Time Delay In Signal Transmission Research Articles

Analytical Studies on Approximate Lag and Anticipating Synchronization in Two Unidirectionally Coupled Hyperchaotic Chen Systems without Time Delay

In this paper, approximate lag synchronization (LS) and anticipating synchronization (AS) between two unidirectionally coupled hyperchaotic Chen systems without time-delay coupling are analytically investigated. Firstly, the synchronization condition for exact LS in two unidirectionally coupled hyperchaotic Chen systems with time delay in signal transmission is analytically obtained. Under such conditions, approximate LS and AS are discussed by replacing the true time-delay terms with their Taylor expansions up to the third order.Differently from other research studies, the condition for exact LS is derived by regarding LS as a special type of generalized synchronization (GS), which has nothing to do with the value of the time delay. It is convenient to individually change the value of the lag and anticipation time of approximate LS and AS without considering the synchronization condition. Our study shows the power of a new method for recreating the past signals or predicting the future signals of a hyperchaotic Chen system by using its current signals. The results provide a simple way to eliminate the negative effects of time delay in the signal transmission between two hyperchaotic systems.

Time delay effect reduction on the wireless networked control system using an optimized FOPI-FOPD controller

Wireless Networked Control System (WNCS) is made up of an actuator, sensor, and controller that communicates through a wireless network rather than typical point-to-point cable connections. Lower maintenance costs, greater flexibility, and increased safety are the main WNCS advantages, so as a result, it has attracted a lot of researchers. Nevertheless, time delays and packet losses in wireless data transmission are classified as complicated problems, which impair WNCS output accuracy and may influence the overall system stability. Integer-Order PI-PD (PI-PD) and Fractional-Order PI-PD (FOPI-FOPD) controllers are proposed to reduce the impact of the control signal transmission's time delay and improve system performance. Matlab Simulink and True-time simulator are used to simulate the WNCS, and ZigBee protocol is used in transceiving the control signal between the controller and the system. Rotary Inverted Pendulum (RIP) acted as the controller's objective. The Grey Wolf Optimization (GWO) technique is utilized to evaluate the best controller parameters. Xbee S2 modules are used to implement the signal transmission process over ZigBee protocol. The FOPI-FOPD controller outperforms the PI-PD controller in the simulation and experimental results in decreasing the influence of time delay on system stability

Robust Speed Tracking Control for Future Electric Vehicles under Network-Induced Delay and Road Slope Variation.

Integrated motor-transmission (IMT) powertrain systems are widely used in future electric vehicles due to the advantages of their simple structure configuration and high controllability. In electric vehicles, precise speed tracking control is critical to ensure good gear shifting quality of an IMT powertrain system. However, the speed tracking control design becomes challenging due to the inevitable time delay of signal transmission introduced by the in-vehicle network and unknown road slope variation. Moreover, the system parameter uncertainties and signal measurement noise also increase the difficulty for the control algorithm. To address these issues, in this paper a robust speed tracking control strategy for electric vehicles with an IMT powertrain system is proposed. A disturbance observer and low-pass filter are developed to decrease the side effect from the unknown road slope variation and measurement noise and reduce the estimation error of the external load torque. Then, the network-induced delay speed tracking model is developed and is upgraded considering the damping coefficient uncertainties of the IMT powertrain system, which can be described through the norm-bounded uncertainty reduction method. To handle the network-induced delay and parameter uncertainties, a novel and less-conservative Lyapunov function is proposed to design the robust speed tracking controller by the linear matrix inequality (LMI) algorithm. Meanwhile, the estimation error and measurement noise are considered as the external disturbances in the controller design to promote robustness. Finally, the results demonstrate that the proposed controller has the advantages of strong robustness, excellent speed tracking performance, and ride comfort over the current existing controllers.

Global Mittag-Leffler Synchronization of Fractional-Order Neural Networks With Time-Varying Delay via Hybrid Sliding Mode Control

In this paper, the global Mittag-Leffler synchronization (GMLS) for fractional-order neural networks with time-varying delay (FNNTVD) is studied based on hybrid sliding mode control (HSMC). First, a class of sliding surface is designed to study the dynamic behavior of FNNTVD by using the integer order Lyapunov direct method, which resolves the problem that the activation function of FNNTVD cannot be applied to the construction of Lyapunov function in the previous literature. Then, a new HSMC with the fixed signal transmission time delay is developed to ensure GMLS of FNNTVD. Next, based on Lyapunov direct method and the designed HSMC, some criteria are put forward to achieve GMLS of FNNTVD. Finally, two examples are given to verify the effectiveness of the proposed synchronization criteria for FNNTVD.

