This paper is concerned with observer-based H ∞ output tracking control for networked control systems. An observer-based controller is implemented through a communication network to drive the output of a controlled plant to track the output of a reference model. The inputs of the controlled plant and the observer-based tracking controller are updated in an asynchronous way because of the effects of network-induced delays and packet dropouts in the controller-to-actuator channel. Taking the asynchronous characteristic into consideration, the resulting closed-loop system is modeled as a system with two interval time-varying delays. A Lyapunov–Krasovskii functional, which makes use of information about the lower and upper bounds of the interval time-varying delays, is constructed to derive a delay-dependent criterion such that the closed-loop system has a desired H ∞ tracking performance. Notice that a separation principle cannot be used to design an observer gain and a control gain due to the asynchronous inputs of the plant and the controller. Instead, a novel design algorithm is proposed by applying a particle swarm optimization technique with the feasibility of the stability criterion to search for the minimum H ∞ tracking performance and the corresponding gains. The effectiveness of the proposed method is illustrated by an example. Copyright © 2013 John Wiley & Sons, Ltd.
This article is concerned with resilient control design for synchronization of multiple harmonic oscillators coupled via vulnerable network suffering from denial-of-service (DoS) attacks. The synchronization of multiple harmonic oscillators can be achieved under consideration of certain DoS attacks. A distinct resilient distributed control protocol is designed for individual harmonic oscillator by proposing a resilient logical packet processor (RLPP). Some sufficient conditions on the duration and frequency of attacks reflected by the bounds of lumped time-varying delay are derived by employing complete-type Lyapunov–Krasovskii functionals (LKFs). The gain matrix can be designed by solving a set of linear matrix inequalities by combining an optimization algorithm. Finally, the proposed synchronization control scheme is applied to a representative model of the single-phase photovoltaic grid interconnection process. Numerical simulations are provided to show the effectiveness of the developed method.
This article addresses the problem of synchronization of impulsive networks with switching topologies. A new synchronization framework is established with an emphasis on settling time estimation. The impulsive networks consist of physical nodes and cyber modules. For physical nodes, states are changed impulsively at discrete time instants due to some switching phenomena or unexpected sudden noises. For cyber modules, two cases of switching scenarios are considered for information exchange patterns during specific time intervals. In the first case, cyber modules lose all the communication links with others, resulting in disconnected topologies. Then, a distributed controller is proposed for nodes without intrinsic nonlinear dynamics. A distinguished feature of this controller is its capability to estimate a bound for settling time, beyond which the synchronization with respect to a virtual target is guaranteed. In the second case, cyber modules lose some communication links but build other new ones with the help of a smart communication center to form connected topologies. A distributed controller is further designed for nodes in the presence of intrinsic nonlinear dynamics. Accordingly, a sufficient condition is derived to achieve synchronization with an estimated settling time bound. For both cases, the estimated bounds are able to reveal the relationship between the impulsive strength and the synchronization performance. Finally, numerical examples including a case study on a modified IEEE 34 bus test feeder are provided to demonstrate the effectiveness of the proposed controllers.
This article proposes a continuous adaptive integral-type sliding-mode control approach for a class of mechatronic systems by taking into consideration matched and unmatched uncertainties, and uncertainty in the control gain. Four different sliding-mode controllers are designed to enable: 1) the avoidance of the singularity by preventing differentiating the system states with fractional power; and 2) the attenuation of the chattering by utilizing full-order sliding manifolds. The control gain adaptation in the full-order sliding-mode controller is presented to avoid the overestimation of the gain. With the continuous control in place, the mechatronic systems have a fast response with high precision. The soften action from carefully designed controllers with the gain adaptation guarantees the trajectories of the mechatronic systems to move smoothly and prevents damage to the mechanical components of the systems. Both the simulation and experimental results demonstrate the effectiveness and feasibility of the proposed control approach.
The plenary speakers discuss the following: Human on the loop applications in robotics and haptics research; Recent advances in networked control systems; Modeling, scheduling and real-time control of cluster tools in semiconductor manufacturing.
This paper is concerned with the problem of distributed H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> filtering for discrete-time sensor networks with/without asymmetric intercommunication delays. Combining with the Kronecker product, a refined technique is provided to realize the complicated decoupling between the specifical sensor node and its underlying neighboring ones in the presence of intercommunication delays. Based on a previous bounded real lemma, a sufficient and necessary condition on distributed H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> filter design without delays is provided. For the case with asymmetric intercommunication delays, a sufficient condition is established for the existence of such distributed H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> filters that render the resulting filter error system asymptotically stable under which a prescribed disturbance attenuation performance index is guaranteed. The filter design problem is posed in terms of linear matrix inequalities (LMIs). The Leslie model which describes a certain pest's structured population dynamics is finally presented to show the effectiveness and feasibility of the developed theoretical results.
For the study of $3+1$ dimensional Einstein vacuum equations (EVEs), substantial progress has been made recently on the problem of trapped surface formation. However, very limited knowledge of existence and associated properties is acquired on the boundary of the emerged trapped region, i.e., the apparent horizon, which is composed of marginally outer trapped surfaces (MOTSs) and is of great physical importance. In this paper, concerning this emerged apparent horizon we prove a folklore conjecture relating to both cosmic censorship and black hole thermodynamics. In a framework set up by Christodoulou and under a general anisotropic condition introduced by Klainerman, Luk and Rodnianski, for $3+1$ EVEs we prove that in the process of gravitational collapse, a smooth and spacelike apparent horizon (dynamical horizon) emerges from general (both isotropic and anisotropic) initial data. This dynamical horizon censors singularities formed in gravitational collapse from non-trapped local observers near the center, and it also enables the extension of black hole thermodynamical theory along the apparent horizon to anisotropic scenarios. Our analysis builds on scale-critical hyperbolic method and non-perturbative elliptic techniques. New observations and equation structures are exploited. Geometrically, we furthermore construct explicit finger-type single and multi-valley anisotropic apparent horizons. They are the first mathematical examples of the anisotropic MOTS and the anisotropic apparent horizon formed in dynamics, which have potential applications in geometric analysis, black hole mechanics, numerical relativity and gravitational wave phenomenology.
