910 publications from this institution
This paper is concerned with the problem of the robust sampled-data H∞ control for an offshore steel jacket platform subject to the self-excited wave force and the external disturbance. First, by using the input delay method, the corresponding closed-loop system with the sampling measurements is transformed into a continuous-time system. Then, based on a Lyapunov functional, the H∞ performance is established and the stability criteria for the closed-loop system is derived. Finally, the effectiveness of the proposed robust sampled-data H∞ controller is demonstrated by a simulation example. The simulation results show that the designed controller is effective to control the offshore platform, Moreover, to obtain almost the same control performance, the required control force under the robust sampled-data H∞ controller is smaller than the one under the robust H∞ controller.
This study provides an overview and in-depth analysis of recent advances in stability of linear systems with time-varying delays. First, recent developments of a delay convex analysis approach, a reciprocally convex approach and the construction of Lyapunov–Krasovskii functionals are reviewed insightfully. Second, in-depth analysis of the Bessel–Legendre inequality and some affine integral inequalities is made, and recent stability results are also summarised, including stability criteria for three cases of a time-varying delay, where information on the bounds of the time-varying delay and its derivative is totally known, partly known and completely unknown, respectively. Third, a number of stability criteria are developed for the above three cases of the time-varying delay by employing canonical Bessel–Legendre inequalities, together with augmented Lyapunov–Krasovskii functionals. It is shown through numerical examples that these stability criteria outperform some existing results. Finally, several challenging issues are pointed out to direct the near future research.
In this paper, we study the generalized Abreu equation on a Delzant ploytope $Δ\subset \mathbb{R}^2$ and prove the existence of the constant scalar metrics of homogeneous toric bundles under the assumption of an appropriate stability.
This paper is concerned with the robust stability analysis problem for a partial element equivalent circuit (PEEC) model of neutral type. Based on the Lyapunov stability theory and a linear matrix inequality (LMI) approach, some sufficient delay-dependent stability conditions are derived. A numerical example shows that the result using the method in the paper is less conservative than that using some existing methods in the literature.
This paper is concerned with network-based output tracking control for a T–S fuzzy system. An event-triggered communication scheme, under which the threshold depends on the latest successfully transmitted sampled-data, is introduced to reduce network resource utilization. Taking the event-triggered communication scheme and the asynchronous operation between the fuzzy system and the fuzzy controller, the resulting system is modeled as an asynchronous threshold–error-dependent system with an interval time-varying delay. A new delay-dependent criterion for L 2 -gain tracking performance of the asynchronous system is derived by applying the deviation bounds of asynchronous normalized membership functions. Based on this performance criterion, some criteria on the existence of the fuzzy tracking controller are established. A co-design algorithm is presented to obtain the control gains and the event-triggering parameters simultaneously. An example is given to illustrate the effectiveness of the proposed method.
This paper studies the time-delay effect on the equivalent control based sliding mode control. Conditions to guarantee the boundedness of the control system steady states under the time delayed equivalent control based sliding mode control are obtained. Maximum upper bound of the delay time to guarantee boundedness is estimated. Simulations are conducted to verify the theoretical results.
A design method for the robust H ∞ control of an uncertain linear system with a time‐varying state delay is proposed. First, an integral inequality that we recently obtained is employed to establish a new delay‐dependent bounded real lemma for a system with a time‐varying delay. The lemma uses neither a model transformation nor a bounding technique for cross terms. Then, the lemma is used in combination with a matrix decomposition method to derive delay‐dependent conditions for the existence of robust H ∞ control based on linear matrix inequalities. Finally, some numerical examples are given to demonstrate the validity of the method.
With the booming of cyber attacks and cyber criminals against cyber-physical systems (CPSs), detecting these attacks remains challenging. It might be the worst of times, but it might be the best of times because of opportunities brought by machine learning (ML), in particular deep learning (DL). In general, DL delivers superior performance to ML because of its layered setting and its effective algorithm for extract useful information from training data. DL models are adopted quickly to cyber attacks against CPS systems. In this survey, a holistic view of recently proposed DL solutions is provided to cyber attack detection in the CPS context. A six-step DL driven methodology is provided to summarize and analyze the surveyed literature for applying DL methods to detect cyber attacks against CPS systems. The methodology includes CPS scenario analysis, cyber attack identification, ML problem formulation, DL model customization, data acquisition for training, and performance evaluation. The reviewed works indicate great potential to detect cyber attacks against CPS through DL modules. Moreover, excellent performance is achieved partly because of several high-quality datasets that are readily available for public use. Furthermore, challenges, opportunities, and research trends are pointed out for future research.
Different classic phased-array that generates only angle-dependent transmit beampattern, frequency diverse array (FDA) offers both angle-dependent and range-dependent transmit beampattern. This paper adopts the information geometry theory to study the fundamental information resolution for a general FDA radar system. The information resolution, associated with the waveform, measurement and noise model and characterized by the Fisher information metric, provides a statistical measure for the FDA radar system. Numerical results show that FDA radar indeed outperforms conventional phased-array radar in information geometry resolution capability.