Influence of Time Delay in Signal Transmission on Synchronization between Two Coupled FitzHugh-Nagumo Neurons

In this paper, the energy method is employed to analytically investigate the influence of time delay in signal transmission on synchronization between two coupled FitzHugh-Nagumo (FHN) neurons. Unlike pre-existing methods that deal with synchronization problems, our major idea is to consider the change rate of the energy of the synchronization error system, since the original system’s synchronization is equivalent to the disappearance of the energy of the error system. In rewriting the original coupled system in the corresponding energy coordinates based on the energy method, we find that the change rate of energy of the error system can be divided into two parts (periodic and non-periodic). The synchronization criterion for the original system can then be obtained by letting the non-periodic part of the change rate of the energy be less than zero. The correctness of the analysis is illustrated with numerical simulations. Our analytical results show that time delay in signal transmission has very significant effects on the synchronization between two FHN neurons. If the time delay in signal transmission is not taken into account in the two coupled FHN neurons, synchronous spikes cannot be achieved in the system for any given coupling strength. By adjusting the value of the time delay in signal transmission, the neural system can freely switch between neural rest and synchronous spikes. This means that time delay in signal transmission is crucial for the occurrence of synchronous spikes in the FHN neural system, which contributes to our understanding of the interaction between neurons. We analytically show the influence of the time delay on the synchronization between two FHN neurons, which was seldom considered by other researchers.

Wide-area damping state feedback and output feedback controller design strategy considering time delays and actuator saturation based on parametric Lyapunov theory

Remote signal transmission time delays are the major factors to affect the performance of wide-area damping controller (WADC) and even deteriorate stability of large-scale power system. If the physical structure and the mathematical model of the system are different, the method of mathematically dealing with time delay is not the same. From the perspective of mathematical application engineering, there are two main ways to deal with the communication time delay: linear matrix inequalities (LMI) theory and conventional time-delay predictive compensation theory. Traditional time delay damping controller based on linear matrix inequalities (LMI) suffers relatively large conservatism and complexity. Traditional time delay damping controller based on time delay compensation has no clear relation between the control parameter and the time delay. On the other hand, the saturation of actuator leads to the deterioration of control performance and even threat system stability. The existing methods for saturation are negative feedback anti-saturation after the actuator is saturated, which is an afterwards control and it is difficult to well eliminate the influence of saturation. In this paper, a novel design strategy for wide-area time-delay damping controller based on parametric Lyapunov theory is derived. The explicit expression of the controller parameter value associated with the time delay is determined. This strategy can deal with arbitrary large time-vary delay theoretically and have extremely low controller dimension, which makes it have potential capability to be applied in large-scale inter-connected power systems. The control strategy is determined according to the system stability original definition (The system energy function is finite and positive and its first derivative is negative), which avoids complex matrix inequalities cyclic solution and reduces the conservatism of the controller. Moreover, it can directly give simple and explicit control law and specific control parameters, which enable this method to adjust its parameters online according to the exact time delay obtained by GPS. In the design process, the saturation characteristics of the actuator are taken into account in the linearization model of the closed-loop system. This makes it very adaptable to actuator saturation, so that the proposed design strategy can ensure the small signal stability of the closed-loop system considering time delays and actuator saturation. Case study is undertaken based on a New England ten-machine 39-bus power system, which stands for a large scale power system to verify the feasibility and effectiveness of the proposed design strategy. Compared with the free weight matrix damping controller (FWMC), which is a kind of LMI-based design strategy with excellent performance, the advantages and superiority of the proposed control strategy are verified. The proposed design strategy based on state feedback and output feedback has better control performance than FWMC.

