Negative Effects Of Time Delays Research Articles

Fuzzy adaptive fixed-time control for output-constrained uncertain nonstrict-feedback time-delay systems

This paper deals with the problem of fuzzy adaptive fixed-time control for a class of uncertain nonlinear nonstrict feedback systems with time delays and output constraints. The negative effects of time delays on system performance and stability are overcome by introducing a new Barrier Lyapunov–Krasovskii (BLK) function and an innovative inequality. In addition, the singularity problem that arises in the process of deriving the control and adaptive laws, is solved by the proposed BLK function. The controller is designed in the backstepping framework which ensures that the system output does not violate predefined constraints. The proposed controller needs less information from the system and therefore has less implementation complexity than previous references, which leads to a more straightforward implementation. A fuzzy system approximation is utilized to overcome the uncertainties of the model. It is guaranteed that all closed-loop system signals converge to small neighborhoods around zero in a fixed time. Finally, an example is presented to verify that the proposed method achieves the control objectives.

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.

Improved sliding mode observer based repetitive control for linear systems with time‐varying input and state delays

SummaryControl systems are frequently subject to the negative effects of time delays and disturbances, which diminish the systems' tracking performance. In response to these challenges, this paper presents a novel approach, that is, the improved sliding mode observer based repetitive control (ISMO‐RC), to enhance the system's periodic signal tracking in the presence of the input and state time delays and the input disturbances. The design takes the advantages of RC and ISMO, in which RC effectively compensates periodic signals, while ISMO compensates both aperiodic disturbances and the time‐varying input and state delays. The stability of the whole system is guaranteed via the linear matrix inequality (LMI) and the Lyapunov–Krasovskii functional analysis. The proposed controller is evaluated through extensive simulations and experiments, which demonstrate its superiority over comparative control methods.

Intention-reflected predictive display for operability improvement of time-delayed teleoperation system

Robotic teleoperation is highly valued for its ability to remotely execute tasks that demand sophisticated human decision-making or that are intended to be carried out by human operators from a distance. However, when using the internet as a communication framework for teleoperation, high latency, and fluctuations make accurate positioning and time-dependent tasks difficult. To mitigate the negative effects of time delay, this paper proposes a teleoperation system that uses cross reality (XR) as a predictive display of the outcome of operators’ intended actions and develops a time-delay aware shared control to fulfill the intention. The system targets a liquid pouring task, wherein a white ring that indicates the intended height of the liquid surface is overlayed onto the beaker in a delayed camera image to close the visual feedback loop on the leader side. Simultaneously, the shared control automatically completes the pouring action to track the intended liquid height. The performance of the proposed system is validated based on liquid pouring experiments performed by human subjects. When compared with direct control, the absolute error rate decreased significantly for a constant round-trip time delay of 0.8 s and 1.2 s, similarly for a time-varying delay of 0.4 s and 0.8 s. Moreover, when the time-varying delay was 0.8 s, operators achieved significantly higher accuracy while maintaining comparable operation time. These results indicate that our proposed system improves operability even in the presence of time-varying delays in communication networks.

Economic Evaluation of Traffic Congestion & Design of Traffic Signal with Simulation at Ottapalam

Abstract: Traffic congestion is the most outstanding performance of the negative externalities of urban road traffic, which is characterized by the negative effects of time delay, energy waste, air pollution and many other impacts. It affects people’s daily life and could cause stress other than time and monetary loss. Traffic congestion causes negative impacts to transport sector and cause a massive increase in the transportation cost. Time is a precious commodity that we all have an equal amount of, and it is something that should not be wasted. A lot of our time is being wasted due to traffic congestion. Therefore, the study of impact of delay at important and busy road stretches in monetary terms is important. This study evaluates the traffic congestion cost at Ottapalam city which prevail heterogeneous traffic conditions. Congestion cost estimations are done by considering the factors including delay, traffic volume, passenger occupancy, and value of travel time of different vehicle types. The results obtained indicated that there was a considerable monetary loss due to traffic delay in the form of opportunity costs. So, there was a need to reduce this monetary loss by bringing suitable measures. The traffic condition of the selected road is found out using simulation by PTV Vissim software after implementing a traffic signal at a busy intersection between the road stretch. The reduction in traffic congestion shows the rightful implementation of the traffic signal.

