Optimal Duty Cycle Research Articles

Optimum Duty Cycle of Unsteady Plasma Aerodynamic Actuation for NACA0015 Airfoil Stall Separation Control**supported by National Natural Science Foundation of China (No. 21276036), Liaoning Provincial Natural Science Foundation of China (No. 2015020123) and the Fundamental Research Funds for the Central Universities of China (No. 3132015154)

Unsteady dielectric barrier discharge (DBD) plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA0015 airfoil by measuring the surface pressure distribution of the airfoil. The performance of the DBD aerodynamic actuation for airfoil stall separation suppression is evaluated under DBD voltages from 2000 V to 4000 V and the duty cycles varied in the range of 0.1 to 1.0. It is found that higher lift coefficients and lower threshold voltages are achieved under the unsteady DBD aerodynamic actuation with the duty cycles less than 0.5 as compared to that of the steady plasma actuation at the same free-stream speeds and attack angles, indicating a better flow control performance. By comparing the lift coefficients and the threshold voltages, an optimum duty cycle is determined as 0.25 by which the maximum lift coefficient and the minimum threshold voltage are obtained at the same free-stream speed and attack angle. The non-uniform DBD discharge with stronger discharge in the positive half cycle due to electrons deposition on the dielectric slabs and the suppression of opposite momentum transfer due to the intermittent discharge with cutoff of the negative half cycle are responsible for the observed optimum duty cycle.

Pulsed-Current Electrochemical Codeposition and Heat Treatment of Ti-Dispersed Ni-Matrix Layers

An electrochemical deposition is a fast and cost-efficient process to produce film or coating. In this research, Ni-Ti electrodeposition is developed by codepositing a Ti-dispersed Ni-matrix layer from a Ni-plating solution suspended with Ti particles. To enhance the coating uniformity and control the atomic composition, the pulsed current was applied to codeposit Ni-Ti layers with varying pulse duty cycles (10 to 100 pct) and frequencies (10 to 100 Hz). The microstructures and compositions of the codeposited layers were analyzed by scanning electron microscopy, X-ray diffraction, and X-ray fluorescent techniques. The pulsed current significantly improved the quality of the Ni-Ti layer as compared to a direct current. The Ni-Ti layers could be electroplated with a controlled composition within 48 to 51 at. pct of Ti. The optimal pulse duty cycle and frequency are 50 pct and 10 Hz, respectively. The standalone Ni-49Ti layers were removed from copper substrates by selective etching method and subsequently heat-treated under Ar-fed atmosphere at 1423 K (1150 °C) for 5 hours. The phase and microstructures of the post-annealed samples exhibit different Ni-Ti intermetallic compounds, including NiTi, Ni3Ti, and NiTi2. Yet, the contamination of TiN and TiO2 was also present in the post-annealed samples.

Study of the optimal duty cycle and pumping rate for square-wave amplitude-modulated Bell–Bloom magnetometers**Project supported by the National Natural Science Foundation of China (Grant No. 11074050).

We theoretically and experimentally study the optimal duty cycle and pumping rate for square-wave amplitude-modulated Bell–Bloom magnetometers. The theoretical and the experimental results are in good agreement for duty cycles and corresponding pumping rates ranging over 2 orders of magnitude. Our study gives the maximum field response as a function of duty cycle and pumping rate. Especially, for a fixed duty cycle, the maximum field response is obtained when the time averaged pumping rate, which is the product of pumping rate and duty cycle, is equal to the transverse relaxation rate in the dark. By using a combination of small duty cycle and large pumping rate, one can increase the maximum field response by up to a factor of 2 or π/2, relative to that of the sinusoidal modulation or the 50% duty cycle square-wave modulation respectively. We further show that the same pumping condition is also practically optimal for the sensitivity due to the fact that the signal at resonance is insensitive to the fluctuations of pumping rate and duty cycle.