Automatic Control Systems for Adaptive Optical Systems. Analytical review. Part 2: Application of the Adaptive Filtering and Control at the Spaced Frequencies

The second part of the analytical review considers in detail an adaptive filtering application in the systems of adaptive optical systems (AOS) from the perspective of the airborne laser platforms. Herein the AOS operates under aero-optical distortions and vibrations, which further complicate the propagation of the laser beam. Adaptive filtering is considered as a way to improve the efficiency of the control system of adaptive optical systems, allowing to improve running an adaptive optics control loop: by 1.5-2 times with compensation for only the aero-optical disturbances, by 1.5 times with compensation only for the free-stream turbulence, and by 2.5-3.5 times for the combination of aero-optics and free-stream turbulence.The article discusses implementation of a new type of the controller, which uses intellectual algorithms to predict (through an artificial neural network) a short-term horizon of evolution of aberrations due to aero-optical effect. This controller allows us to deal with a large time delay in signal transmission (up to 5 time steps of sampling).The application of two deformable mirrors in the adaptive optical system to provide control at the spaced frequencies is especially considered. A low-frequency mirror is used to correct the lower-order aberrations (tip-tilt, defocusing, astigmatism, coma) requiring large strokes of executive mechanisms (actuators) in the deformable mirror. A high-frequency mirror is used to correct the higher-order aberrations requiring small strokes of drives. Various control algorithms to control the system from two adaptive mirrors are briefly reviewed.The obtained results, conclusions, and recommendations are supposedly to be used in development of specification of requirements for systems of adaptive optics.

Recovery Time of Silicon Photomultiplier with Epitaxial Quenching Resistors

The silicon photomultiplier (SiPM) is a promising semiconductor device for low-level light detection. The recovery time, or the photon-counting rate of the SiPM is essential for high-flux photon detection in such applications as photon counting computer tomography (CT). A SiPM with epitaxial quenching resistors (EQR SiPM) has advantages in fabricating small APD microcells connected in series with lower quenching resistors, therefore, APD cells with a low RC time constant and a short recovery time can be expected. In this report, the recovery time of EQR SiPM has been investigated using both the double light pulse method and the waveform analysis method. The results show that the recovery time of EQR SiPM is strongly dependent on the size of the active area and the number of fired pixels. For a 3 × 3 mm2 device, while total about 90,000 pixels were fired, the recovery time was 31.1 ± 1.8 ns; while fired pixels were controlled to about 2000, the recovery time decreased significantly to 6.5 ± 0.4 ns; and the recovery time of one fired pixel was 3.1 ± 0.2 ns. For 1.4 × 1.4 mm2 device, the recovery time was 15.2 ± 0.5 ns, while a total of about 20,000 pixels were fired. Effects that may affect the recovery time of the SiPM, including strength of the pulse light, signal transmission time delay, and the readout electronics are discussed.

Tunnel personnel positioning method based on TOA and modified location-fingerprint positioning

To position personnel in mines, the study discussed in this paper built on the tunnel personnel positioning method on the basis of both TOA and location-finger print (LFP) positioning. Given non-line of sight (NLOS) time delay in signal transmission caused by facilities and equipment shielding in tunnels and TOA measurement errors in both LFP database data and real-time data, this paper puts forth a database data de-noising algorithm based on distance threshold limitation and modified mean filtering (MMF), as well as a real-time data suppression algorithm based on speed threshold limitation and MMF. On this basis, a nearest neighboring data matching algorithm based on historical location and the speed threshold limitation is used to estimate personnel location and realize accurate personnel positioning. The results from both simulation and the experiment suggest that: compared with the basic LFP positioning method and the method that only suppresses real-time data error, the tunnel personnel positioning methods based on TOA and modified LFP positioning permits effectively eliminating error in TOA measurement, making the measured data close to the true positional data, and dropping the positioning error: the maximal positioning error in measurements from experiment drops by 9 and 3m, respectively, and the positioning accuracy of 3m is achievable in the condition used in the experiment.

