Overload Control Research Articles

Research on missile overload control technology with prescribed performance

Considering that the present control methods for missile overload don’t take the transient and steady state with prescribed performance into consideration. On the basis of backstepping idea, a controller design method with prescribed performance is proposed for longitudinal channel overload motion model of missile in order to improve the performance of missile control systems. It is proved that the system is stable in the sense of Lyapunov, the tracking error of the system satisfy the prescribed transient and steady performance. The given simulation results demonstrate the effectiveness of the proposed control method.

Improved Throughput Stabilizing Scheme for Group Paging in mMTC: A Traffic Scattering Perspective

Group paging (GP) is a typical overload control scheme for massive machine-type communications (mMTC). To further improve the performance of GP, a traffic scattering scheme has been proposed where MTC devices being paged are scattered into different random access (RA) slots to access the network. However, the throughput of the scheme dramatically decreases when the paging interval is long and the number of devices is large. To solve this problem, we propose an improved throughput stabilizing scheme for GP, where a backoff-free traffic scattering strategy is adopted to reduce the average access delay. In particular, by comprehensively considering the influence of the number of RA requests the eNB can serve, a new analysis model is proposed to study the system throughput. Based on the results, we obtain the optimal scattering factor, i.e., the optimal number of devices scattered into each RA slot, with which the throughput can be stabilized at a high level. Simulation results verify the validity of our scheme.

Evaluating Probabilistic Traffic Load Effects on Large Bridges Using Long-Term Traffic Monitoring Data.

With the steadily growing of global transportation market, the traffic load has increased dramatically over the past decades, which may develop into a risk source for existing bridges. The simultaneous presence of heavy trucks that are random in nature governs the serviceability limit for large bridges. This study investigated probabilistic traffic load effects on large bridges under actual heavy traffic load. Initially, critical stochastic traffic loading scenarios were simulated based on millions of traffic monitoring data in a highway bridge in China. A methodology of extrapolating maximum traffic load effects was presented based on the level-crossing theory. The effectiveness of the proposed method was demonstrated by probabilistic deflection investigation of a suspension bridge. Influence of traffic density variation and overloading control on the maximum deflection was investigated as recommendations for designers and managers. The numerical results show that the congested traffic mostly governs the critical traffic load effects on large bridges. Traffic growth results in higher maximum deformations and probabilities of failure of the bridge in its lifetime. Since the critical loading scenario contains multi-types of overloaded trucks, an effective overloading control measure has a remarkable influence on the lifetime maximum deflection. The stochastic traffic model and corresponding computational framework is expected to be developed to more types of bridges.

Correlation between Changes in Cardiac Iron and Hepatic Iron in Pediatric Patients with Thalassemia Major

