Main Control Parameters Research Articles

Sliding Mode Bifurcation Control Based on Acceleration Feedback Correction Adaptive Compensation for Maglev Train Suspension System With Time-Varying Disturbance

In order to ensure the suspension stability of maglev train, the active control problems of static suspension and dynamic suspension are studied. First, the mathematical model of dynamic suspension characteristics of medium- and low-speed maglev train is established. Second, the PID controller is studied. The results show that the controller is very sensitive to time-varying disturbances such as nonuniformity and load, which leads to the decrease in system robustness. In order to suppress the disturbance effectively, a suspension control method based on the sliding mode reaching law is proposed. Based on the bifurcation phenomenon, the bifurcation point is solved to determine the main control parameters. On the basis of this, an acceleration feedback correction and adaptive control module based on the radial basis function (RBF) network is constructed to effectively suppress the vibration of the electromagnet. The controller consists of a sliding mode bifurcation control law, an acceleration feedback correction module, and an adaptive compensation loop. The simulation and experimental results show that the proposed control algorithm can significantly reduce the variation range of suspension gap with a smoother control current in the presence of complex disturbances and significantly suppress the coupled vibration.

Selection of the Main Control Parameters for the Dst Index Prediction Model Based on a Layer-wise Relevance Propagation Method

The prediction of the Dst index is an important subject in space weather. It has significant progress with the prevalent applications of neural networks. The selection of input parameters is critical for the prediction model of the Dst index or other space-weather models. In this study, we perform a layer-wise relevance propagation (LRP) method to select the main parameters for the prediction of the Dst index and understand the physical interpretability of neural networks for the first time. Taking an hourly Dst index and 10 types of solar wind parameters as the inputs, we utilize a long short-term memory network to predict the Dst index and present the LRP method to analyze the dependence of the Dst index on these parameters. LRP defines the relevance score for each input, and a higher relevance score indicates that the corresponding input parameter contributes more to the output. The results show that Dst, E y , B z , and V are the main control parameters for Dst index prediction. In order to verify the LRP method, we design two more supplementary experiments for further confirmation. These results confirm that the LRP method can reduce the initial dimension of neural network input at the cost of minimum information loss and contribute to the understanding of physical processes in space weather.

Biogeography of bird and mammal trophic structures

Does climate determine the trophic organization of communities around the world? A recent study showed that a limited number of community trophic structures emerge when co‐occurrence of trophic guilds among large mammals is examined globally. We ask whether the pattern is general across all terrestrial mammals (n = 5272) and birds (n = 9993). We found that the six community‐trophic structures previously identified with large mammals are largely maintained when all mammals and birds are examined, both together and separately, and that bioclimatic variables, including net primary productivity (NPP), are strongly related to variation in the geographical boundaries of community trophic structures. We argue that results are consistent with the view that trophic communities are self‐organized structures optimizing energy flows, and that climate likely acts as the main control parameter by modulating the amount of solar energy available for conversion by plants and percolated through food webs across trophic communities. Gradual changes in climate parameters would thus be expected to trigger abrupt changes in energy flows resulting from phase transitions (tipping points) between different dynamical stable states. We expect future research to examine if our results are general across organisms, ecosystems, scales and methodologies, and whether inferences rooted in complex systems theory are supported. The emergence of general patterns in the functional properties of animal communities at broad scales supports the emergence of food‐web biogeography as a sub‐discipline of biogeography focused on the analysis of the geographical distributions of trophic relationships among organisms.

Experimental Investigation on the Effects of Injection Parameters on the Air-Assisted Diesel Spray Characteristics

The air-assisted fuel injection (AAFI) system may be installed in the spark ignition aviation piston engine for the atomization of heavy fuels. However, studies on the effects of injection parameters on the spray characteristics are insufficient, which affects the improvement of AAFI engine performance. In this study, air-assisted diesel spray characteristics are investigated experimentally using a high-speed backlit imaging technique. The effects of main air-assisted injection control parameters such as fuel injection pressure, fuel temperature, and fuel injection duration on the spray characteristics are examined. The results show that spray shape changes from “spindle” to “cone” with an increase in fuel injection pressure. As the fuel injection pressure increases to 1.0 MPa, both the spray penetration and spray width increase significantly. “Protrusions” appear on the spray edge at high fuel temperatures. When the fuel temperature drops to 268 K, the spray penetration and spray width increase slightly. The spray shrinks significantly in both the axial and radial directions with an increase in fuel injection duration. Key parameters that directly affect air-assisted spray characteristics include the difference between the fuel-air mixture injection pressure and the ambient pressure, the density of fuel-air mixture in the air-assisted injector premixed chamber, and the kinetic energy density of the fuel. The former two parameters affect the spray penetration while the latter affects the spray width. The study is beneficial for the design of AAFI engines.