Time Delay Mitigation in Aerial Telerobotic Operations Using Heterogeneous Stereo-Vision Systems

This paper investigates the use of a heterogeneous stereo-vision system to mitigate the effects of time delays in a drone-based visual interface presented to a human operator. Time delays in the display for a telerobotic interface refer to the time difference between the operator’s input action and the corresponding visible outcome. In human/machine interfaces, time delays can arise due to computation, telecommunication, and mechanical limitations. These delays can degrade the performance of the human/machine system. A heterogeneous stereo-vision predictive algorithm is presented that can reduce the negative effects of time delays in the operator’s display. The heterogeneous stereo-vision system consists of an omnidirectional camera and a pan/tilt/zoom camera. Two predictive display setups were developed that modify the delayed video imagery that would otherwise be presented to the operator in a way that provides an almost immediate visual response to the operator’s control actions. The usability of the system is determined through human performance testing with and without the predictive algorithms. The results indicate that the predictive algorithm allows more efficient, accurate, and user-friendly operation.

Decreasing the Negative Impact of Time Delays on Electricity Due to Performance Improvement in the Rwanda National Grid

One of the most common power problems today is communication and control delays. This can adversely affect decision interaction in grid security management. This paper focuses on communication signal delays and how to identify and address communication system failure issues in the context of grid monitoring and control, with emphasis on communication signal delay. An application to solve this problem uses a thyristor switch capacitor (TSC) and a thyristor-controlled reactor (TCR) to improve the power quality of the Rwandan National Grid (RNG) with synchronous and PV generators. It is to counteract the negative effects of time delays. To this end, the TSC and TCR architectures use two methods: the fuzzy logic controller (FLC) method and the modified predictor method (MPM). The experiment was performed using the Simulink MATLAB tool. The power quality of the system was assessed using two indicators: the voltage index and total harmonic distortion. The FLC-based performance was shown to outperform the MPM for temporary or permanent failures if the correct outcome was found. As a result, we are still unsure if TSC and TCR can continue to provide favorable results in the event of a network cyber-attack.

Compensatory motion scaling for time-delayed robotic surgery.

Round trip signal latency, or time delay, is an unavoidable constraint that currently stands as a major barrier to safe and efficient remote telesurgery. While there have been significant technological advancements aimed at reducing the time delay, studies evaluating methods of mitigating the negative effects of time delay are needed. Herein, we explored instrument motion scaling as a method to improve performance in time-delayed robotic surgery. This was a robotic surgery user study using the da Vinci Research Kit system. A ring transfer task was performed under normal circumstances (no added time delay), and with 250ms, 500ms, and 750ms delay. Robotic instrument motion scaling was modulated across a range of values (- 0.15, - 0.1, 0, + 0.1, + 0.15), with negative values indicating less instrument displacement for a given amount of operator movement. The primary outcomes were task completion time and total errors. Three-dimensional instrument movement was compared against different motion scales using dynamic time warping to demonstrate the effects of scaling. Performance declined with increasing time delay. Statistically significant increases in task time and number of errors were seen at 500ms and 750ms delay (p < 0.05). Total errors were positively correlated with task time on linear regression (R = 0.79, p < 0.001). Under 750ms delay, negative instrument motion scaling improved error rates. Negative motion scaling trended toward improving task times toward those seen in non-delayed scenarios. Improvements in instrument path motion were seen with the implementation of negative motion scaling. Under time-delayed conditions, negative robotic instrument motion scaling yielded fewer surgical errors with slight improvement in task time. Motion scaling is a promising method of improving the safety and efficiency of time-delayed robotic surgery and warrants further investigation.

Predictor-feedback synthesis in coordinate-free formation control under time-varying delays

This paper investigates new coordinate-free formation control strategies of multi-agent systems to overcome the negative effects of time delays. To this end, we present a single predictor-feedback scheme to compensate the multiple communication delays, assumed to be unknown but bounded and arbitrarily-fast time-varying. Although delays cannot exactly be compensated due to time-varying delay mismatches, the trade-off between robustness and convergence speed can be notably improved if the control gain is suitably designed. Hence, with the objective of enlarging the time-varying delay interval for a given convergence speed, an LMI-based iterative algorithm is presented to solve the control gain synthesis.

Minimization of Adverse Effects of Time Delay on Power Quality Enhancement in Hybrid Grid

One of the most challenging issues of the modern power grid is the communication delay, which has adverse effects on the power quality. This paper proposes two methods, such as the fuzzy logic controller (FLC) based approach and the modified predictor method, to minimize the negative effects of time delay on the power quality enhancement in a hybrid power grid consisting of synchronous and wind generators. The thyristor switched capacitor has been used as a power quality enhancement means for the grid. Time delays ranging from 0–700 ms have been considered for the analysis. Both balanced and unbalanced temporary and permanent faults at different locations in the power network have been considered. Two indices, namely the voltage index and the total harmonic distortion have been used to evaluate the power quality of the system. The performance of the FLC-based method has been compared with that of the modified predictor method. Simulations have been performed by using the MATLAB/Simulink software. Simulation results show that both the proposed methods can minimize the negative effects of time delays on the power quality enhancement of the system. However, the FLC method performs better than the modified predictor method.