Introduction. A prospective magnetic resonance imaging (MRI) study demonstrated a good control of myocardial iron overload (MIO) in terms of prevention and treatment in children with thalassemia major (TM). The aim of the present study was to evaluate if changes in MIO were related to baseline hepatic iron or changes in hepatic iron overload (HIO). Methods. We considered 68 TM patients enrolled in the MIOT (Myocardial Iron Overload in Thalassemia) project with less than 18 years at the first MRI scan and who performed a follow-up (FU) study at 18±3 months. Myocardial and hepatic iron burdens were quantified by the T2* technique. The value of 20 ms was used as conservative normal value for the global T2* value. Liver T2* values were converted into liver iron concentration (LIC) values. A LIC<3 mg/g/dw indicated significant no HIO, between 3 and 7 mg/g/dw mild HIO, between 7 and 15 mg/g/dw moderate HIO, and ≥15 mg/g/dw severe HIO. Results. Thirty-six patients were females and mean age at the time of the baseline MRI was 13.74±3.09 years. Baseline global heart T2* values were 29.72±11.21 ms and 16 (23.5%) patients showed significant baseline MIO. The percentage changes in global heart T2* values per month in the whole patient population were 0.66±1.70 and they resulted significantly higher in the 16 patients with significant baseline MIO versus the patients with no baseline MIO (1.99±2.53% vs 0.25±1.09% ms; P=0.002). Percentage changes in global heart T2* values per month were not influenced by initial MRI LIC values (R=0.048; P=0.695) (Figure 1A) and were comparable among the 4 groups of patients identified on the basis of baseline MRI LIC values (14 no HIO: 0.29±1.12% vs 21 mild HIO: 0.75±1.56% vs 15 moderate HIO: 0.82±2.03% vs 18 severe HIO: 0.71±2.00%; P=0.876). Percentage changes in global heart T2* values per month were not associated to final MRI LIC values (R=-0.134; P=0.277) (Figure 1B). The correlation between % changes in global heart T2* and MRI LIC values did not reach the statistical significance (R=-0.244; P=0.067) (Figure 1C). In patients with baseline MIO no correlation was found between % changes in global heart T2* values per month and initial MRI LIC values (R=-0.325; P=0.219) or % changes in MRI LIC values per month (R=-0.353; P=0.180). Conclusion. In pediatric TM patients changes in cardiac iron are not correlated to baseline MRI LIC values and changes in hepatic iron. So, our data seem not supporting the hypothesis for which it is necessary to clean the liver before removing iron from the heart. Figure 1 Disclosures Pepe: Chiesi Farmaceutici S.p.A., ApoPharma Inc., and Bayer: Other: No profit support.

Overload Control with Hybrid SIP Signaling - Using Smart Reliability and Priority Queuing Strategies

Session Initiation Protocol is an IP based application level signaling protocol. SIP employs request retransmission for enabling reliability over UDP transport. This research work proposes a Hybrid SIP System that integrates the congestion control techniques from the proposed Smart Reliable SIP and Overload control using Advanced Smart Priority (ASP) Queuing Strategy. The proposed system reduces retransmissions and queuing delays in SIP servers. Smart Reliable SIP (SRSIP) implements the modified Selective Repeat ARQ protocol for enabling reliability of SIP requests without violating the SIP core functionality. SRSIP reduces the number of retransmissions. ASP Queuing Strategy prioritizes the SIP requests based on the retransmissions. The proposed system reduces the queuing delays for request processing at the downstream server and the retransmissions over the network. The Hybrid models integrates the features of both Smart Reliable SIP and ASP queuing strategy resulting in a system with almost zero retransmissions and reduced queuing delay for request processing.

Effect of fluid balance control in critically ill patients: Design of the stepped wedge trial POINCARE-2

A high number of recent studies have shown that a positive fluid balance is independently associated with impaired prognosis in specific populations of patients hospitalized in intensive care unit (ICU): acute kidney injury, acute respiratory distress syndrome (ARDS), sepsis, high risk surgery. However, to date, there is no evidence that control of fluid overload reduces mortality in critically ill patients. The main objective is to assess the efficacy of a strategy limiting fluid overload on mortality in unselected critically ill patients hospitalized in ICU. We hypothesized that a strategy based on a weight-driven recommendation of restricted fluid intake, diuretics, and ultrafiltration initiated from 48 h up to 14 days after admission in critically ill patients would reduce all-cause mortality as compared to usual care. We use a stepped wedge cluster randomized controlled trial combined with a quasi-experimental (before-and-after) study. Patients under mechanical ventilation, admitted since >48 h and < 72 h in ICU, and with no discharge planned for the next 24 h are eligible. A total of 1440 patients are expected to be enrolled in 12 ICUs. Sociodemographic and clinical data are collected at inclusion, and outcomes are collected during the follow-up. Primary outcome is all-cause mortality at 60 days after admission. Secondary outcomes are patients weight differences between admission and day7 (or day 14), 28-day, in-hospital, and 1-year mortality, end-organ damages, and unintended harmful events. Analyses will be held in intention-to-treat. If POINCARE-2 strategy proves effective, then guidelines on fluid balance control might be extended to all critically ill patients.Trial registration: ClinicalTrials.govNCT02765009