Experimental and numerical visualizations of swirling flow in a vertical pipe

This paper presents a comparison between the experimental and numerical simulations of turbulent swirling flow induced by twisted tape in vertical pipe. A novel measurement technique, phased array ultrasonic velocity profiler (UVP), has been developed for 2D velocity field visualization in swirling flow. A phased array with basic frequency 4 MHz has been designed, it has eight piezoelectric elements and each element transmits ultrasound beam. The advantage of this sensor is that the ultrasound beam can be controlled easily by changing the time delay of signal transmission for each element. A vector reconstruction algorithm is presented showing how the velocity vector of particles can be calculated from Doppler-shift frequencies taken from the output signals of two receiver elements. Two-dimensional velocity field has been visualized and it is found, as expected, that the presence of swirl cause a significant increase in the magnitude of the measured tangential velocity. Furthermore, a numerical calculation is performed and qualitatively compared with experimental results. The numerical result is obtained by solving three-dimensional, Reynolds-averaged Navier–Stokes equations by the commercial CFD code FLUENT® v.14.5 with RNG k-e turbulence model. The qualitative comparison between phased array UVP and CFD results shows good agreement with the average velocity field. Experimental and numerical findings and parametric trends based on the effects of swirling flow are summarized and discussed.

Global Lagged Finite-Time Synchronization of Two Chaotic Lur’e Systems Subject to Time Delay

This paper investigates the global lagged finite-time synchronization of the master-slave Lur’e systems subject to time delay of signal transmission. By designing a variable-substitution and feedback controller, a master-slave finite-time synchronization scheme for the Lur’e systems with time delay is built up. Two delay-independent global lagged finite-time synchronization criteria are proved in the forms of linear matrix inequalities (LMIs), and the corresponding settling time of synchronization is analytically estimated. The obtained LMI criteria are applied to Chua’s oscillators, obtaining some easily implemented algebraic criteria under various single-variable-substitution and feedback controller, which are then optimized to improve their conservative property. Finally, several numerical examples are illustrated to verify the effectiveness of the optimized criteria.

Design and implementation of a measurement-based adaptive wide-area damping controller considering time delays

Wide-area measurement systems enable the wide-area damping controller (WADC) to use remote signals to enhance the small signal stability of large scale interconnected power systems. System operating condition variations and signal transmission time delays are the major factors to worsen the damping effect and even deteriorate the system stability. This paper proposes a novel measurement-based adaptive wide-area damping control scheme using oscillation mode prediction and system identification techniques. These techniques adjust the parameters of WADC as well as the time delay compensation in an online environment. To achieve fast online implementation, an identified high order multi-input multi-output (MIMO) model is deformed into a low order single-input single-output (SISO) model according to the residue of MIMO model. The SISO model can accurately represent the power system dynamics in the form of a transfer function, capturing the dominant oscillatory behaviors in the frequency range of interest. Moreover, the WADC has been implemented on a hardware test-bed (HTB) by adding its output signal to the excitation system of a selected generator. The effectiveness of the proposed measurement-based adaptive WADC has been demonstrated in a two-area four-machine system on the HTB under various disturbance scenarios.

Adaptive Wide-Area Damping Control Scheme for Smart Grids with Consideration of Signal Time Delay

As an important part of the smart grid, a wide-area measurement system (WAMS) provides the key technical support for power system monitoring, protection and control. But 20 uncertainties in system parameters and signal transmission time delay could worsen the damping effect and deteriorate the system stability. In the presented study, the subspace system identification technique (SIT) is used to firstly derive a low-order linear model of a power system from the measurements. Then, a novel adaptive wide-area damping control scheme for online tuning of the wide-area damping controller (WADC) parameters using the residue method is proposed. In order to eliminate the effects of the time delay to the signal transmission, a simple and practical time delay compensation algorithm is proposed to compensate the time delay in each wide-area control signal. Detailed examples, inspired by the IEEE test system under various disturbance scenarios, have been used to verify the effectiveness of the proposed adaptive wide-area damping control scheme.

Influence of the time delay of signal transmission on synchronization conditions in drive-response systems

Conditions for complete and lag synchronizations in drive-response systems are considered under the unified framework of generalized synchronization. The question is addressed that whether the synchronization conditions achieving complete synchronization is still valid for lag synchronization when the time delay of signal transmission between the drive and response systems increases from 0. Theoretical and numerical results show that whether the synchronization conditions is stable for the influence of the time delay of signal transmission depends on a particular form of equilibria of the drive and response systems. Furthermore, it seems that the less the number of the equilibria of the drive system, the more likely the synchronization conditions are stable for the time delay of signal transmission.

