Xiaohong Nian

Second-order consensus in multi-agent systems based on second-order neighbours’ information

This paper mainly investigates the consensus of second-order multi-agent systems by using the second-order neighbours’ information. The comparison between the convergence rate of second-order neighbour protocol and the one of general protocol is developed. When multi-agent system achieves maximum speed consensus, the relation between the parameter in general protocol and that in second-order neighbour protocol is analysed. If there exists delay in communication, the delay margins of general protocol and second-order neighbour protocol are derived. Numerical examples are given to illustrate the effectiveness of the proposed methods.

Adaptive pinning control of cluster synchronization in complex networks with Lurie-type nonlinear dynamics

In this paper, cluster synchronization problem is investigated for a kind of complex dynamical networks with Lurie-type non-linear dynamics. With the aid of a local update law, a pinning adaptive control strategy is proposed to solve the cluster synchronization problem of the networks. Some simple criteria for cluster synchronization are presented for the networks with external disturbances and time delays. Firstly, sufficient conditions are established to realize cluster synchronization of the networks without disturbances and delays. Then, the cluster synchronization problem of the networks with external disturbances is considered. Finally, the cluster synchronization in the networks with time-varying delays is further studied. Numerical examples are given to verify and illustrate the theoretical results. HighlightsThe cluster synchronization in networks with disturbances and delays is studied.An adaptive control strategy is presented for the networks with Lurie-type dynamics.The results in this paper do not require the global information of the networks.

Robust Decentralized Coordinated Control of a Multimotor Web-Winding System

Due to the strong coupling, model uncertainties, and external perturbations, the multimotor web-winding system presents a great control challenge. In order to deal with these problems, a decentralized coordinated control (DCC) strategy is proposed in this paper. First, the web-winding system is regarded as a synthetic system with several dynamic interval subsystems, and an interval matrix is introduced to cope with the modification of the set point and the change of parameters. Then, a decentralized coordinated controller is designed based on state feedback. By virtue of choosing suitable state variables of neighbor subsystems as coordination variables, the proposed control strategy can improve perturbation rejection performance and reduce the coupling existing between subsystems. Sufficient conditions of asymptotic stabilization of the system are derived based on the Lyapunov stability theory. Controller gain matrices are obtained by solving linear matrix inequalities. Finally, a three-motor web-winding system is considered as an application example, and the effectiveness of the proposed DCC is evaluated by both simulations and experimental tests.

The design of delay-dependent wide-area DOFC with prescribed degree of stability α for damping inter-area low-frequency oscillations in power system

In this paper, the delay-dependent wide-area dynamic output feedback controller (DOFC) with prescribed degree of stability is proposed for interconnected power system to damp inter-area low-frequency oscillations. Here, the prescribed degree of stability α is used to maintain all the poles on the left of s=-α in the s-plane. Firstly, residue approach is adopted to select input-output control signals and the schur balanced truncation model reduction method is utilized to obtain the reduced power system model. Secondly, based on Lyapunov stability theory and transformation operation in complex plane, the sufficient condition of asymptotic stability for closed-loop power system with prescribed degree of stability α is derived. Then, a novel method based on linear matrix inequalities (LMIs) is presented to obtain the parameters of DOFC and calculate delay margin of the closed-loop system considering the prescribed degree of stability α. Finally, case studies are carried out on the two-area four-machine system, which is controlled by classical wide-area power system stabilizer (WAPSS) in reported reference and our proposed DOFC respectively. The effectiveness and advantages of the proposed method are verified by the simulation results under different operating conditions.

Observer-Based Stabilization Control of Time-Delay T-S Fuzzy Systems via the Non-Uniform Delay Partitioning Approach