Modeling and simulation of suction-driven flow and heat transfer with temperature-dependent thermal conductivity in a porous channel

In this paper, the heat transfer equation is coupled to the Navier-Stokes equations for a steady flow induced by uniform suction on two porous walls kept at different temperatures. The incompressibility of the fluid and the fact that the velocity field has two components lead to introduce the stream function in the governing equations. A similarity method is used in order to transform the resulting set of partial differential equations satisfied by the stream function and temperature into two ordinary differential equations for the same problem. The analysis is focused on the description of the behaviors of the normal and axial velocities, the streamlines, and temperature through multiple solution branches under different values of the main control parameters of the problem which are the Reynolds number, the Péclet number and the sensitivity of the thermal conductivity to the variations of temperature.

Polarisation-optical model of a controlled random number generator

The subject of the paper is an original model of a tunable optical random number generator. The purpose of the article is to analyse the possibilities of using the proposed model to ensure the protection of the control signals in the projected telecommunication management system of the robotized agro-industrial complex of the Republic of South Ossetia.The research was carried out by methods of mathematical and information-logical modeling. The main results of the study are the information-logical model of the hardware implementation prototype, the descriptive mathematical model of its functioning and the obtained dependences of the quantitative characteristics of the generated random numbers statistical distributions on the main control parameter of the experimental setup.These results can be used in the design and the operation of the remote production facilities monitoring and management telecommunication systems’ components. The possibilities of prototype creating and functioning were demonstrated by visualising the schematic chart of the experimental equipment and by the quantitative estimates of “one” and “zero” signals observation probabilities under the different polarisation rotator orientations relative to the plane of the optical signals detecting system.

Expansion planning of electric vehicle charging stations considering the benefits of peak‐regulation frequency modulation

The China Energy Administration has issued policies to encourage energy storage to participate in the electric auxiliary service market, which will provide ideas for electric vehicle charging stations (EVCSs) to collectively participate in peak-regulation and frequency modulation (FM). Taking into account the benefits of EVs participating in peak-regulation and FM, this paper studies expansion planning for EVCSs. First, the orderly scheduling strategy of EVs under vehicle-to-grid (V2G) technology is established in this paper. And a peak regulation method is proposed to maximize the economic benefits of charging and discharging during peak and valley periods. Second, based on the temporal and spatial prediction model of EV charging demand, the expansion planning model of EVCSs is constructed considering the benefits of peak-regulation and FM. Aiming at minimizing the comprehensive annual social cost of charging stations, the expansion site selection and capacity scheme of EVCSs are obtained. Finally, taking the 24 nodes in Xiangzhou District of Zhuhai City as an example, the location and capacity of the final annual expansion plan are obtained. And the influence of main control parameters on the results of the whole model and method is analysed in detail, the feasibility and effectiveness of the whole model and method are verified.

Managed Pressure Drilling Technology: A Research on the Formation Adaptability

Existing pressure drilling technologies are based on different principles and display distinct characteristics in terms of controlling the pressure and degree of formation adaptability. In the present study, the constant bottom hole pressure (CBHP) and controlled mud level (CML) dual gradient drilling methods are considered. Models for the equivalent circulating density (ECD) are introduced for both drilling methods, taking into account the control pressure parameters (wellhead back pressure, displacement, mud level, etc.) and the relationship between the equivalent circulating density curve in the wellbore and two different types of pressure profiles in deep-water areas. The findings suggest that the main pressure control parameter for CBHP drilling is the wellhead back pressure, while for CML dual gradient drilling, it is the mud level. Two examples are considered (wells S1 and B2). For S1, CML dual gradient drilling only needs to adjust the ECD curve once to drill down to the target layer without risk. By comparison, CBHP drilling requires multiple adjustments to reach the target well depth avoiding a kick risk. In well B2, the CBHP method can drill down to the desired zone or even deeper after a single adjustment of the ECD curve. In contrast, CML dual-gradient drilling requires multiple adjustments to reach the target well depth (otherwise there is a risk of lost circulation). Therefore, CML dual-gradient drilling should be a better choice for well S1, while CBHP drilling is more suitable for well B2.

