Academic literature on the topic 'Variable stability simulator'
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Journal articles on the topic "Variable stability simulator"
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Chandrasekaran, Kamali, Vijeesh Theningaledathil, and Archana Hebbar. "GROUND BASED VARIABLE STABILITY FLIGHT SIMULATOR." Aviation 25, no. 1 (April 7, 2021): 22–34. http://dx.doi.org/10.3846/aviation.2021.13564.
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This paper discusses the development of a ground based variable stability flight simulator. The simulator is designed to meet the pilot training requirements on flying qualities. Such a requirement arose from a premier Flight-Testing School of the Indian Air Force. The simulator also provides a platform for researchers and aerospace students to understand aircraft dynamics, conduct studies on aircraft configuration design, flight mechanics, guidance & control and to evaluate autonomous navigation algorithms. The aircraft model is built using open source data. The simulator is strengthened with optimization techniques to configure variable aircraft stability and control characteristics to fly and evaluate the various aspects of flying qualities. The methodology is evaluated through a series of engineer and pilot-in-the-loop simulations for varying aircraft stability conditions. The tasks chosen are the proven CAT A HUD tracking tasks. The simulator is also reconfigurable to host an augmented fighter aircraft that can be evaluated by the test pilot team for the functional integrity as a fly-through model.
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Wang, De Shun, Gui Gang Han, Xin Long Zhang, and Bo Yang. "The Development of Multi-Functional Multi-Level Variable Voltage Variable Frequency Power Supply." Advanced Materials Research 1070-1072 (December 2014): 1263–67. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.1263.
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In order to adapt the grid test study of distributed generation system, a multifunctional variable voltage and variable frequency power supply is proposed. The power supply could work in four quadrant operations, so that energy generated by distributed systems could flow into grid. The fundamental voltage and harmonic voltage are controlled respectively: multiple feedback loop control scheme is applied in fundamental mode and effective value feedback control scheme is applied in harmonic mode. The DSP and FPGA platform are used for implementing the system control and the experimental results show that the performance of the simulator is good and has high stability.
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Sheta, A. A., E. H. Ali, R. M. Fikry, T. A. Mahmoud, S. M. El-Araby, and M. I. Mahmoud. "Intelligent Control for Pressurizer System in Nuclear Power Plants." Journal of Physics: Conference Series 2128, no. 1 (December 1, 2021): 012022. http://dx.doi.org/10.1088/1742-6596/2128/1/012022.
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Abstract Fine control of output power for nuclear power plants is the essential goal for safe operation. In this work, a Fuzzy analytical proportional-integral-derivative (FPID) controller with different configurations is designed to adjust and control the pressure of the PZR system. The stability analysis of the FPID controller with variable gains is established, and conditions for bounded-input bounded-output stability conditions (BIBO) are derived using the small gain theory. Two scenarios are applied for evaluating the dynamic response of applied controllers. In addition, performance indices are compared between the PZR model and data measured from the PCtran VVER-1200 simulator. Finally, a simulation platform is developed for MATLAB / Simulink to implement the three-region nonlinear non-equilibrium PZR model and the designed pressure controllers. The analysis and evaluation results showed good durability of the designed controllers and satisfactory performance of the control. These results further show that the nonlinear PZR model is accurate, feasible, and valuable for dynamic simulation and control unit design.
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Pan, Chun Ping, and Hsin Guan. "The Control of Hexapod Parallel Mechanism." Applied Mechanics and Materials 195-196 (August 2012): 1030–34. http://dx.doi.org/10.4028/www.scientific.net/amm.195-196.1030.
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In order to enhance the innervations fidelity of simulators, an adaptive nonlinear controller is developed, which guarantees parallel mechanisms closed loop system global asymptotical stability and the convergence of posture tracking error in Cartesian space. The problem of rapid tracking under the condition of the wide range, nonlinear and variable load is solved. After the adaptive nonlinear controller is actually applied to the hexapod parallel mechanisms of simulator, the dynamic-static capabilities of motion system is tested by amplitude-frequency response and posture precision. The experimental results show that the static precision improves ten times and system output amplitude increase and the phase lag reduce with respect to the same input signal in Cartesian space in comparison with the traditional proportional and derivative controlling method in joint space. Therefore the adaptive nonlinear controller can effectively improve the dynamic-static response performance of the hexapod parallel mechanisms of simulators in Cartesian space.
