2,312 publications from this institution
This paper describes a method based on self-feedback for controlling both chaotic and nonchaotic forms of the H\'enon map with and without additive Gaussian white noise. We describe a nonlinear self-tuning controller that makes use of a feedback reference signal and a linear autoregressive formulation for the gain. This controller is effective at stabilizing the map to a variety of fixed point or period-two orbits. We contrast our approach with the method of Ott, Grebogi, and Yorke [Phys. Rev. Lett. 64, 1196 (1990)] which has been used to control some chaotic processes and recently, some nonchaotic, stochastic ones.
In this paper, stabilization of fixed points of n-scroll Chua's circuit is investigated. Two adaptive control methods are proposed. One is based on an unstable low pass filter; the other is based on a stable and an unstable low pass filter. The simulation results verify the effectiveness of the two proposed control methods and performance comparisons show that the second control method is superior to the first one with regard to control speed and attraction basins.
In this paper, the stability problem of formation of multi-agents subject to failures in their communication links is addressed. The objective of the formation control problem is to maintain the inter-agent distances to be constants over time using a distributed control algorithm implemented in each agent. Previous research results showed that a distributed gradient-based control can locally asymptotically stabilize an undirected formation. However, in the case of failures in the inter-agent communication network, the degrees of freedom for some nodes might become uncontrollable and, consequently, the formation starts deviating from the desired conditions due to uncertainties and noise. In this paper, it is proved that in a faulty formation system, if there still exists a path between the agents on the both sides of the failed link, the gradient-based control signal can recover the formation without adding any new link to the network. Based on this feature, an algorithm for recovering the formation from the fault is developed. Simulation results show that the proposed recovery algorithm can tolerate small values of delays in data communications.
This article introduces the notion of chaotification (or, anticontrol of chaos), which means to make an originally non-chaotic dynamical system chaotic, or to enhance the existing chaos of a chaotic system, via feedback control techniques. The discrete case is discussed in somewhat detail, while the continuous case is outlined briefly. Basic theories and methods are described, and potential applications are mentioned as motivation of the research.
Recently, an ultra-wideband (UWB) system with frequency-modulated differential chaos shift keying (FM-DCSK) modulation has attracted increasing interest for its many distinctive superiorities over its conventional counterparts, especially in low-rate and low-power wireless personal area network (WPAN) applications. However, some of its drawbacks, such as low energy efficiency, complex implementation and weak multiaccess capacity, have also been noticed, which restrict its further acceptance and applications. To overcome these problems, an architecture, named single-input and multiple-output (SIMO) FM-DCSK UWB system, is introduced in this paper. With chaotic transmitted signals based on a high-order Walsh function and multiple antennas diversity reception, this paper demonstrates the superiorities of the new system in bit error rate (BER) performance as well as in moderation complexity. Furthermore, by transmitting chaotic pulse cluster signals, an improved emission signal structure of the SIMO FM-DCSK UWB system is proposed so as to overcome the delay line implementation constraints and to further enhance the BER performance. Based on this new signal format, a method of combining time division and Walsh function division is introduced into the existing Walsh function division scheme, thereby resolving the inherent obstacle in user capability which was known to be limited by the order of the Walsh function.
In this work, a flexible triboelectric nanogenerator (TENG) integrated with an artificial petal micro/nanostructure surface is proposed and fabricated. The flexible printed circuit is designed to expose the copper electrodes and integrate with the artificial polydimethylsiloxane (PDMS) petal surface as a flexible TENG. The artificial PDMS petal micro/nanostructure surface was fabricated by the rose petal replication process and integrated into the TENG to enhance triboelectric charge transfer. The power generated by the TENG from coupling between the triboelectric effect and electrostatic induction by external mechanical loads can be collected. The generated output open-circuit peak-to-peak voltage can be up to 45.8 V when the externally applied normal pressure is 40 kN m−2. Additionally, a maximum output power of 0.01 μW is achieved with a 1.7 MΩ loading resistance and a critical external applied pressure frequency of 26 Hz.
In this paper, a new approach for synchronization of complex dynamical networks is proposed based on state observer design. Unlike the common diagonally coupling networks, where full state coupling is typically needed between two nodes, here it is suggested that only a scalar coupling signal is required to achieve network synchronization. Some conditions for synchro- nization, in the form of an inequality, are established based on the Lyapunov stability theory, which can be transformed to a linear matrix inequality and easily solved by a numerical toolbox. Two typical dynamical network configurations, i.e., global coupling and nearest-neighbor coupling, with each node being a modified Chua's circuit, are simulated. It is demonstrated that the proposed scheme is effective in achieving the expected chaos synchronization in the complex network. Index Terms—Complex dynamical network, linear matrix in- equality (LMI), Lyapunov stability, state observer, synchroniza- tion.
