Synchronized Output Regulation Research Articles

Scalable exact output synchronization of discrete‐time multi‐agent systems in the presence of disturbances and measurement noise with known frequencies

AbstractThis article aims to achieve scalable exact output and regulated output synchronization for discrete‐time multi‐agent systems in presence of disturbances and measurement noise with known frequencies. Both homogeneous and heterogeneous multi‐agent systems are considered, with parts of agents' states accessible in the latter case. The key contribution of this article is to establish scalable exact synchronization results under disturbances and measurement noise, which is achieved by using distributed protocols that only use information about agent models and no information about the communication network or the number of agents. The validity of the protocol is verified by numerical simulations with arbitrarily chosen number of agents.

Scale-Free Collaborative Protocol Design for Output Synchronization of Heterogeneous Multi-Agent Systems With Nonuniform Communication Delays

In this paper, we study regulated output synchronization for continuous- or discrete-time heterogeneous multi-agent systems with linear right-invertible agents subject to unknown, nonuniform and arbitrarily large communication delays. It is assumed that all the agents are introspective, meaning that they have access to their own local measurements. A scale-free design framework utilizing localized information exchange has been adopted. The scale-free protocol design is solely based on the knowledge of the agent models such that we do not require any information about the communication networks and the number of agents.

Formula omitted] and [formula omitted] almost output and regulated output synchronization of heterogeneous multi-agent systems: A scale-free protocol design

This paper studies scale-free protocol design for H∞ and H2 almost output and regulated output synchronization of heterogeneous multi-agent systems with linear, right-invertible and introspective agents in presence of external disturbances. The proposed collaborative linear dynamic protocol designs are based on localized information exchange over the same communication network which do not require any knowledge of the directed network topology, spectrum of the associated Laplacian matrix, and the number of agents. Moreover, the proposed scale-free protocols achieve H∞ and H2 almost output and regulated output synchronization with a given arbitrary degree of accuracy for any size of the network.

H2 input load disturbance rejection controller design for synchronised output regulation of time-delayed multi-agent systems with frequency domain method

ABSTRACTAn analytical H2 input load disturbance rejection (ILDR) controller design approach is presented for the synchronised output regulation (SOR) of homogeneous time-delayed multi-agent systems. First, a closed-loop multi-input multi-output framework with transfer functions is introduced, and an SOR condition is given. Second, the decomposition method is utilised to simplify the analysis of internal stability and H2 performance index of the whole system to a set of independent optimisation problems with respect to the eigenvalues of the topology matrix. Finally, for each decomposed subsystem, the H2 optimal ILDR controller can be computed from all the stabilising controllers. By comparison with the conventional given-structured controllers, the contributions of the new approach are that the design procedure is calculated analytically for multi-agent systems with input disturbances, and a simple quantitative tuning way is developed to trade-off the nominal performance and robustness. The simulation example shows the effective ILDR capability of the proposed control strategy.

Synchronized output regulation of leader-following heterogeneous networked systems via repetitive controllers

In this paper, the synchronized output regulation (SOR) problem of leader-following heterogeneous linear networked systems aiming at tracking periodical signals is investigated. Only the output information of each agent is delivered throughout the communication network. For tracking a general periodic signal consisting many sinusoid functions, the dimension of the internal model compensator embedded in each agent will be too high to be implemented in practice. To cope with this difficulty, a distributed repetitive control method is proposed in this paper. A stability condition is developed, as well as the bound of error size. Then it is shown that the controller always exists for any given bound of tracking error. At last, the efficacy of analytic results is illustrated by simulation examples.

Optimal disturbance rejection controllers design for synchronised output regulation of time‐delayed multi‐agent systems

An optimal disturbance rejection controller design method is put forward analytically for the synchronised output regulation of time-delayed multi-agent systems (MAS). All kinds of linear MAS can be described by a novel block diagram based on transfer functions in a unified framework. For each subsystem without intercommunication, the optimal output, input and balancing output–input load disturbance rejection controllers are designed independently. A filter is used to be in series with each controller to not only stabilise the whole systems but also achieve a tradeoff between nominal performance and robustness by adjusting a single tuning parameter. The proposed distributed H 2 controllers calculated by algebraic solution perform better capacity of disturbance attenuation than the conventional given-structured protocols. Two simulation examples demonstrate the validity of the new algorithm.

Seamless Transfer of Single-Phase Utility Interactive Inverters with a Synchronized Output Regulation Strategy

This study presents a strategy using the synchronized output regulation method (SOR) for controlling inverters operating in stand-alone and grid-connected modes. From the view point of networked dynamic systems, SOR involves nodes with outputs that are synchronized but also display a desirable wave shape. Under the SOR strategy, the inverter and grid are treated as two nodes that comprise a simple network. These two nodes work independently under the stand-alone mode. An intermediate mode, here is named the synchronization mode, is emphasized because the transition from the stand-alone mode to the grid-connected mode can be dealt as a standard SOR problem. In the grid-connected mode, the inverter operates in an independent way, in which the voltage reference changes for generalized synchronization where its output current satisfies the required power injection. Such a relatively independent design leads to a seamless transfer between operation modes. The closed-loop system is analyzed in the state space on the basis of the output regulation theory, which improves the robustness of the design. Simulations and experiments are performed to verify the proposed control strategy.