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Fekih, Afef, Saleh Mobayen, and Chih-Chiang Chen. "Adaptive Robust Fault-Tolerant Control Design for Wind Turbines Subject to Pitch Actuator Faults." Energies 14, no. 6 (March 23, 2021): 1791. http://dx.doi.org/10.3390/en14061791.
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This paper proposes an adaptive fault tolerant control (FTC) design for a variable speed wind turbine (WT) operating in the high wind speeds region. It aims at mitigating pitch actuator faults and regulating the generator power to its rated value, thereby reducing the mechanical stress in the high wind speeds region. The proposed FTC design implements a sliding mode control (SMC) approach with an adaptation law that estimates the upper bounds of the uncertainties. System stability and uniform boundedness of the outputs was proven using the Lyapunov stability theory. The proposed approach was validated on a 5 MW three-blade wind turbine modeled using the National Renewable Energy Laboratory’s (NREL) Fatigue, Aerodynamics, Structures and Turbulence (FAST) wind turbine simulator. The controller’s performance was assessed in the presence of several pitch actuator faults and turbulent wind conditions. Its performance was also compared to that of a standard SMC approach. Mitigation of blade pitch actuator faults, generation of uniform power, smoother pitching actions and reduced chattering compared to standard SMC approach are among the main features of the proposed design.
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Chadburn, Sarah E., Eleanor J. Burke, Angela V. Gallego-Sala, Noah D. Smith, M. Syndonia Bret-Harte, Dan J. Charman, Julia Drewer, et al. "A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme (JULES vn5.8_accumulate_soil) for northern and temperate peatlands." Geoscientific Model Development 15, no. 4 (February 25, 2022): 1633–57. http://dx.doi.org/10.5194/gmd-15-1633-2022.
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Abstract. Peatlands have often been neglected in Earth system models (ESMs). Where they are included, they are usually represented via a separate, prescribed grid cell fraction that is given the physical characteristics of a peat (highly organic) soil. However, in reality soils vary on a spectrum between purely mineral soil (no organic material) and purely organic soil, typically with an organic layer of variable thickness overlying mineral soil below. They are also dynamic, with organic layer thickness and its properties changing over time. Neither the spectrum of soil types nor their dynamic nature can be captured by current ESMs. Here we present a new version of an ESM land surface scheme (Joint UK Land Environment Simulator, JULES) where soil organic matter accumulation – and thus peatland formation, degradation and stability – is integrated in the vertically resolved soil carbon scheme. We also introduce the capacity to track soil carbon age as a function of depth in JULES and compare this to measured peat age–depth profiles. The new scheme is tested and evaluated at northern and temperate sites. This scheme simulates dynamic feedbacks between the soil organic material and its thermal and hydraulic characteristics. We show that draining the peatlands can lead to significant carbon loss, soil compaction and changes in peat properties. However, negative feedbacks can lead to the potential for peatlands to rewet themselves following drainage. These ecohydrological feedbacks can also lead to peatlands maintaining themselves in climates where peat formation would not otherwise initiate in the model, i.e. displaying some degree of resilience. The new model produces similar results to the original model for mineral soils and realistic profiles of soil organic carbon for peatlands. We evaluate the model against typical peat profiles based on 216 northern and temperate sites from a global dataset of peat cores. The root-mean-squared error (RMSE) in the soil carbon profile is reduced by 35 %–80 % in the best-performing JULES-Peat simulations compared with the standard JULES configuration. The RMSE in these JULES-Peat simulations is 7.7–16.7 kg C m−3 depending on climate zone, which is considerably smaller than the soil carbon itself (around 30–60 kg C m−3). The RMSE at mineral soil sites is also reduced in JULES-Peat compared with the original JULES configuration (reduced by ∼ 30 %–50 %). Thus, JULES-Peat can be used as a complete scheme that simulates both organic and mineral soils. It does not require any additional input data and introduces minimal additional variables to the model. This provides a new approach for improving the simulation of organic and peatland soils and associated carbon-cycle feedbacks in ESMs.
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Hasan, Ibtihal A., and Osama A. Awad. "AN OPTIMIZED FUZZY LOGIC CONTROLLER FOR WIRELESS NETWORK CONTROL SYSTEM USING PSO." Iraqi Journal of Information and Communication Technology 5, no. 1 (April 29, 2022): 1–15. http://dx.doi.org/10.31987/ijict.5.1.180.
