Ligang Wu

Ligang Wu
Harbin Institute of Technology | HIT · School of Astronautics

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157
Publications
6,116
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7,515
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January 2012 - present
January 2008 - present
January 2008 - present
The University of Hong Kong

Publications

Publications (157)
Article
Full-text available
This paper is concerned with the problems of delay-dependent robust passivity analysis and robust passification for uncertain Markovian jump linear systems (MJLSs) with time-varying delay. The parameter uncertainties are time varying but norm bounded. For the robust passivity problem, the objective is to seek conditions such that the closed-loop sy...
Article
This paper is concerned with the H ∞ filtering problem for a continuous-time linear switched system with time-varying delay in its state. To reduce the overdesign of the quadratic framework, this paper proposes a parameter-dependent filter design procedure, which is much less conservative than the quadratic approach. By using an average dwell time...
Article
This paper is concerned with the problem of H(∞) model reduction for Takagi-Sugeno (T-S) fuzzy stochastic systems. For a given mean-square stable T-S fuzzy stochastic system, our attention is focused on the construction of a reduced-order model, which not only approximates the original system well with an H(∞) performance but also translates it int...
Article
This paper is concerned with the problems of dynamic practical-sliding-mode control (SMC) and estimation of unknown functions for singular Markovian jump systems (MJSs) with system perturbations, by using an ellipsoidal-type interval type-2 fuzzy neural networks (FNNs). For the interval type-2 FNN, both the system states and control inputs are util...
Article
This paper investigates the direct trajectory optimization of the free-floating space manipulator (FFSM). The main purpose is to plan the joint space trajectories to reduce the spacecraft motion due to the joint rotation during the FFSM performing tasks. To improve the calculation efficiency, the adaptive Radau pseudospectral method (A-RPM) is appl...
Preprint
This paper studies a distributed online constrained optimization problem over time-varying unbalanced digraphs without explicit subgradients. In sharp contrast to the existing algorithms, we design a novel consensus-based distributed online algorithm with a local randomized zeroth-order oracle and then rescale the oracle by constructing row-stochas...
Chapter
This chapter investigates the problem of how to design an optimal DoS attack sequence to deteriorate the performance of the remote estimator from the attacker’s perspective. For the system setup, the system designer utilizes multiple communication channels to transmit data to the remote estimator. In this way, the reliability of the cyber layer can...
Chapter
Even the reliable distributed filtering problem has been investigated in [139] using type-1 T-S fuzzy model, there exist some space to improve the results, which lies in both how to describe the uncertainties and reduce modeling errors and how to enhance the flexibility of fuzzy distributed filter. Recalling the advanced properties in describing un...
Chapter
This chapter is focused on the optimal secure control scheme for CPSs based on the game-theoretical approach. The physical plant is described as a linear time-invariant discrete-time model with Gaussian noises. Assume the controller and the actuator are distributed and connected over communication network. The attacker can hijack the network and mo...
Chapter
In this chapter, the deep reinforcement learning based secure control problem of CPSs under actuator attacks is first investigated. A reinforcement learning algorithm is proposed to learn the secure policy for CPSs, based on which deep neural networks are constructed and offline trained. In the inference, trained deep neural networks are deployed t...
Chapter
Some main preliminaries are provided in this section. First, we describe the considered nonlinear NCSs, which are transformed from traditional systems due to the use of communication networks. Pade approximation method is followed to demonstrate how to separate network-induced delay from controller. At the end of this section, a clear description f...
Chapter
The diagram of the system frame is described in Fig. 4.1, which shows that the controller and the actuator interact with each other using the cyber layer. The adversary can implement DoS attacks to prevent the cyber realm from transmitting the control signal to the actuator. In this section, we give a model to describe the physical dynamics. A comm...
Chapter
This chapter investigates the problem of secure state reconstruction for CPSs subject to both malicious attacks and unknown input. Firstly, CPSs are described as a discrete linear time invariant state space model. A parse vector is adopted to model malicious attacks, which can reflect its natural property well. Secondly, a sliding mode observer-bas...
