Disturbed Conditions Research Articles

Adaptive tracking of multisinusoidal signal for linear system with input delay and external disturbances

The problem of adaptive tracking of the output variable of a linear stationary plant behind a multiharmonic signal under conditions of control delay and external disturbances is considered. The state vector of the object is not available for direct measurements. The reference and disturbance signal parameters (amplitudes, phases, and harmonic frequencies) are a priori unknown, and a new algorithm is proposed to improve the performance of frequency estimation of a multisinusoidal signal. Examples are given that confirm the relevance of the proposed approach.

Driving Factors for Black-Odor-Related Microorganisms and Potential Self-Remediation Strategies

The black-odor phenomenon has been widely reported worldwide and recognized as a global ecological risk for aquatic environments. However, driving factors for black-odor-related microorganisms and potential self-remediation strategies are still poorly understood. This study collected eight water samples (sites A–H) disturbed by different factors from the Jishan River located in Jinmen, Hubei Province, China. Black-odor-related environmental factors and functional bacterial structure were further measured based on the basic physicochemical parameters. The results indicated that different types of disturbed conditions shape the distribution of water quality and microbial community structures. Site B, which was disturbed by dams, had the worst water quality, the lowest abundance of functional microbes for Mn, Fe, and S biotransformation, and the highest abundance of functional microbes for fermentation. The natural wetlands surrounding the terminus of the river (site H) were keys to eliminating the black-odor phenomenon. Potential black-odor-forming microorganisms include Lactococcus, Veillonella, Clostridium sensu stricto, Trichococcus, Rhodoferax, Sulfurospirillum, Desulfobulbus, and Anaeromusa-Anaeroarcus. Potential black-odor-repairing microbes include Acinetobacter, Mycobacterium, and Acidovorax. pH and COD were paramount physiochemical factors contributing to blackening-odor-related microorganisms. This study deepens our understanding of driving factors for black-odor-related microorganisms and provides a theoretical basis for eradicating the black-odor phenomenon.

Design and Simulation of a PID Neural Network Controller for PMDC Motor Speed and Position Control

Direct current (DC) motors have many difficulties when controlling angular velocity in a variety of applications. The perfect controller cannot be carried out by traditional control alone due to the nonlinear properties of DC motors, design constraints, and mechanical variations caused by the operation conditions. This study proposes a design for an artificial neural network based PID controller (ANNPID) to control the speed of a permanent magnet DC motor (PMDC) in two methods. A detailed analysis is performed based on the simulation results of both methods. The proposed controllers are numerically simulated for various test conditions including; set-point changes, step changes in the load torque, and parameter variations, then the suggested techniques were compared in a comparative study with a traditional PID controller based on the transient response specifications and the performance indices to validate the performance of the controllers. The simulation results demonstrated that the controllers have improved dynamics, static performance, and less overshoot. The methods described here achieve control more effectively than the conventional control approaches under both nominal and disturbed test conditions over different operating ranges.

Exploring the Enhanced Performance of a Static Synchronous Compensator with a Super-Capacitor in Power Networks

The use of a super-capacitor as a storage device integrated with a Voltage source converter-based shunt-connected Static Synchronous Compensator (STATCOM) is proposed for improving the STATCOM performance during sudden large disturbances in a power network. The super-capacitor was applied across the STATCOM capacitor during the disturbance condition. MATLAB simulations were carried out for the verification of a secondary function of the STATCOM like oscillation damping, transient stability improvement, and security of the power network with the storage device. The validation of the proposed super-capacitor was carried out in MATLAB.

Pareto optimality based PID controller design for vehicle active suspension system using grasshopper optimization algorithm

In this paper, a Pareto multiobjective and grasshopper optimization algorithm (GOA) based optimum proportional–integral–derivative (P–I–D) controller design is proposed for improving the vehicle active suspension system dynamics under road disturbance conditions. The Pareto objectives considered are minimization of sprung mass suspension deflection, tyre deflection, sprung mass acceleration minimization and eigenvalue-based objective function. State space model for quarter vehicle active suspension system with P–I–D controller is developed for analyzing the stability and dynamic performance of the system. The sinusoidal-based bump road disturbances are used for testing the robustness of the proposed control technique. Simulation results have been presented to show the advantage of the proposed Pareto multiobjective and GOA-based P–I–D controller over the weighted multiobjective and genetic algorithm-based P–I–D controller in terms of stability and dynamics of the active suspension system.