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Wireless Networked Control System (WNCS), has the advantage of control signal efficiency, reduced costs, robust, and more flexible over the wired Networked Control System (NCS). However, one of the most important challenges of WNCS is the variable and random time delay associated with the network that effect on the whole system stability. In this paper, a fuzzy PID controller is proposed to overcome this issue by controlling the DC motor over the Wi-Fi network. PSO algorithm is used to tune the controller, and TrueTime simulator is used to simulate the Wi-Fi network. Experimental results showed that the tuned Fuzzy PID controller is efficiently reduced the effect of the time delay. The results show that the network can handle up to 7500 and 6000 nodes when the bandwidth is 0.4 and 0.9 respectively without a sensible degradation in the system performance of the tackled system.
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Alipour, M. Reza, F. Fani Saberi, and M. Kabganian. "Modelling, design and experimental implementation of non-linear attitude tracking with disturbance compensation using adaptive-sliding control based on quaternion algebra." Aeronautical Journal 122, no. 1247 (November 20, 2017): 148–71. http://dx.doi.org/10.1017/aer.2017.122.
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ABSTRACTIn this paper, a non-linear tracking control algorithm is extended. The control objective of this research is to track a desired time-varying attitude of a satellite in the presence of inertia uncertainties and external disturbances, in order to be more suitable for implementation in a real-world application. In this investigation, the actuators are reaction wheels and the actuator dynamics are modelled in addition to the spacecraft dynamics. Thus, the control signal is DC motor voltage which is the most fundamental control variable and can be generated easily by a motor driver in practical cases. To achieve robust tracking of the desired time-varying attitude, a sliding mode controller is designed, and adaptive techniques are developed based on sliding mode control to overcome the inertia uncertainties and to estimate and compensate external disturbances. The kinematic equations of the satellite are expressed using quaternion parameters, and a novel control law will be derived by using a new facilitating approach in controller design, which is based on quaternion algebra, because of quaternion advantages, such as singularity rejection. Using this approach it will be more comfortable to deal with tedious mathematical operations, and on contrary with most of the previous studies, the terms corresponding to derivatives of the desired attitude are not neglected, and tracking capability is retained. The global stability of both methods (Sliding Mode Control (SMC) and adaptive sliding) is investigated using Lyapunov’s stability theorem. In order to validate the control methods, first, Simulink-ADAMS co-simulation of a 3-DOF attitude control is used to verify the algorithm performance and integrity, and finally, the control strategy is implemented on the Amirkabir University of Technology (AUT) 3-DOF attitude simulator for different types of non-linear attitudes. Both co-simulation and implementation results clearly illustrate the designed attitude control algorithm’s excellent performance in the various manoeuvres.
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Ma, Jie, Shule Li, and Xinyu Wang. "Condition Monitoring of Rolling Bearing Based on Multi-Order FRFT and SSA-DBN." Symmetry 14, no. 2 (February 4, 2022): 320. http://dx.doi.org/10.3390/sym14020320.
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Owing to the symmetry of the rolling bearing structure and the rotating operation mode, the rolling bearing works in a complex environment. It is very easy to be submerged by noise and misdiagnosis. For the non-stationary signal in variable speed state, this paper presents a condition monitoring method based on deep belief network (DBN) optimized by multi-order fractional Fourier transform (FRFT) and sparrow search algorithm (SSA). Firstly, the fractional Fourier transform based on curve feature segmentation is used to filter the fault vibration signal and extract the fault feature frequency. Then, the fault features are input into the SSA-DBN model for training, and the bearing fault features are classified, identified, and diagnosed. Finally, the rotating machinery fault simulator in the laboratory of Ottawa University is taken as the practical application object to verify the effectiveness of the method. The experimental results show that the proposed method has higher recognition accuracy and stronger stability.
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Mohapatra, Bhabasis, Binod Kumar Sahu, Swagat Pati, Mohit Bajaj, Vojtech Blazek, Lukas Prokop, Stanislav Misak, and Mosleh Alharthi. "Real-Time Validation of a Novel IAOA Technique-Based Offset Hysteresis Band Current Controller for Grid-Tied Photovoltaic System." Energies 15, no. 23 (November 22, 2022): 8790. http://dx.doi.org/10.3390/en15238790.
