Variable Structure Systems Research Papers (original) (raw)

2025, Physical Review Letters

We examine excitation (by a short laser pulse) of a hydrogen atom in parallel electric and magnetic fields, from an initial tightly bound state to a state above the classical ionization threshold. We predict that the atom ionizes by emitting a train of electron pulses. This prediction is based on the classical dynamics of electron escape. In particular, the pulse train is due to classical chaos, which occurs for nonvanishing magnetic field. We connect the structure of the pulse train to fractal structure in the escape dynamics, and discuss several issues of experimental interest, with a particular emphasis on understanding the resolution of individual pulses. A brief account of this work appeared previously as a Letter [Phys. Rev. Lett. 92, 073001 (2004)].

2025, Physica D: Nonlinear Phenomena

Homoclinic and heteroclinic tangles are fundamental phase space structures that help organize the transport defined by a chaotic map on a two-dimensional phase space. Previous work introduced the technique of "homotopic lobe dynamics" to study the topology of a homoclinic tangle. The present work generalizes homotopic lobe dynamics to describe the topology of a network of nested homoclinic and/or heteroclinic tangles. Using this theory, we demonstrate that the topological analysis of a network of nested tangles can lead to an efficient symbolic description of a chaotic phase space, even in the vicinity of islands of stability. By increasing the amount of topological information used (e.g. by introducing additional tangles at finer scales), this technique suggests an efficient route for defining accurate symbolic dynamics for phase spaces that exhibit a mixture of chaos and regularity.

2025, Physica D: Nonlinear Phenomena

We develop a topological approach, called homotopic lobe dynamics, for describing the qualitative structure of homoclinic tangles. This approach begins from an efficient and accurate description of the initial development of a tangle, up to some finite number of iterates J, where the value of J indicates the amount of information that one puts into the theory. Our approach can then compute the topologically forced structure of the tangle at all iterates after J. This allows one, for example, to predict a minimal set of homoclinic intersections. This technique places few assumptions on the homoclinic tangles considered. In fact, one main advantage is its ability to describe the wide variety of behavior seen in physically significant tangles.

2025, IEEE Transactions on Industrial Electronics

An interleaving fixed switching frequency quasi-sliding control algorithm based on the Zero Average Dynamics (ZAD) approach is reported and applied to the design of a modular system of parallel-connected single-phase inverters. This approach is used in a laboratory prototype of three inverters with an FPGA control-based implementation embedding this algorithm. Experimental results are provided to illustrate the design features in terms of AC output voltage regulation, balanced current sharing among mismatched modules, interleaved fixed switching frequency operation and robustness with respect to load variations.

2025, Lecture Notes in Control and Information Sciences

2025, Biophysical Journal

Combining an azobenzene chromophore with the bis-cysteinyl active-site sequence of the protein disulfide isomerase (PDI) we constructed a simple but promising model for allosteric conformational rearrangements. Paralleling cellular signaling events, an external trigger, here absorption of a photon, leads to a structural change in one part of the molecule, namely the azobenzene-based chromophore. The change in geometry translates to the effector site, in our case the peptide sequence, where it modifies covalent and nonbonded interactions and thus leads to a conformational rearrangement. NMR spectroscopy showed that the trans-azo and cis-azo isomer of the cyclic PDI peptide exhibit different, but well-defined structures when the two cystine residues form a disulfide bridge. Without this intramolecular cross-link conformationally more variable structural ensembles are obtained that again differ for the two isomeric states. Ultrafast UV/Vis spectroscopy confirmed that the rapid isomerization of azobenzene is not significantly slowed down when incorporated into the cyclic peptides, although the amplitudes of ballistic and diffusive pathways are changed. The observation that most of the energy of an absorbed photon is dissipated to the solvent in the first few picoseconds when the actual azo-isomerization takes place is important. The conformational rearrangement is weakly driven due to the absence of appreciable excess energy and can be described as biased diffusion similar to natural processes.