Adaptive wide-area damping control scheme with stochastic subspace identification and signal time delay compensation

Remote signals available from the wide-area monitoring system could be used to enhance the stability of large interconnected power systems with the help of a wide-area damping controller (WADC). Uncertainty in system parameters and signal transmission time delay are the major factors, which could worsen the damping effect and deteriorate the system stability. This study presents a novel adaptive wide-area damping control scheme in which oscillation modes will be identified online using stochastic subspace identification for online tuning of the WADC structure and parameters using the residue method. A simple and practical signal time delay compensation algorithm will also be proposed to measure and compensate the time delay in each wide-area control signal so as to eliminate the effects of signal time delay on the proposed adaptive WADC. The effectiveness and robustness of the proposed adaptive wide-area damping control scheme have been verified with simulation studies on the IEEE 16-generator 5-area test system under various disturbance scenarios.

Spacecraft Formation Orbit Estimation Using WLPS-Based Localization

This paper studies the implementation of a novel wireless local positioning system (WLPS) for spacecraft formation flying to maintain high-performance spacecraft relative and absolute position estimation. A WLPS equipped with antenna arrays allows each spacecraft to measure the relative range and coordinate angle(s) of other spacecraft located in its coverage area. The dynamic base station and the transponder of WLPS enable spacecraft to localize each other in the formation. Because the signal travels roundtrip in WLPS, and due to the high spacecraft velocities, the signal transmission time delay reduces the localization performance. This work studies spacecraft formation positions estimation performance assuming that only WLPS is available onboard. The feasibility of estimating the spacecraft absolute position using only one-dimensional antenna array is also investigated. The effect of including GPS measurements in addition to WLPS is studied and compared to a GPS standalone system.

Time-delay-induced phase-transition to synchrony in coupled bursting neurons

Signal transmission time delays in a network of nonlinear oscillators are known to be responsible for a variety of interesting dynamic behaviors including phase-flip transitions leading to synchrony or out of synchrony. Here, we uncover that phase-flip transitions are general phenomena and can occur in a network of coupled bursting neurons with a variety of coupling types. The transitions are marked by nonlinear changes in both temporal and phase-space characteristics of the coupled system. We demonstrate these phase-transitions with Hindmarsh-Rose and Leech-Heart interneuron models and discuss the implications of these results in understanding collective dynamics of bursting neurons in the brain.

Phase synchronization of inhibitory bursting neurons induced by distributed time delays in chemical coupling

Considering the fact that signal transmission time delays between different pairs of synaptically coupled neurons in the brain are different, we study the effects of distributed time delays on phase synchronization of bursting neurons. We consider the case of inhibitory coupled bursting Hindmarsh-Rose neurons and find that distributed time delays in chemical coupling can induce a variety of phase-coherent dynamic behaviors. The critical mean time delay for the emergence of coherent behaviors is inversely proportional to both the coupling strength and the average degree. This phenomenon is robust to nonidentical external inputs and is independent of network topology. A physical theory is formulated to explain the emergence of coherent neuronal activity.

Simple zero singularity analysis in a coupled FitzHugh–Nagumo neural system with delay

A FitzHugh–Nagumo (FHN) model with delayed coupling is considered to investigate the steady state bifurcation due to the coupling strength and delay. The center manifold reduction and normal form method are employed to study the bifurcation from zero singularity. We show that the coupling strength can induce both the pitchfork and transcritical bifurcations and the coupled delay has the most significant impact on these bifurcations. An example is applied to display the above results. Our investigation will contribute to the understanding of the influence of the time delay in signal transmission on the dynamics of coupled neurons.

Laser-Enhanced Gas Phase Surface Modifications of Teflon AF1600 for Increased Copper Adhesion

Multilevel interconnect devices, made of alternating layers of a low permittivity polymer (e.g., Teflon AF1600TM) and a low resistivity metal (e.g., copper), are increasingly being used in microelectronics in order to decrease the RC signal transmission time delay. The mechanical stability of the multilevel interconnects is related to the adhesion developed at the metal-dielectric interface. Since Cu/Teflon AF1600 adhesion is moderate and may not satisfy the requirements of the microelectronics industry, new treatments of the fluoropolymer surface are needed to improve it. In this note, we present several surface modifications, such as the formation of reactive sites during intense X-ray exposure, and S- or N-grafting, activated by UV radiation in the presence of H2S and NH3; copper is well known to react with both thiols (R—SH) and amines (R—NH2) to form strong bonds. Both X-ray exposure and N-grafting lead to enhanced adhesion.