Constant Time Delay Research Articles

Adaptive Neural Network Control of Time Delay Teleoperation System Based on Model Approximation.

A bilateral neural network adaptive controller is designed for a class of teleoperation systems with constant time delay, external disturbance and internal friction. The stability of the teleoperation force feedback system with constant communication channel delay and nonlinear, complex, and uncertain constant time delay is guaranteed, and its tracking performance is improved. In the controller design process, the neural network method is used to approximate the system model, and the unknown internal friction and external disturbance of the system are estimated by the adaptive method, so as to avoid the influence of nonlinear uncertainties on the system.

Large-Scale 3D Baseline Measurement Based on Phase-Stabilized GNSS-Over-Fiber System

Multi-antenna GNSS-over-fiber system is considered an effective solution for three-dimension (3D) baseline measurement. By precisely determining the transmission time delays between the antennas and the receiver, the vertical precision can be improved based on the single difference (SD) model. This method, however, would encounter problems if the baseline is too long, since a high precision measurement of the time delay of a long fiber link is usually time-consuming. Here, we propose and demonstrate a high-speed phase-stabilized GNSS-over-fiber system for large-scale 3D baseline measurement. A relatively slow but accurate time delay measurement module is used to calibrate the link delay, then a fast active compensation device is employed to keep the time delay constant. If the delay variation exceeds the compensation range, the time delay measurement module would measure the link delay again and bias the active compensation device at a new operating state. In a proof-of-concept experiment, the precision of the 3D baseline measurement obtained by the proposed system with a 20-km optical fiber is around 2.82 mm thanks to the rigid active compensation and the high-precision time delay measurement. If the active compensation device is disabled, the vertical precision of the baseline measurement obtained would be degraded from 2.82 mm to 16.46 mm in 10 minutes.

Finite-time bounded sampled-data control of switched time-delay systems with sector bounded nonlinearity

In this paper, finite-time bounded sampled-data control problem of switched systems with sector bounded nonlinearity and constant time delay is investigated. During the sampled-data control process, two cases, sampling period with or without switches, are discussed. Mismatching errors cased by the asynchronous switching signal and sampling points, are considered. Different from the qualitative properties of Lyapunov stability, the trajectory upper-bound of switched systems is quantitatively estimated to make it finite-time bounded. Moreover, anti-disturbance capability of switched systems can be measured with finite-time weighted L2-gain of switched systems. The proposed method is verified by numerical simulations.

Underwater multilateral tele-operation control with constant time delays

In the complex underwater environment, it is difficult to complete teleoperation tasks due to dynamic environments. Through cooperation among manipulators, a multilateral teleoperation system has the potential to achieve better performance than conventional bilateral teleoperation systems. In this paper, we propose a multilateral teleoperation control method that can be easily applied for underwater grasping tasks. Specifically, a new structure involving two (or multiple) masters and a single slave is investigated, which is treated as a linear combination of multiple subsystems under time delays. A control method based on linear matrix inequality exponential convergence and nonlinear disturbance is presented to estimate the model uncertainties of the system and unknown external disturbances during grasping process. The asymptotic stability is analyzed using the established Lyapunov–Krasovskii functional. Numerical simulations and real experiments performed for the task of grasping a plastic foam block are reported to verify the proposed control method in real applications.

Effects of a Systematic Augmentative and Alternative Communication Intervention Using a Speech-Generating Device on Multistep Requesting and Generic Small Talk for Children With Severe Autism Spectrum Disorder.

Purpose The purpose of this study was to determine the effects of augmentative and alternative communication (AAC) intervention using a speech-generating device (SGD) on acquisition, maintenance, and generalization of multistep requesting and generic small talk in three children with severe autism spectrum disorder (ASD) between the ages of 7 and 13 years. Method A multiple-baseline design across participants combined with a posttreatment multiple-generalization-probe design was used to assess acquisition, generalization, and maintenance of target communicative behaviors with the experimenter and the participants' familiar communication partners (FCPs). Intervention was composed of systematic instruction in the use of an SGD using least-to-most prompting, constant time delay, error correction, and reinforcement. Results Visual analysis established a strong functional relationship between the independent variable and the two dependent variables (i.e., requesting preferred activities, engaging in generic small talk) for all three participants. Effect size indicator analyses corroborated these findings, indicating strong effects for performing multistep requesting and medium effects for engaging in generic small talk. All participants were able to generalize the acquired communicative behaviors to request new and untrained snacks and activities and engage in generic small talk with FCPs who were not part of the training. Maintenance of acquired communicative behaviors was demonstrated 3 weeks post completion of intervention. Conclusion This study provides preliminary evidence that AAC intervention using an SGD and incorporating least-to-most prompting, constant time delay, error correction, and reinforcement is effective in terms of multistep requesting and generic small talk behaviors in children with severe ASD. Supplemental Material https://doi.org/10.23641/asha.16663630.

