Delay Control Research Articles

Stabilizing the Boost PFC Converter with a Time Delay Feedback Controller

The One-Cycle Controlled Boost Power Factor Correction converter has one voltage control loop, which may exhibit instability when the load is light. The instability results in a low Power Factor. To ensure that the Power Factor is high, a time delay circuit was adopted in this paper to control the instability of the converter. The architecture of the time delay circuit is described, and its transfer function is derived. The double averaging method was applied to the converter to determine the parameters in the control method. Experimental results verified the time delay control method in the converter. The power factor increased from 0.82 to 0.99 after activating the delay control circuit.

Systemwide Identification of Signal Retiming Opportunities with Connected Vehicle Data to Reduce Split Failures

Road networks are significantly affected by traffic signal operations, which contribute from 5% to 10% of all traffic delay in the U.S.A. It is important for agencies to be able to systematically monitor traffic signal performance and have procedures to identify locations as proactively as possible where the redistribution of green time has the greatest potential of reducing congestion. Currently, Automated Traffic Signal Performance Measures (ATSPMs) require extensive communication networks and detectors on all phases at each intersection to effectively monitor the traffic signal performance for every traffic movement. This study utilizes commercially available connected vehicle (CV) trajectory data to identify overcapacity movements where there is availability of unused green time and no downstream blockage by an adjacent signal. Over 100 intersections, 400,000 trajectories, and 6,800,000 Global Positioning System points are evaluated using this method to prioritize signal retiming opportunities in a proposed Relative Performance Diagram (RPD) by assessing split failures and downstream blockage of all traffic movements. Out of the intersections identified as having opportunities for operational improvements, three were selected for retiming. A post-retiming review of the traffic signal performance measures showed up to 30% reductions in split failures, 53 s/veh reductions in control delay, and 21% increase in arrivals on green at the benefited movements. The techniques easily scale to any intersection where CV data is available without the need for vehicle detection or communication technology.

Integrated Design of Filter and Controller Parameters for Low-Switching-Frequency Grid-Connected Inverter Based on Harmonic State-Space Model

In high-power grid-connected inverter for new energy power generation system, low switching frequency makes the control loop, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -filter resonant peak and sideband harmonics generated by modulation coupled, so that the parameter design of filter and controller affects each other. This increases the difficulty of design of filter parameters and controller parameters. To solve this problem, an accurate current harmonic calculation method based on harmonic state-space model and considering switching frequency and control delay is proposed in this article firstly. Secondly, based on the above model, the parameter optimization process considering current harmonic distortion rate, filter cost and so on is constructed. The integrated optimization design of filter and controller parameters of low-switching-frequency <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> grid-connected inverter is completed through intelligent algorithm. Thus the filter cost is minimized on the premise that inverter performances meet the specific requirements. In addition, considering the non-ideal characteristic of grid, a scheme of integrated parameter design which can adapt to the large-scale change of grid strength is proposed. Finally, the effectiveness of the proposed method and scheme is verified by simulation and experiment.

Primary Frequency Control of Wind-solar-storage Power Station Considering Discrete Control Nonlinearity

With the gradual advancement of dual-carbon goals, the wind-solar-storage power station has become the mainstream trend in constructing new energy stations due to their wind energy and luminous complementary characteristics. However, the current research on primary frequency control of new energy stations is still focused on a single-machine strategy. The communication delay and control period caused by long control links are not considered. It is difficult to describe the influence of the difference in dynamic characteristics of wind-solar-storage power on primary frequency control performance. Therefore, this paper takes the multi-layer control link wind-solar-storage power station as the research object, establishes the nonlinear control model considering the influence of control delay and control period, and puts forward the wind-solar-storage power plant primary frequency control method, which is suitable for participating in the frequency control of power grid.

Ridged Meandered Waveguides for 3-D Routing and Phase Delay Control and Its Application to Discrete Lenses

In this paper, an innovative procedure to design ridged meandered waveguides is introduced. By modulating the meandered centerline of a waveguide connecting two fixed points, new degrees of freedom to control the phase delay are obtained. Ridged meandered waveguides represent a good compromise between coaxial cables, which feature broadband operation and can be easily bended still introducing high losses and conventional waveguides, which are characterized by low losses but also narrow operational bandwidth. Ridged meandered waveguides are especially well-suited for isophase lattice expanders that can be used in beamforming networks, phased arrays or discrete 3D lens antennas. The article describes a methodology to design meandered waveguides, which is verified both analytically and experimentally through the synthesis, fabrication and test of a discrete 3D lens antenna in Ka-band (27.5-30 GHz) made using additive manufacturing.