2025

 Reinforcement Learning (RL) is a branch of machine learning that focuses on how agents can learn to make decisions through trial and error to maximize cumulative rewards.  RL allows machines to learn by interacting with an environment and receiving feedback based on their actions. This feedback comes in the form of rewards or penalties.  Reinforcement Learning revolves around the idea that an agent (the learner or decision-maker) interacts with an environment to achieve a goal.  The agent performs actions and receives feedback to optimize its decision-making over time. o Agent: The decision-maker that performs actions. o Environment: The world or system in which the agent operates. o State: The situation or condition the agent is currently in. o Action: The possible moves or decisions the agent can make. o Reward: The feedback or result from the environment based on the agent's action.  The RL process involves an agent performing actions in an environment, receiving rewards or penalties based on those actions, and adjusting its behavior accordingly.  This loop helps the agent improve its decision-making over time to maximize the cumulative reward. o Policy: A strategy that the agent uses to determine the next action based on the current state. o Reward Function: A function that provides feedback on the actions taken, guiding the agent towards its goal. o Value Function: Estimates the future cumulative rewards the agent will receive from a given state. o Model of the Environment: A representation of the environment that predicts future states and rewards, aiding in planning. 1. Q-Learning: A model-free algorithm where the agent learns a value function Q(s,a), which represents the expected utility of taking action a in state s and following the optimal policy thereafter. 2. SARSA (State-Action-Reward-State-Action): Similar to Q-Learning, but updates the Qvalue based on the action actually taken, considering the policy followed by the agent.  Positive Reinforcement  Negative Reinforcement 1. Positive Reinforcement  Positive Reinforcement is defined as when an event, occurs due to a particular behavior, increases the strength and the frequency of the behavior. In other words, it has a positive effect on behavior.  Advantages: Maximizes performance, helps sustain change over time.  Disadvantages: Overuse can lead to excess states that may reduce effectiveness.  Negative Reinforcement is defined as strengthening of behavior because a negative condition is stopped or avoided.  Advantages: Increases behavior frequency ensures a minimum performance standard.  Disadvantages: It may only encourage just enough action to avoid penalties.  In reinforcement learning, a common example of an agent getting "lost" is when it fails to learn an effective policy or strategy to reach its goal in a given environment.  This can happen due to factors like insufficient exploration, difficulty in generalizing to new situations, or problems with credit assignment.

2025

A. [abanovi}, Nadira [abanovi}, K. Jezernik Sliding Modes in Sampled-data Systems 1 d d d d d d d d d d d d

2025, Lecture Notes in Control and Information Sciences

Control system design of switching power converters and electrical machines based on the sliding mode approach is presented. The structural similarities among switching converters and electrical machines are used to show that the same structure of the controller could be used for plants under consideration. The controller is designed as a cascade structure with inner current loop designed as a sliding mode system with discontinuous control and outer loop (voltage or mechanical motion) being designed as a discrete-time sliding mode controller.

2025, 2006 IEEE International Symposium on Circuits and Systems

In this paper a methodology to the analysis of bifurcations of variable structure systems is proposed. This methodology, based on the use of symbolic computation packages, is derived from the conditions of the existence of variable structure bifurcations of planar systems, allowing a multi-parametric analysis, without intensive numeric computations. The proposal is applied to a predator-prey model with human intervention.

2025

The aim of this study is to improve road safety by analyzing road influence on vehicle stability. Nowadays, vehicle stability is enhanced by electronic systems. It can be expected that, in a near future, stability systems will rely on complete vehicle dynamics models. This means measuring, on each axle, the forces and deformations of -especially-tires and suspensions. In that perspective, the contact forces can be obtained by using dynamometrical wheels or load bearing sensors (SKF-TNO), which are likely to become available at a sufficiently low cost. For the deformation concern, we can think of lots of possibilities to gauge the suspension parts, but, at the present time, the tire vertical deformation remains difficult to acquire. Although different techniques exist to determine the tire crushing, the most popular consists in measuring the distance between a laser sensor fitted on a wheel and the corresponding local road surface. Nevertheless, this kind of sensor is expensive, difficult to adapt on standard cars and its measurements are highly influenced by the road texture state (water depth, markings ...). The whole new idea is that, assuming the availability of bearing load sensors on a vehicle for force measurement, tire height could be evaluated without any additional equipment by measuring torques and forces applicated to this wheel. So, we propose to evaluate the effectiveness of equivalence between the tensor components and optical crushing measurements. Experiments have been worked out at various speeds and curves. These experiments tend to show that the longitudinal torque and lateral force at the wheel center can be used to determine the wheel radius in the maximum loaded phases. Dynamometrical measurements present the possibility to be used under extreme weather conditions, for particular road texture contrary to optic techniques and at an expected affordable cost in a near future. More deepened studies will be launched to estimate the influence of tire structure, road curvature, evenness and texture on the proposed methodology.