A Systematic Review and Meta-analysis of Nonpharmacologic-based Interventions for Aortic Stiffness in End-Stage Renal Disease

IntroductionIncreased carotid-femoral pulse wave velocity (cf-PWV) in end-stage renal disease (ESRD) indicates enhanced aortic stiffness and mortality risk. We conducted a systematic review and meta-analysis of nonpharmacologic interventions in adults with ESRD to determine their effects on cf-PWV, systolic blood pressure (SBP), and intervention-associated adverse events.MethodsMEDLINE, EMBASE, and EBM databases were searched. Study screening, selection, data collection, and methodological quality assessments were performed by 2 independent reviewers. Pooled-effect estimates from mean differences and 95% confidence intervals (CIs) were calculated using random effect models.ResultsA total of 2166 subjects with ESRD from 33 studies (17 randomized; 16 nonrandomized) were included. Four intervention-comparator pairs were meta-analyzed. Quality of evidence ranged from very low to moderate. Kidney transplantation decreased cf-PWV (−0.70 m/s; CI: –1.3 to −0.11; P = 0.02) and SBP (−8.3 mm Hg; CI: −13.2 to −3.3; P < 0.001) over pretransplantation. In randomized trials, control of fluid overload by bio-impedance reduced cf-PWV (−1.90 m/s; CI: −3.3 to −0.5); P = 0.02) and SBP (−4.3 mm Hg; CI: −7.7 to −0.93); P = 0.01) compared with clinical assessment alone. Cross-sectional studies also demonstrated significantly lower cf-PWV and SBP in normovolemia compared with hypervolemia (P ≤ 0.01). Low calcium dialysate decreased cf-PWV (−1.70 m/s; CI: −2.4 to −1.0; P < 0.00001) without affecting SBP (−1.6 mm Hg; CI: −8.9 to 5.8; P = 0.61). Intradialytic exercise compared with no exercise reduced cf-PWV (−1.13 m/s; CI: −2.2 to −0.03; P = 0.04), but not SBP (+0.5 mm Hg; CI: −9.5 to 10.4); P = 0.93).ConclusionsSeveral nonpharmacologic interventions effectively decrease aortic stiffness in ESRD. The impact of these interventions on cardiovascular outcomes and mortality risk reduction in ESRD requires further study.

Overload control for virtual network functions under CPU contention

In this paper, we analyze the problem of overloads caused by physical CPU contention in cloud infrastructures, from the perspective of time-critical applications (such as Virtual Network Functions) running at guest level. We show that guest-level overload control solutions to counteract traffic spikes (e.g., traffic throttling) are counterproductive against overloads caused by CPU contention. We then propose a general guest-level solution to protect applications from overloads also in the case of CPU contention. We reproduced the phenomena on a IP Multimedia Subsystem (IMS) testbed based on OpenStack on top of KVM. The results show that the approach can dynamically adapt the service throughput to the actual system capacity in both cases of traffic spikes and CPU contention, by guaranteeing at the same time the IMS latency requirements. • Resource contention is a common cause of overload in virtualized infrastructures. • CPU contention causes side effects on the QoS of time-critical applications. • Guest OS CPU metrics are often misinterpreted when dealing with CPU contention. • NFV Load throttling solutions can misbehave in the case of physical CPU contention. • Avoiding idle CPU time preemption helps to protect systems from contention effects.

Machine-to-Machine Communications With Massive Access: Congestion Control

With the deployment of machine-to-machine (M2M) communications, it is expected that the number of devices will enormously increase. When these devices attempt to concurrently access the network, a radio access network overload problem arises. In this case, the conventional random access procedure used in Long Term Evolution-Advanced (LTE-A) networks is rendered inefficient due to the frequent collisions that lead to excessive delay and resource wastage. In this paper, we propose an efficient scalable overload control algorithm for M2M with massive access. The proposed algorithm can allocate the uplink resources within bounded contention time in a distributed manner. Hence, it can achieve full resource utilization that leads to reduced: access delay, energy consumption, and blocking probability. Additionally, we provide a method for estimating the number of backlogged devices in the network. The performance of the proposed algorithm is evaluated analytically and using simulations. To prove its effectiveness, the performance of the proposed algorithm is compared to the dynamic-access class-barring scheme, where the results depict the superiority of the proposed scheme. Finally, a binary integer programming problem is formulated, where we show that the achieved access delay using the proposed algorithm approaches the optimal value.