An Enhanced Adaptive Time Delay Control-Based Integral Sliding Mode for Trajectory Tracking of Robot Manipulators

This article proposes an enhanced adaptive time delay controller (ATDC) for robot manipulators subjected to external disturbances. This approach is model-free and uses time delay estimation (TDE) to estimate complex and unknown robot dynamics. First, to remove the reaching phase and improve the robustness of the control, an integral sliding surface (ISS) is used. Second, to speed up the convergence and compensate for the TDE errors and external disturbances, the gains of time delay control and the sliding mode have been made adaptive. In this article, we clearly point out using the Lyapunov method that the position and velocity tracking errors are guaranteed to be uniformly ultimately bounded (UUB). The effectiveness and the robustness of the designed controller over existing methods are experimentally verified on a parallel Delta robot. The novel model-free proposed control is robust and highly accurate, which is appropriate and recommended for industrial robotic applications.

Event-triggered delayed impulsive control for synchronization of stochastic complex networks under deception attacks

This paper analyzes a class of stochastic complex networks (SCNs) subjected to deception attacks via the event- triggered delayed impulsive control (ETDIC) strategy. Noting the universality of delay, we consider the delay in impulsive control. The impulse is combined with the event-triggered mechanism (ETM), that is, the impulsive instant is determined by the ETM, which is defined by the network topology and the Lyapunov function. Based on this ETM, through a combination of the Lipschitz-Razumikhin method and graph theory, we obtain the conditions to avoid Zeno behavior and give some criteria of pth moment exponential synchronization (PMES) for SCNs under deception attacks. The criteria are related to the topology of the network, the event-triggered parameters, and the attack signals sent by the enemy. Finally, we analyze a class of coupling Chua’s circuits subjected to deception attacks and present numerical examples to verify the validity and practicability of our theoretical results.

A regular sampling method based on the immediate mode for improving the stability of inverters

The shadow mode-based regular sampling methods are usually used in the digital control of power inverters, which introduce a control delay of one and a half sampling periods. The control delay affects the closed loop bandwidth and the stability of dc–ac inverters. Recently, regular sampling methods based on the immediate mode is emerging and helpful for reducing the digital control delay. When employing the immediate mode, the induced vertical crossings may arouse the duty-cycle loss and dead-band effect during the modulation process, which deteriorate the normal operation of the inverters. Although the duty-cycle loss can be avoided by forcing the PWM signal to flip at the occurrence of vertical crossings, the introduced dead bands still exist. Thus, this paper investigates the phenomenon of vertical crossings and proposes a control algorithm composed of predicting the occurrence of vertical crossings and compensating the dead-band effect for regular sampling methods based on the immediate mode. Finally, experimental results on a single-phase dc–ac inverter prototype are provided to compare the efficacy of different approaches.