Chapter
This chapter draws conclusions on the book, and points out some possible research directions related to the work done in this book. By using some traditional and art-of-the-state techniques, for example, optimal theory, sliding mode control, game theory, moving target defense, deep neural networks and reinforcement learning, the problems of securin...
Chapter
This chapter addresses the problem of resilient control for CPSs under DoS attacks, which are modeled by using DoS frequency and DoS duration inequalities. Under such a DoS attack model, a switched physical system is derived, based on which a resilient sliding mode control scheme is proposed to guarantee that the physical process is exponentially s...
Chapter
Either the absence of an attack isolation algorithm or no available controllable pairs \((A,\mathcal {B}_{l})\) to alter can make the CPSs undergo attacks all the time. The system performance can be steadily deteriorated. To solve the problems, this chapter proposes attack detection, isolation and MTD control schemes for CPSs in a united framework....
Chapter
This chapter investigates the problem of observer-based adaptive neural tracking control for nonlinear nonstrict-feedback systems in presence of the actuator fault. Neural networks are introduced to identify the unknown nonlinear characteristics. Compared with the existing results, for example.
Chapter
This chapter employs radial basis function (RBF) neural network to approximate the unknown function. For a continuous function d(x) on a compact set ⨆ and εm, there exists a RBF neural network θTξ(x) such that 11.1supx∈⊔d(x)-θTξ(x)≤εm,where θ=[θ1,θ2,...,θl]T is the weight vector, and ξ(x)=[ξ1(x),ξ2(x),...,ξl(x)]T is basis function vector commonly u...
Chapter
In this chapter, two adaptive control strategies are designed for dc/dc buck converter, i.e., single-loop adaptive control strategy and double-loop adaptive control strategy. As the names imply, single-loop adaptive control strategy has only voltage regulation loop which directly regulate the output voltage, while double-loop adaptive control strat...
Chapter
This chapter proposes a control strategy consisting of adaptive control and H∞ technique for three-phase two-level ac/dc power converters. Cascaded two loop control structure in VOC mode is adopted. For outer voltage regulation loop, an efficient adaptive controller is designed to regulate dc-link output voltage to its reference in the presence of...
Chapter
Buck converter is a type of dc/dc power converters, which converts a direct current source from one voltage level to another. They are used for power supplies for office equipments, personal computers, telecommunications equipments, and spacecraft power systems, as well as drive control of dc motors [1]. Depending on circuit topology and applicatio...
Chapter
In Chap. 2, four different types of disturbance observer have been proposed for voltage regulation of a grid-connected power converter. With similar other conditions, the linear disturbance observer (LDO) obtains a relatively good disturbance rejection performance. It is of ease use as there is only one parameter to be adjusted. However, due to thi...
Chapter
From the simulation results in Chap. 2, it can be seen that the second-order sliding mode observer (SMO) obtains the best disturbance observation, and offers the best compensation for the sliding mode controller. However, it has similar shortcoming as the linear observer in Chap. 2, i.e., if it needs to accelerate the observation speed, the observe...
Chapter
Two-level converters are widely applied in middle and high voltage fields. In high voltage applications, though the over-voltage problem can be mitigated by using multiple switches in series and/or parallel, this evokes other problems like dynamic and/or static voltage and current sharing problems of the switches, which increases uncertain factors...
Chapter
This chapter draws conclusions on the book, and points out some possible research directions related to the work done in this book.
Article
In this paper, a two-stage control scheme consisting of an adaptive-gain second-order sliding mode (SOSM) controller and a switched high-gain observer (HGO) is proposed for the three-level neutral-point-clamped (NPC) converter. The adaptive-gain SOSM control method is applied both in the voltage regulation loop and instantaneous power tracking loop...
Article
In this paper, a novel adaptive sliding mode control (ASMC) strategy is presented for attitude and altitude stabilization of a quadrotor unmanned aerial vehicle (UAV), where the input saturation is taken into consideration. The nonlinear dynamic model of quadrotor UAV subject to system uncertainty and external disturbance is firstly derived using t...
Article
This paper investigates the secure control problem for cyber-physical systems when the malicious data is injected into the cyber realm which is directly connecting to the actuators. Based on moving target defense and reinforcement learning, we propose a novel proactive and reactive defense control scheme. First, the system $(A,B)$ is modeled as a...