A Distributed AGC Method considering Two-Channel Random Delays and Their Difference between Interconnected Power Systems

With the emergence of the concept of smart grid, the networked automatic generation control (AGC) method has been more and more important for secondary frequency control due to its characteristics such as openness and flexibility. However, the networked AGC system also presents some defects such as time delays and packet dropouts. The existence of time delays makes the traditional AGC strategies more challenging. A novel AGC method is proposed in this paper to mitigate the negative effects of time delays. Firstly, a multiarea power system model is built under the consideration of two-channel time delays: from controller to actuator and from sensor to controller. More practically, the difference of delays between areas is also exhibited in the model. Thus, from the predictive characteristics of model predictive control (MPC), a method of selection with optimization is presented to obtain the appropriate control variable when delays exist. Furthermore, three cases, (a) no processing for delay, (b) control sequence selection, (c) control sequence selection with optimization, are analyzed. The frequency and area control error (ACE) performance are evaluated with step load perturbation and random load perturbation. The simulation results indicate that the system controlled by the proposed method has desired dynamic performances. Consequently, the feasibility and effectiveness of the proposed method are verified.

Connectivity preservation of second-order nonlinear multiagent systems with hybrid event-driven and time-driven control

ABSTRACTIn practice, the capability of communication between each pair of agents is within a finite range. This paper investigates how to preserve connectivity for nonlinear multiagent systems while reaching consensus under event-driven control technique. By introducing an appropriate potential function based on the distance of two agents, we can demonstrate that all the agents will not lose connectivity if the initial undirected graph is connected. Furthermore, due to the existence of friction and time delay, we utilise the Young's inequality and a Lyapunov–Krasovskii functional to eliminate the negative effects of time delay. The use of impulse functions is considered which can avoid the singularity in the control input. Moreover, the hybrid event-driven and time-driven control technique is utilised to reduce the requirements of communication resources. Finally, numerical simulations are conducted to demonstrate the effectiveness of our methodology.

A Long Time Coming: Delays in Collective Apologies and Their Effects on Sincerity and Forgiveness

Political apologies by one group to another often occur a significant period of time after the original transgression. What effect does such a delay have on perceptions of sincerity and forgiveness? A delayed apology could reflect the offender group's reluctance to apologize, or, alternatively, it could represent time and consideration spent on developing an appropriate response. In the latter case, the delayed apology would represent a sincere acknowledgment of the harm done, whereas in the former case it would not. In two studies, we found that a verbal collective apology, when delayed, was perceived to be less sincere than when offered more immediately following a transgression, and this translated to less forgiveness. However, in Study 2, the negative effects of time delay on sincerity and forgiveness were mitigated or reversed when the apology was in the form of commemoration. The commemorative apology, in particular when delayed, gave rise to favorable attributions (including representativeness of apologizing group, commitment to remember, and giving voice to victims), which mediated the effects on sincerity. The results suggest that collective apologies that are offered with considerable delay appear less meaningful and less deserving of a forgiving response, unless the apologizing group is able to express consideration and thoughtfulness through the apology process.

Connectivity preserved nonlinear time-delayed multiagent systems using neural networks and event-based mechanism

This paper studies how to preserve connectivity for nonlinear time-delayed multiagent systems using event-based mechanism. By using the idea of divide-and-conquer, we divide the distributed controller into five parts to deal with different requirements of the time-delayed multiagent systems, such as eliminating the negative effects of time delays, preserving connectivity, learning the unknown dynamics and achieving consensus. To reduce the communication times among the agents, a centralized event-based protocol is introduced and an event-triggered function is devised to control the frequency of the communication without Zeno behavior. The technique of $$\sigma $$ -functions is used to exclude the singularity of the established distributed controller. In the simulation example, the results demonstrate the validity of our developed methodology.

Evaluation of Display Methods for Teleoperation of Road Vehicles

During teleoperation of road vehicles, live images from the vehicle are sent to an operator via a cellular connection, who then inputs his control demands. Time delays resulting from signal processing and transmission times can cause instabilities in the control loop and decrease driving performance. To mitigate the negative effects of time delays, predictive displays have long been used in the field of robotics. This paper presents the “Frame Prediction” method for drawing a predictive display for teleoperation of road vehicles. It also shows the results of an experiment in a simulated environment which compared the presented method to 1) driving under the influence of time delays and 2) a display method where the video images are modified as if there was no time delay present. Results revealed that the Frame Prediction method significantly increases driving performance and decreases operator workload for delayed systems. For some scenarios it even supersedes the driving performance without delays.