Search

With the advent of Industry 4.0 and the popularization of smart terminal equipment, the interaction between industrial field information systems and production equipment has intensified. To meet the real-time transmission of time-triggered flow and the coordinated transmission of best effort flow, time-sensitive network-related technologies are used to implement flow queue forwarding by strictly following the gate control list. First, response-time analysis method is proposed to predict the upper bound of delay under a scheduling model following IEEE 802.1Qbv. Second, according to response-time analysis, a deadline monotonic scheduling algorithm with temporary priority expansion is proposed to divide the priority into more levels, which is not limited by the queue type, so as to ameliorate the transmission sequence of switch export flow. Finally, an adaptive priority adjustment scheduling algorithm with temporary priority expansion is designed to construct the optimal scheduling method further improving the scheduling success rate and reducing worst-case end-to-end delays. Compared with similar algorithms, the algorithm proposed improves the scheduling success rate by at least 30%, reduces the total delay by at least 21% and the TT flow delay by 11% in high network utilization conditions. [ABSTRACT FROM AUTHOR]

In this article, the scheduling problem over a delayed network is investigated. Different from the existing literature, we propose a hybrid stochastic model which incorporates both delay and packet loss. Based on this proposed model, an energy-efficient co-design problem is considered under power-limited scenarios. A global optimal offline solution is presented explicitly. Aided by arriving information feedback, we propose an online schedule based on an absolute threshold. The optimality of our proposed schemes and thresholds selection is theoretically analyzed. Meanwhile, we have extended the conclusions of the single-system case to the multisystem case. Optimal strategies from both offline and online perspectives are provided with rigorous proof, respectively. The stability condition is given for the estimator to converge in an infinite-time horizon. The comparisons between offline and online strategies are proved the global superiority of the online strategy to the offline one. Numerical simulations have validated the correctness and superiority of our proposed algorithms. [ABSTRACT FROM AUTHOR]

This article considers the distributed output-feedback consensus control problem for nonlinear multiagent systems subject to input delays. Different from the existing related works, the input delay of each agent is described as an unknown time-varying function and is different from each other in this article. To deal with this problem, for each follower, we first construct a novel distributed observer based on the relative output information to asymptotically estimate the state information of the leader, then we introduce a classical observer to asymptotically estimate the state information of the follower based on its output information. By means of two observers, the leader-following consensus problem is transformed into the stability problem of the nonlinear system with unknown input delays. Subsequently, the distributed controller independent of delays is proposed for each follower by the use of the truncated prediction method under some conditions. Based on the Lyapunov stability theory, it is strictly proved that the distributed controller can render all agents achieving consensus. Finally, the effectiveness of the theoretical results is illustrated on the basis of numerical simulations on a group of single-link manipulators. [ABSTRACT FROM AUTHOR]

This article studies the finite-time observer-based leader-following consensus problem for a class of nonlinear multiagent systems with nonuniform time-varying input delays. Existing works usually assume that input delays are the same constants and the input of the leader is available for each follower. In this article, we propose a new distributed consensus algorithm to relax the conservative condition. A novel finite-time distributed observer is designed for each follower, which can accurately estimate the state information of the leader in a setting time. By means of the observer, the distributed controller is proposed for each follower, and it depends only on the state information of the follower and the estimated-state information of its neighbor agents. Based on the Lyapunov stability theory, it is strictly proved that all agents can achieve a consensus. Finally, the effectiveness of the theoretical results is verified by numerical simulation on a group of single-link manipulators. [ABSTRACT FROM AUTHOR]

This article investigates the dynamic event-triggered H∞ control problem for nonlinear networked control systems with unreliable communication channel, variable communication delays, and limited bandwidth. The nonlinear plant is represented by discrete-time polynomial fuzzy model. First, a decentralized dynamic event-triggered mechanism is proposed to determine whether the measured data are transmitted or not, and in order to exclude data collision caused by limited bandwidth, novel try-once-discard and flexible round-robin scheduling protocols are proposed to assign communication channel to certain sensor node. Then, Bernoulli distribution is employed to model the unreliable communication channel, and a new random sequence is developed to model the received data sequence under the effect of data losses and scheduling protocols. Furthermore, a discrete-time stochastic system model with both state and error delays is constructed, and sufficient conditions in the form of sum-of-squares are developed for the design of H∞ controllers such that the closed-loop system is stochastically stable and preserves guaranteed H∞ performance. Finally, two simulation examples are provided to illustrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]

The dissipative stability problem for a class of Takagi–Sugeno (T–S) fuzzy systems with variable sampling control is the focus of this paper. The controller signals are assumed to transmit with a constant delay. Our aim is to design the sampled-data controller such that the T–S fuzzy system is globally asymptotically stable with a $(\mathcal {Q},\mathcal {S},\mathcal {R})$ - $\gamma $ -dissipative performance index. The stability is analyzed by using a novel piecewise Lyapunov–Krasovskii functional (LKF) together with a looped-functional and free-matrix-based (FMB) inequality method. First, several useful linear matrix inequality (LMI) conditions are derived to verify the dissipative stability of the T–S fuzzy system and then the controller gains matrices are expressed by resorting the LMI approach with the maximal-allowable upper bound (MAUB) of sampling periods. The proposed LMI conditions can be easily solved by using the MATLAB tool box. Finally, the numerical example of a truck–trailer system is considered and analyzed by the proposed scheme to illustrate the benefit and superiority. [ABSTRACT FROM AUTHOR]