A W-Band Radiometer with the Offset Parabolic Antenna for Radiometric Measurements

This paper deals with the development of a W-band noise-adding radiometer which combines the millimeter-wave (MMW) radiometric measurements with a high-resolution imager. The offset parabolic antenna is presented to achieve an accurate measurement and a high resolution. To reduce the cross-polarization level of the antenna, a multimode feed horn with a multistep structure is proposed to match the focal region fields of the reflector. It has advantages over the corrugated horns in lower mass and easier manufacturing. In addition, due to an unavoidable settling time for the noise-adding radiometer output signal passing through the low-pass filter, a theoretical criterion for the optimum duty cycle determination to reject extraneous contributions from the transient is proposed in this paper. The appropriate duty cycle threshold is 0.33 for the developed W-band radiometer. Also, a geometric correction method is presented to correct the obtained passive image suffering from a distortion for a better image interpretation. Preliminary experimental results are given to illustrate and verify the presented techniques.

Maximum Power Point Tracking (MPPT) Using Artificial Bee Colony Based Algorithm for Photovoltaic System

The Artificial Bee Colony based algorithm (ABC) studied in this paper is assigned as an intelligent control of photovoltaic system. The output power of a photovoltaic panel depends on solar irradiation and temperature. Therefore, it is important to operate the photovoltaic (PV) panel in its maximum power point. In this aim, the ABC consists to track the optimal duty cycle of the electronic converter, in order to lead to the Maximum Power Point (MPP) of the PV system. Moreover, the classical method Perturb and Observe (P&O) [1-2] is studied in the sake of comparison with the ABC method in Matlab/Simulink, by taking into consideration the efficiency, the speed and the robustness performance when the meteorological conditions change.

Improved Voltage Vector Sequences on Model Predictive Control for a Grid Connected Three Phase Voltage Source Inverter

In this paper, improved voltage vector sequences on model predictive control is proposed for a grid connected three-phase voltage source inverter. Two adjacent voltage vectors and zero voltage vectors are utilized in one switching period. Optimal duty cycles for all sectors are calculated. Voltage vector pair with minimum value of the cost function is selected and applied in the next switching period. Voltage vector sequences are arranged similar to the swing patterns generated by the space vector PWM. Thus, minimum number of switching transition and even loss distribution can be achieved. Computer simulation is carried out to validate viablity of the proposed method. The simulation results confirm that the proposed MPC has superior performance compared to the convention MPC.

Inductance Surface Learning for Model Predictive Current Control of Switched Reluctance Motors

In this paper, an inductance surface estimation and learning for utilization with a stochastic model predictive control (MPC) scheme for the current control of switched reluctance motors (SRMs) is introduced. This MPC is equipped with state estimators and is implemented as a recursive linear quadratic regulator for practical deployments in hybrid vehicle applications. Additionally, a learning mechanism is developed to dynamically adapt to the inductance profile of the machine and update the MPC and Kalman filter parameters. The introduced control scheme can cope with noise as well as uncertainties within the machine nonlinear inductance surface. The introduced system will benefit from a fixed switching frequency and will offer low current ripples by calculating the optimal duty cycles using the SRM model. Finally, simulations and experimental results are provided to evaluate the proposed method.

Predictive Duty Cycle Control of Three-Phase Active-Front-End Rectifiers

This paper proposed an online optimizing duty cycle control approach for three-phase active-front-end rectifiers, aiming to obtain the optimal control actions under different operating conditions. Similar to finite-control set model predictive control strategy, a cost function previously constructed based on the desired control performance is adopted here, which is essential for the solving process of the optimizing problem. On the other hand, differently, with respect to the proposed strategy, duty cycle signals are optimized, instead of possible switching states. The determination of optimal duty cycles is made by predicting the effect of duty cycles on instantaneous current variations and minimizing the cost function. Due to the adoption of behavior prediction, the proposed controller inherits the excellent dynamic characteristics of predictive controllers. Moreover, the application of optimal duty cycles determined by cost function minimization automatically ensures optimum operations of converters within each sampling period. Improved transient and steady-state features of the proposed strategy are confirmed by experimental validations and in-depth comparisons with linear controllers, deadbeat predictive controllers, and finite-control set model predictive control strategies.

Scheme to Improve the Line Current Distortion of PFC Using a Predictive Control Algorithm

This paper presents a scheme to improve the line current distortion of power factor corrector (PFC) topology at the zero crossing point using a predictive control algorithm in both the continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The line current in single-phase PFC topology is distorted at the zero crossing point of the input AC voltage because of the characteristic of the general proportional integral (PI) current controller. This distortion degrades the line current quality, such as the total harmonic distortion (THD) and the power factor (PF). Given the optimal duty cycle calculated by estimating the next state current in both the CCM and DCM, the proposed predictive control algorithm has a fast dynamic response and accuracy unlike the conventional PI current control method. These advantages of the proposed algorithm lower the line current distortion of PFC topology. The proposed method is verified through PSIM simulations and experimental results with 1.5 kW bridgeless PFC (BLPFC) topology.