2025, Asian Journal of Control

This work presents a Dual-Mode Adaptive Robust Controller applied to the angular shaft speed control of a three-phase induction motor. A liaison between a Model Reference Adaptive Controller (MRAC) and a Variable Structure Model Reference Adaptive Controller (VS-MRAC) through a tuning parameter is obtained using fuzzy logic. The basic idea of the Dual-Mode controller is adding both the advantages of the VS-MRAC transient behavior with the steady-state properties of the conventional MRAC.

2025

This paper develops a new method for estimating the structural parameters of (discrete choice) dynamic programming problems. The method reduces the computational burden of estimating such models. We show the valuation functions characterizing the expected future utility associated with the choices often can be represented as an easily computed function of the state variables, structural parameters, and the probabilities of choosing alternative actions for states which are feasible in the future. Under certain conditions, nonparametric estimators of these probabilities can be formed from sample information on the relative frequencies of observed choices using observations with the same (or similar) state variabIes. Substituting the estimators for the true conditional choice probabilities in formulating optimal decision rules, we establish the consistency and asymptotic normality of the resulting structural parameter estimators. To illustrate our new method, we estimate a dynamic model of parental contraceptive choice and fertility using data from the National Fertility Survey. 1. See Eckstein and Wolpin (1989b) for a recent survey of this fast growing field.

2025

In the present paper we investigate a EOQ model for imperfect items under time variable linear demand. The defective items is being screened out by a 100 % screening process and then sold in a single batch by the end of the 100% screening process with a salvage price. The unsold perfect item during the cycle is sold at a different salvage price at the end of cycle. Two different types for cost parameters are considered namely crisp constant and uncertain variable. For each case, optimal policy is obtained. We have considered expected value model and uncertain chance constraint programming for the Uncertain EOQ model. Numerical example and sensitivity analysis are provided to illustrate the effectiveness of the above models.

2025

Hybrid Offshore-wind and Tidal Turbine" (HOTT) generation system (Rahman and Shirai, HOTT energy Conversion I [6-pulse GTO rectifier and inverter], 2008; HOTT energy conversion II [6-Pulse GTO Rectifier DC connection and Inverter], 2009) interconnecting method for a DC side cluster of wind and tidal turbine generators system are proposed. This method can be achieved using wind and tidal turbine generating system. Four tidal and a wind turbines generator can be interconnected easily with the proposed method, and high reliability and electric output power with high quality are also expected. This method is able to send generated power through a long-distance DC transmission line. The configuration of the hybrid wind and tidal turbine generator system is explained first, and a dynamic model of the hybrid system is developed. The dynamic performances of the HOTT system when the wind and tidal velocity is changing are then discussed. Finally, a control system to keep the DC voltage constant of the HOTT system is introduced.

2025, International Workshop on Variable Structure Systems, 2006. VSS'06.

In this paper, a feedback linearization-based controller with a high-order sliding mode observer running parallel is applied to a quadrotor unmanned aerial vehicle. The high-order sliding mode observer works as an observer and estimator of the effect of the external disturbances such as wind and noise. The whole observer-estimatorcontrol law constitutes an original approach to the vehicle regulation with minimal number of sensors. Performance issues of the controller-observer are illustrated in a simulation study that takes into account parameter uncertainties and external disturbances.