Preprint
Full-text available
Communication efficiency is a major bottleneck in the applications of distributed networks. To address the problem, the problem of quantized distributed optimization has attracted a lot of attention. However, most of the existing quantized distributed optimization algorithms can only converge sublinearly. To achieve linear convergence, this paper p...
Article
In this paper, a nonlinear high-gain observer (NHGO) based second-order sliding mode (SOSM) control strategy is proposed for the three-phase three-level neutral-point-clamped (NPC) converter. This controller applies the advanced SOSM algorithm both in the voltage regulation loop and in power tracking loop, which provides a fast dynamic for the dc-l...
Article
This paper investigates the problem of optimal tracking control for cyber-physical systems (CPS) when the cyber realm is attacked by denial-of-service (DoS) attacks which can prevent the control signal transmitting to the actuator. Attention is focused on how to design the optimal tracking control scheme without using the system dynamics and analyz...
Article
This paper proposes a novel robust control strategy for three-phase power converters operated under unbalanced grid conditions. A consolidated control objective is obtained in the stationary $\alpha \beta$ frame, which can be flexibly adjusted according to the degree of oscillation in the active and reactive powers and the balance of the three-ph...
Article
Energy storage systems (ESSs) are the key to overcoming challenges to achieve the distributed smart energy paradigm and zero-emissions transportation systems. However, the strict requirements are difficult to meet, and in many cases, the best solution is to use a hybrid ESS (HESS), which involves two or more ESS technologies. In this article, a bri...
Article
To handle the common existing constraints, that is, limited energy supplies and limited communication bandwidth in multiagent systems (MASs), this article investigates the consensus problem in MASs with event-triggered communication (ETC) and state quantization. In order to compensate for the effect brought by mismatched disturbances, we also propo...
Article
Full-text available
In this paper, four control strategies for DC-DC buck converters are proposed, compared and analyzed: a single-loop adaptive control strategy (SA), a double-loop adaptive control strategy (DA), a single-loop disturbance observer-based control strategy (SDOB) and a double-loop disturbance observer-based control strategy (DDOB). First, the nominal sy...
Article
This article proposes a sliding-mode-observer (SMO)-based control strategy to regulate the dc-link voltage for a three-phase two-level active front end (AFE). The SMO is designed for the voltage control loop to estimate the external load which is abruptly connected to the AFE dc-link and consequently causes the dc-link voltage fluctuation. The esti...
Article
In this paper, we investigate a distributed online constrained optimization problem with differential privacy where the network is modeled by an unbalanced digraph with a row-stochastic adjacency matrix. To address such a problem, a distributed privacy preserving algorithm without introducing a trusted third-party is proposed to guarantee that the...
Article
Full-text available
This study proposes an extended state observer‐based sliding mode control (ESO‐SMC) strategy for trajectory tracking of a four mecanum wheeled mobile platform (FMWMP) with unknown disturbances and model uncertainties (UDMU) considered. Especially, the extended state observer (ESO) is designed to estimate not only the UDMU but also the unmeasured ve...
Article
In this paper, a practical state estimation strategy against joint sensor and actuator attacks is proposed for cyber-physical systems (CPSs). The CPSs are formulated based on delta operator for the requirement of real control systems with high-sampling or variable-sampling periods. The attacks fulfilling sparse observation condition are supposed to...
Article
In this paper, the problems of stability analysis and stabilization are investigated for discrete-time two-dimensional (2-D) switched systems, which are formulated by the well-known Fornasini–Marchesini local state-space model. Firstly, by using the switched quadratic Lyapunov function approach, a sufficient stability condition is established for s...
Article
Based on the nonlinear stable inversion approach, an exact output tracking control law is designed for flexible air-breathing hypersonic vehicles (FAHVs). This problem is challenging because of the inherent couplings between the propulsion system, the airframe dynamics, and the presence of strong flexibility effects. Because of the complex nonlinea...
Chapter
Dissipativity theory has played a critical part in the analysis and control design of linear and nonlinear systems, especially for high-order systems, since from the practical application point of view, many systems need to be dissipative for achieving effective noise attenuation [51]. It has been recognized that for more abstract systems one can s...