Counter flow atomizer: Effect of the area ratio of the outlet orifice and the inlet air canal

The need to reduce the energy demand of processes also creates pressure to make atomizers more efficient. A promising development path could be counterflow atomizers (CFA). An atomizer, or synonymously a nozzle, is a device that turns a liquid into a spray. The CFA is a twin-fluid type of atomizer because both the liquid and the atomizing gas are fed into it. Initial results suggest that CFA is capable of the same quality of atomization but using half the air mass flow rate compared to conventional twin-fluids atomizers when operated at identical inlet pressure. This means half the energy requirements with the same efficiency. This atomizer also shows a great promise in the atomization of highly viscous substances such as waste-based fuels and biomass oils. In CFA, the air expands twice; first, at the discharge from the air inlet canal into the mixing tube, and second, at the discharge from the atomizer to the surrounding atmosphere. Therefore, one of the main control parameters is the area ratio of the exit orifice and the air inlet canal. This study experimentally investigates the effect of this ratio on the spray quality for two different CFA atomizers using Phase Doppler Anemometry (PDA), which provides the velocity and size of individual droplet in the spray. The atomizers were operated at the air inlet pressure of 100 and 200 kPa and gas-to-liquid mass (GLR) ratios of 5, 10 and 20%. The effect of the double expansion can be well observed in the pressure differences between the air inlet and the pressure inside the mixing tube. The length of the air counterflow insert had a significant effect on the atomizer performance. For the shorter counterflow channel, a minimal effect on flow was observed; this atomizer behaved like a conventional twin-fluid atomizer and all expansions occurred downstream of the exit orifice. The longer counterflow canal changed the internal expansion ratios, larger droplets, wider spray and higher discharge coefficients (Cd) were obtained.

Adaptive Energy Management Strategy to Avoid Battery Temperature Peaks in Fuel Cell Electric Trucks

Thermal management is essential in electric vehicles to preserve battery life. In particular, avoiding temperature peaks is critical to prevent accelerated degradation. The battery thermal management problem is crucial in fuel cell electric trucks due to the heavy vehicle weight, especially on mountain or hilly roads. Therefore, this paper proposes an energy management strategy that reduces battery degradation by limiting its usage at high temperatures to allow its cooldown and avoid peaks. The energy management strategy is adaptive because the main control parameters for the fuel cell/battery power-split are adjusted depending on the battery temperature. The comparison between adaptive and non-adaptive strategies proves the effectiveness of the proposed formulation in avoiding temperature peaks without hindering fuel consumption or fuel cell degradation. The robustness of the proposed energy management strategy is validated with simulations of several real-world driving cycles with various speed and elevation profiles.

Hysteretic Behavior on Asymmetrical Composite Joints with Concrete-Filled Steel Tube Columns and Unequal High Steel Beams

In order to acquire the hysteretic behavior of the asymmetrical composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, 36 full-scale composite joints were designed, and the CFST hoop coefficient (ξ), axial compression ratio (n0), concrete cube compressive strength (fcuk), steel tube strength (fyk), beam, and column section size were taken as the main control parameters. Based on nonlinear constitutive models of concrete and the double broken-line stress-hardening constitutive model of steel, and by introducing the symmetric contact element and multi-point constraint (MPC), reduced-scale composite joints were simulated by ABAQUS software. By comparing with the test curves, the rationality of the modeling method was verified. The influence of various parameters on the seismic performance of the full-scale asymmetrical composite joints was investigated. The results show that with the increasing of fcuk, the peak load (Pmax) and ductility of the specimens gradually increased. With the increasing of n0, the Pmax of the specimens gradually increases firstly and then gradually decreases after reaching a peak point. The composite joints have good energy dissipation capacity and the characteristic of stiffness degradation. The oblique struts force mechanism in the full-scale asymmetrical composite joint domain is proposed. By introducing influence coefficients (ξ1 and ξ2), the expression of shear bearing capacity of composite joints is obtained by statistical regression, which can provide theoretical support for the seismic design of asymmetrical composite joints.