This paper studies the fault-tolerant trajectory tracking control problem of twin-propeller non-rudder unmanned surface vehicles (TPNR USVs) subject to propeller faults. Firstly, a propeller model of TPNR USVs is constructed by decomposing propeller thrusts on the body-fixed reference frame. A propeller fault model is also established by taking into account floating and loss-of-effectiveness faults. Secondly, to ensure tracking errors stay in reasonable ranges, a novel guaranteed transient performance method is proposed. Meanwhile, corresponding error transformation functions are constructed. Thirdly, by utilizing the excellent nonlinearity approximation performance of neural networks (NNs), an adaptive fault-tolerant trajectory tracking control scheme, which can guarantee TPNR USVs track the desired trajectory quickly and accurately even in the event of propeller faults, is proposed. Finally, the fault-tolerant trajectory tracking performance analysis demonstrates the efficiency of the proposed control scheme.
This paper is concerned with L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -stochastic stability and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -gain performance analysis of a continuous-time positive Markov jump linear system with a time-delay. By constructing a novel linear co-positive stochastic Lyapunov functional based on the positivity of the system, and characterizing the system equation of the mathematical expectation of the markovianized states, some necessary and sufficient delay-dependent conditions for L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -stochastic stability and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> -gain performance are presented in terms of linear programming. A numerical example is provided for showing the effectiveness of the obtained conditions, especially for exploring and revealing both the negative effect and the positive effect of the time-delay on stochastic stability of the positive Markov jump linear system with a time-delay.
This chapter introduces some basic results of finite-time and fixed-time stability and stabilization. To illustrate these results, three interesting examples are first presented to give an insight into the key feature on a standard structure of finite-time and...
This article presents a collaborative neurodynamic optimization (CNO) approach to multivehicle task assignments (TAs). The original combinatorial quadratic optimization problem for TA is reformulated as a quadratic unconstrained binary optimization (QUBO) problem with a quadratic utility function and a penalty function for handling load capacity and cooperation constraints. In the framework of CNO with a population of discrete Hopfield networks (DHNs), a TA algorithm is proposed for solving the formulated QUBO problem. Superior experimental results in four typical multivehicle operation scenarios are reported to substantiate the efficacy of the proposed neurodynamics-based TA approach.
This paper is concerned with the cooperative target stalking for a multi-unmanned surface vehicle (multi-USV) system. Based on the multi-agent deep deterministic policy gradient (MADDPG) algorithm, a multi-USV target stalking (MUTS) algorithm is proposed. Firstly, a V-type probabilistic data extraction method is proposed for the first time to overcome shortcomings of the MADDPG algorithm. The advantages of the proposed method are twofold: 1) it can reduce the amount of data and shorten training time; 2) it can filter out more important data in the experience buffer for training. Secondly, in order to avoid the collisions of USVs during the stalking process, an action constraint method called Safe DDPG is introduced. Finally, the MUTS algorithm and some existing algorithms are compared in cooperative target stalking scenarios. In order to demonstrate the effectiveness of the proposed MUTS algorithm in stalking tasks, mission operating scenarios and reward functions are well designed in this paper. The proposed MUTS algorithm can help the multi-USV system avoid internal collisions during the mission execution. Moreover, compared with some existing algorithms, the newly proposed one can provide a higher convergence speed and a narrower convergence domain.
In this article, the issues of secure estimation, attack reconstruction, and isolation are addressed for cyber–physical systems in the presence of malicious attacks. It is assumed that disturbances and noises are unknown-but-bounded. Based on different rank constraints, both zonotopic completely unknown input observer and zonotopic partially unknown input observer are designed to estimate system states. Then, malicious attacks are reconstructed and isolated based on the proposed zonotopic observers. By utilizing switching technique, the corresponding feedback controllers are designed, which can guarantee that the closed-loop system is stable. Finally, numerical simulations are provided to illustrate the validity of the presented approach.
This paper is concerned with active control for an offshore steel jacket platform subjected to wave-induced force and parameter perturbations. An uncertain dynamic model for the offshore platform is first established, where uncertainties not only on the natural frequency and the damping ratio of both the offshore platform and the active tuned mass damper (TMD) but also on the damping and stiffness of the TMD are considered. Then, by intentionally introducing a proper time delay into the control channel, a novel sliding mode control scheme is proposed. This scheme uses information about mixed current and delayed states. It is shown through simulation results that this scheme is more effective in both improving the control performance and reducing control force of the offshore platform than some existing ones, such as delay-free sliding mode control, nonlinear control, dynamic output feedback control, and delayed dynamic output feedback control. Furthermore, it is shown that the introduced time delay in this scheme can take values in different ranges while the corresponding control performance of the offshore platform is almost at the same level.
This chapter deals with T-STakagi-Sugeno (T-S) fuzzy dynamic positioning controller design for a UMVUnmanned Marine Vehicles (UMVs) in network environments. Network-based T-S fuzzy DPS models for the UMVUnmanned Marine Vehicles (UMVs) are first established. Then, by taking into consideration an asynchronous difference between the normalized membership function of the T-S fuzzy DPSDynamic Positioning Systems (DPSs) and that of the controller, stabilityStability and stabilizationStabilization criteria are derived.