Impact of Medicaid expansion on outcomes after abdominal aortic aneurysm repair

ObjectiveLack of insurance has been independently associated with an increased risk of in-hospital mortality after abdominal aortic aneurysm repair, possibly due to worse control of comorbidities and delays in diagnosis and treatment. Medicaid expansion has improved insurance rates and access to care, potentially benefiting these patients. We sought to assess the association between Medicaid expansion and outcomes after abdominal aortic aneurysm repair. MethodsA retrospective analysis of Healthcare Cost and Utilization Project State Inpatient Databases data from 14 states between 2012 and 2018 was conducted. The sample was restricted to first-record abdominal aortic aneurysm repairs in adults under age 65 in states that expanded Medicaid on January 1, 2014 (Medicaid expansion group) or had not expanded before December 31, 2018 (non-expansion group). The Medicaid expansion and non-expansion groups were compared between pre-expansion (2012-2013) and post-expansion (2014-2018) time periods to assess baseline demographic and operative differences. We used difference-in-differences multivariable logistic regression adjusted for patient factors, open vs endovascular repair, and standard errors clustered by state. Our primary outcome was in-hospital mortality. Outcomes were stratified by insurance type. ResultsWe examined 8995 patients undergoing abdominal aortic aneurysm repair, including 3789 (42.1%) in non-expansion states and 5206 (57.9%) in Medicaid expansion states. Rates of Medicaid insurance were unchanged in non-expansion states but increased in Medicaid expansion states post-expansion (non-expansion: 10.9% to 9.8%; P = .346; expansion: 9.7% to 19.7%; P < .001). One in 10 patients from both non-expansion and Medicaid expansion states presented with ruptured aneurysms, which did not change over time. Rates of open repair decreased in both non-expansion and Medicaid expansion states over time (non-expansion: 25.1% to 19.2%; P < .001; expansion: 25.2% to 18.4%; P < .001). On adjusted difference-in-differences analysis between expansion and non-expansion states pre-to post-expansion, Medicaid expansion was associated with a 1.02% absolute reduction in in-hospital mortality among all patients (95% confidence interval, −1.87% to −0.17%; P = .019). Additionally, among patients who were either on Medicaid or were uninsured (ie, the patients most likely to be impacted by Medicaid expansion), a larger 4.17% decrease in in-hospital mortality was observed (95% confidence interval, −6.47% to −1.87%; P < .001). In contrast, no significant difference-in-difference in mortality was observed for privately insured patients. ConclusionsMedicaid expansion was associated with decreased in-hospital mortality after abdominal aortic aneurysm repair among all patients and particularly among patients who were either on Medicaid or were uninsured. Our results provide support for improved access to care for patients undergoing abdominal aortic aneurysm repair through Medicaid expansion.

Slow-Scale Nonlinear Control of a H-Bridge Photovoltaic Inverter

Aiming at the slow-scale nonlinear behaviors of a dual-loop control H-bridge photovoltaic inverter, a slow-scale nonlinear control method based on time-delay feedback control is proposed. Firstly, a feedback signal is formed by the difference between the current error signal and its own delay, and the feedback signal is made to pass through a proportion link so as to obtain a time-delay control signal. Then, based on the necessary conditions of the stability criterion, the value range of the delay feedback proportional coefficient is quickly determined, and the best delay time is chosen by determining the variation curve of the largest Lyapunov exponent. Finally, based on the double-loop PI regulation, the time-delay control signal is added to the original control signal to form the final control signal applied to the inverter. The results obtained show that the slow-scale nonlinear behaviors in the system can be absolutely eliminated, and the stable operation domain of the inverter can be remarkably expanded. When the sun irradiance and temperature change, the proposed control method still has a good control effect and shows strong robustness. In addition, the complex calculation in determining the control coefficient and delay time can be avoided by the method.

Nonclassical photon-pair source based on noiseless photon echo

The Duan-Lukin-Cirac-Zoller (DLCZ) scheme is a potential method to establish remote entanglements and realize large-scale quantum networks. Here we propose a DLCZ-like scheme based on the noiseless photon echo in rare-earth ion-doped crystals. Correlated photon pairs with a controllable delay can be created by the direct optical rephasing. Theoretical analysis indicates that the protocol is efficient in the low-optical-depth regime. This protocol could be feasibly implemented to establish long-lived quantum correlations between a photon and a spin-wave excitation in rare-earth ion-doped crystals.

Stereotactic body radiotherapy for mediastinal lymph node with CyberKnife®: Efficacy and toxicity

PuprposeStereotactic body radiotherapy is more and more used for treatment of oligometastatic mediastinal lymph nodes. The objective of this single-centre study was to evaluate its efficacy in patients with either a locoregional recurrence of a pulmonary or oesophageal cancer or with distant metastases of extrathoracic tumours. Patients and methodsPatients with oligometastatic mediastinal lymph nodes treated with CyberKnife from June 2010 to September 2020 were screened. The primary endpoint was to assess local progression free survival and induced toxicity. Secondary endpoints were overall survival and progression free survival. The delay before introduction of systemic treatment in the subgroup of patients who did not receive systemic therapy for previous progression was also evaluated. ResultsFifty patients were included: 15 with a locoregional progression of a thoracic primary tumour (87% pulmonary) and 35 with mediastinal metastasis of especially renal tumour (29%). Median follow-up was 27 months (6–110 months). Local progression free survival at 6, 12 and 18 months was respectively 94, 88 and 72%. The rate of local progression was significantly lower in patients who received 36Gy in six fractions (66% of the cohort) versus other treatment schemes. Two grade 1 acute oesophagitis and one late grade 2 pulmonary fibrosis were described. Overall survival at 12, 18 and 24 months was respectively 94, 85 and 82%. Median progression free survival was 13 months. Twenty-one patients were treated by stereotactic body irradiation alone without previous history of systemic treatment. Among this subgroup, 11 patients (52%) received a systemic treatment following stereotactic body radiotherapy with a median introduction time of 17 months (5–52 months) and 24% did not progress. ConclusionStereotactic body irradiation as treatment of oligometastatic mediastinal lymph nodes is a well-tolerated targeted irradiation that leads to a high control rate and delay the introduction of systemic therapy in selected patients.

