Small Synchronization Error Research Articles

Study of Multi-motor Synchronous Operation Based on Sliding Mode Virtual Spindle Adjacent Cross-coupling Control

Aiming at the problems of uneven parameter differences and load torque distribution, which cause the tracking accuracy and synchronization performance of the multi-motor control system to be reduced, a multi-motor system control strategy with sliding mode virtual spindle adjacent cross-coupling control is proposed. First, the feedback torque of each motor is regulated by establishing a virtual spindle to improve the coordination of the system. Secondly, a speed compensator is designed to couple each motor to improve the system synchronization. Meanwhile, the sliding mode control strategy is used for the control of a single motor. The robustness and tracking accuracy of the system are tuned up. The simulation experiment results show that compared with the sliding mode cross-coupling control, sliding mode adjacent deviation coupling control, and PI virtual spindle-adjacent deviation coupling control, the system has a small synchronization error, strong anti-interference ability, and realizes high-precision coordinated control of multiple motors.

Minimal underactuated synchronization with applications to secure communication

This work deals with the synchronization of a class of underactuated hyperchaotic systems. The proposed method is based on Lyapunov theory, and it assumes a small initial synchronization error to simplify the synchronizer structure. The proposed synchronization method ensures the convergence of the synchronization error to a neighborhood of the origin, even employing a scalar proportional control law and in the presence of full-state disturbances. A comparison study is accomplished to depict the advantages of the proposed method. Furthermore, a secure communication system based on the proposed synchronization approach is implemented using analog electronics to show a typical application.

Anticipatory synchronization via low-dimensional filters

An anticipatory chaotic synchronization scheme based on a low-order all-pass filter is proposed. The filter is designed as a Padé approximation to the transfer function of an ideal delay line, which is used in a standard Voss scheme. We show that despite its simplicity, the filter works in an anticipatory scheme as well as an ideal delay line. It provides extremely small synchronization error in the whole interval of anticipation time where the anticipatory manifold is stable. The efficacy of our scheme is explained by an analytically solvable model of unidirectionally coupled unstable spirals and confirmed numerically by an example of unidirectionally coupled chaotic Rössler systems.

The effect of non-synchronous sensing on structural identification and its correction

The goal of this study is to investigate the effect of non-synchronous sensing when using wireless sensors on structural identification and to attempt correcting such errors in order to obtain a better identification result. The sources causing non-synchronous sensing are discussed first and the magnitudes of such synchronization errors are estimated based on time stamps of data samples collected from Imote2 sensors; next the impact of synchronization errors on power spectral densities (PSDs) and correlation functions of output responses are derived analytically; finally a new method is proposed to correct such errors. In this correction method, the corrected PSDs of output responses are estimated using non-synchronous samples based on a modified FFT. The effect of synchronization errors in the measured output responses on structural identification and the application of this correction method are demonstrated using simulation examples. The simulation results show that even small synchronization errors in the output responses can distort the identified modal and stiffness parameters remarkably while the parameters identified using the proposed correction method can achieve high accuracy.

Robust output synchronization of second-order systems

A technique to synchronize a network of dynamical systems described by second-order ordinary differential equations is presented. Each system can be driven by a coupling control signal, which is synthesized such that, at steady-state, the outputs of two given systems, say y i and y j , i ≠ j, satisfy a specified ratio, that is, y i /y j = α i /α j , α i ≠ 0 ≠ α j . Among others, this includes the cases where the outputs are synchronized in-phase or anti-phase. The proposed synchronization technique is robust; this means that a small synchronization error is preserved at steady-state, even if the systems were perturbed by external disturbances. Some level of parameter uncertainty can also be tolerated. The coupling control signals are synthesized based on a classical controller and a robust observer that estimates the generalized velocities and provides an estimation of the perturbation terms. Some experimental results, showing the performance of the proposed synchronization technique, are included.