Aircraft Guiding in Windshear through Differential Game-Based Overload Control

The problem of aircraft take-off under windshear conditions is considered as a differential game. A simplified five-dimensional nonlinear model of aircraft dynamics, assuming the flight in a vertical plane, is used. The overloads, differences between the projections of the thrust and drag, respectively lift, forces are considered as control variables. The corresponding technically relevant control, the aerodynamic angle of attack, can always be retrieved. Stable numerical algorithms for solving Hamilton-Jacobi-Bellman-Isaacs equations arising from differential games with state constraints are used to compute the value function and design an appropriate feedback control.

Fault Overload Control Method for High-Proportion Wind Power Transmission Systems Based on Emergency Acceleration of Doubly-Fed Induction Generator

With a high proportion of wind power being transmitted through ac and dc lines, a new power grid pattern has gradually emerged. A dc inverter is prone to commutation failure, which may lead to cascading trip of ac lines for overload, resulting in serious consequences. However, existing control methods have problems of over- or under-shedding and are unsuitable for high-proportion wind power transmission systems. Accordingly, a new fault overload control method based on emergency acceleration of doubly fed induction generator (DFIG) is proposed. The fast power control capability of DFIG is fully utilized; the active power of power grid could be rapidly balanced. First, the fault characteristics of a wind power ac/dc transmission system under the fault of dc receiving-end grid are analyzed, and the power flow transfer after self-recovery from the dc commutation failure is derived. Second, by analyzing the power characteristics of DFIG, a fault overload control idea of the wind power transmission system is proposed based on emergency acceleration of DFIG. At last, the maximum controllable capacity of a wind farm is analyzed, and a fault overload control strategy of the wind power transmission system is proposed. The simulation results prove that the proposed method can rapidly reduce the output of wind farms and prevent the overload of ac lines.

On Multiple Access of a Large Number of Machine-Type Devices in Cellular Networks

Introduction: Machine-to-machine communication assumes data transmission from various wireless devices and attracts attention of cellular operators. In this regard, it is crucial to recognize and control overload situations when a large number of such devices access the network over a short time interval.Purpose:Analysis of the radio network overload at the initial network entry stage in a machine-to-machine communication system.Results: A system is considered that features multiple smart meters, which may report alarms and autonomously collect energy consumption information. An analytical approach is proposed to study the operation of a large number of devices in such a system as well as model the settings of the random-access protocol in a cellular network and overload control mechanisms with respect to the access success probability, network access latency, and device power consumption. A comparison between the obtained analytical results and simulation data is also offered.

An Enhancing Fault Current Limitation Hybrid Droop/V-f Control for Grid-Tied Four-Wire Inverters in AC Microgrids

Microgrid integration and fault protection in complex network scenarios is a coming challenge to be faced with new strategies and solutions. In this context of increasing complexity, this paper describes two specific overload control strategies for four-wire inverters integrated in low voltage four-wire alternating current (AC) microgrids. The control of grid-tied microgrid inverters has been widely studied in the past and mainly focused on the use of droop control, which hugely constrains the time response during grid-disconnected operation. Taking into account the previous knowledge and experience about this subject, the main contribution of these two proposals regards providing fault current limitation in both operation modes, over-load capability skills in grid-connected operation and sinusoidal short-circuit proof in grid-disconnected operation. In the complex operation scenarios mentioned above, a hybrid combination of AC droop control based on dynamic phasors with varying virtual resistance, and voltage/frequency master voltage control for grid-(dis)connected operation modes are adopted as the mechanism to enhance time response. The two proposals described in the present document are validated by means of simulations using Matlab/Simulink and real experimental results obtained from CENER (The National Renewable Energy Centre) experimental ATENEA four-wire AC microgrid, obtaining time responses in the order of two-three grid cycles for all cases.

