Category: IEEE Transactions on Automatic Control

Previous small-gain results for interconnected integral input-to-state (iISS) systems have been restricted to systems that are strongly iISS. This paper removes this restriction by allowing cross terms between external inputs and states in the Lyapunov decrease of component systems, and subsequently constructing a nonseparable Lyapunov function. An example demonstrates the use of this new small-gain formulation.

This paper investigates the interaction between control and communications in networked systems by studying a class of stochastic approximation algorithms that accommodate random network topology switching processes, time-varying functions, nonlinear dynamics, additive and nonadditive noises, and other uncertainties. Interaction among control strategy and the multiple stochastic processes introduces critical challenges in such problems. By modeling the random switching as a discrete-time Markov chain and studying multiple stochastic uncertainties in a unified framework, it is shown that under broad conditions, the algorithms are convergent. The performance of the algorithms is further analyzed by establishing their rate of convergence and asymptotic characterizations. Simulation case studies are conducted to evaluate the performance of the procedures in various aspects.

This paper concerns the treatment of swing dynamics in a power grid using a continuous approach. Rather than addressing the problem as oscillations in a discrete system, we model the swing dynamics as a propagating electro-mechanical wave using a partial differential equation. A ring geometry with a one-dimensional wave equation is used to analyze the underlying dynamics. A control method is proposed to damp the system dynamics using the concept of Interior Wave Suppression. Unlike domains with boundaries such as strings, any concentrated input to the ring generates waves in two directions, thereby preventing total absorption. Using a judicious combination of concentrated control inputs, it is shown that a near unidirectional wave can be generated, with minimal backwaves. The resulting closed-loop system is proved to be stable. The overall modeling and control methods are shown to be implementable in a power grid using phasor measurement units as sensors and flexible ac transmission system devices, such as thyristor controlled series compensator, as actuators. How, the proposed methods of modeling and control can be applied to a network of rings is briefly discussed. Numerical simulations are carried out to validate the theoretical derivations.

This note is devoted to study the stabilization problem of stochastic nonlinear delay systems with exogenous disturbances and the event-triggered feedback control. By introducing the notation of input-to-state practical stability and an event-triggered strategy, we establish the input-to-state practically exponential mean-square stability of the suggested system. Moreover, we investigate the stabilization result by designing the feedback gain matrix and the event-triggered feedback controller, which is expressed in terms of linear matrix inequalities. Also, the lower bounds of interexecution times by the proposed event-triggered control method are obtained. Finally, an example is given to show the effectiveness of the proposed method. Compared with a large number of results for discrete-time stochastic systems, only a few results have appeared on the event-triggered control for continuous-time stochastic systems. In particular, there have been no published papers on the event-triggered control for continuous-time stochastic delay systems. This note is a first try to fill the gap on the topic.