Synchronization and Adaptive Anti‐Synchronization Control for Lorenz Systems under Channel Noise with Applications

AbstractThis paper studies synchronization and adaptive anti‐synchronization control for Lorenz systems with applications to secure communication, where the transmission channel is subject to noise disturbance and the parameters of the Lorenz systems are allowed to be uncertain. Based on the methods of the Lyapunov function, input‐to‐state stability theory, nonlinear parametric variation, and the Barbalat Lemma, estimates for errors of synchronization and adaptive anti‐synchronization are derived. These estimates help to design the feedback control and adaptive control laws with relatively small synchronization error bounds. Moreover, the information signal error in secure communication is also derived, which is used to design a secure communication scheme with a lower disturbance from channel noise and with higher security. Simulations are given to demonstrate the results.

Bounds on the Capacity of Discrete Memoryless Channels Corrupted by Synchronization and Substitution Errors

We study the capacity of discrete memoryless channels with synchronization errors and additive noise. We first show that with very large alphabets, their capacity can be achieved by independent and identically distributed input sources, and establish proven tight lower and upper capacity bounds. We also derive tight numerical capacity bounds for channels where the synchronization between the input and output is partly preserved, for instance using incorruptible synchronization markers. Such channels include channels with duplication errors, channels that only insert or delete zeros, and channels with bitshift errors studied in magnetic recording. Channels with small alphabets and corrupted by synchronization errors have an infinite memory. Revisiting the theoretical work of Dobrushin and adapting techniques used to compute capacity bounds for finite-state source/channel models, we compute improved numerical capacity lower bounds for discrete memoryless channels with small alphabets, synchronization errors, and memoryless noise. An interesting and some- what surprising result is that as long as the input sequences are not completely deleted, the capacity of channels corrupted by discrete timing errors is always nonzero even if all the symbols are corrupted.

A Hybrid Interference Cancellation technique for overloaded CDMA with timing offset error

A novel method of Hybrid Parallel/Successive Interference Cancellation (HIC) for Overloaded Direct Sequence Code Division Multiple Access (OCDMA) system involving two groups of users is proposed in this paper. The impact of timing synchronization error on acceptable channel load in a synchronous binary spread CDMA system is studied by mitigating the effect of multi-access interference (MAI). A small timing synchronization error is introduced in the DS-CDMA system under study to disturb the orthogonality of group-1 users and group-2 users. This orthogonality loss leads to Multi User Interference (MUI) in group-1 users and it is cancelled using Parallel Interference Cancellation (PIC). The interference of group-2 users on group-1 users is cancelled using Successive Interference Cancellation (SIC). The analytical expressions of the Bit Error Rate (BER) are derived. The simulation results prove that the BER performance of the proposed HIC method is better than the conventional PIC and SIC.

A Method for Correcting Synchronization Errors in Wireless Sensors for Structural Modal Identification

The effect of non-synchronous sensing when using wireless sensors on structural modal identification is addressed and a methodology for correcting such errors is proposed herein. This paper first discusses the potential sources causing non-synchronous sensing and estimates the extent of non-synchronous sensing based on data collected from Imote2 sensors, and then investigates the impact of synchronization errors in the measured output response on modal identification using numerical simulations. The simulation results show that even small synchronization errors in the output response can distort the identified mode shapes. A new methodology is proposed herein for eliminating such errors. This methodology estimates the power spectral densities (PSDs) of output responses using non-synchronous samples directly based on a modified FFT. As long as the corrected PSDs are obtained, the correlation functions can also be easily obtained by IFFT. Then these corrected PSDs or correlation functions can be fed into various outputonly modal identification algorithms. The proposed methodology is validated using numerical simulations. It is found that the simulation results closely match the identified parameters based on synchronous data.

Time Synchronization for Cooperative Communication in Wireless Sensor Networks

Time synchronization is crucial for the implementation of cooperative communication in wireless sensor networks. In this paper, we explore the effect of synchronization error on cooperative communication utilizing distributed Alamouti code. The analysis and simulation results show that small synchronization error has negligible effect on bit error rate (BER) performance. In order to synchronize the distributed sensor nodes within an acceptable error, we propose a physical layer synchronization scheme. This scheme consists of an initial synchronization of the cooperative transmitters, synchronization error estimation at the cooperative receiver and finally a feedback phase. A maximum likelihood method is proposed to make the synchronization error estimation. It achieves better performance than the matched filter method at the price of moderate increase in computational complexity and memory space. Two strategies after synchronization error estimation have been analyzed. They provide better BER performance in the existence of initial synchronization error. They are practical to be implemented in the sensor nodes before the Alamouti decoding.