Distributed consensus tracking control based on state and disturbance observations for mixed-order multi-agent mechanical systems

In this paper, we study the cooperative consensus control problem of mixed-order (also called hybrid-order) multi-agent mechanical systems (MMSs) under the condition of unmeasurable state, unknown disturbance and constrained control input. Here, the controlled mixed-order MMSs are consisted of the mechanical agents having heterogeneous nonlinear dynamics and even non-identical orders, which means that the agents can be of different types and their states to be synchronized can be not exactly the same. In order to achieve the ultimate synchronization of all mixed-order followers, we present a novel distributed adaptive tracking control protocol based on the state and disturbance observations. Wherein, a distributed state observer is used to estimate the followers’ and their neighbors’ unmeasurable states. And, a novel estimated-state-based disturbance observer (DOB) is proposed to reduce the effect of unknown lumped disturbance for the mixed-order MMSs. The proposed control protocol and observers are fully distributed and can be calculated for each follower locally. Lyapunov theory is used for proving the stability of the proposed control algorithm and the convergence of the cooperative tracking errors. A practical cooperative longitudinal landing control example of unmanned aerial vehicles (UAVs) is given to illustrate the effectiveness of the presented control protocol.

Дослідження властивостей коефіцієнтів дискретного косинусного перетворення як основа метода виявлення порушення цілісності цифрового зображення

One of the most common representations of information today are digi-tal images, unauthorized changes of which can lead to negative conse-quences for an individual, institution, firm, and the state as a whole, which makes the detection of digital image integrity violation one of the most ur-gent tasks of information security. The main drawback of the existing ex-pert methods is their focus on detecting the results of a specific disruptive action, but in practice the expert often does not have information about the specifics of an attack on a digital image, while his set of tools is always limited, which can lead to a situation where the investigated digital image is erroneously recognized as original. The first «defense line» here should be methods that are effective regardless of the type of disruptiveaction, i.e. universal. At present, there are a very small number of such methods in open sources; most of them are not free from shortcomings, the main of which is a significant decrease in efficiency in conditions of minor disturb-ances. The aim of the paper is to develop a theoretical basis for an effective universal method of detection of digital image integrity violation, in par-ticular, in conditions of minor disturbances. In the course of achieving the aim of the paper: the justified expediency of using a block approach when organizing an examination of the integrity of a digital image; the area of discrete cosine transformation (DCP) of the block is chosen as the area of examination; justified selection of specific DCP coefficients for organizing the detection of violations of the integrity of digital images, the values of which do not depend on the value of the quality coefficient used when ob-taining the original image, as well as on the specific type of digital images; the difference in the nature ofchanges in the selected formal parameters during re-saving of lossy digital images, depending on whether it is origi-nal or non-original, is investigated. The obtained results of theoretical stud-ies, which are confirmed by the results of computational experiments, con-stitute the theoretical basis for the development of an effective universal method of examination of the integrity of digital images, in particular, in conditions of minor disturbances.

Automatic Landing for Carrier-Based Aircraft Under the Conditions of Deck Motion and Carrier Airwake Disturbances

This article studies the automatic landing problem for the carrier-based aircraft in the presence of deck motion and carrier airwake disturbance. First, an automatic regressive model based prediction algorithm is proposed to generate the motion information of the deck, which in turn is used to generate corrections in the commands of the aircraft's heading and flight path to guarantee landing accuracy. Then, a fast fixed-time stable system (FFSS) is proposed. Based on the FFSS, the sliding-mode-based command differentiators are designed to estimate the first-order derivatives of the reference commands in finite time. Moreover, using the modified reaching law, the incremental sliding mode control (ISMC) is presented to design the landing guidance and control system to provide fast and accurate flight control to touchdown, where the airwake disturbances are compensated by the designed adaptive super twisting extended state observers (ASTESOs). Besides, to improve the stability during the final approach, an approach power compensation subsystem maintaining the angle of attack is proposed using the ISMC and ASTESO. The stability of the closed-loop system is analyzed using the Lyapunov theorem. Finally, comparative simulation results demonstrate the effectiveness of the proposed control scheme over state-of-the-art methods on the landing accuracy and robustness.