To overcome the performance loss of noncoherent detectors of differential chaos-shift keying (DCSK), some improved versions of DCSK have been proposed. However, little has been done to improve the multiuser DCSK system based on Walsh codes (WCs), i.e., referred to as DCSK-WC, although it is considered more feasible in practice among the existing multiuser DCSK systems. This brief introduces a novel differentially DCSK (DDCSK) technique into such a multiuser system so as to build the desirable DDCSK-WC, obtaining significant performance gain, as compared with the conventional DCSK-WC, while retaining its hardware complexity unchanged. Moreover, the proposed system can greatly enhance the robustness against intersymbol interference in a wireless multipath fading channel. Therefore, the new system is deemed to provide a good alternative transmission scheme for wireless communication based on chaotic modulation, in such as indoor applications of the transmitted-reference ultrawideband. The theoretical analysis and simulated noise performances of the proposed system demonstrate their high consistence.
In this paper, we extend the OGY chaos-control method to be one based on the invariant manifold theory and the sliding mode control concept. This extended-control method not only can deal with higher order chaotic systems in the same spirit of the OGY method, but also can remove the reliance of the control on eigenvalues and eigenvectors of the system Jacobians, resulting in an even simpler but more effective controller. The novelty of the new design lies in the construction of suitable invariant manifolds according to the desired dynamic properties. The controller is then forcing the system state to lie on the intersection of the selected invariant manifolds, so that once the invariant manifolds are reached,the chaotic system will be guided toward a desired fixed point that corresponds to an originally targeted unstable periodic orbit of the given system. Such an idea is directly relevant to the sliding mode control approach. This new method is particularly useful for controlling higher order chaotic systems, especially in the case where some of the eigenvalues of the system Jacobian are complex conjugates. The effectiveness of the proposed method is tested by numerical examples of the third-order continuous-time Lorenz system and the fourth-order discrete-time double rotor map.
This paper presents two nonsmooth leader-following formation protocols for nonidentical Lipschitz nonlinear multi-agent systems with directed communication network topologies. One protocol is used to achieve finite-time formation for first-order systems, and the other to achieve asymptotic formation for second-order systems. In these protocols, the states of all the agents, including the leader and the followers, are available only locally within their neighborhoods. Some sufficient conditions for reaching formations are derived for nonidentical nonlinear systems satisfying locally Lipschitz conditions. To prove the stability, a new nonsmooth Lyapunov function is constructed, with stability conditions derived under a nonsmooth analysis framework. The proposed formation protocols are applied to multi-spacecraft systems in deep-space exploration, with numerical simulations demonstrating the effectiveness of the theoretical results.
In this paper, we present a new approach for constructing left and right coprime factorizations for a large class of (stable and unstable) nonlinear feedback control systems developed recently by the authors [7], under relatively weak conditions. The coprime factorization under investigation here was formulated by Hammer mer [14]. We will describe the proposed constructive scheme for obtaining explicit and closed-form solutions. The same technique presented in this paper works also for the left coprime factorization for a class of nonlinear control systems described by standard vector-valued nonlinear ordinary differential equations formulated by Verma [20], which has been demonstrated in the authors' [6].
This paper describes the design principle, tracking performance, and stability analysis of a fuzzy proportional-derivative (PD) controller. First, the fuzzy PD controller is derived from the conventional continuous-time linear PD controller. Then, the fuzzification, control-rule base, and defuzzification in the design of the fuzzy PD controller are discussed in detail. The resulting controller is a discrete-time fuzzy version of the conventional PD controller, which has the same linear structure in the proportional and the derivative parts but has nonconstant gains: both the proportional and derivative gains are nonlinear functions of the input signals. The new fuzzy PD controller thus preserves the simple linear structure of the conventional PD controller yet enhances its self-tuning control capability. Computer simulation results have demonstrated this advantage of the fuzzy PD controller, particularly when the process to be controlled is nonlinear. After a detailed stability analysis, where a simple and realistic sufficient condition for the bounded-input/bounded-output stability of the overall feedback control system was derived, several computer simulation results are compared with the conventional PD controller. Although the conventional and fuzzy PD controllers are not exactly comparable, the authors compare them in order to have a sense of how well the fuzzy PD controller performs. For this reason, in the simulations several first-order and second-order linear systems, with or without time-delays, are first used to test the performance of the fuzzy PD controller for step reference inputs: the fuzzy PD control systems show remarkable performance, as well as (if not better than) the conventional PD control systems. Moreover, the fuzzy PD controller is compared to the conventional PD controller for a particular second-order linear system, showing the advantage of the fuzzy PD controller over the conventional one in the sense that in order to obtain the same control performance the conventional PD controller has to employ an extremely large gain while the fuzzy controller uses a reasonably small gain. Finally, in the case of nonlinear systems, the authors provide some examples to show that the fuzzy PD controller can track the set-points satisfactorily but the conventional PD controller cannot.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
The important tracking problem by radar of an incoming ballistic missile system, which contains uncertainty in modeling and noise in both dynamics and measurements, is studied. The classical extended Kalman filter (EKF) is no longer applicable to such an uncertain system, and so a new extended interval Kalman filter (EIKF) is developed for tracking the missile system. Computer simulation is presented to show the effectiveness of the EIKF algorithm for this uncertain and nonlinear ballistic missile tracking problem.