In this paper, we address the consensus tracking problem for the multiagent system (MAS) based on a nonfragile memory sampled-data controller. Considering the effect of controller gain fluctuation and communication delay, a novel sampled-data control scheme with variable sampling interval is designed for each agent. By developing some new terms, an improved piecewise Lyapunov–Krasovskii functional (LKF) is constructed to take full advantage of characteristic about real sampling pattern. Furthermore, some relaxed matrices constructed in the LKF are not necessarily positive definite. Making full use of the LKF and free-matrix-based integral inequality, some sufficient criteria are developed to ensure the consistency of the MAS. Then, by solving a group of linear matrix inequalities with the maximal sampling interval, the desired sampled-data control gain matrix is obtained. Finally, the numerical example of a 5-agent system is given to illustrate the effectiveness of the proposed approach in this paper. [ABSTRACT FROM AUTHOR]

Many marine missions demand a single remotely operated underwater vehicle (ROV) or multiple ROVs to achieve position tracking. However, the time-varying communication delay in water makes it challenging to achieve the tracking task. This paper is concerned with single-vehicle tracking and multi-vehicle tracking problems. With the consideration of time-varying communication delay, two model-free proportional-derivative (PD) tracking controllers are designed. For the proposed controllers, Lyapunov–Krasovskii functions are constructed to analyze the stability, and then sufficient conditions for asymptotic stability are presented. In particular, the relationship between controller gains and time delay is established by using linear matrix inequality (LMI), such that the allowable upper bound of time delay can be calculated. Finally, simulation and experiment results are performed to validate the effectiveness. [ABSTRACT FROM AUTHOR]

This paper investigates the leader-following consensus problem for multiagent systems (MASs) with communication delays. A novel hybrid event-triggered control scheme is developed and a hybrid system approach is proposed to design the event-triggering condition. Meanwhile, by means of temporal regularization, a strictly positive lower bound on the interevent times can be guaranteed, that is, Zeno-freeness can be guaranteed. The MASs are first described as a closed-loop system with both flow dynamics and jump dynamics, where the jump dynamics is induced from the triggering events and communication delays. Then, a hybrid model of the MASs is constructed under a hybrid systems framework. Based on this hybrid model, how to construct the Lyapunov function is given and the event-triggering condition design is also developed, such that the asymptotic consensus is achieved. Finally, an example is provided to show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper investigates the sampled-data stabilization problem for a Takagi–Sugeno (T-S) fuzzy system with time delay. By taking the information of states within the intervals from $t_{k}$ to $t$ and $t$ to $t_{k+1}$ into account, a new two-side delay-dependent looped-functional is introduced which can not only relax the monotonic constraint of Lyapunov–Krasovskii functional (LKF), but also make better use of the actual sampling pattern. Furthermore the sampled-data fuzzy controller is designed to contain both the present and delayed state information, thereby enhancing the control performance and design flexibility. Based on the novel augmented LKF and improved bounding technique, less conservative stability criteria are derived in the form of linear matrix inequalities. The superiority of proposed results is shown by two simulation examples. [ABSTRACT FROM AUTHOR]

This paper investigates the cooperative stabilization problem for a class of linear switched systems under asynchronous switching. Based on a novel class of switching signals which prevail over the traditional average dwell time scheme, a sufficient condition of global asymptotic stability is proposed for the considered system. Unlike the existing results, the provided condition permits the Lyapunov-like function to increase not only in the period of mode-identifying process but also in normal-working period with matched controller. Compensating the increment by an increased decrement, the proposed approach can guarantee the decrease of the Lyapunov-like function from a whole perspective. Moreover, the solvability condition is established as well to obtain the gains for corresponding controllers. Finally, a simulation example is provided to verify the validity of the presented method. [ABSTRACT FROM AUTHOR]

The problem of tracking control is considered for a class of non‐linear time‐delay systems in the presence of unknown dead‐zone input and tracking error satisfying the prescribed performance. The new state transformation for tracking error is firstly utilised to ensure that the tracking error is within the prescribed boundaries. At the same time, the indirect adaptive neural networks and a new inequality are used to deal with the unknown non‐linear time‐delay terms and the completely unknown dead‐zone input, respectively. Then, the authors design the controller based on the dynamic surface control technique. By constructing the Lyapunov functional, it is shown that the resulting closed‐loop system is stable in the sense of uniformly ultimate boundedness and that the tracking error converges to a small residual set with the prescribed performance. Finally, simulation examples are given and the results show the effectiveness of the proposed control design method. [ABSTRACT FROM AUTHOR]