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Renewable energy sources have power quality and stability issues despite having vast benefits when integrated with the utility grid. High currents and voltages are introduced during the disconnection or injection from or into the power system. Due to excessive inverter switching frequencies, distorted voltage waveforms and high distortions in the output current may be observed. Hence, advancing intelligent and robust optimization techniques along with advanced controllers is the need of the hour. Therefore, this article presents an improved arithmetic optimization algorithm and an offset hysteresis band current controller. Conventional hysteresis band current controllers (CHCCs) offer substantial advantages such as fast dynamic response, over-current, and robustness in response to impedance variations, but they suffer from variable switching frequency. The offset hysteresis band current controller utilizes the zero-crossing time of the current error for calculating the lower/upper hysteresis bands after the measurement of half of the error current period. The duty cycle and hysteresis bands are considered as design variables and are optimally designed by minimizing the current error and the switching frequency. It is observed that the proposed controller yields a minimum average switching frequency of 2.33 kHz and minimum average switching losses of 9.07 W in comparison to other suggested controllers. Results are validated using MATLAB/Simulink environment followed by real-time simulator OPAL-RT 4510.
Dissertations / Theses on the topic "Variable stability simulator"
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Scamps, Alexander. "Development of a Variable Stability Flight Simulation Facility Re-engineering of Flight Control Loading and Motion Systems." Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/567.
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A Variable Stability Flight Simulator is being developed in the School of Aerospace, Mechanical and Mechatronic Engineering at the University of Sydney, Australia. The device is being developed both as a teaching tool for use in flight mechanics courses in the department and as a research tool. It is reasonable to state that learning is enhanced through the experience of concepts outside of the classroom environment. It is intended that the device will be integrated into the department�s teaching program in aircraft flight mechanics. Initial studies centred around a PC based flight simulation developed at the Cranfield College of Aeronautics in the United Kingdom. This system utilises a distributed architecture with several computers connected via Ethernet. It also employs a Primary Image three channel visual system. The system has been further enhanced by the addition of a Link flight simulator provided by the Royal Australian Air Force (RAAF). The RAAF had been using the simulator as a training tool for some years until it had become surplus to requirements. Most of the work in the project has centred around re-engineering this simulator into a viable research/education tool. The Cranfield system has been incorporated into the Link simulator�s hardware to provide a fixed base simulation. The majority of the work described in this thesis revolved around the re-engineering of the flight control loading and motion systems. Previously these items were controlled by analogue circuitry with minimal digital interfaces to the main simulation software. The systems have been re-designed to replace much of the single model analogue circuitry with re-configurable digital control software. Doing so allows changes to be made to the systems in real time through a software interface. The software resides on a common computer that extensively interfaces with the rest of the simulation. To support the hardware involved and to provide for system operation and safety, an extensive Supervisory system has also been implemented. This system along with the motion and control loading software has been implemented in the Matlab / Real-Time Workshop environment. This gives the capability of making real-time changes to any part of the overall simulation. A variable stability module (vsm) is under development. The addition of this module will allow changes to be made to the simulation itself in real-time. The simulator is now functional with the motion and control loading systems operating as designed. Tuning of both systems has been done subjectively by the author. An initial objective analysis of the motion system has been undertaken in an attempt to verify the fidelity of the motion cues generated. A significant outcome of this project has been to create a safe, easily maintainable, re-configurable flight simulator from a large, complex, legacy system. The facility now forms a significant research and teaching tool in areas such as flight mechanics, propulsion, aircraft handling qualities and human factors.
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Scamps, Alexander. "Development of a Variable Stability Flight Simulation Facility Re-engineering of Flight Control Loading and Motion Systems." University of Sydney. Aerospace, Mechanical, 2003. http://hdl.handle.net/2123/567.
