This article investigates consensus problems of multiple-input-multiple-output (MIMO) linear multiagent systems (MASs) with directed topology under event-triggered (ET) sampling. First, an observer based on relative outputs is designed to estimate relative full states by utilizing an unknown input observer technique. Second, a controller with static coupling strength and a dynamic ET mechanism (DETM) is proposed. And by developing a Lyapunov function, we show that asymptotical consensus is achieved if the coupling strength is larger than a positive threshold. The threshold, however, depends on some global parameters which are difficult to acquire. Later, an adaptive controller with dynamic coupling strengths as well as a DETM is proposed. And we show that asymptotical consensus is achieved in a fully distributed fashion. Moreover, we show Zeno behavior is avoided. Finally, two examples are given to validate theoretical results.

We study the asymptotical consensus problem for multi-agent systems (MASs) consisting of a high-dimensional leader and multiple followers with unknown nonlinear dynamics under directed switching topology by using a neural network (NN) adaptive control approach. First, we design an observer for each follower to reconstruct the states of the leader. Second, by using the idea of discontinuous control, we design a discontinuous consensus controller together with an NN adaptive law. Finally, by using the average dwell time (ADT) method and the Barbǎlat's lemma, we show that asymptotical neuroadaptive consensus can be achieved in the considered MAS if the ADT is larger than a positive threshold. Moreover, we study the asymptotical neuroadaptive consensus problem for MASs with intermittent topology. Finally, we perform two simulation examples to validate the obtained theoretical results. In contrast to the existing works, the asymptotical neuroadaptive consensus problem for MASs is firstly solved under directed switching topology.

It is challenging and critical to achieve zero error consensus tracking in multiagent systems (MASs) with nonautonomous leaders (i.e., leaders with nonzero inputs). The traditional approach is to use discontinuous controllers which may cause a chattering phenomenon. How to achieve zero error consensus tracking via a chattering-free controller is still open. We propose a class of adaptive continuous controllers to achieve zero error consensus tracking for Lipschitz nonlinear MASs with a nonautonomous leader and directed communication topology. Unlike existing works that use discontinuous functions to eliminate the impacts of leaders’ inputs, we use a continuous function by introducing an exponential decay function into the denominator. First, we design a continuous controller with fixed coupling strengths and prove that zero error consensus tracking can be achieved if the coupling strengths are greater than some positive constants. Second, we design a continuous controller with dynamic coupling strengths under which fully distributed zero error consensus tracking can be achieved. Moreover, the case with undirected communication topology is studied. Finally, three examples are given to verify the theoretical results. Specifically, convergence results between the continuous controller here and that is developed via the boundary layer technique are compared. Compared with existing works, the designed adaptive continuous controllers here can not only achieve zero error consensus tracking but also is chattering free.

We aim to address the consensus tracking problem for multiple-input-multiple-output (MIMO) linear networked systems under directed switching topologies, where the leader is subject to some nonzero but norm bounded inputs. First, based on the relative outputs, a full-order unknown input observer (UIO) is designed for each agent to track the full states' error among neighboring agents. With the aid of such an observer, a discontinuous feedback protocol is subtly designed. And it is proven that consensus tracking can be achieved in the closed-loop networked system if the average dwell time (ADT) for switching among different interaction graph candidates is larger than a given positive threshold. By using the boundary layer technique, a continuous feedback protocol is skillfully designed and employed. It is shown that the consensus error converges into a bounded set under the designed continuous protocol. Second, as part of the full states' error can be constructed via the agents' outputs, a reduced-order UIO is thus designed based on which discontinuous and continuous feedback protocols are, respectively, proposed. By using the stability theory of the switched systems, it is proven that the consensus error converges asymptotically to 0 under the designed discontinuous protocol, and converges into a bounded set under the designed continuous protocol. Finally, the obtained theoretical results are validated through simulations.

One fundamental yet challenging issue in security control for resilient complex networks is to construct distributed control laws for the networks to perform various cooperative tasks in the presence of failures and attacks, where resilient indicates that the complex networks are exposed to the environment with cyber uncertainties and malicious adversaries. This is particularly important in today's critical infrastructure networks since most of them are vulnerable to attacks in the era of the Internet. Inspired by this observation, this paper focuses on synchronization control for resilient complex networks subject to cyber and physical attacks, where the states of nodes being attacked may change abruptly (i.e., the synchronization error may suffer impulsive disturbances), and some nodes as well as their corresponding connections may not work in some instances. Suppose that a smart control center is equipped in the considered network to detect the attacks in real time. Furthermore, the nodes and communication channels are assumed to be recovered through some repair work after detecting the attacks. On the theoretical side, by using the M-matrix theory, we get a few sufficient criteria to guarantee the achievement of secure synchronization against attacks on both nodes and communication links. On the algorithmic side, security control algorithm and architecture are proposed to select the coupling strength and the feedback gain matrix to realize synchronization. Finally, we perform two simulation examples to validate our theoretical results.