Forecasting COVID-19 Chile’ second outbreak by a generalized SIR model with constant time delays and a fitted positivity rate

The COVID-19 disease has forced countries to make a considerable collaborative effort between scientists and governments to provide indicators to suitable follow-up the pandemic’s consequences. Mathematical modeling plays a crucial role in quantifying indicators describing diverse aspects of the pandemic. Consequently, this work aims to develop a clear, efficient, and reproducible methodology for parameter optimization, whose implementation is illustrated using data from three representative regions from Chile and a suitable generalized SIR model together with a fitted positivity rate. Our results reproduce the general trend of the infected’s curve, distinguishing the reported and real cases. Finally, our methodology is robust, and it allows us to forecast a second outbreak of COVID-19 and the infection fatality rate of COVID-19 qualitatively according to the reported dead cases.

Probability of Loss of Assured Safety in Systems with Multiple Time-Dependent Failure Modes: Incorporation of Delayed Link Failure in the Presence of Aleatory Uncertainty

Probability of loss of assured safety (PLOAS) is modeled for weak link (WL)/strong link (SL) systems in which one or more WLs or SLs could potentially degrade into a precursor condition to link failure that will be followed by an actual link failure after some amount of elapsed time. The descriptor loss of assured safety (LOAS) is used because failure of the WL system places the entire system in an inoperable configuration while failure of the SL system before failure of the WL system, although undesirable, does not necessarily result in an unintended operation of the entire system. Thus, safety is “assured” by failure of the WL system before failure of the SL system. The following topics are considered: (i) Definition of precursor occurrence time cumulative distribution functions (CDFs) for individual WLs and SLs, (ii) Formal representation, approximation and illustration of PLOAS with (a) constant delay times, (b) aleatory uncertainty in delay times, and (c) delay times defined by functions of link properties at occurrence times for link failure precursors, and (iii) Procedures for the verification of PLOAS calculations for the three indicated definitions of delayed link failure.

Modelling and stability analysis of a longitudinal wheel dynamics control loop with feedback delay

Vehicle safety is an important field of today's engineering practice and the scientific research as well. One of the basics of the modern vehicle system dynamics control systems is braking or driving torque control. Ensuring proper connection between the tyre and the road surface is essential for safety and good handling behaviour. Fundamental questions may arise about the details of the model, such as feedback delay, sampling effect, numerical differentiation in the control algorithm or the dynamical characteristics of the tyre model. In this article, a connected dynamical system is presented which contains a wheel model and a PID type traction controller. Steady state and dynamical brush type tyre models are presented and compared. Two different ways are described to model the feedback delay. The fully continuous time model contains constant time delay, while there is another case, where the sampling effect and the numerical differentiation methods of the control algorithm are presented. Finally, stability analysis of the delayed system is performed. The stability and performance characteristics and different bifurcations are presented using stability charts. The type of the tyre model has significant effect on the stability characteristics.

Global synchronization of uncertain fractional-order BAM neural networks with time delay via improved fractional-order integral inequality

This paper is concerned with the problem of global synchronization for a class of uncertain fractional-order bidirectional associative memory (FOBAM) neural networks (NNs) with constant time delay. Some linear matrix inequality (LMI) based conditions have been established for ensuring the stability behavior of the governing augmented system derived from the considered fractional-order master system and the constructed slave system. In such LMI conditions, for utilizing the information on the time delay terms and the order of the fractional derivative, some fractional-order integral inequalities have been developed. Next, by defining a new Lyapunov–Krasovskii functional (LKF) and based on the improved fractional-order inequalities, the global synchronization criteria have been established in terms of a solvable set of LMIs for the considered class of uncertain FOBAM NNs without uncertain matrices. Further, the obtained results have been extended to the case of uncertain FOBAM NNs. Finally, a numerical example is presented to illustrate the feasibility and effectiveness of the proposed theoretical results.

A less‐conservative stability criterion for networked control systems with time‐varying packet delays

A networked output feedback loop subject to packetized transmissions of the output signal is considered. Based on the small gain theorem, an easy-to-use stability criterion covering two important cases is presented. In the first case a packet numbering mechanism is employed whereas in the second case neither packet numbering nor synchronization between sender and receiver is assumed. The analysis makes use of acausal subsystems and deduces the optimal constant time delay with respect to the minimization of the ℓ2 gain due to uncertain packet delays. This additional delay is then used in a nominal controller design such that additional admissible packet delay variations introduced by the network are maximized. A simulation example of a networked control system with a filtered Smith predictor illustrates the application of the proposed criterion. It is shown that the proposed novel technique is less-conservative than existing stability criteria based on the small gain theorem.