2024, Journal of Power of Technologies

This paper presents a modified chaotic gravitational search algorithm (CGSA) as a novel heuristic algorithm for coordinate design of fuzzy logic controller-based thyristor controlled series capacitor (FLC-TCSC) and power system stabilizers (PSSs) in multi-machine power system. The coordinate design of PSS and FLC-TCSC damping controllers is converted to a single optimization problem with the time-domain objective function which is solved by the proposed CGSA algorithm which has strong ability for finding the most optimistic results. By minimizing the employed fitness function in which oscillatory characteristics between areas are included, the interactions among the FLC-TCSC controller and PSS under transient conditions in the multi-machine power system are enhanced. The generator speed and the electrical power are chosen as global input signals. The system performance is assessed through the time multiplied absolute value of the error (ITAE), Eigenvalues and figure of demerit (FD) analysis performance indices. The robustness is tested by considering several operating conditions to establish the superior performance with the proposed controller over the other stabilizers.

2024

In this paper, selection of the state feedback gains by Particle Swarm Optimization (PSO) technique is presented contrary to the selection of the feedback gains reported in literature. The proposed design has been applied to the inverter fed induction motor drive system. The system performance has been simulated and compared with some previous methods such as Variable Structure Controller (VSC) method, and Genetic Algorithm (GA) approach. Simulation results show that the dynamic system performance has been improved much with PSO compared to other two methods such as VSC and GA . The results show the effectiveness of the proposed technique.

2024

In this paper a new robust load frequency controller for two area interconnected power system is presented to quench the deviations in frequency and tie line power due to different load disturbances. The dynamic model of the interconnected power system is developed without the integral control. The area control error is also not included. The frequency and derivatives are zero under normal operation and after the disturbance effects are died. Then the problem is restructured as the problem of state transfer from the initial steady state to final steady state without oscillations in less time. The fuzzy controller designed here consists of two crisp inputs namely deviation of frequency and the other is derivative of frequency deviation. The output of the fuzzy controller is the control input to each area. The studies power system is subjected to a wide range of load disturbances to validate the effective ness of the proposed fuzzy controller. The simulated results are obtained for di...

2024, Annual Reviews in Control

Modern modeling languages for general physical systems, such as Modelica, Amesim, or Simscape, rely on Differential Algebraic Equations (DAEs), i.e., constraints of the form f (x , x, u) = 0. This drastically facilitates modeling from first principles of the physics, as well as the reuse of models. In this paper, we develop the mathematical theory needed to establish the development of compilers and tools for DAE-based physical modeling languages on solid mathematical bases. Unlike Ordinary Differential Equations (ODEs, of the form x = g(x, u)), DAEs exhibit subtle issues because of the notion of differentiation index and related latent equations-ODEs are DAEs of index zero, for which no latent equation needs to be considered. Prior to generating execution code and calling solvers, the compilation of such languages requires a nontrivial structural analysis step that reduces the differentiation index to a level acceptable by DAE solvers. The models supported by tools of the Modelica class involve multiple modes, with modedependent DAE-based dynamics and state-dependent mode switching. However, multimode DAEs are much more difficult to handle than DAEs, especially because of the events of mode change. Unfortunately, the large literature devoted to the mathematical analysis of DAEs does not cover the multimode case, typically saying nothing about mode changes. This lack of foundations causes numerous difficulties to the existing modeling tools. Some models are well handled, others are not, with no clear boundary between the two classes. In this paper, we develop a comprehensive mathematical approach supporting compilation and code generation for this class of languages. Its core is the structural analysis of multimode DAE systems. As a byproduct of this structural analysis, we propose sound criteria for accepting or rejecting multimode models. Our mathematical development relies on nonstandard analysis, which allows us to cast hybrid system dynamics to discrete-time dynamics with infinitesimal step size, thus providing a uniform framework for handling both continuous dynamics and mode change events.