An Online Modulation Strategy to Control the Matrix Converter Under Unbalanced Input Conditions

Due to absence of a dc-link energy storage element in the direct matrix converter (MC), any abnormality/disturbance in the input voltages is directly reflected on the output voltages. In this paper, a new modulation strategy to control the 3×3 MC under unbalanced input voltage conditions is proposed. The proposed strategy is based on modification of the space vector modulation strategy, which formulates and solves an optimization problem to determine the best switching states and their corresponding optimal duty cycles, such that the errors in the output voltages and the input currents under unbalanced input voltage conditions are minimized. The salient feature of the proposed strategy is its capability to extend the output operating range of the MC. The proposed strategy ensures that optimal performance of the MC over the entire operating range, including the case when the converter operates with an output voltage greater than the maximum attainable balanced output voltage under unbalanced input voltage conditions, is achieved. Performance of the proposed strategy is evaluated and validated based on time-domain simulation studies in the MATLAB/Simulink software environment and experimentation on a scaled-down laboratory prototype.

Distributed Photovoltaic Architecture for HVDC-bus Feeding with a Simple Evaluation of Optimal Tracking

This contribution describes, compares, and analyses two structures and their operating modes dedicated to renewable energy production from photovoltaic (PV) sources. Between the two different technical approaches, photovoltaic sources placed in a distributed architecture supplying a high DC voltage HVDC bus points large advantages. Thus, after preliminary comparison of both solutions and concluding phases, this efficient solution finally constitutes the main original analysis presented in this contribution. The distributed PV structure is investigated, implemented and simulated in an original way under the OrCAD/Pspice software environment. The adaptation stage for maximum power transfer is modelled in detail. A method to calculate the optimal duty cycle for optimal use of PV panels power is proposed, tested and validated by the use of a marketed PV module datasheet.

Model Predictive Current Control of Switched Reluctance Motors With Inductance Auto-Calibration

This paper investigates application of an unconstrained model predictive controller (MPC) known as a finite horizon linear quadratic regulator (LQR) for current control of a switched reluctance motor (SRM). The proposed LQR can cope with the measurement noise as well as uncertainties within the machine inductance profile. This paper utilizes MPC to generate the optimal duty cycles for drive of SRMs using pulse-width modulation (PWM) in oppose to delta-modulation. In this paper, first a practical MPC scheme for embedded implementation of the system is introduced. Afterward, Kalman filtering is used for state estimation while an adaptive controller is used to dynamically tune and update both MPC and Kalman models. Hence, the overall control structure is considered as a stochastic MPC with adaptive model calibration. Finally, simulation and experimental results are provided to demonstrate the effectiveness of the proposed method.

Energy storage based on maximum power point tracking in photovoltaic systems: A comparison between GAs and PSO approaches

In this paper, a comparison between GAs and PSO Approaches is considered to select and generate an optimal duty cycle which varies with photovoltaic parameter in order to extract the maximum Power from Photovoltaic System using real values of temperature and insolation. The energy storage has very important role in renewable energy. To illustrate the energy storage, we have used a battery type lead-acid simulated in Matlab/Simulink. The obtained simulations results show the effectiveness and the robustness of the proposed approaches.

SU‐E‐T‐247: Determinations of the Optimal Phase for Respiratory Gated Radiotherapy From Statistical Analysis Using a Visible Guidance System

