUTHOR]

In this paper, the observer-based output consensus of leader-following fractional-order heterogeneous nonlinear multi-agent systems with potentially different state dimensions and different dynamics are investigated. Considering the agents' states may be not available in practice, the distributed state observer is designed for each agent. Then corresponding distributed control protocols based a proposed virtual exosystem are proposed to convert the output consensus problem into the stabilisation problem. By employing matrix theory, algebraic graph theory and the stability theory of fractional system, the state consensus of the virtual exosystem and the output consensus of heterogenous fractional nonlinear MAS is achieved. Moreover, the sufficient conditions are also obtained. Simulation examples are presented to verify the effectiveness of the main results. [ABSTRACT FROM AUTHOR]

Summary: This article addresses the leaderless fixed‐time consensus (LLFTC) and leader‐following fixed‐time consensus (LFFTC) problems for multiagent systems (MASs) via impulsive control. First, a novel fixed‐time stability for impulsive dynamical system is developed. Then the novel fixed‐time impulsive control protocols are designed to achieve leaderless and leader‐following consensus for MASs. Based on the impulsive control theory, fixed‐time stability theory and algebraic graph theory, some sufficient conditions are derived for each agent to achieve LLFTC and LFFTC under the proposed control protocols. Finally, numerical simulations are put forward to validate the theoretical results. [ABSTRACT FROM AUTHOR]

This paper investigates the second-order nonlinear multi-agent systems subject to the cluster-delay consensus. The multi-agent systems consist of leader and agents, whose dynamics are second-order nonlinear. The objective is that the agents track the leader asymptotically with different time delays, i.e., the agents in different groups reach delay consensus, while the agents in the same group reach identical consensus. To guarantee the cluster-delay consensus for the second-order multi-agent systems, a new control protocol is proposed. Then some corresponding conditions for cluster-delay consensus are derived by using Lyapunov directed method and matrix theory. Finally, the effectiveness of the theoretical analysis results are verified by some numerical simulations. [ABSTRACT FROM AUTHOR]

This brief addresses the time-varying formation control (TVFC) problem for fractional-order multi-agent systems (MASs) with general linear dynamics under fixed and switching directed interaction topologies respectively, where the fractional-order $\alpha $ satisfies a general condition of ${\alpha \in (0,n]}$. Considering only the output information are available, the observer-based distributed control protocols are proposed to realize TVFC. By a class of linear transformations, the TVFC problem converts into the asymptotical stability problem of a new system. Sufficient conditions for fractional-order MASs are derived by employing the stability theory of fractional-order systems, matrix theory, algebraic graph theory, Laplace transformation, and Mittag–Leffler function. Finally, two numerical simulations are presented to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper addresses the distributed formation tracking control problem for multi-vehicle systems with nonholonomic constraints, by the aid of event-triggered and sampled-data control methods. Two classes of event-triggered communication and control strategies with fixed sampling period are considered. By designing different event conditions, the communications amongst neighbouring vehicles are allowed at each sampling time instant in the first strategy, whereas the control input of each vehicle is updated only when its own or neighbours' event conditions are violated. Furthermore, both communication and control update are allowed only when the events of itself or neighbours are triggered in another strategy. To this end, an unified event-triggered and distributed observer-based controller with globally asymptotic convergence rate is proposed. And corresponding sufficient conditions are derived regarding to two types of event conditions, based on Lyapunov technique, matrix analysis and algebraic graph theory. It is worth noting that the Zeno-behaviour of systems with the presented controllers and event conditions is naturally avoided for all the vehicles due to the advantageous property of sampled-data control. Finally, simulations are provided to verify the effectiveness of the obtained theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, group multiple lags consensus of fractional-order leader-following multi-agent systems with nonlinear dynamics are investigated, in which two kinds of lag consensus are considered. One is said to be outergroup lag consensus, which means that different group leaders reach lag consensus. The other one is called innergroup lag consensus, that is to say, the followers will reach lag consensus with their own group leader. Based on Mittag–Leffler stability for fractional-order systems, algebraic graph theory, a class of novel control protocols is designed and the corresponding sufficient conditions are derived to guarantee the achievement of group multiple lags consensus. Furthermore, considering parametric uncertainties, an adaptive control technology is employed to solve the group multiple lags consensus for fractional order multi-agent systems, and the corresponding adaptive control protocols and sufficient conditions are proposed. Finally, numerical simulations are given to demonstrate the effectiveness of the obtained results. [ABSTRACT FROM AUTHOR]