Teleoperating cyber-physical system (TCPS) is referred to as a promising technology to extend human actions and intelligences to remote locations. Many applications of TCPS demand operator and slaves to keep a desired formation. However, the cyber- and physical-constrained characteristics on TCPS make it challenging to achieve such a formation task. This brief is concerned with a formation control problem for multislave TCPS, subject to time-varying delays in cyber channels and actuator saturation in physical channels. We design a decentralized controller to enforce the formation of master and slave robots. Sufficient conditions for stability are provided to show that the formation controller can stabilize the master-slave TCPS. In order to estimate the domain of attraction, the stability conditions are rearranged into a form of linear matrix inequalities (LMIs), and then, the required initial stability conditions for master and salves are developed. The transparent interaction between human operator and environment is also provided. Finally, simulations and experiments are performed for illustration and validation purposes. [ABSTRACT FROM AUTHOR]

This study investigates the stabilisation problem for a class of discrete‐time two‐dimensional (2D) switched systems. Here the 2D systems mean that the state evolves following two independent directions, which are usually represented as horizontal states and vertical states. The considered systems are represented by Roesser model and incorporate both stable and unstable modes. Based on a switching signal regulation approach, which restricted the switching number as well as the running time ratio between the unstable and stable modes, the exponential stability condition is established for the 2D switched systems with synchronous switching. Besides, solving the proposed stabilisation results in linear matrix inequality form, the stabilising controller gains can be obtained. Moreover, considering the time delay in the controllers when the switching occurs, the proposed results are extended to the stabilisation problem for the 2D switched systems under asynchronous switching. A numerical example further demonstrates the validity of the developed results. [ABSTRACT FROM AUTHOR]

In this correspondence paper, an exact method is developed to guarantee asymptotic stability of a bilateral teleoperation system that is subjected for a time-delayed communication. This extends the prior art of searching for the maximum upper bound of time delay. In order to improve the flexibility in controller design and obtain better performance, a fractional-order PD ^ \alpha controller is proposed. The exactly stable regions of delays are explored for both integral-order and fractional-order controllers. Compared with conditions in most previous works which are deduced by the Lyapunov–Krasovskii functional and rely on the solution of some linear matrix inequalities, the stability conditions proposed in this paper are established from the frequency domain point of view, and thus, the results are not only sufficient but also necessary. To illustrate accuracy of the conditions, they are simulated on a delayed teleoperation system composed of a pair of robots. [ABSTRACT FROM PUBLISHER]

This study studies the leader–following consensus problem for a class of multi‐agent systems with unknown non‐linear uncertainties. It is proved that the global consensus can be achieved by distributed feedback controller subject to actuator saturation for switching topologies and time‐varying delays. Sufficient conditions in terms of linear matrix inequalities are derived to ensure that all following agents could reach consensus asymptotically with a leader, which provide the allowable upper bound of communication delay. Stability analysis is mainly based on algebraic graph theory, non‐linear analysis and Barbalat's lemma. Numerical simulations are given to demonstrate the effectiveness of the main results. [ABSTRACT FROM AUTHOR]

This paper considers the resource allocation problem in an orthogonal-frequency-division-multiple-access (OFDMA)-based cognitive radio (CR) network, where the CR base station adopts a full-overlay scheme to transmit both private and open information to multiple users with average delay and power constraints. A stochastic optimization problem is formulated to develop flow control and radio resource allocation to maximize the long-term system throughput of open and private information in a CR system and ensure the stability of the primary system. The corresponding optimal condition for employing full overlay is derived in the context of concurrent transmission of open and private information. An online resource allocation scheme is designed to adapt the transmission of open and private information based on monitoring the status of the primary system, as well as the channel and queue states in the CR network. The scheme is proven to be asymptotically optimal in solving the stochastic optimization problem without knowing any statistical information. Simulations are provided to verify the analytical results and efficiency of the scheme. [ABSTRACT FROM PUBLISHER]

For many wireless sensor networks, high accuracy and low complexity localization techniques are crucial to their successful deployment. The radio interferometric positioning system (RIPS) has been introduced for accurate localization with low complexity. In this paper, a dual-tone radio interferometric positioning system (DRIPS) is proposed to localize multiple targets simultaneously. In DRIPS, multiple asynchronous targets emit dual-tone signals, and synchronous anchor receivers (nodes with known positions) extract phase information of low-frequency differential tones created by squaring the received dual-tone signals. Multiple time-of-arrivals (TOAs) coupled with unknown offsets due to the asynchronous targets are estimated based on the phase information. Accordingly, a localization algorithm taking the integer ambiguity issue into account is developed. Moreover, considering the case without accurate knowledge of the frequencies of the differential tones, an ESPRIT-type algorithm is proposed to estimate the frequencies. The proposed DRIPS is robust to flat-fading channels, immune to uncertainties of local oscillators, and able to distinguish different targets. In order to show more insights of the performance limit of the DRIPS, Cramér-Rao bounds (CRBs) are derived. Simulation results illustrate the merits of the proposed DRIPS. [ABSTRACT FROM PUBLISHER]