Purpose:Respiratory gated radiation therapy (RGRT) is used to minimize the radiation dose to normal tissue in lung cancer patients. Determination of the optimal point in the respiratory phase of a patient is important in RGRT but it is not easy. The goal of the present study was to see if a visible guidance system is helpful in determining the optimal phase in respiratory gated therapy.Methods:The breathing signals of 23 lung cancer patients were recorded with a Real‐time Position Management (RPM) respiratory gating system (Varian, USA). The patients underwent breathing training with our visible guidance system, after which their breathing signals were recorded during 5 min of free breathing and 5 min of guided breathing. The breathing signals recorded between 3 and 5 min before and after training were compared. We performed statistical analysis of the breathing signals to find the optimal duty cycle in guided breathing for RGRT.Results:The breathing signals aided by the visible guidance system had more regular cycles over time and smaller variations in the positions of the marker block than the free breathing signals. Of the 23 lung cancer patients, 19 showed statistically significant differences by time when the values obtained before and after breathing were compared (p < 0.05); 30% and 40% of the duty cycle, respectively, was determined to be the most effective, and the corresponding phases were 30 60% (duty cycle, 30%; p < 0.05) and 30 70% (duty cycle, 40%; p < 0.05).Conclusion:Respiratory regularity was significantly improved with the use of the RPM with our visible guiding system; therefore, it would help improve the accuracy and efficiency of RGRT.

Energy-Neutral Communication Protocol for Very Low Power Microbial Fuel Cell Based Wireless Sensor Network

A major challenge faced by wireless sensor networks (WSNs) for monitoring purposes is their energy supply. Renewable energy sources are useful for sustainable monitoring, but still very limited today due to various implementation constraints. Fortunately, microbial fuel cells (MFCs) provide a renewable power source, which can be integrated into terrains, wetlands, and some civil structures for environmental monitoring. However, as MFCs may only provide ultralow and dynamic power, an energy-neutral communication protocol is crucial for MFC-powered WSNs. Herein a duty-cycle-based energy-neutral communication protocol is proposed for MFC-powered WSNs. Mathematical models for optimal duty-cycling that minimize the probe packet reception time are first proposed. Then, an energy-neutral joint scheduling and routing protocol in multihop MFC networks is introduced. Finally, a MATLAB-based simulation tool is developed to evaluate the protocol performance. Simulation results show that WSNs adopting the proposed protocol can achieve sustainable network operations. It is also demonstrated that the protocol enables reliable data transmission when using ultralow and time-varying MFC power inputs.

50% duty cycle may be inappropriate to achieve a sufficient chest compression depth when cardiopulmonary resuscitation is performed by female or light rescuers.

ObjectiveCurrent guidelines for cardiopulmonary resuscitation recommend chest compressions (CC) during 50% of the duty cycle (DC) in part because of the ease with which individuals may learn to achieve it with practice. However, no consideration has been given to a possible interaction between DC and depth of CC, which has been the subject of recent study. Our aim was to determine if 50% DC is inappropriate to achieve sufficient chest compression depth for female and light rescuers.MethodsPreviously collected CC data, performed by senior medical students guided by metronome sounds with various down-stroke patterns and rates, were included in the analysis. Multiple linear regression analysis was performed to determine the association between average compression depth (ACD) with average compression rate (ACR), DC, and physical characteristics of the performers. Expected ACD was calculated for various settings.ResultsDC, ACR, body weight, male sex, and self-assessed physical strength were significantly associated with ACD in multivariate analysis. Based on our calculations, with 50% of DC, only men with ACR of 140/min or faster or body weight over 74 kg with ACR of 120/min can achieve sufficient ACD.ConclusionA shorter DC is independently correlated with deeper CC during simulated cardiopulmonary resuscitation. The optimal DC recommended in current guidelines may be inappropriate for achieving sufficient CD, especially for female or lighter-weight rescuers.

New application of predictive direct torque control in permanent magnet synchronous generator-based wind turbine

This paper concerns the application of the predictive direct torque control (PDTC) method to a permanent magnet synchronous generator (PMSG). In classical methods for controlling a PMSG, the sampling frequency of the controller must be precisely determined. However, the use of PDTC in this study enables three optimal duty cycles to be predicted at the moment of sampling, significantly reducing the ripple of the electromagnetic torque and the amplitude of the stator flux below those caused by conventional control methods. Therefore, the new method allows a lower sampling frequency than the traditional method. To operate the machine side converter, the DC bus capacitor voltage must be maintained within an acceptable and stable range. Voltage-oriented vector control is used to control the active power and the reactive power, which are delivered from the DC bus capacitor, as well as to control the voltage. In this study, a complete wind turbine system is considered, including a focus on the aerodynamics and structure of each wind turbine, using Fatigue, Aerodynamics, Structures and Turbulence (FAST). Also, to prevent the rotor speed of the wind turbine from exceeding the rated rotor speed too much, a very simple pitch controller system is considered.