PLL phase margin design and analysis for mitigating sub/super-synchronous oscillation of grid-connected inverter under weak grid

Under weak grid, the grid-connected inverter can easily cause sub/super-synchronous oscillations, which are determined by the oscillation modes of system. Firstly, based on the eigenvalue analysis, the sub/super-synchronous oscillation modes of the grid-connected inverter are revealed with considering the phase-locked loop (PLL) and control delay. With the decline of grid stiffness, the typical roots of sub-synchronous oscillation (SSO) mode gradually shift from the left-half plane to the right-half plane, which means that the grid-connected inverter will oscillate under weak grid. By analyzing the participation factor of SSO mode, it finds that PLL is the dominant factor. Based on the root locus analysis, the stable regions of PLL parameter are obtained. Then, according to the stable regions of PLL parameter, the phase margin of PLL can be calculated, which can make the grid-connected inverter operate stably. It finds that PLL phase margin should be increased for suppressing this SSO. However, when the PLL phase margin is greater than a certain value, the system will enter a supersynchronous oscillation mode, which can cause a supersynchronous oscillation. Thus, to suppress the sub/super-synchronous oscillations of the grid-connected inverter under weak grid, the phase margin of PLL should neither be too small nor too large. Finally, the proposed suppression strategy of the sub/super-synchronous oscillations for the inverter integrated into a weak grid is validated with the simulation and experimental studies.

Two-color polarization control of angularly resolved attosecond time delays

Measured photoionization time delays may exhibit large variations as a function of the emission angles, even for spherically symmetric targets, as shown in recent reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) experiments. The contributions from different pathways to the two-photon quantum channels can explain the observed phase jumps that shape those angular distributions. Here we propose a simple analytical model to describe angularly resolved RABBITT spectra as a function of the relative polarization angle between the ionizing attosecond pulse train and the assisting IR field. We demonstrate that the angular dependences of the measured delays can be analytically predicted and the position of the phase jumps reduced to the analysis of a few relevant parameters.

Attosecond Monitoring of Nonadiabatic Molecular Dynamics by Transient X-ray Transmission Spectroscopy

Tracing the evolution of molecular coherences can provide a direct, unambiguous probe of nonadiabatic molecular processes, such as the passage through conical intersections of electronic states. Two techniques, attosecond transient absorption spectroscopy (ATAS) and Transient Redistribution of Ultrafast Electronic Coherences in Attosecond Raman Signals (TRUECARS), have been used or proposed for monitoring nonadiabatic molecular dynamics. Both techniques employ the transmission of a weak attosecond extreme-ultraviolet or X-ray probe to interrogate the molecule at controllable time delays with respect to an optical pump, thereby extracting dynamical information from transient spectral features. The connection between these techniques has not been firmly established yet. In this theoretical study, we provide a unified description of both transient transmission techniques, establishing their relationship as limits of the same pump-probe spectroscopy technique for different pulse parameter regimes. We demonstrate this by quantum dynamical simulations of thiophenol photodissociation and show how complementary coherence information can be revealed by the two techniques.

Load Balancing Strategy of Power Communication Network Based on SDN Controller

A load balancing strategy based on SDN controller is proposed to solve the load and security problems caused by the large number of services carried by power communication network in this article. Firstly, integrated with the actual situation of the network, the basic framework of gradual hierarchical transformation of power communication network is put forward. Then, the SDN controller response delay model is discussed in detail in the modeling process, and a multi controller deployment model and its solution algorithm are also proposed. The simulation results verify the effectiveness of the SDN centralized control function, and optimize the load balance, QoS and resource utilization, so as to reduce the impact of power grid communication link failure on the control delay.