Multi‐Event Analysis of the Correlation Between Chorus Waves and Electron Butterfly Distribution Using Van Allen Probes Observation

AbstractIn this study, using Van Allen Probes observations we identify 81 events of electron flux bursts with butterfly pitch angle distributions for tens of keV electrons with close correlations with chorus wave bursts in the Earth's magnetosphere. We use the high‐rate electron flux data from Magnetic Electron Ion Spectrometer available during 2013–2019 and the simultaneous whistler‐mode wave measurements from Electric and Magnetic Field Instrument Suite and Integrated Science to identify the correlated events. The events are categorized into 67 upper‐band chorus (0.5–0.8 fce) dominated events and 14 other events where lower‐band chorus (0.05–0.5 fce) has modest or strong amplitudes (fce represents electron cyclotron frequency). Each electron flux burst correlated with chorus has a short timescale of ∼1 min or less, suggesting potential nonlinear effects. The statistical distribution of selected electron burst events tends to occur in the post‐midnight sector at L > 5 under disturbed geomagnetic conditions, and is associated with chorus waves with relatively strong magnetic wave amplitude and small wave normal angle. The frequency dependence of the electron flux peaks agrees with the cyclotron resonant condition, indicating the effects of chorus‐induced electron acceleration. Our study provides new insights into understanding the rapid nonlinear interactions between chorus and energetic electrons.

Embracing inherent and imposed sources of heterogeneity in rangeland bird management

AbstractRangeland simplification is a global threat to biodiversity. Historically, rangelands exhibited varied vegetation structure, which provided a diverse wildlife habitat. Vegetation heterogeneity resulted from interactions between topoedaphic (inherent heterogeneity) and disturbance factors (imposed heterogeneity). Until recently, these interactive sources of heterogeneity have been ignored in rangeland management and study. Under an emerging paradigm that embraces heterogeneity, contributions of disturbance and topoedaphic conditions to rangeland biodiversity remain largely unknown. Using the avian community, we assessed the effects of wetland area, ecological site, and topographic roughness (inherent heterogeneity) and four grazing strategies (imposed heterogeneity; patch‐burn grazing with one or two seasons of fire, season‐long grazing, and modified twice‐over rotational grazing with variably stocked paddocks) on vegetation structure, avian diversity, avian community composition, and avian densities. The interaction between inherent and imposed heterogeneity influenced avian community composition but not species‐specific densities. The effects of management on vegetation structural heterogeneity varied over years, though patch‐burn management generated heterogeneity and temporal stability in vegetation structure compared to season‐long grazing and modified twice‐over rotational grazing. Patch‐burn and season‐long grazing pastures had higher diversity than modified twice‐over rotational grazing. Community composition was sensitive to ecological site, topographic roughness, and wetland area, suggesting that both the fire‐grazing interaction and inherent heterogeneity maintain biodiversity. Out of our six grassland obligate focal bird species, two responded to inherent heterogeneity, while three were most sensitive to imposed heterogeneity. One species, western meadowlark (Sturnella neglecta), did not respond to either source of heterogeneity, potentially indicating responsiveness to factors outside our study, such as annual precipitation or heterogeneity at fine scales. Our results indicate that both inherent and imposed heterogeneity are important in shaping grassland bird abundance, diversity, and community composition and that conserving rangeland biodiversity in the future will require managing for greater imposed heterogeneity while embracing existing landscape variability.

Symbol Diversity as a Means to Make PAM-4 Modulation More Resilient in Harsh Electromagnetic Environments

In this article, symbol diversity is presented for the pulse amplitude modulation PAM-4 encoding scheme. This technique is implemented in order to incorporate electromagnetic resilience in a triple modular redundant communication channel that is subjected to electromagnetic disturbances in reverberant environments. An in-depth numerical study is carried out in light of new electromagnetic disturbance condition monitoring definitions that provide a better insight into the actual state of the system. An explanation of the different fault mechanisms based on the new definitions is provided for the proposed PAM-4 symbol diversity setup and is compared with an undiverse PAM-4 system with a two-out-of-three majority voter. The results show that the proposed symbol diversity technique is quite an effective measure for incorporating fault tolerance in the system design.