Inverse optimal synchronization control of competitive neural networks with constant time delays

Inverse optimal synchronization control of competitive neural networks with constant time delays

Strategi Mengajarkan Keterampilan Hidup Sehari-Hari Untuk Anak dan Remaja Dengan Retardasi Mental: Sebuah Review Literatur

Abstract
 Educational programs for students with mental retardation emphasize the preparation of students to live independently after finishing school. One educational strategy for children and adolescents with mental retardation is to teach daily life skills. The purpose of this study is to conduct a literature review on strategies to teach daily life skills to children and adolescents with mental retardation. Literature searches were carried out on seven databases, namely ERIC, SpringerLink, ScienceDirect, SAGE, JSTOR, Emerald Insight and Google Schoolar. The keywords used in this search are "teaching daily living skills" and "mental retardation"; "Teaching daily living skills" and "intellectual disability". A total of 5 articles (N = 614) will be reviewed through a screening process based on inclusive and exclusive criteria. The results show that there are strategies to teach daily life skills to children and adolescents with mental retardation by using video prompting, video modeling, constant-time delay and most-to-least prompt.
 Keyword: daily living skills; mental retardation; video prompting; video modeling; constant-time delay; most-to-least prompt procedures; literature review

Adaptive tracking of uncertain nonlinear systems under different types of input delays with urban traffic perimeter control application

AbstractPragmatic design method of direct model reference adaptive control (MRAC) is developed for a class of uncertain systems, where various input channels might have different delays and taking into account the effect of control saturation. To overcome the difficulty of directly predict the plant state and cope with different kinds of input delays, the proposed control design relies on implicit time‐delay prediction by using auxiliary linear Smith‐like dynamic units with adjustable gains. The design is unified to different time delay categories, that is, constant, time‐varying, or dependent on the current plant state. Within the context of the proposed approach, various adaptive control feedback strategies are designed for problems of continuous and sample‐and‐hold control implementations. Simulation results of a perimeter control for two interacting aggregate urban traffic regions are presented.

A mathematical study for chaotic dynamics of dissolved oxygen- phytoplankton interactions under environmental driving factors and time lag

Dynamics of the species in the ecosystem is constantly influenced by environmental variations, e.g. salinity, nutrient and temperature are among commonly investigated factors by ecologists. The changes in the environmental factors are expected to have an impact on the rate of photosynthesis. The main objective of this study is to theoretically analyse the temporal and spatial changes in the oxygen and phytoplankton dynamics with time delay as response to varying oxygen production rate over the daily cycle. In order to analyse the effect of environmental driving forces, two forms of time dependent oxygen production rate are considered: (i) linear form and (ii) bell shape form that, in theory, mimics the peaks in the oxygen production in a daily cycle. The model equations are investigated with constant time delay in phytoplankton growth to transform the systems into a biologically more realistic form. In fact, the numerical and theoretical investigations of this paper show that, regardless of the parameter choice, the spatial and non-spatial versions of the model are not rewarded with complex dynamics in the absence of time delay and do not have a tendency to oscillate. It is confirmed that sufficiently large values of time delay not only induce chaotic oscillations at the onset of a travelling population front but also play a destabilising role, leading to oscillatory limit-cycle behaviour in the dynamics. The findings of this paper show that, when the time delay is incorporated in plankton growth terms, time dependent oxygen production rate through environmental variations may have a substantial impact on the persistence, extinction and stability of species in the ecosystem.

Using e-mail as performance feedback to teach paraprofessionals to implement constant time delay with braille words

Equipping paraprofessionals to implement evidence-based instructional practices with fidelity can enhance the education of students with visual impairments. We used a multiple probe across participants design to evaluate the ability of paraprofessionals to follow constant time delay procedures with high fidelity when teaching braille words. We delivered performance feedback by e-mail and examined student learning outcomes. All three paraprofessionals achieved 100% correct implementation of constant time delay and maintained this high level of implementation over time. All three students successfully learned the targeted words. The combination of the training and support with e-mail feedback was effective at equipping them to deliver an evidence-based practice. Paraprofessionals affirmed the social validity of the intervention and considered e-mail performance feedback as an easy-to-understand way of receiving much-needed guidance. E-mail feedback is a cost-effective and simple tool for providing constructive feedback, while also ensuring paraprofessionals deliver instruction with high fidelity.

Intermittent fault detection for delayed stochastic systems over sensor networks

This paper is concerned with the intermittent fault (IF) detection problem for a class of linear discrete-time stochastic systems over sensor networks with constant time delay. By utilizing the lifting method, the distributed decoupled observers are proposed based on the output information of neighbor nodes and the node itself. In order to detect the appearing time and disappearing time of the IF, the truncated residuals are designed by introducing a sliding-time window. Furthermore, the IF detection and location thresholds are determined based on the hypothesis testing technique and the detectability of the IF is analyzed in the framework of stochastic analysis. Finally, a simulation example is presented to illustrate the effectiveness of the derived results.