Method of ballistic control and projectile rotation in a novel railgun

Abstract In order to realize the ballistic control of the railgun and the flight stability of the projectile, a new type of railgun is designed, which can control the muzzle velocity and rotation rate. The method of the muzzle velocity and overload control is to adjust the voltage or other parameters of pulse power supply. It would be easy to change velocity accurately in large wide. Another widespread concern problem is launching the spinning stability projectile by railgun. This paper designed a new structure of additional rails to generate an unsymmetrical magnetic field to produce rotational torque in armature. The structure is simple and can control the rotation rate by linear changing the barrel parameters. The calculation formulas of interior ballistic are derived by Biot-Safar law. The important parameter is the deflection angle of the additional rails relative to the symmetry plane of main rail. The larger the angle, the greater the rotation torque generated in the armature. To maintain the flight stability of the projectile, the barrel structural parameters should be proportional to the projectile structural parameters. When changing the muzzle velocity, the rotation rate will also be the equal proportion change. So that the gyro stability is the same. The experiment proves that the railgun designed in this paper can launch the projectile to rotate. And the rotational projectile may not cause the transition or much arcs. This method expands the application of the railgun.

Load Control Using Sensitivity Identification by Means of Smart Transformer

The higher variability introduced by distributed generation leads to fast changes in the aggregate load composition, and thus in the power response during voltage variations. The smart transformer, a power electronics-based distribution transformer with advanced control functionalities, can exploit the load dependence on voltage for providing services to the distribution and transmission grids. In this paper, two possible applications are proposed: 1) the smart transformer overload control by means of voltage control action and 2) the soft load reduction method, that reduces load consumption avoiding the load disconnection. These services depend on the correct identification of load dependence on voltage, which the smart transformer evaluates in real time based on load measurements. The effect of the distributed generation on net load sensitivity has been derived and demonstrated with the control hardware in loop evaluation by means of a real time digital simulator.

SUPPLY QUALITY SERVICE VOIP THROUGH CALL SIGNALING OVERLOAD CONTROL

SIP (session initiation protocol (is an application layer protocol to create, maintain and ending the multimedia sessions. These protocols have no suitable mechanism for encountering with the overload, so when a server is overloaded, it`s effectiveness is reduced and eventually server’s real throughput reaches zero. To control the overload, various methods have been proposed, but there are some basic challenges presented in presented methods that lead to poor performance while there is an overloaded server in the network. The current study focusing on server – server’s overload, a distributed overload control method, based on dynamic window and implicit feedback is proposed to control overload. In order to extend the originally proposed algorithm which uses the violation of the calling delay from a specific threshold as an incentive for reducing the sending load to downstream proxy, adaptive methods are proposed. The performance of the proposed algorithms has been evaluated.

Overload control of artificial gravity facility using spinning tether system for high eccentricity transfer orbits

As the major part of space life supporting systems, artificial gravity requires further study before it becomes mature. Spinning tether system is a good alternative solution to provide artificial gravity for the whole spacecraft other than additional devices, and its longer tether length could significantly reduce spinning velocity and thus enhance comfortability. An approximated overload-based feedback method is proposed to provide estimated spinning velocity signals for controller, so that gravity level could be accurately controlled without complicated GPS modules. System behavior in high eccentricity transfer orbits is also studied to give a complete knowledge of the spinning stabilities. The application range of the proposed method is studied in various orbit cases and spinning velocities, indicating that it is accurate and reliable for most of the mission phases especially for the final constant gravity level phase. In order to provide stable gravity level for transfer orbit missions, a sliding mode controller based on estimated angular signals is designed for closed-loop control. Numerical results indicate that the combination of overload-based feedback and sliding mode controller could satisfy most of the long-term artificial gravity missions. It is capable of forming flexible gravity environment in relatively good accuracy even in the lowest possible orbital radiuses and high eccentricity orbits of crewed space missions. The proposed scheme provides an effective tether solution for the artificial gravity construction in interstellar travel.