2024

In this paper, we consider the stabilization problem of the wave equation with pointwise delay feedback. We propose a control methodology having the advantage of the assignation of the closed-loop exponential decay. The methodology involves a four-parameter autoregressive control structure for which the design strategy is based on multiplicity manifolds. The proof of the main result is based on spectral analysis, thereby conveying a positive outlook on the control of further classes of partial differential equations.

2024

The hallmark of Gram-negative bacteria is their cell envelope, which is composed of two membranes, the inner or cytoplasmic membrane (IM), and the outer membrane (OM), separated by a compartment (the periplasm) that contains a thin peptidoglycan layer. Lipopolysaccharide (LPS) is the major component of the OM, and it acts as a selective barrier together with the OM proteins (OMPs), preventing the entry of many toxic molecules into the cell. Despite the structure and composition of OM have been elucidated in pivotal ...

2024, Annual Reviews in Control

2024, 2006 IEEE International Symposium on Circuits and Systems

2024, Feedback

Abstract: This paper proposes the design of a cascade control using fuzzy logic. A new set of fuzzy logic rules are added to a conventional Fuzzy Logic Controller (FLC) to build the Fuzzy Controller with Intermediate Variable (FCIV). The... more

2024, Advances in Variable Structure Systems

2024, SPIE Proceedings

Dogu Anatolu Gözlemevi (DAG-Eastern Anatolia Observatory) Project is a 4m class optical, near-infrared Telescope and suitable enclosure which will be located at an altitude of ~3.170m in Erzurum, Turkey.

2024, IEEE Conference Proceedings

Discrete-time linear systems with switching in the repetitive mode are considered. The systems are subjected to random disturbances, and the measurements are corrupted by additive noises. Two iterative learning control design methods are proposed. Both of the methods involve an auxiliary 2D model in the form of a discrete repetitive process. The first method is based on the dissipativity conditions established for the auxiliary model with a special choice of the supply rate and storage function. This choice allows finding a control law (in the general case, nonlinear) that ensures the convergence of the learning process. The second method adopts a linear iterative learning control update law of a given form, while the convergence of the learning process is ensured by the stability conditions of the auxiliary 2D model. The structure of both control laws includes a stationary Kalman filter. The stability conditions are obtained using the divergent method of vector Lyapunov functions. An example is given to demonstrate the capabilities and features of the new method.

2024

This paper proposes a method for the organization of real sliding movements, which are caused by finite switching frequency of control systems. In one of two proposed structures for the organization of sliding modes, the control is formed according to the principle of feedback connections; in the other proposed structure, the control is formed according to the principle of discrete control where the discrete levels are defined by crossing (hitting) points on a hyperplane. The proposed method allows users to solve practically oriented problems of organization of sliding movements while taking into account real boundaries existing in systems. The proposed models are simulated using MATLAB/SIMULINK.

2024, Proceedings of the 41st International Universities Power Engineering Conference

Large torque ripple of the Switched Reluctance Motor (SRM) is a major problem that is an obstacle to spreading over an industry. Nonlinear inductance profile and pulse magnetizing make the torque ripple unavoidable. In order to reduce the torque ripple, it is necessary to control the torque directly because the torque of the SRM is not linearly proportional to a current. This paper shows direct torque control scheme that reduces the torque ripple of the SRM dramatically. To verify the feasibility of control scheme, simulation and experiment are carried out.

2024, IAEME PUBLICATION

This paper presents the application of evolutionary computation namely Genetic Algorithm (GA) for estimation of feedback controller parameters of Static Var Compensator (SVC) and Power System Stabilizer (PSS) for a single machine and multi machine Power Systems. The performance of the systems is analyzed with various control strategies such as GA based PSS, GA based SVC and GA based coordinated design of PSS and SVC and the results are presented. GA offers certain advantages such as simple computational steps, derivative free optimization, reduced number of iterations and assured near global optima.