Distributed filtering stochastic parameter learning algorithm for discrete-time random nonlinear systems with delay

Distributed filtering algorithm for a discrete time random nonlinear stochastic systems associated with state delay for the distributed wireless communication sensors are discussed in this paper. Stochastic Parameter Learning Algorithm (SPLA) is tend to aim at obtaining a collection of stochastic filter parameters in a finite limited time horizon, that minimize the traces of the upper limits which is permitted to reduce the error variance matrices of the concerned stochastic filter system’s states and delay measurements. Filter gain values of the filter derived by the determination of Riccati type difference equations, estimates systems states with delay. Two different filter rules are taken into account for the SPLA discrete time random nonlinear systems with steady state space equations model. Zero mean distinct covariance matrix along with the constructive state values and constant time delay are focused in compatible dimensions. The variance of the projected systems predicted noise and the actual estimated noise are validated through numerical examples.

Evolution of neutron capture elements in dwarf galaxies

ABSTRACT We study the evolution of europium (Eu) and barium (Ba) abundances in Local Group dwarf spheroidal and ultrafaint dwarf galaxies by means of detailed chemical evolution models and compare our results with new sets of homogeneous abundances. The adopted models include gas infall and outflow and have been previously tested. We investigate several production scenarios for r-process elements: merging neutron stars and magnetorotational-driven supernovae. Production of Ba through the main s-process acting in low- and intermediate-mass stars is considered as well. We also test different sets of nucleosynthesis yields. For merging neutron stars we adopt either a constant and short delay time for merging or a delay time distribution function. Our simulations show that (i) if r-process elements are produced only by a quick source, it is possible to reproduce the [Eu/Fe] versus [Fe/H], but those models fail in reproducing the [Ba/Fe] versus [Fe/H]. (ii) If r-process elements are produced only with longer delays the opposite happens. (iii) If both a quick source and a delayed one are adopted, such as magnetorotational-driven supernovae and merging neutron stars with a delay time distribution, the [Eu/Fe] abundance pattern is successfully reproduced, but models still fail in reproducing the [Ba/Fe]. (iv) On the other hand, the characteristic abundances of Reticulum II can be reproduced only if both the Eu and the r-process fraction of Ba are produced on short and constant time delays during a single merging event. We discuss also other possible interpretations, including an inhomogeneous mixing of gas that might characterize this galaxy.

Dynamic behavior and stability of energy efficient electro-magnetic suspension of rotors involving time delay

Energy efficient contact less suspension of high-speed rotor shafts in application areas such as power-plants and Flywheel Energy Storage Systems (FESS), can be achieved through Active Magnetic Bearings (AMBs). Inevitably, there exists time delay in sensing the rotor displacement and actual application of control force by electromagnets, thus leading to system instability. This paper therefore analyses stability of AMBs, with constant time delay. FESS is modelled as a rigid rotor-AMB system. Performance of two different control laws, (i) PID and (ii) a recently introduced Four-Element (FE) law, are compared. The governing equations are transformed to frequency domain, to exploit Pade's approximation in modeling time delayed value of feedback signal and stability analysis is carried out by analyzing the system poles. This methodology has been verified using experimental results from the existing literature. Numerical simulation of delay differential equations is also used to validate analytical results. The FE control law shows promise in tolerating delay, as compared to conventional PID controller thus leading to AMB system with higher possible spin speed and relaxed sampling constraints on AMB system instrumentation. One of the prospective applications of this work is in design of flywheel energy storage systems for an electric vehicle.

Essential Enzyme Kinetics: A Textbook for Molecular Life Scientists

Energy efficient contact less suspension of high-speed rotor shafts in application areas such as power-plants and Flywheel Energy Storage Systems (FESS), can be achieved through Active Magnetic Bearings (AMBs). Inevitably, there exists time delay in sensing the rotor displacement and actual application of control force by electromagnets, thus leading to system instability. This paper therefore analyses stability of AMBs, with constant time delay. FESS is modelled as a rigid rotor-AMB system. Performance of two different control laws, (i) PID and (ii) a recently introduced Four-Element (FE) law, are compared. The governing equations are transformed to frequency domain, to exploit Pade's approximation in modeling time delayed value of feedback signal and stability analysis is carried out by analyzing the system poles. This methodology has been verified using experimental results from the existing literature. Numerical simulation of delay differential equations is also used to validate analytical results. The FE control law shows promise in tolerating delay, as compared to conventional PID controller thus leading to AMB system with higher possible spin speed and relaxed sampling constraints on AMB system instrumentation. One of the prospective applications of this work is in design of flywheel energy storage systems for an electric vehicle.