Chapter
In this chapter, we consider the \(\mathcal{H}_{\infty}\) model approximation problem for continuous-time T-S fuzzy stochastic systems. For a given high-order T-S fuzzy stochastic system, our attention is focused on the construction of a reduced-order model, which guarantees the corresponding approximation error system to be mean-square asymptotica...
Chapter
New stability analysis methods are investigated for discrete-time T-S fuzzy time-delay systems, which include the basis-dependent LKF method, the delay partitioning method, the small gain theorem based input-output method, and the reciprocally convex method. Our main attention is focused on reducing the conservativeness of the stability conditions...
Chapter
Air-breathing hypersonic vehicles (AHVs) are a promising and cost-efficient technology for launching low-earth-orbit satellites and providing rapid globalresponse capabilities [55]. As the application of air-breathing scramjet engines [30, 85], AHVs can carry more payload than traditional expendable rockets, because the scramjet engines can obtain...
Chapter
In this chapter, the stabilization and DOF control problems are investigated for discrete-time T-S fuzzy time-delay systems. By utilizing a novel idea of delay partitioning technique, a delay-dependent stability condition with less conservativeness is proposed at first. Then, based on the stability result, the stabilization problem via the non-PDC...
Chapter
In this chapter, the \(\mathcal{H}_{\infty}\) model approximation problem is studied for discretetime T-S fuzzy time-delay systems. For a given high-order T-S fuzzy system, our attention is focused on the construction of reduced-order models, which approximate the original system well in an \(\mathcal{H}_{\infty}\) sense. To reduced the conservativ...
Chapter
This chapter is concerned with the distributed fuzzy filter design problem for a class of sensor networks described by discrete-time T-S fuzzy systems with time-varying delays and multiple probabilistic packet losses. In the sensor networks, each individual sensor can receive not only the data packets from its own measurement but also from its neig...
Chapter
The fault detection problem is an important topic in systems science and control engineering from the viewpoint of improving system reliability. The basic idea of fault detection is to construct a residual signal and, based on this, to determine a residual evaluation function to compare with a predefined threshold. When the residual evaluation func...
Chapter
In this work, a novel model transformation will be analyzed and applied for the \(\mathcal{H}_{\infty}\) desired filter design of discrete-time T-S fuzzy Ito stochastic systems with time-varying delays in the state. First, model transformation of the original discrete-time T-S fuzzy Ito stochastic time-varying delay system is studied by way of that...
Chapter
This chapter aims to investigate the \(\mathcal{L}_{2}-\mathcal{L}_{\infty}\) DOF control for T-S fuzzy stochastic systems with time-varying delay. The slack matrix approach is used to derive a delay-dependent sufficient condition to guarantee the meansquare asymptotic stability with an \(\mathcal{L}_{2}-\mathcal{L}_{\infty}\) performance for the c...
Chapter
This chapter is concerned with system performance analysis and filter design for T-S fuzzy systems with time-varying delay. Sufficient conditions of stability analysis satisfying the given performance level are presented for the augmented filtering error system by the input-output approach. Based on these conditions, the filtering problem for the c...
Chapter
In this chapter, we intend to investigate the stability and stabilization problems for discrete-time T-S fuzzy stochastic systems with time-varying delay. For a given T-S fuzzy stochastic system, our attention is focused on obtaining the sufficient conditions assuring its mean-square asymptotic stability, and designing the stabilization controller...
Article
This paper investigates the problem of Hankel-norm output feedback controller design for a class of T–S fuzzy stochastic systems. The full-order output feedback controller design technique with the Hankel-norm performance is proposed by the fuzzy-basis-dependent Lyapunov function approach and the conversion on the Hankel-norm controller parameters....
Article
This paper investigates the nonfragile-guaranteed cost control problem for a class of uncertain nonlinear singular state-delayed systems that is described by Takagi-Sugeno models. The upper bound of state delay is assumed to be available. A linear quadratic cost function is specified as the performance index of the closed-loop system. Attention is...