2024, 2011 IEEE Jordan Conference on Applied Electrical Engineering and Computing Technologies (AEECT)

The Smooth Variable Structure Filter (SVSF) is a newly-developed predictor-corrector filter for state and parameter estimation [1]. The SVSF is based on the Sliding Mode Control concept. It defines a hyperplane in terms of the state trajectory and then applies a discontinuous corrective action that forces the estimate to go back and forth across that hyperplane. The SVSF is suitable for fault detection and identification applications because of its stability and robustness in modeling uncertainties. The SVSF has two indicators of performance; the a posteriori output error and the chattering. The latter-as a signalcontains the system's information which is proven and explored in this paper. The SVSF is applied for the identification of pneumatic systems in order to verify the proposed method. Furthermore, the proposed method is compared with neural network and the results reveal that SVSF is better in identifying nonlinear systems.

2024, Religions

Moral disengagement in sports refers to the psychological process through which individuals distance themselves from the ethical implications of their actions within the sporting context. This study aims to examine the role of religious commitment between personality traits and moral disengagement and investigate the role of prosocial and antisocial behaviours and moral identity. Student-athletes were recruited from individual and team sports, including football, basketball, handball, volleyball, wrestling, combat sports, swimming, track and field, cycling, badminton, and futsal. We hypothesised that extrovert personality traits directly predict moral identity, religious commitment, and prosocial/antisocial behaviours. Extraversion predicted moral disengagement with the mediation roles of internalisation, symbolisation, religious commitment, and pro- and antisocial behaviours. Our findings provide insights into the complex relationships between personality traits, internalisation, symbolisation, religious commitment, social behaviours, and their impact on moral disengagement. They highlight the importance of considering internalisation, symbolisation, and religious commitment mediating roles in understanding the relationships between extraversion, social behaviours, and moral disengagement. Understanding the complex relationship among these factors can inform the development of tailored interventions that address individual athletes’ needs and characteristics. Our study contributes to the growing body of literature on the psychological underpinnings of ethical behaviour in sports. By elucidating the roles of extraversion, moral identity, religious commitment, and social behaviours in moral disengagement, this research provides a more nuanced understanding of the factors influencing ethical decision-making and behaviour in student-athletes.

2024

Transient stability analysis is an important part of power planning and operation. For large power systems, such analysis is very demanding in computation time. On-line transient stability assessment will be necessary for secure and reliable operation of power systems in the near future because systems are operated close to their maximum limits. In this manuscript swallowtail catastrophe is used to determine the transient stability regions. The bifurcation set represents the transient stability region in terms of the power system transient parameters bounded by the transient stability limits. The transient stability regions determined are valid for any changes in loading conditions and fault location. The system modeling is generalized such that the analysis could handle either one or any number of critical machines. This generalized model is then tested on numerical examples of multi-machine power system (Cigre seven machine systems) shown very good agreement with the time solution in the practical range of first swing stability analysis. The method presented fulfills all requirements for on-line assessment of transient stability of power system

2024, J. Electrical Systems

This paper aims to present an improved On-Off control of wind energy conversion system based on a Squirrel cage induction generator (SCIG) using a Multi-Objective Particle swarm optimization algorithm (MOPSO). The chattering phenomenon, which can have a negative impact on the lifespan of wind turbines, has arisen in the On-Off Control System, an efficient and straightforward form of feedback control that benefits from its robustness in the presence of model disturbances and uncertainties. The Improved On-Off Control System uses the particle swarm optimization algorithm (PSO) to address this issue effectively. However, individual targeting to reduce the electromagnetic torque ripple by using PSO to solve this phenomenon significantly decreased the amount of maximum power produced. Also, in the case of individual targeting using the particle swarm optimization algorithm to maximize the power coefficient, this leads to a significant return to the phenomenon of chattering. To resolve this problem, an improved on-off control conversion system using a multiobjective particle swarm optimization algorithm (MOPSO) was proposed. So, this work aims to minimize the electromagnetic torque ripple and maximize the power coefficient using an improved On-Off controller tuned by MOPSO. To evaluate the suggested controller's performance, a wind profile tested using the von Karman spectrum in The International Electrotechnical Commission (IEC) standard. The proposed controller's findings are compared with those achieved by the improved On-Off control conversion system using PSO.