One typical reflection of our understanding on multiagent systems (MASs) is our ability to design the emergence mechanism responsible for their various cooperative behaviors. This paper is concerned with the cooperative robust containment control problem of multileader MASs subject to unknown nonlinear dynamics and external disturbances. Specifically, quasi-containment and asymptotic containment problems are, respectively, considered by using tools from neural network (NN) approximation theory and Lyapunov stability theory of nonsmooth systems. A new kind of containment controllers consisting of a linear local information-based feedback term, a neuro-adaptive approximation term and a nonsmooth feedback term are designed to complete the goal of quasi-containment. Under the assumption that the subgraph depicting the coupling configuration among followers is detail-balanced and each follower can be influenced by at least one leader, it is proven that the containment error vector of the closed-loop MASs will be uniformly ultimately bounded if the control parameters of the proposed containment controllers are suitably designed. By introducing a pseudo ideal weighting matrix for NN approximator embedded at each follower, a novel class of containment controllers are further designed to precisely achieve asymptotic containment in the considered MASs where the Euclidean norm of containment error vector asymptotically converges to zero. At last, numerical simulations are given to verify the validity of these derived theoretical results.

In this note, the consensus tracking problem is studied for MASs with undirected switching communication topologies under impulsive disturbances. Unlike the impulsive disturbances considered in most existing literature which are caused by sudden noise, frequency change and so forth, the disturbances under consideration are owing to malicious attacks on the agents. By constructing a topology independent multiple Lyapunov function, we shall prove that consensus tracking could be achieved by selecting appropriate coupling strength and feedback gain matrix provided that the average dwell time is greater than a positive threshold. The obtained theoretical result is finally validated by simulation.

In this note, the asymptotic consensus tracking problem is addressed for uncertain multi-agent systems (MASs) with undirected communication topologies and a high-dimensional leader, where the uncertainties may contain unmodeled dynamics and external disturbance which are prior unknown. To remove the effect of high-dimensional leader, an observer based compensation controller is firstly designed. A neural-adaptive based feedback controller is then designed. Note that the feedback term contains a discontinuous controller which is used to eliminate the effect of imprecise approximation of neural network. Furthermore, if the leader is assumed to be globally reachable, it is shown that asymptotic consensus tracking is achieved in MAS by choosing appropriate control parameters. The obtained theoretical result is finally validated by simulation.

Distributed practical node-to-node state consensus problem is studied in this paper for a class of two-layer multi-agent systems. It is supposed that there are two layers, i.e., the leaders' layer and followers' layer, in the considered multi-agent systems. Unlike most existing results on distributed consensus of multi-agent systems, the control objective in this paper is to make the states of each follower located on followers' layer track those of its corresponding leader located on leaders' layer. Furthermore, the network topologies of the leaders and the followers may be heterogeneous. Based on the assumption that the states of leaders are uniformly bounded, some sufficient criteria for node-to-node practical consensus are obtained by using differential equation theory.

This paper deals with node-to-node consensus tracking problem for multi-agent systems (MASs) with linear dynamics and directed switching topologies. The coordination goal in the present framework is to employ some distributed control laws such that each follower can track its corresponding leader. Unlike most existing works where the relative full state information of neighboring agents are utilized, it is assumed that only the relative output measurements of neighboring agents are available for coordination. To achieve node-to-node consensus in the considered MASs, a new class of observer-based protocols is proposed. By appropriately constructing a topology-dependent multiple Lyapunov function, it is theoretically shown that such a node-to-node consensus in the closed loop MASs equipped with the designed protocols can be guaranteed if each follower can directly or indirectly sense at least one leader over some uniformly bounded time intervals. Finally, a numerical simulation is performed to verify the effectiveness of the theoretical result.

To meet the requirements of railway track point cloud processing, an OpenCL-accelerated Point Feature His-togram method is proposed using heterogeneous computing to improve the low computation efficiency. Ac-cording to the characteristics of parallel computing of OpenCL, the data structure for point cloud storage is re-configured. With the kernel performance analysis by CodeXL, the data reading is improved and the load of ALU is promoted. In the test, it obtains 1.5 to 40 times speedup ratio compared with the original functions at same precision of CPU algorithm, and achieves better real-time performance and good compatibility to PCL.

This paper presents a random dynamic element matching (DEM) technique for current-steering digital-to-analog converters (DACs). It randomizes the element selection process, and keeps the number of transitions to minimum. As a result, it does not introduce extra dynamic errors caused by inter-symbol interference (ISI). This technique also alleviates the impact of linear gradient errors due to the fabrication process. A behavioral Matlab model for 12-bit segmented current-steering DAC is developed. Simulation results proves that the proposed algorithm improves the DAC linearity effectively.

This paper reports a voltage-controlled oscillator (VCO)-based single-loop continuous-time (CT) ΣΔ analog-to-digital converter (ADC) that does not need any OTA-based analog integrator. It achieves the second-order noise shaping by cascading two VCO-based integrators and removing the sampling operation in the first VCO-based integrator. Behavioral simulations confirm the validity of the proposed ADC architecture.

In this paper, a novel overlapping coil structure for dual band power and data telemetry systems is proposed. Through carefully choosing the coil structural parameters, overlapping structure can achieve both low power interference and ease of manufacturing at the same time. Two design examples are presented and analyzed. Compared with conventional structures which set coils on the same plane, the overlapping structure shows higher power interference rejection and better overall signal quality.