Conference Paper
In this paper, the problem of H∞ control for electromagnetic suspension (EMS) systems is addressed, and cases of both finite and entire frequency are discussed. Firstly a linear state-space model is applied to approximated the complex EMS system, and then H∞ performance index is adopted to measure ride comfort in circumstance of more general exogen...
Article
This paper presents a T–S model-based fuzzy controller design approach for electromagnetic suspension systems. The T–S fuzzy model is firstly applied to represent the nonlinear electromagnetic suspension systems. Then, based on the obtained T–S fuzzy model, a fuzzy state feedback controller is used to ensure the required mixed ℓ2–ℓ∞ performance of...
Conference Paper
In this paper, the problem of fuzzy-model-based control is investigated for electromagnetic suspension (EMS) systems. Firstly, the nonlinear EMS system is represented by a 4 rules' T-S fuzzy model. Then, a fuzzy state feedback controller is obtained to ensure the required mixed ℓ2-ℓ∞ performance of original EMS system to be achieved. The nonparalle...
Article
This paper proposes a fuzzy integral sliding mode control strategy for flexible air-breathing hypersonic vehicles with input nonlinearity. Based on the complex nonlinear dynamics in the considered vehicles, a control-oriented model, which can retain the dominant features of the higher-fidelity model, is adopted for the control design. First, the T-...
Article
This study is concerned with the passivity and passification problems for Takagi-Sugeno fuzzy descriptor systems subject to stochastic perturbation and time-varying delay. The stochastic disturbance is given in the form of one-dimensional Brownian motion and the delay is assumed to be time-varying and differentiable. By utilising the Lyapunov funct...
Article
This paper focuses on analyzing a new model transformation of discrete-time Takagi-Sugeno (T-S) fuzzy systems with time-varying delays and applying it to dynamic output feedback (DOF) controller design. A new comparison model is proposed by employing a new approximation for time-varying delay state, and then, a delay partitioning method is used to...
Article
This paper presents a novel approach to detect and discriminate abnormal and cueing signatures in mammography through enhancing the imaging contrast. Partial gland and adipose tissues are removed, and thus, the visual effect of mammography will be enhanced. Inspired by single image haze removal, we remove the majority of background tissues by intro...
Article
This technical brief is concerned with dissipativity analysis and dissipativity-based sliding mode control (SMC) of continuous-time switched stochastic systems. Firstly, a sufficient condition is proposed to guarantee the mean-square exponential stability and strict dissipativity for the switched stochastic system. Then, an integral-type sliding su...
Article
This paper investigates the problem of quantized H8 filtering for a class of discrete-time linear parameter-varying systems with Markovian switching under data missing. The measured output of the plant is quantized by a logarithmic mode-independent quantizer. The data missing phenomenon is modeled by a stochastic variable. The purpose of the proble...
Article
Full-text available
We would like to express appreciation to the authors for their excellent contributions and patience in assisting us. Finally, the fundamental work of all reviewers on these papers is also very greatly acknowledged.
Article
This paper is concerned with the dissipativity analysis for Takagi–Sugeno (T–S) fuzzy descriptor systems with time-delay. By using of delay partitioning approach, a delay-dependent criterion is established in terms of strict linear matrix inequalities (LMIs), which guarantees the considered system to be admissibility and strict (Q,R,S)(Q,R,S)-αα-di...
Article
In this paper, the problem of l2- l∞ filtering for a class of discrete-time Takagi-Sugeno (T-S) fuzzy time-varying delay systems is studied. Our attention is focused on the design of full- and reduced-order filters that guarantee the filtering error system to be asymptotically stable with a prescribed H∞ performance. Sufficient conditions for the o...
Article
This paper is concerned with the generalized H2H2 fault detection for two-dimensional (2-D) discrete-time Markovian jump systems. The mathematical model of the 2-D system is established upon the well-known Roesser model, and the measurement missing phenomenon, which appears typically in a network environment, is modeled by a stochastic variable sat...
Article
In this paper, we investigate the problem of sliding mode control (SMC) of Markovian jump singular time-delay systems. The aim is to consider the bounded ℒ2ℒ2 gain performance in the analysis of sliding mode dynamics, thus to improve the transient performance of the SMC system. Firstly, a delay-dependent bounded real lemma is proposed for the under...