ROBUST SYNCHRONIZATION OF CHAOTIC LUR'E SYSTEMS VIA REPLACING VARIABLES CONTROL

The sufficient conditions for chaos synchronization of two nonidentical systems by replacing variables control have not been proposed until now. In this paper, synchronization of two chaotic Lur'e systems with parameter mismatch by replacing variables control is studied. First of all, we present a master-slave Lur'e systems synchronization scheme with both parameter mismatch and replacing variables control, and derive a responsive error system for the scheme. A new definition of synchronization with finite L 2-gain is then introduced. Based on the definition, the sufficient synchronization criteria which are in the form of linear matrix inequality (LMI) are proved using a quadratic Lyapunov function. By means of MKY lemma the frequency domain criteria are further derived from the obtained LMIs. These frequency domain criteria are illustrated on the master-slave Chua's circuits with parameter mismatch so that the ranges of the parameters of Chua's circuit are analytically solved in the sense of the synchronization with finite L 2-gain by replacing singe-variable control. The illustrative examples verify that within the ranges of the parameters it is possible to synchronize the master-slave Chua's circuits up to a small synchronization error bound, even the qualitative behaviors of the slave circuit are different from that of the master one, such as the trajectory of the master circuit is chaotic and that of the slave divergent. The relation between the synchronization error bound and parameter mismatch is shown.

Synchronization sensitivity of multicarrier systems

AbstractIn this paper, we give an overview of the sensitivity of a number of multicarrier systems to carrier and clock synchronization errors. A comparison is made between orthogonal frequency division multiplexing/multiple access (OFDM(A)) and two combinations of the orthogonal multicarrier technique and the code‐division multiple access (CDMA) technique, i.e. multicarrier CDMA (MC‐CDMA), where the spreading is accomplished in the frequency domain and multicarrier direct‐sequence CDMA (MC‐DS‐CDMA), where the spreading is done in the time domain. We evaluate the effect of small synchronization errors on the BER performance by deriving simple analytical expressions for the BER degradation that are based upon truncated Taylor series expansions. To allow a fair comparison, all considered systems are able to accommodate the same number of users and each user operates at the same data rate. Under these conditions, we show that all multicarrier systems exhibit the same sensitivity to carrier phase jitter and timing jitter. Further, when the number of carriers is equal to the maximum number of users, the different multicarrier systems also are equally affected by a carrier frequency offset or a clock frequency offset. Copyright © 2004 AEI

When are synchronization errors small?

We address the question of bounds on the synchronization error for the case of nearly identical nonlinear systems. It is pointed out that negative largest conditional Lyapunov exponents of the synchronization manifold are not sufficient to guarantee a small synchronization error and that one has to find bounds for the deformation of the manifold due to perturbations. We present an analytic bound for a simple subclass of systems, which includes the Lur'e systems, showing that the bound for the deformation grows as the largest singular value of the linearized system gets larger. Then, the Lorenz system is taken as an example to demonstrate that the phenomenon is not restricted to Lur'e systems.

A CDMA based bidirectional communication system for hybrid fiber-coax CATV networks

Hybrid fiber-coax CATV networks are considered a promising infrastructure for the implementation of future interactive services. Efficient utilization of the available CATV spectrum requires a communication system which is dedicated to the specific properties of these networks. This paper presents the physical layer of a bidirectional communication system for HFC CATV networks which is based on CDMA, a technique that has a certain robustness to the ingress noise found in the CATV bandwidth. Because the application of asynchronous CDMA results in a poor spectral efficiency, a transmission scheme based on synchronous CDMA is adopted. Using synchronous CDMA and QPSK modulation, a capacity of 64 channels of 64 kbit/s each can be achieved in a bandwidth of 6 MHz. It is found that small synchronization errors can be tolerated without significant performance degradation. Next, a description is given of the cable modems responsible for the communication between subscribers and a CATV headend. The design exploits the typical CATV network configuration to enable a cost-effective hardware realization. Sensitivity of system performance to linear distortion is investigated by computer simulation. Especially linearly varying group delay and uneven amplitude response are shown to be potential causes of performance degradation.