Forced vibration analysis model for pumped storage power station based on the 1D–3D coupling and pipe walls vibration

AbstractHydraulic vibration is a common phenomenon in pumped storage power stations (PSPS) and hydropower plants. Evaluating the performance of the PSPS and water conveyance system under the hydraulic vibration condition is significant for the safety of the electric power and the PSPS system. In this study, the one‐dimensional (1D) and three‐dimensional (3D) coupling model for the entire PSPS system is established based on the open‐source software OpenFOAM and in‐house C++ codes. The coupling data exchange is realized by writing and reading files. The coupling model is validated by comparing the results with the pure 1D method under small load disturbance conditions. The forced vibration source is modeled by the pipe walls vibration method in the 3D region, and the 1D method takes charge of other parts in the PSPS system. The combination of the pipe walls vibration and 1D–3D coupling could fully consider the incident and reflected characteristics of the pressure waves. The established model could evaluate the overall performance of the PSPS system under forced vibration. Sensitive analysis of the vibration magnitude is carried out, and the results are consistent with the theoretical analysis, demonstrating that the established model is applicable for the forced vibration analysis.

Torsional vibration of open-ended pipe piles in saturated soil considering the construction disturbance

A soil-pipe pile-inner soil torsional dynamic interaction model is developed accounting for the radial inhomogeneity of the outer saturated soil as well as the soil plug (inner soil) due to the construction disturbance. Both the outer and inner saturated soils are divided into a series of annular zones in the radial direction with linearly varying soil properties from zone to zone. The governing equation of motion for each soil zone is established based on the Biot's two-phase linear theory and is solved to derive the circumferential shear stress at the pipe pile-soil interface in conjunction with the continuous conditions at the interface of adjacent soil zones. Further, the governing equation for the open-ended pipe pile is established and is solved to derive an analytical solution for the torsional vibration of the pile in the frequency domain. The developed solution is validated against the results of available analytical solutions. The validated solution is then used to examine the torsional vibration characteristics of the open-ended pipe pile under different saturated soil parameters and construction disturbance conditions. The results show that: (1) The pile resistance to torsional dynamic load is enhanced as the soil strengthening range or degree increases, while is reduced as the soil porosity, soil weakening range or degree increases; (2) The inner soil contributes a lot to the enhancement of pile torsional resistance.

Adaptive Terminal Sliding Mode Control of Picking Manipulator Based on Uncertainty Estimation

In this paper, a robust nonsingular fast terminal sliding mode control scheme for the picking manipulator under the condition of load change and nonlinear friction disturbance is presented. Firstly, the dynamic equation of the picking manipulator under the condition of load change and nonlinear friction disturbance is established. Then, in order to avoid the singularity problem existing in the terminal sliding mode and improve the convergence time, a new nonsingular fast terminal sliding mode control strategy is adopted to design the control law of the picking manipulator, which can guarantee the finite time convergence. The adaptive law is used to estimate the uncertainties of the system, and the finite time convergence of the system state is proved by the Lyapunov criterion. In addition, the genetic algorithm is used to identify the friction parameters to realize the nonlinear friction compensation control of the system. Finally, the simulation results of the picking manipulator under different load conditions show that the controller designed in this paper realizes the fast and accurate positioning of the picking manipulator under load change and nonlinear friction, and the control strategy is reasonable and effective.

Evaluation of adaptogenic activity of Neurotip capsules by swimming endurance and chronic stress model

Stress is the disturbed homeostatic condition of the organism, and it is represented by non-specific response of the body to any demand imposed on it. Stress brings various changes in physiological condition of the organism, but various mechanism of the body will counteract to maintain homeostasis. Neurotip capsule is effective Ayurvedic treatment for stress related disorders. Neurotip capsules have unique combination of herbs like Jatamansi, Guduchi, Shankapushpi, Ashwagandha, and Probiotics. These herbs are known to sooth the mind, promote calmness and act as a stress buster. In present research study Neurotip formulation was screened for acute toxicity study and sub chronic oral toxicity study on adult albino mice. Animals were observed for behavioural changes, neurological changes and autonomic profile changes. There was no noticeable toxicity and death observed in animals when treated with highest dose of 5000mg/ kg of the formulation. Neurotip was tested on swimming endurance of mice. The results were compared with standard group treated with Geriforte. Test formulation was evaluated by chronic stress model in rats using Omeprazole as standard drug. Assessment of ulcer induction was done to check adaptogenic potential of Neurotip. Ulcer protection by test formulation was found to be 68.44% showing good antistress effects.