Delay Analysis of IEEE 802.11be Multi-Link Operation Under Finite Load

Multi-link Operation (MLO), arguably the most disruptive feature introduced in IEEE 802.11be, will cater for delay-sensitive applications by using multiple radio interfaces concurrently. In this paper, we analyze the delay distribution of MLO under non-saturated traffic. Our results show that upgrading from legacy single-link to MLO successfully contains the $95$th percentile delay as the traffic load increases, but also that adding extra interfaces yields rapidly diminishing gains. Further experiments we conduct on Google Stadia traces, accounting for realistic traffic with batch arrivals, confirm the insights stemming from our theoretical analysis, vouching for MLO to support high-resolution real-time video with a controlled delay.

A small‐area and low‐power all‐digital duty cycle corrector with de‐skew circuit

AbstractThis paper proposes a small‐area and low‐power all‐digital duty cycle corrector with de‐skew circuit. By adopting the proposed delay unit containing a pre‐charge transistor, half cycle delay line can accurately generate half‐cycle delay, thus ensuring that the circuit can achieve duty cycle correction with small area and low power. To achieve high‐precision clock synchronization, the proposed de‐skew circuit utilizes a high‐resolution two‐stage digital control delay line to eliminate the additional clock skew between the input clock and output clock of the circuit. The test chip is fabricated in 130 nm CMOS process and the area only occupies 0.009 mm2. The chip testing results show that duty cycle correction error is within 3.2% and phase error is less than 16 ps when input duty cycle from 20% to 80% at the frequency range from 380 MHz to 1.25 GHz. And the proposed circuit only consumes 3 mW when supply voltage is 1.2 V and clock frequency is 1 GHz.

Real-Time Monitoring and Control of the Breakthrough Stage in Ultrafast Laser Drilling Based on Sequential Three-Way Decision

Real-time monitoring and control of breakthrough stage are essential issues in ultrafast laser drilling (ULD) process. This paper proposed a novel intelligent methodology to address the decision bias problem in monitoring and control of breakthrough stage. Eight time-domain statistical features were extracted after analyzing the correlation between the optical emission signal and the drilling process and data processing. To build the identification model of breakthrough stage, support vector machine (SVM) method was adopted and the identification accuracy can up to 98.42%. Even so, there is a large deviation between the prediction breakthrough time by the identification model and the actual breakthrough time, which can up to 3.81s. Considering the decision bias, the comprehensive Gaussian weight sequential three-way decision (CGW-S3WD) method was proposed for the first time. Compared to the actual breakthrough time, the mean decision time is only delayed by 0.375s based on the combination of the identification model and CGW-S3WD method under simulated conditions. Finally, the method was applied to monitoring and control of breakthrough stage in the actual ULD process. Experimental results demonstrate that the control delay time is only 0.354s and the high-quality holes and protection of the back wall can be achieved simultaneously. The research confirms that the method can reduce the decision bias and provides a new perspective for accurate monitoring of complex industrial scenarios.

Robust unified dissipativity vibration control design for offshore steel jacket platform in ocean environments under self-excited nonlinear wave force

This paper addresses the challenge of delayed proportional integral control (DPIC) of an offshore steel jacket platform (OSJP) subjected to a self-excited nonlinear wave force and structural uncertainty using the unified criteria. By introducing discrete and distributed state delays in the control input, a DPIC was established to stabilize the OSJPs. The goal of this study is to design a proper controller that will stabilize the dynamic of an OSJP while subjected to structural uncertainty and nonlinear wave force. The OSJP is investigated as a nonlinear dynamics with mixed state delays, allowing us to study its robust asymptotic stability using the Lyapunov-Krasovskii function (LKF) in the context of the extended dissipativity performance index. A novel closed-loop system-based stability criterion is derived as a result of using tighter integral inequalities to estimate the upper bounds of the delay and influential control gains can be achieved if a set of linear matrix inequalities (LMIs) is checked by simulation results, that the proposed control scheme can significantly improve the control’s performance. Finally, it was demonstrated that the proposed control approach is more effective and multi-dynamic performances have been illustrated through the comparisons to previously published results in the literature.