Maneuver control of the hypersonic gliding vehicle with a scissored pair of control moment gyros

A maneuver control approach using a scissored pair of control moment gyros is proposed to improve the penetration ability of a hypersonic gliding vehicle (HGV) with a relatively high lift-drag ratio. Then, a multivariable strong coupling nonlinear bank-to-turn dynamical model is established for the case of lateral maneuvering of an HGV equipped with a scissored pair of control moment gyros. According to the requirement of coordinated turning of the HGV in a lateral maneuver, a decoupling controller based on feedback linearization and a linear quadratic optimal algorithm is designed. Finally, the large airspace maneuvering trajectories of the HGV including S-shaped, cycloid and spiral maneuvering modes are designed by applying overload control technology. Simulations demonstrate that the designed maneuvering trajectory significantly increases the airspace range and flexibility of the vehicle. The coordinated turn control system achieves an accurate and rapid tracking of the maneuvering trajectories in large airspace.

Effects of resisted sprint training on sprinting ability and change of direction speed in professional soccer players

ABSTRACTResisted sprint training consists of performing overloaded sprints, which may produce greater effects than traditional sprint training. We compared a resisted sprint training with overload control versus an unresisted sprint training program on performance in soccer players. Eighteen elite athletes were randomly assigned to resisted (RST) or unresisted sprint training protocol (UR). Before and after a 6-week training period, sprinting ability, change of direction speed (COD), vertical jumps (SJ and CMJ), mean power (MP) and mean propulsive power (MPP) at distinct loads were assessed. Both groups improved sprinting ability at all distances evaluated (5m: UR = 8%, RST = 7%; 10m: UR = 5%, RST = 5%; 15m: UR = 4%, RST = 4%; 20m: UR = 3%, RST = 3%; 25m: UR = 2%, RST = 3%;), COD (UR = 6%; RST = 6%), SJ (UR = 15%; RST = 13%) and CMJ (UR = 15%; RST = 15%). Additionally, both groups increased MP and MPP at all loads evaluated. The between-group magnitude-based inference analysis demonstrated comparable improvement (“trivial” effect) in all variables tested. Finally, our findings support the effectiveness of a short-term training program involving squat jump exercise plus sprinting exercises to improve the performance of soccer players.

Performance Analysis of a Novel Hybrid S-ALOHA/TDMA Protocol for Beta Distributed Massive MTC Access.

Simultaneous random access of massive machine type communications (MTC) devices are expected to cause congestion in the radio access network. Not only the performance of MTC, but the coexisting human to human (H2H) communications would also degrade dramatically without an appropriate medium access control (MAC) protocol. However, most existing solutions focus on the random access procedure without dealing with the sunsequent data transmission procedure. In this paper, we firstly derive a packet size threshold based on the capacity analysis of slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) protocols. Then a novel hybrid S-ALOHA/TDMA MAC protocol (HSTMAC) is presented for massive MTC access, in which the resources are separated for beta distributed machine to machine (M2M) traffic with small size packets and high priority H2H traffic with large size packets. Considering access class barring (ACB) scheme as an overload control method, the system equilibrium under arbitrary retransmission limit is analyzed rigorously, which can provide insights on quality of service (QoS) guarantee. Finally, a dynamic pre-backoff (DPBO) algorithm is designed for load balance by adaptively scattering the highly synchronized M2M traffic over the transmission interval. Numerical and simulation results validate our analysis and show that the HSTMAC protocol is superior to pure S-ALOHA protocol and pure TDMA protocol. The proposed DPBO algorithm can achieve a higher success probability and resource utilization ratio with a much reduced average delay than that of uniform pre-backoff (UPBO) scheme.