Sub-Sampled Imaging for STEM: Maximising Image Speed, Resolution and Precision Through Reconstruction Parameter Refinement

Sub-sampling during image acquisition in scanning transmission electron microscopy (STEM) has been shown to provide a means to increase the overall speed of acquisition while at the same time providing an efficient means to control the dose, dose rate and dose overlap delivered to the sample. In this paper, we discuss specifically the parameters used to reconstruct sub-sampled images and highlight their effect on inpainting using the beta-process factor analysis (BPFA) methodology. The selection of the main control parameters can have a significant effect on the resolution, precision and sensitivity of the final inpainted images, and here we demonstrate a method by which these parameters can be optimised for any image in STEM. As part of this work, we also provide a link to open source code and a tutorial on its use, whereby these parameters can be tested for any datasets. When coupled with the hardware necessary to rapidly sub-sample images in STEM, this approach can have significant implications for imaging beam sensitive materials and dynamic processes.

Interval of restitution coefficient for chattering in impact damper

Based on the impact damper, a dynamic model of a non-fixed constrained collision system was established. The coefficient of restitution is used as the main control parameter to analyze the system’s periodic movement and its bifurcation region. The chattering movement characteristics of the system were revealed. The interval of restitution coefficient for the chattering of collision system under various mass ratio and frequency ratio was obtained. The results show that the chattering phenomenon occurs in the collision system when the coefficient of restitution is greater than 0.5; as the mass ratio decreases, the interval of restitution coefficient for chattering continues to expand; as the frequency increases, the interval of restitution coefficient for chattering narrows.

Enhanced control of voltage source converters considering virtual inertia theory

This article presents an enhanced control strategy for voltage source converters (VSCs) based on virtual inertia concept. Considering the significant share of renewable-based generations, frequency stability is noted as one of the most significant challenges of modern low-inertia power systems. Therefore, as the first contribution of this article, dynamic equations of the converter are utilized in order to study its proficient active and reactive power compensation capabilities. Then, this effective power factor correction of the proposed VSC is improved by adding inertia emulation characteristics in order to provide a more synchronous generator (SG) like behavior, which is beneficial from the frequency stability point of view. In addition to that, the impacts of changes in the main control parameters such as inertia and damping on dynamic performance are analyzed using the root locus method. This applied eigenvalue analysis has then been used to support a proper selection of parameter values, which is considered as another novelty of this article. In this regard, the designed algorithm providing auto adjustment capability of controller parameters based on a desired frequency response characteristic can improve the dynamic frequency stability of the system. The functionality of the proposed controller is validated through state-space analysis and simulations with MATLAB/Simulink. The superior performance of the proposed algorithm demonstrated through simulation results confirms that the proposed control method can be considered as a simple yet effective solution for the challenges of a reduced inertia power system.

Fixed-Time Synchronization Control of Delayed Dynamical Complex Networks.

Fixed-time synchronization problem for delayed dynamical complex networks is explored in this paper. Compared with some correspondingly existed results, a few new results are obtained to guarantee fixed-time synchronization of delayed dynamical networks model. Moreover, by designing adaptive controller and discontinuous feedback controller, fixed-time synchronization can be realized through regulating the main control parameter. Additionally, a new theorem for fixed-time synchronization is used to reduce the conservatism of the existing work in terms of conditions and the estimate of synchronization time. In particular, we obtain some fixed-time synchronization criteria for a type of coupled delayed neural networks. Finally, the analysis and comparison of the proposed controllers are given to demonstrate the validness of the derived results from one numerical example.

Optimal sizing of photovoltaic-wind-diesel-battery power supply for mobile telephony base stations

The paper proposes a novel planning approach for optimal sizing of standalone photovoltaic-wind-diesel-battery power supply for mobile telephony base stations. The approach is based on integration of a comprehensive probabilistic sequential Monte Carlo simulator and a black-box optimizer using DIRECT (DIviding RECTangles) method. The main property of the simulator is that input variables are modeled as correlated random processes rather than independent random variables without a time index. By taking into account autocorrelation and mutual correlation, temporal properties of all input variables are kept realistic, such as sunrise and sunset times in irradiance model, daily and seasonal changes in temperature model, and consumption of cooling devices and electronic equipment which depends on the ambient temperature and setting of the parameters of the control devices. The optimization target is to select rated capacities of major system components and to tune the main control parameters for achieving minimum total annual costs without compromising system reliability. The proposed algorithm is tested on planning a typical 2 kW potential base station located on a windy and sunny hill in the Mediterranean region.