Leaderless consensus for the fractional-order nonlinear multi-agent systems is investigated in this paper. At the first part, a control protocol is proposed to achieve leaderless consensus for the nonlinear single-integrator multi-agent systems. At the second part, based on sliding mode estimator, a control protocol is given to solve leaderless consensus for the the nonlinear single-integrator multi-agent systems. It shows that the control protocol can improve the systems’ convergence speed. At the third part, a control protocol is designed to accomplish leaderless consensus for the nonlinear double-integrator multi-agent systems. To judge the systems’ stability in this paper, two classic continuous Lyapunov candidate functions are chosen. Finally, several worked out examples under directed interaction topology are given to prove above results. [ABSTRACT FROM AUTHOR]

Consensus for the fractional‐order double‐integrator multi‐agent systems is mainly studied in this study. First, a control law based on the sliding mode estimator is proposed to achieve consensus for the multi‐agent systems, where the linear systems and the non‐linear systems are discussed, respectively. Second, a distributed control law based on the sliding mode estimator is given to accomplish distributed consensus for the multi‐agent systems, the linear systems and the non‐linear systems are also considered, respectively. The validity of the designed control laws is proved by choosing the adaptive Lyapunov candidate functions. Finally, several examples are presented to demonstrate the obtained results and show the advantage of the proposed control laws in the convergence speed. [ABSTRACT FROM AUTHOR]

This study investigates the robust fixed‐time consensus tracking problem of second‐order multi‐agent systems under fixed topology. A novel type of non‐linear protocol and the corresponding sufficient conditions for achieving robust fixed‐time consensus tracking are proposed with the aid of sliding mode technique and Lyapunov theory. Compared to finite‐time consensus tracking, the convergence time of the tracking errors is globally bounded for any initial conditions of the agents, which is also the global information for each agent. Furthermore, the results obtained for second‐order multi‐agent systems are also extended to deal with the fixed‐time formation tracking problem for unicycle‐type robots. Extensive numerical experiments are performed to illustrate the effectiveness of the present theoretical results. [ABSTRACT FROM AUTHOR]

This article investigates the control problem for formation tracking of multiple nonholonomic robots under distributed manner which means each robot only needs local information exchange. A class of general state and input transform is introduced to convert the formation-tracking issue of multi-robot systems into the consensus-like problem with time-varying reference. The distributed observer-based protocol with nonlinear dynamics is developed for each robot to achieve the consensus tracking of the new system, which namely means a group of nonholonomic mobile robots can form the desired formation configuration with its centroid moving along the predefined reference trajectory. The finite-time stability of observer and control law is analysed rigorously by using the Lyapunov direct method, algebraic graph theory and matrix analysis. Numerical examples are finally provided to illustrate the effectiveness of the theory results proposed in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the consensus problem of fractional-order multi-agent systems with a reference state is studied under fixed directed communication graph. At the beginning, the convergence speeds of fractional-order multi-agent systems are investigated based on the Mittag-Leffler function. Then, a common consensus control law and a consensus control law based on error predictor are proposed, and it is shown that the consensus tracking can be achieved using the above control laws when a communication graph has a directed spanning tree. Finally, the convergence speeds of fractional-order systems are compared, and it is discovered that the convergence of systems is faster using the control law based on error predictor than using the common one. [ABSTRACT FROM AUTHOR]

Distributed consensus tracking for the fractional-order multi-agent systems is mainly studied in this paper. Firstly, the simple Lyapunov candidate function is discussed to judge the validity of the proposed controller. Secondly, according to the sliding mode control method, a controller is designed to achieve the consensus tracking problem when the followers are described by the fractional-order linear dynamics. Thirdly, the case when the dynamics of followers own the intrinsic nonlinear function is discussed, it proves that the designed sliding mode controller is still valid for this case under the certain conditions. For the above two parts, the systems stabilities are judged based on the result of the first part. Finally, several simulations are presented to verify the obtained results. [ABSTRACT FROM AUTHOR]