A Combination of Near-Infrared Hyperspectral Imaging with Two-Dimensional Correlation Analysis for Monitoring the Content of Alanine in Beef.

Alanine (Ala), as the most important free amino acid, plays a significant role in food taste characteristics and human health regulation. The feasibility of using near-infrared hyperspectral imaging (NIR-HSI) combined with two-dimensional correlation spectroscopy (2D-COS) analysis to predict beef Ala content quickly and nondestructively is first proposed in this study. With Ala content as the external disturbance condition, the sequence of chemical bond changes caused by synchronous and asynchronous correlation spectrum changes in 2D-COS was analyzed, and local sensitive variables closely related to Ala content were obtained. On this basis, the simplified linear, nonlinear, and artificial neural network models developed by the weighted coefficient based on the feature wavelength extraction method were compared. The results show that with the change in Ala content in beef, the double-frequency absorption of the C-H bond of CH2 in the chemical bond sequence occurred prior to the third vibration of the C=O bond and the first stretching of O-H in COOH. Furthermore, the wavelength within the 1136-1478 nm spectrum range was obtained as the local study area of Ala content. The linear partial least squares regression (PLSR) model based on effective wavelengths was selected by competitive adaptive reweighted sampling (CARS) from 2D-COS analysis, and provided excellent results (R2C of 0.8141, R2P of 0.8458, and RPDp of 2.54). Finally, the visual distribution of Ala content in beef was produced by the optimal simplified combination model. The results show that 2D-COS combined with NIR-HSI could be used as an effective method to monitor Ala content in beef.

An Improved Predictor-Corrector Guidance Algorithm for Reentry Glide Vehicle Based on Intelligent Flight Range Prediction and Adaptive Crossrange Corridor

For traditional predictor-corrector guidance algorithm for reentry glide vehicle, it cost a lot of time to obtain predicted flight range with a slow speed to iterate. In this paper, according to residual network (ResNet)’s block and dynamic model of vehicle, through analyzing the characteristics of predicted flight range with constraints, the flight range prediction block and flight range prediction neural network are designed, which can obtain the predicted range accurately and quickly; then aiming at the separation between guidance logic and no-fly zone avoidance logic, which may lead to guidance failure and increasing of the sign variation number of the bank angle, the no-fly zone crossrange and the no-fly zone mapping crossrange are proposed in this paper. According the repulsion force of artificial potential field, an adaptive crossrange corridor combining guidance logic and no-fly zone avoidance logic is proposed, and the convergence of the corridor is analyzed theoretically. Through simulation, the block number of flight range prediction network is determined firstly. By this method, the efficiency of lateral guidance can be improved. Then, through the simulation with the different no-fly zones under different disturbed conditions, the stability and validity of the guidance method are verified. Finally, compared with other predictor-corrector algorithms, the proposed method can realize guidance with less sign variation number of bank angle and better avoidance for no-fly zones.

Prediction Method of Unsteady Flow Load of Compressor Stator under Working Condition Disturbance