Full textAbstract:
A Variable Stability Flight Simulator is being developed in the School of Aerospace, Mechanical and Mechatronic Engineering at the University of Sydney, Australia. The device is being developed both as a teaching tool for use in flight mechanics courses in the department and as a research tool. It is reasonable to state that learning is enhanced through the experience of concepts outside of the classroom environment. It is intended that the device will be integrated into the department�s teaching program in aircraft flight mechanics. Initial studies centred around a PC based flight simulation developed at the Cranfield College of Aeronautics in the United Kingdom. This system utilises a distributed architecture with several computers connected via Ethernet. It also employs a Primary Image three channel visual system. The system has been further enhanced by the addition of a Link flight simulator provided by the Royal Australian Air Force (RAAF). The RAAF had been using the simulator as a training tool for some years until it had become surplus to requirements. Most of the work in the project has centred around re-engineering this simulator into a viable research/education tool. The Cranfield system has been incorporated into the Link simulator�s hardware to provide a fixed base simulation. The majority of the work described in this thesis revolved around the re-engineering of the flight control loading and motion systems. Previously these items were controlled by analogue circuitry with minimal digital interfaces to the main simulation software. The systems have been re-designed to replace much of the single model analogue circuitry with re-configurable digital control software. Doing so allows changes to be made to the systems in real time through a software interface. The software resides on a common computer that extensively interfaces with the rest of the simulation. To support the hardware involved and to provide for system operation and safety, an extensive Supervisory system has also been implemented. This system along with the motion and control loading software has been implemented in the Matlab / Real-Time Workshop environment. This gives the capability of making real-time changes to any part of the overall simulation. A variable stability module (vsm) is under development. The addition of this module will allow changes to be made to the simulation itself in real-time. The simulator is now functional with the motion and control loading systems operating as designed. Tuning of both systems has been done subjectively by the author. An initial objective analysis of the motion system has been undertaken in an attempt to verify the fidelity of the motion cues generated. A significant outcome of this project has been to create a safe, easily maintainable, re-configurable flight simulator from a large, complex, legacy system. The facility now forms a significant research and teaching tool in areas such as flight mechanics, propulsion, aircraft handling qualities and human factors.
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Pettersson, Henrik Bengt. "Variable Stability Transfer Function Simulation." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33503.
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Simulation, whether in-flight or ground-based, is an invaluable tool for testing and
evaluating aircraft. Classically, a simulation model is specific to a single particular airframe,
only able to model those flying characteristics. Vast information can be gained from a
simulation that is able to model a wide range of aircraft, through a comparison of the
performance of these aircraft.
Such a variable stability simulation model was created based on 46 stability parame-ters,
including natural frequencies, damping ratios, time constants, and gains. The simula-tion
was obtained using transfer functions representing the aircraft state responses to control
inputs. These transfer functions were converted into state space systems used to create the
linear equations for the model.
The model was first developed as a desktop simulation and then converted for use
with the Virginia Techâ s 2F122A flight simulator. This conversion required a simple dynamic
inversion of the body axis force and moment terms. To reduce the error in these terms, a
model following scheme was incorporated.
A series of canned inputs and real-time pilot-in-the-loop tests were flown to evaluate
the variable stability model. Results in this paper have demonstrated the successful creation
of a variable stability simulation model.Master of Science
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Germann, Kenneth Paul. "T-6A TEXAN II IN-FLIGHT SIMULATION AND VARIABLE STABILITY SYSTEM DESIGN." MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-12162009-091123/.
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In-flight variable stability aircraft and in-flight simulation are described. The uses of these vehicles and the associated requirements are described. Several forms of control architecture are identified for use in a T-6A in-flight simulator. A non-linear model of the T-6A Texan II is developed for use in MATLAB/SIMULINK®. This model is used to design a feedforward response-feedback controller, based on simplified dynamic inversion. This controller is shown to exercise precise control over the T-6A host aircraft dynamics. This architecture is then used to demonstrate simulation of the A-4 and the F-15 by the T-6A. In addition to proving simplified dynamic inversion for in-flight simulation, it is shown that the same configuration is useful in handling qualities training of military test pilots.
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Walther, Marc. "Variable-Density Flow Processes in Porous Media On Small, Medium and Regional Scales." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-153365.
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Nowadays society strongly depends on its available resources and the long term stability of the surrounding ecosystem. Numerical modelling has become a general standard for evaluating past, current or future system states for a large number of applications supporting decision makers in proper management. In order to ensure the correct representation of the investigated processes and results of a simulation, verification examples (benchmarks), that are based on observation data or analytical solutions, are utilized to evaluate the numerical modelling tool.
In many parts of the world, groundwater is an important resource for freshwater. While it is not only limited in quantity, subsurface water bodies are often in danger of contamination from various natural or anthropogenic sources. Especially in arid regions, marine saltwater intrusion poses a major threat to groundwater aquifers which mostly are the exclusive source of freshwater in these dry climates. In contrast to common numerical groundwater modelling, density-driven flow and mass transport have to be considered as vital processes in the system and in scenario simulations for fresh-saltwater interactions.
In the beginning of this thesis, the capabilities of the modelling tool OpenGeoSys are verified with selected benchmarks to represent the relevant non-linear process coupling. Afterwards, variable-density application and process studies on different scales are presented. Application studies comprehend regional groundwater modelling of a coastal aquifer system extensively used for agricultural irrigation, as well as hydro-geological model development and parametrization. In two process studies, firstly, a novel method to model gelation of a solute in porous media is developed and verified on small scale laboratory observation data, and secondly, investigations of thermohaline double-diffusive Rayleigh regimes on medium scale are carried out.