Power Decoupling Control of MMC and Small-Signal Stability Analysis of AC/DC Distribution Network With Renewable Energy

AC/DC hybrid distribution network can realize the high penetration utilization of renewable energy and modular multilevel converter (MMC) is the key equipment to connect AC grid and DC grid. In this paper, the direct modulation based on the virtual resistor and the reference value of dc-bus voltage is adopted, and instantaneous-value model of three-phase half-bridge MMC is derived by introducing differential-mode and common-mode component representation. Then, the decoupling control of AC active power and reactive power is designed based on the linear active disturbance rejection control theory (LADRC). The total disturbances including the coupling term and capacitor voltage fluctuation can be estimated by extended state observer (ESO), and then cancelled exactly. Based on the simplified average-value model of MMC, the small signal stability analysis of three-terminal AC/DC distribution network with 26-level MMCs corresponding to the Tangjiawan-Jishan1-Jishan2 demonstration project is carried out by root locus and bode diagram method, which gives the guidance for the choice of the main circuit component and controller parameters, and shows that the virtual resistor greatly reduces the resonant peak of AC/DC distribution network. Simulation and experiment results verify the effectiveness of the power decoupling control strategy of MMC and the AC/DC distribution network can realize complex multi-directional power flow.

Study of the double poling kinematics of elite cross-country skiers

Highly skilled cross-country skiers often prefer the double poling technique due to its speed and versatility. This work is aimed at developing a biomechanical model of a skier using the double poling technique. To do this, using video recordings of the competition, experimental data of eight elite-level athletes (four males and four females) were prepared and analyzed, who used the indicated technique while passing the distance. The analysis made it possible to determine the dependence of the angles in some joints on time, as well as to assess the repeatability of the double poling movement from cycle to cycle. As a result, the main control parameters were identified by which the skier regulates the pace of his movement along the track and the geometric characteristics important for modeling. Statistically significant differences in technique for male and female are shown (P < 0,01), which is extremely important in the development of personalized models of movement. The conclusions drawn will contribute to the correctness of the construction of a mathematical model of double poling biomechanics.

Tailoring Broadband Kerr Soliton Microcombs via Post-Fabrication Tuning of the Geometric Dispersion.

Geometric dispersion in integrated microresonators plays a major role in nonlinear optics applications, especially at short wavelengths, to compensate the natural material normal dispersion. Tailoring of geometric confinement allows for anomalous dispersion, which in particular enables the formation of microcombs which can be tuned into the dissipative Kerr soliton (DKS) regime. Due to processes like soliton-induced dispersive wave generation, broadband DKS combs are particularly sensitive to higher-order dispersion, which in turn is sensitive to the ring dimensions at the nanometer-level. For microrings exhibiting a rectangular cross section, the ring width and thickness are the two main control parameters to achieve the targeted dispersion. The former can be easily varied through parameter variation within the lithography mask, yet the latter is defined by the film thickness during growth of the starting material stack, and can show a significant variation (few percent of the total thickness) over a single wafer. In this letter, we demonstrate that controlled dry-etching allows for fine tuning of the device layer (silicon nitride) thickness at the wafer level, allowing multi-project wafers targeting different wavelength bands, and post-fabrication trimming in air-clad ring devices. We demonstrate that such dry etching does not significantly affect either the silicon nitride surface roughness or the optical quality of the devices, thereby enabling fine tuning of the dispersion and the spectral shape of the resulting DKS states.

Onset of internal transport barriers in tokamaks

Barriers have been identified in magnetically confined plasmas reducing the particle transport and improving the confinement. One of them, the primary shearless barriers are associated to extrema of non-monotonic plasma profiles. Previously, we identified these barriers in a model described by a map that allows the integration of charged particles motion in drift waves for a long time scale. In this work, we show how the existence of these robust barriers depends on the fluctuation amplitude and on the electric shear. Moreover, we also find control parameter intervals for which these primary barriers onset and break-up are recurrent. Another noticeable feature, in these transitions, is the appearance of a layer of particle trajectory stickiness after the shearless barrier break-up or before its onset. Besides the mentioned primary barriers, we also observe sequences of secondary shearless barriers, not reported before, created and destroyed by a sequence of bifurcations as the main control parameters, the fluctuation amplitude and electric shear, are varied. Furthermore, in these bifurcations, we also find hitherto unknown double and triple secondary shearless barriers which constitute a noticeable obstacle to the chaotic transport.