2024, DergiPark (Istanbul University)

The symbiotic organisms search (SOS), which has been recently introduced, is a robust powerful metaheuristic global optimizer. This nature-inspired algorithm imitates the symbiotic interaction strategies in an ecosystem exercised by organisms involved in interrelationships to survive and reproduce. One of the main beneficial features of the SOS in contrast to many other competent metaheuristic algorithms is that the algorithm does not need any specific algorithm parameters or tuning process. This paper applies the SOS algorithm to simultaneously design optimal controllers of a power system equipped with both a power system stabilizer (PSS) and a thyristor-controlled series compensator (TCSC). The algorithm of SOS is utilized to concurrently tune the variables of controllers for both the PSS and TCSC in the nonlinear optimization process. Simulation results reveal that the optimal SOS-based coordinated controllers can significantly stabilize the system and efficiently damp oscillations under severe disturbances. Results will also show that the optimal controllers obtained perform slightly better than the optimal controllers obtained using the two commonly used global optimization solvers, the genetic algorithm (GA) and particle swarm optimization.

2024

Además de la producción de madera y leña, para la valoración del Parque Chaqueño Seco, es importante determinar su capacidad para fijar carbono y ofrecer otros productos no maderables. Un primer paso para ello es la construcción de funciones que permiten estimar la biomasa aérea individual de sus árboles y arbustos. Aquí se presentan los resultados de las determinaciones de biomasa por pesada directa en 30 quebrachos blancos (Aspidosperma quebracho- blanco) de dos sitios del Parque Chaqueño Seco en la Provincia de Santiago del Estero, Argentina. Mediante técnicas de regresión (mínimos cuadrados lineales y no lineales y utilizando diversas variables indepen-dientes, entre ellas una "dummy" para representar la localidad) se seleccionó una ecuación que permite estimar el peso seco individual total en función del diámetro y el sitio. También se estudiaron relaciones estructurales para describir la forma de la especie en los dos sitios. Further the production of wood and firewo...

2024, Angkasa Putra & Wongyu Park

Seasonal variations of the zooplankton community were investigated around Seogwipo, Jeju Island from 2020 to 2021. Zooplankton were collected at 30 stations using NORPAC net from near the bottom to the surface, along with environmental factors. The mean sea surface temperature was highest in summer, lowest in winter, and intermediate in spring and autumn. The mean sea surface salinity was highest in autumn and winter, lowest in summer, and intermediate in spring. A total of 256 taxa (mostly at the species level) in 10 phyla were identified. The mean abundance was highest in spring and lowest in winter. The number of species was highest in winter and lowest in spring. The zooplankton community was dominated by small copepods such as Paracalanus, Oithona, and Oncaea species throughout all seasons. The density variations of dominant species between stations and seasons were correlated with environmental factors. Zooplankton communities varied with sampling seasons, influenced by seasonal oceanographic variations.

2024

This paper proposes a new power system stabilizer based on fuzzy systems. The new controller is applied to a wind turbine generating system comprising of a wind turbine driving a 3-phase synchronous generator connected to a large power system. The new controller significantly improves system performance. The enhancement in the dynamic response of the system is verified through simulation results of a system under different operating points and exposed to both small and large disturbances. Extension to the wind energy distributed generation based multi-machine case is also included to illustrate the effectiveness of the proposed stabilizer in damping power system swing mode oscillations that follow disturbances.

2024, Journal of the Franklin Institute

A novel approach for internet congestion control is presented here, using a static feedback law. A congestion controller for Network TCP/IP Routers is derived, to ensure stability for a large set of admissible initial conditions. From a formal point of view, we propose a static state-feedback for discrete-time delayed systems, with both saturating inputs and link capacity disturbances, that ensures simultaneously closed-loop stability and a prescribed level of performance. The effectiveness of the proposed approach is verified via simulation, comparing the results to PI and RED controllers.