It is well known that intelligent control technology plays an important role in the design of many control systems, and intelligent control has aroused wide attention from scholars. Fuzzy control is also the case because fuzzy control is one branch of intelligent control. The Takagi-Sugeno (T-S) fuzzy model is an effective approach when dealing with complex nonlinear systems, and the advantages of fuzzy controller design is that the linear control methods can be used. In addition, nonlinearity and time delay are inherent and not all states are available in many practical system. Therefore, the observer-based stabilization control for time-delay T-S fuzzy systems is of great significance. With the help of the non-uniform delay partitioning approach, a novel method is put forward to analyze the stability of the time-delay T-S fuzzy system and design the observer-based feedback controller via the parallel distributed compensation (PDC) scheme. The sufficient conditions of asymptotic stability for both nominal and uncertain time-delay T-S fuzzy system are derived based on the Lyapunov stability theory and linear matrix inequality (LMI) techniques. What is more, the solving methods to obtain the controller gain matrices, observer gain matrices, and upper bound of time delay are presented. Two illustrative examples are given to demonstrate the effectiveness and verify the superiority of our developed methods. From the simulation results, it can be found that the most prominent advantages of our proposed methods lie on larger delay bound and less decision variables compared with other related methods. The problem of observer-based stabilization control for continuous nonlinear time-delay systems is investigated in this paper, and the delay-dependent stability criteria are derived to achieve greater delay bound by virtual of the non-uniform delay partitioning approach. Numerical examples further confirmed the effectiveness and advantages of our developed methods.

Robust decentralized control for large-scale web-winding systems: A linear matrix inequality approach

In this paper, a robust decentralized control scheme is proposed for web-winding systems. The control input for each subsystem is divided into two parts, a reference control input and a control compensation. First, the reference control inputs and the error dynamic models are presented. Then, based on the error dynamic model, a decentralized controller is designed to compute the control compensation, and the relevant sufficient condition for the existence of the decentralized controller is derived in terms of linear matrix inequalities (LMIs). By virtue of regarding some parameters as interval variables, the proposed controller has good robustness with regard to parameter variations and is adapted to the changes of set point. Finally, a three-motor web-winding system is considered as an application example, and simulation and experimental tests illustrate the effectiveness of the proposed controller.

Second-Order Consensus in Multiagent Systems via Nonlinear Protocol

This paper focuses on theoretical analysis of second-order consensus in multiagent system. As an extension of the general linear protocol, a nonlinear protocol is designed for multiagent system with undirected communication topology. The nonlinear protocol is also applied to achieve reference velocity consensus. Through choosing the appropriate Lyapunov functions and using LaSalle’s invariance principle, some consensus conditions are derived. Simulation examples are provided to demonstrate the effectiveness of the proposed results.

Some synchronization criteria for general complex networks with coupling delays

A general complex delayed dynamical network model with asymmetric coupling matrix is considered in this paper. For reducing the conservativeness of synchronization criteria, several novel synchronization stability conditions are presented by using delay decomposition methods. Numerical examples which are widely used to study delay-dependent synchronization stability are given to illustrate the effectiveness of the proposed methods.

Robust observer design for multi-motor web-winding system

Abstract This paper develops a novel observer design method for multi-motor web-winding system. Firstly, the multi-motor web-winding system is regarded as a synthetic system with several subsystems, where the dynamic model for each subsystem is given. Then, the nonlinear diffeomorphism transformation is introduced to obtain a transformed system with block triangular structure and the interconnections among the subsystems are allowed. Next, a decentralized high-gain observer with sliding mode is designed for the transformed system, based on which the estimation error dynamics can be got. Sufficient condition of asymptotic stability for estimation error dynamics is derived by the Lyapunov stability theory and the observer gain is obtained. After that, the observer for original multi-motor web-winding system is achieved via inverse transformation. Finally, the simulation and analysis are performed in the three-motor web-winding system to verify the effectiveness of the proposed observer.

Robust fuzzy tracking control of a quad-rotor unmanned aerial vehicle based on sector linearization and interval matrix approaches

In this paper, the robust H∞ fuzzy tracking control strategy for a quad-rotor unmanned aerial vehicle (UAV) with strong coupling and highly nonlinear is put forward based on the Takagi-Sugeno(T-S) fuzzy error model. Firstly, the quad-rotor UAV system is divided into altitude subsystem, position subsystem and attitude subsystem. Through selecting appropriate premise variables, three T-S fuzzy error models, which are equivalent to the error dynamic model, are established by the sector linearization approach. Next, the uncertainties in drag coefficients, moments of inertia are taken into account, and the interval matrix is introduced to describe them in altitude, position and attitude T-S fuzzy error models. Then the robust H∞ fuzzy feedback controllers are designed to stabilize T-S fuzzy subsystems. Besides, according to the Lyapunov stability theorem, it is obtained that the LMI sufficient conditions of exponential stability with the prescribed H∞ performance for T-S fuzzy closed-loop subsystems. Meanwhile, the method for solving the gain matrices of controller is presented. Finally, simulation results are given to demonstrate the effectiveness, robustness and advantages of the proposed method. Then the feasibility of the proposed method is further verified by experimental results.