Design of a terahertz even splitter and its tolerance analysis

A novel method is presented in this paper to realize terahertz even beam splitting by using a subwavelength binary simple periodic rectangular structure, for making comprehensive application of both the RCWA (Rigorous Couple-Wave Analysis) and the GA (Genetic Algorithm). By applying RCWA, the efficiency of each diffraction order can be numerically solved by using the structure parameters. To design an even beam splitter with a subwavelength structure is to find the optimal duty cycle f, period d, the grating depth h1 and the substrate thickness h2 to approach the minimum zero-order diffraction efficiency, the maximum sum of each non-zero-order diffraction efficiency, and the uniform distribution. Considering the three goals above, an evaluation function is established. GA is applied to optimize the evaluation function F, and then the optimal parameters of the splitter are obtained. When its period, groove depth, substrate thickness and duty ratio respectively equal to 269.7 μm, 175.2 μm, 18.1 μm and 0.409, the normal-incident TE-polarized terahertz plane wave with its frequency equal to 2.52 THz is divided evenly into the diffraction orders±1 and±2. It has a total efficiency up to 92.23% with a preferable result of reducing zero-order diffraction efficiency to 0.192% and an error of uniformity down to 6.51×10- 6, indicating an excellent performance of diffraction efficiency, uniformity and zero-order suppression as a terahertz even splitter. These results break the limitation of realizing even beam splitting in which the traditional scalar theory applies. In addition, this paper exposes the law of influence of the structure parameters, including ridge width, groove width, groove depth, duty ratio and substrate thickness, on the diffraction efficiency and its uniformity. It is found that only a small deviation of the structure parameters, corresponding to a deviation of ridge width a, groove width b, groove depth h1, and substrate thickness h2, less than 1 μm from the optimum design values, the element maintains good beam splitting performance. P0 is permitted to suppress to less than 2%, the error of uniformity U is better than 19.60%, and the diffraction efficiency maintains higher than 79.10%. With a substantial deviation from the design values of the structure parameters, the performance of the splitter will severely degrade and need to be redesigned.

Isotope exchange by Ion Cyclotron Wall Conditioning on JET

The isotopic exchange efficiencies of JET Ion Cyclotron Wall Conditioning (ICWC) discharges produced at ITER half and full field conditions are compared for JET carbon (C) and ITER like wall (ILW). Besides an improved isotope exchange rate on the ILW providing cleaner plasma faster, the main advantage compared to C-wall is a reduction of the ratio of retained discharge gas to removed fuel. Complementing experimental data with discharge modeling shows that long pulses with high (∼240kW coupled) ICRF power maximizes the wall isotope removal per ICWC pulse. In the pressure range 1–7.5×10−3Pa, this removal reduces with increasing discharge pressure. As most of the wall-released isotopes are evacuated by vacuum pumps in the post discharge phase, duty cycle optimization studies for ICWC on JET-ILW need further consideration. The accessible reservoir by H2-ICWC at ITER half field conditions on the JET-ILW preloaded by D2 tokamak operation is estimated to be 7.3×1022 hydrogenic atoms, and may be exchanged within 400s of cumulated ICWC discharge time.

Model Predictive Torque Control of Induction Motor Drives With Optimal Duty Cycle Control

Model predictive torque control (MPTC) is emerging as a powerful control scheme for high performance control of induction motor (IM) drives. Compared to direct torque control, MPTC is more effective and accurate in voltage vector selection by incorporating the system model directly with the finite switching states. However, for two-level inverter-fed IM drives, the sampling frequency of MPTC has to be high to achieve good performance due to the limited number of voltage vectors. Recently, the concept of duty cycle control was introduced in MPTC by inserting a null vector along with the selected active voltage vector to achieve torque ripple reduction. The active vector is first selected from conventional MPTC and then its duration is determined based on a certain principle. The cascaded processing of active vector and its duration leads to poor low-speed performance and the sampling frequency still has to be high. This paper proposes an improved MPTC with duty cycle control by optimizing the vector selection and its duration simultaneously when minimizing both torque and flux errors. As a result, better steady-state performance at both low and high speeds is achieved, even if the sampling frequency is reduced by half. The effectiveness of the proposed MPTC is verified by both simulation and experimental results.