<inline-formula> <tex-math notation="LaTeX">${\cal H}_{\infty}$</tex-math></inline-formula> Almost Output Synchronization for Heterogeneous Networks Without Exchange of Controller States

We consider the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> almost output synchronization and regulated output synchronization problem for heterogeneous directed networks with external disturbances where agents are introspective (i.e., agents have access to a part of their own states). A decentralized protocol is designed for each agent, without exchanging internal controller states with neighboring agents, to achieve output synchronization and regulated output synchronization while making the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norm from the disturbances to the synchronization errors in the network arbitrarily small. Furthermore, the idea for output synchronization is applied to a formation problem in the presence of disturbances. The method is illustrated by simulation examples.

Synchronised output regulation of heterogeneous networks with delayed and sampled‐data communications

This article studies a synchronised output regulation (SOR) problem exchanging information at sampled time. Each node has a continuous-time internal model controller and a local exosystem providing a reference output signal. At sampled time, each node sends the exosystem state to its neighbouring nodes, as well as updates the exosystem dynamics by the received sampled data. A necessary and sufficient condition that the sampled period should satisfy for SOR with fixed digraph and time delay is presented. A numerical simulation shows an efficacy of analytic results.

Synchronised output regulation of nonlinear multi-agent systems

This paper considers a synchronised output regulation (SOR) problem of nonlinear multi-agent systems with switching graph. The SOR means that all agents have their outputs synchronised but also ultimately evolve on a manifold determined by a predefined exosystem. Each agent constructs its local copy of the predefined exosystem and exchanges the state information of the local exosystem to realise the synchronisation of local exosystem. A controller based on the nonlinear output regulation theory is then presented to force the agent's output track the output of local exosystem. It is shown that the SOR is solvable under the assumptions same as that for nonlinear output regulation of a single agent, if the switching graph satisfies the bounded interconnectivity times condition. Both state feedback and output feedback are addressed. A numerical simulation is made to show the efficacy of the analytic results.

Synchronised output regulation of leader-following heterogeneous networked systems via error feedback

A dynamic error feedback controller is presented for the synchronised output regulation (SOR) of leader-following heterogeneous linear networked systems. The nodes in the networked systems are divided into two kinds: the leader node accessible to the regulated error and the following nodes inaccessible to the regulated error but accessible to the relative output errors with respect to their neighbouring nodes. By using the small-gain theorem, a sufficient criterion for the SOR problem is developed for more general networks. This criterion can be regarded as imposing an additional H∞ constraint on the classical output regulation problem. The synthesis problem is then addressed by means of linear matrix inequality technique. The efficacy of the analytic results is illustrated by simulation examples.

Synchronized output regulation of switching networks based on synchronization observer

This paper studies the synchronized output regulation (SOR) problem of networked dynamic systems with switching topology that is uniformly connected and leader-rooted. In these networked systems, the tracked signal or the rejected disturbance is generated by the same exosystem, and however, the state of the exosystem is only available for leader nodes. First, a synchronization observer of the exosystem is proposed in this paper to overcome the difficulty caused by the unavailable state of the exosystem for follower nodes with directed switching information flow. It is shown that the observer state will synchronize to the state of the exosystem. Then, two feedback controllers based on decentralized dynamic error and state are presented to solve this SOR problem. Furthermore, the main idea in this paper will provide a promising way for realizing the multirobot systems’ tracking and formation requirement. Numerical simulation results are presented to demonstrate the effectiveness of the theoretical results.

Remarks on “Synchronized Output Regulation of Linear Networked Systems”

This technical note further considers the synchronized output regulation problem of linear networked systems proposed in the paper by Xiang We first make the assumptions of the problem more accurate and present a more straightforward solution for the problem. Then we further point out that, under a different detectability condition, the problem can be solved by a decentralized control scheme.

Synchronized Output Regulation of Linear Networked Systems

This note addresses the problem of synchronized output regulation of linear networked system where all the nodes have their outputs track signals produced by the same exosystem and the state of exosystem is accessible only to leader nodes, while follower nodes regulate their outputs via a distributed synchronous protocol. This problem can be decoupled into two: one is the output regulation problem on the synchronous manifold and the other is the stability problem of synchronous manifold. The proposed synchronous protocol is independent of the network topology. The stability of synchronous manifold is analyzed through the permissible eigenvalue region and the requirements of information graph. Finally, a numerical example illustrates the efficacy of the presented results.