Abstract: In this paper, we consider the analysis of the
acquisition process for a hybrid double-dwell system with antenna
diversity for DS-CDMA (direct sequence-code division multiple
access) using an adaptive threshold. Acquisition systems with a fixed
threshold value are unable to adapt to fast varying mobile
communications environments and may result in a high false alarm
rate, and/or low detection probability. Therefore, we propose an
adaptively varying threshold scheme through the use of a cellaveraging
constant false alarm rate (CA-CFAR) algorithm, which is
well known in the field of radar detection. We derive exact
expressions for the probabilities of detection and false alarm in
Rayleigh fading channels. The mean acquisition time of the system
under consideration is also derived. The performance of the system is
analyzed and compared to that of a hybrid single dwell system
Abstract: This letter further improves and extends the work of Kemih et al. In detail, feedback passivity synchronization with only one controller for a unified chaotic system is discussed here. It is noticed that the unified system contains the noted Lorenz, Lu, and Chen systems. Numerical simulations are given to show the effectiveness of these methods.
Abstract: Nuclear spin generator (NSG) is a high-frequency oscillator which generates and controls the oscillations of the motion of a nuclear magnetization vector in a magnetic field. This system exhibits a large variety of chaotic behaviors and displays much richer structures. So it is “a better archetypal system than the Lorenz system”. Based on the property of passive system, the essential conditions were studied; by which nuclear spin generator system could be equivalent to passive system. Using Lyapunov stability theory, the convergence condition deciding the system’s characters was discussed. In the convergence condition area, the equivalent passive system could be globally asymptotically stabilized by smooth state feedback. Simulation results are provided to show the effectiveness of the proposed control method
Abstract: In this work, we propose an approach for the application of the
input constrained generalized predictive control, GPC, to
nonlinear systems. To solve the problem of non linearity of the
system, we propose a method of fuzzy modeling of Sugeno
closely connected the concepts of multi model. On the other
hand, we propose and compare methods for online solution of
the constrained optimization problem which are variants of the
classical Dichotomy and gradient conjugate method. The
simulation study is carried for the control of continuously stirred
reactor, CSTR
Abstract: Recently, how to apply chaos has become the researching focus. Chaos control and anti-control is the big problem of the application of chaos. This paper presents the generalized predictive control under constraint coupled with Genetical algorithm applied to control chaotic Lu system. Simulation results indicated that the proposed chaos control method is very effective in Lu chaotic system.
Notes: constrained generalized predictive control;chaotic Lu system;chaos control;genetical algorithm;
Abstract: A new approach for the control of a micro-satellite is presented. This new approach is based on a generalized predictive control using conjugate gradient scheme which determines the required torque input so that the predicted responses match the desired trajectories. This is accomplished by minimizing the norm-squared local errors between the predicted and desired quantities. Using a constraints reduction method developed elsewhere, we show how the gradient method can be applied to solve the constrained generalised predictive control efficiently and with less computation burden than that of the recursive least squares method. The simulation results are shown which use the new control strategy to stabilize the Micro-satellite.
Abstract: There exists an increasing demand for reliable, high capacity under-water acoustic networks (UANS), as evidenced by the large volume of research invested over the last decade in overcoming the difficulties inherent with propagation of information bearing signals through shallow water regions. In this paper, we investigate the problem synchronization of chen system based on passivity technique for Code Division Multiple Access (CDMA) underwater communication in order to minimize interference (MAI) caused by the multiple access by using Chen system for spreading sequence, assure the transmitter-receiver synchronization and secure the transmission information. The numerical result presented show that system is quickly and perfectly synchronized with the proposed method.
Abstract: In direct sequence code division multiple access (DS-CDMA) applications, system performance depends on the autocorrelation and cross-correlation properties of the used spreading sequences. In this paper, we propose the uses of chaotic Chen system to generate binary sequences for spreading codes in a direct sequence spread CDMA system. To minimize multiple access interference (MAI) we propose the use of genetic algorithm for optimum selection of Binary chaotic spreading sequences. Experimental results showed that MAI could be greatly reduced.
Abstract: Control chaos of the Lu, system was discussed by using the passive control theory, with the study of the property of passive system, the essential conditions under which the Lu system could be equivalent to a passive system via smooth state feedback were derived. It was found that the new system transformed by the Lu chaotic system, could be globally asymptotically stabilized at different equilibrium points, provided that suitable controllability-like rank conditions were satisfied. Simulation results indicated that the proposed chaos control method is very effective in Lu chaotic system.
Abstract: This paper presents the generalized predictive control under constraint coupled with Genetical algorithm applied to the magnetic levitation (MAGLEV) system. In certain process the change of a control variable affects several variables to control these interactions between the variables of the process generate very weak performances of the system to control and even provoke the instability. In this work the design of the controller that can maintain the balance between the magnetic force and the weight of the ball is based on a method of constraint reduction. A GA is proposed whose aim is to find on line the optimal values for the tuning parameters, mainly prediction and control horizon. The algorithm proposed provides a robust closed-loop magnetic levitation system which can stabilize the system over a large range of variations of the suspended mass. In order to verify the feasibility of this method the results obtained by Constrained generalized predictive control (CGPC) coupled with an estimation of design parameters by GA are compared to those obtained by CGPC control using Gradient conjuged method.
Abstract: This paper investigates the problem of spreading
sequence and receiver code synchronization techniques for satellite
based CDMA communications systems. The performance of CDMA
system depends on the autocorrelation and cross-correlation
properties of the used spreading sequences. In this paper we propose
the uses of chaotic Lu system to generate binary sequences for
spreading codes in a direct sequence spread CDMA system. To
minimize multiple access interference (MAI) we propose the use of
genetic algorithm for optimum selection of chaotic spreading
sequences. To solve the problem of transmitter-receiver
synchronization, we use the passivity controls. The concept of
semipassivity is defined to find simple conditions which ensure
boundedness of the solutions of coupled Lu systems. Numerical
results are presented to show the effectiveness of the proposed
approach
Abstract: In this paper, an adaptive control based on the gradient method is proposed for the predictive control of monovariable systems subject constraints. Using a constraints reduction method developed elsewhere, we show how the conjugate gradient algorithm can be applied to solve the constrained generalised predictive control efficiently and with less computation burden than other methods. It is also shown that this method with genetic algorithm for system identification can give good results
Abstract: In this paper, we develop a software package on C++Builder language that consists to made a combination between chaos based spread sequence for DS-CDMA combined with covolutional code and with the discrete wavelet transform in microsatellite communication. The proposed strategy is based on tow key ideas. The first concept consist the use of the chaotic spread-spectrum using discrete-time synchronization in order to minimize interference (MAI) caused by the multiple access, to assure the transmitter-receiver synchronization and to secure the transmission information. The second idea consist the use of convolutional code with Viterbi algorithm and discrete wavelet transform to decreases SNR in order to increases system capacity. The attractable software obtained can be suitably inserted as a routine code in a large software package.