Due to the complexity of the compressor operating conditions and the existence of various disturbances and unsteady effects in the flow field, the analysis of compressor stator vibration characteristics becomes particularly critical. The convolutional neural network model combined with a transient CFD method was introduced to solve the difficulty of analyzing the flow load of the compressor stator blade. This paper mainly focuses on two key points: the complex change of the aerodynamic load and the accurate prediction of the blade excitation. Considering the stator–rotor interference, the unsteady effects, and the variable working condition characteristics, the random disturbance analysis model of the flow field boundary was generated to simulate the unsteady flow excitation of the stator under complex working conditions. By establishing the neural network of boundary disturbance and flow excitation characteristics, the prediction model was trained and generated under the support of large-scale data. The most important role of the model was to establish the end-to-end data mapping between the disturbance condition and the aerodynamic load of the stator blade. The conclusions demonstrate that the introduction of an airflow disturbance is helpful to obtain the excitation characteristics of the stator under complex working conditions. The model established in this paper based on 1000 groups of disturbed working condition data can effectively predict the aerodynamic load of the blades under complex working conditions. In addition, the construction of the model is beneficial for saving a lot of computing resources, and the prediction accuracy also reaches a good level. The method presented in this paper provides a reference for the vibration analysis of the compressor stator.

Modified Multi–Source Water Supply Module of the SWAT–WARM Model to Simulate Water Resource Responses under Strong Human Activities in the Tang–Bai River Basin

In the past few decades, the water resources in the Tang–Bai River Basin showed a declining trend, due to the human–driven alteration of surface water and groundwater management. There are potential risks to the sustainable utilization of future water resources in response to agricultural, industrial, and domestic water supply. In this work, we used the water allocation and regulation model based on SWAT (SWAT–WARM model) to quantify the characteristics of water resources response under human activities in this basin. The multi–source water supply module was modified to improve the applicability of the SWAT–WARM model in this basin. We validated our simulations against observed runoff, water consumption, and supply. The main results were as follows: (a) We used the percent bias, the correlation coefficient, and the Nash–Sutcliffe efficiency coefficient to measure the model validity and found that the modified model did not show obvious advantages in runoff simulations, whereas it reproduced water consumption and supply better than the original model. The modified model had more advantages in reflecting the process of water resources transformation and utilization in the basin driven by strong human activities. (b) By comparing the variation of watershed water circulation fluxes under natural and human disturbance conditions in the Tang–Bai River Basin from 1995 to 2016, we found that human activities increased evapotranspiration by 6.8% and surface runoff increased by 10.0%, while groundwater resources decreased by 0.23 million m3/yr. (c) There was water shortage in the basin at different flow frequencies, among which agricultural water shortage accounted for the largest proportion, >70%. The basin should further strengthen agricultural and industrial water saving, reduce water consumption fundamentally, and ensure the sustainable development of economy and society.

Responses of synanthropic vegetation to composting facility

Composting facilities are habitats where biological materials are bio-oxidized. Biological waste represents a source of plant species diaspores and may promote changes in the species composition of the surrounding. The studied composting facility is situated in the Bohemian-Moravian Highlands, Czech Republic. Four sites, the composting pile and three habitats nearby were chosen of different use and disturbance conditions. Phytosociological plots were recorded in each of the habitat and the results were processed using multivariate analyses of ecological data. The information about plant species indication values was also analysed: (i) the relationship between soil disturbance and plant species occurrence, (ii) seed dormancy, (iii) seed bank, and (iv) vector of seed dispersion. During the research, 119 plant taxa were found in total. Conditions of the composting process (frequent disturbances, excessive available nutrients, enough water, and supply of new diaspores) represent a challenge for plant species. The presence of plant diaspores in the biowaste is a reason why the fundamental principle of appropriate composting process has to be adhered to. Another important task is to give attention to the methods determining the share of living diaspores in the final compost, which is still missing in practice. Compost might become a vehicle for spreading weeds. The capacity of vegetation to survive and multiply on the premises of composting facilities increases the importance of vegetation monitoring and control of the adjacent areas. The usual occurrence of rural brownfields near composting facilities increases the risk of diaspores being transmitted into biowaste or compost, thus increasing the share of undesirable viable diaspores. Composting facilities generate specific synanthropic conditions for the vegetation. Therefore, the composting facility projects should take into consideration the surrounding areas and vegetation management. It is recommended that the project should include semi-natural vegetation, which can create efficient barriers to the spreading of undesirable ruderal plant species. The novelty of this study is the confirmation that composting facilities and compost become a new factor affecting vegetation, which has been disregarded so far. The link between composting facilities and vegetation has to be included in the legislation related to parameters of compost quality. Moreover, the issue of weeds, their reproductive organs and their spread should be considered in the guidelines for the design, location, construction, and operation of composting facilities.