2024, International Journal of Robust and Nonlinear Control

SummaryActive queue management (AQM) is a well‐known technique to improve routing performance under congested traffic conditions. It is often deployed to regulate queue sizes, thus aiming for constant transmission delay. This work addresses AQM using an approach based on control theory ideas. Compared with previous results in the literature, the novelty is the consideration of heterogeneous traffic, ie, multiclass traffic. Thus, each traffic class may have different discarding policies, queue sizes, and bandwidth share. This feature brings the proposal nearer to real network management demands than previous approaches in the literature. The proposed technique assumes that each class already has a simple controller, designed a priori, and focuses on designing a static state‐feedback controller for the multiclass system, where the design is based on using LMIs for the calculations. For this, optimization problems with LMI constraints are proposed to compute the state‐feedback gains th...

2024, AVCS

This paper develops a nonlinear observer and controller applied to a helicopter with 4 rotors. We show how to design a powerful nonlinear control law in term of robustness. In addition, this technique allows reducing the number of sensors to be embedded in the flying system by observing non available or non measurable entities. Performances and the stability of the suggested controller are analyzed through simulations carried out on the model (kinematics and dynamic equations).

2024, arXiv (Cornell University)

2024, IEEE Transactions on Automatic Control

Most of the proposed controllers for switched affine systems are able to drive the system trajectory to a sufficiently small neighborhood of a desired state. However, the trajectory behavior in this neighborhood is not generally considered despite the fact that the system performance may be judged by its steady operation as the case of power converters. This note investigates the local stabilization of a desired limit cycle in switched affine systems using hybrid Poincaré map approach. To this end, interesting algebraic properties of the Jacobian of the hybrid Poincaré map are firstly discussed and used for the controller design to achieve asymptotic stability conditions of the limit cycle. A DC-DC four-level power converter is considered as an illustrative example to highlight the developed results.

2024, Personal Relationships

Data from groups often have a multimember multigroup (MMMG) structure. Examples are two‐parent families with a female or male child (three members, two groups), two same‐gender and opposite‐gender peers of different status (two members, four groups), or gay, lesbian, and heterosexual couples (two members, three groups). To analyze such data, a framework called MMMG actor–partner interdependence model (MMMG APIM) is presented considering group composition. Three models are discussed in detail: the three‐member two‐group APIM, the two‐member four‐group APIM, and the two‐member three‐group APIM. Structural equation modeling and cross‐sectional and longitudinal data are used to illustrate the approach. To ease the interpretation of APIM findings, a proposal of a general classification scheme is made.

2024, Personal Relationships

Potential moderators of effects in the actor–partner interdependence model (APIM) include variables that vary within dyads, between dyads, or both between and within dyads (i.e., mixed moderators). Another factor in the moderation of the APIM is whether dyads are indistinguishable (e.g., same‐sex friendship pairs) or distinguishable (e.g., heterosexual couples). For each possibility, what are the potential moderator effects (up to 8), how they might be estimated and tested, and how they can be interpreted are discussed. Submodels are also presented, based on patterns of moderation of the actor and partner effects, which are statistically simpler, more conceptually meaningful, and more powerful in testing moderator effects. Example analyses illustrate the recommended steps involved in an APIM moderation analysis.

2024, International Journal of Automation and Computing

Several methods of chattering reduction have been reported. One approach [5] places a boundary layer around the switching surface such that the relay control is replaced by a saturation function. Another method [6] replaces a max-min-type control by a unit vector function. These approaches involve a trade-off between chattering and robustness. The aim of this paper is to develop a Fuzzy sliding mode controller (FSMC) with a nonlinear sliding surface for a coupled Tanks system. In the present work, a first-order nonlinear sliding surface is presented, on which the developed control law is based. Mathematical proof for the stability and convergence of the system is presented. In order to reduce the chattering in sliding mode controller (SMC), a fixed boundary layer around the switch surface is used. Within the boundary layer, since the fuzzy logic control is applied, the chattering phenomenon, which is inherent in a sliding mode control, is avoided by smoothing the switch signal. Outside the boundary, the sliding mode control is applied to driving the system states into the boundary layer. Experimental studies carried out on a coupled Tanks system indicate that the proposed approach is a good candidate for control applications.

2024, International Journal of Automation and Computing