With the growing world population and, thus, increasing pressure on non-renewable resources, intelligent management strategies intensify demand for potent simulation tools and development of novel methods. In that way, this thesis highlights not only OpenGeoSys’ potential of density-dependent process modelling, but the comprehensive importance of variable-density flow and transport processes connecting, both, avant-garde scientific research, and real-world application challenges.
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Lardjane, Nicolas. "Étude théorique et numérique des écoulements cisaillés libres à masse volumique fortement variable." Phd thesis, Université d'Orléans, 2002. http://tel.archives-ouvertes.fr/tel-00006483.
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L'objet de ce travail concerne l'application de la méthode de simulation des grandes échelles au mélange de deux fluides à propriétés thermodynamiques différentes.L'origine des erreurs numériques liées à la discrétisation des équations de Navier-Stokes ainsi que leur interaction avec un modèle sous-maille sont étudiées pour une turbulence homogène et isotrope en auto-amortissement. Un code de calcul à haut pouvoir de solution est alors développé pour la simulation de couches de mélange bi-espèces. La réduction de l'amplitude des ondes acoustiques initiales est assurée par l'utilisation d'un champ en similitude temporelle.
L'importance relative des termes sous-maille issus des équations filtrées est mesurée à partir du filtrage explicite des champs de simulations numériques directes des couches de mélange temporelles $N_2/O_2$ et $H_2/O_2$.
L'utilisation d'une fermeture implicite autour d'un schéma numérique dissipatif est ensuite évoquée.
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Chalayer, Rénald. "Méthodes de projection pour des écoulements à seuil, incompressibles et à densité variable." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC089.
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Cette thèse traite de l'utilisation de méthodes de projection pour la simulation de fluides à seuil, incompressibles et à densité variable. Elle se découpe en trois parties. La première partie est consacrée à la présentation du modèle mathématique, à la construction du schéma de semi-discrétisation en temps du modèle, ainsi qu'à l'analyse du schéma ainsi obtenu. Pour construire le schéma, nous avons d'une part adapté un schéma de type pas de temps fractionné existant pour les écoulements newtoniens au cas des écoulements à seuil et d'autre part, nous avons utilisé une formulation en terme de projection pour le tenseur des contraintes qui nous permet de résoudre le couplage entre la vitesse et la contrainte dans l'équation de conservation de la quantité de mouvement avec une méthode de type Uzawa. Nous démontrons mathématiquement la stabilité et la convergence du schéma, et on obtient une estimation d’erreur en temps d’ordre un pour la vitesse, la densité, la viscosité ainsi que le seuil de plasticité. La deuxième partie est consacrée à la discrétisation en espace et à l’implémentation du schéma. La discrétisation en espace est effectuée à l’aide d’une méthode de type volumes finis sur grilles décalées. L’implémentation de l’algorithme a été réalisée à partir d’un code Fortran 90 parallélisé et utilisant les bibliothèques PetsC et MPI. La dernière partie de cette thèse est consacrée à la réalisation de simulations numériques à l'aide du code de calcul que l’on a ainsi construit. Dans la configuration de l’instabilité de Rayleigh-Taylor, on réalise des simulations en faisant varier le seuil de plasticité, en décrivant l’évolution de la position des deux phases et la localisation des zones rigides. Dans la configuration de rupture de barrage, nous mettons en oeuvre les conditions aux limites de type glissement à seuil, plus réalistes physiquement que les conditions de Dirichlet, et nous comparons les résultats obtenus à l’aide de notre nouveau schéma à la littérature existanteThis thesis deal with the use of projection methods for incompressible viscoplastic flows with a variable density. This manuscript is organized following three main lines. The first part is devoted to the mathematical model, the time-discretization of the model and the analysis of the numerical scheme. To construct the numerical scheme, on one side we adapt a time-stepping method already used for newtonian flows to viscoplastic flows and on the other side, we use a projection formulation of the stress tensor to solve the coupling between the velocity and the plastic part of the stress tensor in the momentum equation with an Uzawa-like method. Stability and error analysis of the numerical scheme are provided and a first-order estimate of the time error is derived for the velocity field, the density, the viscosity and the yield stress. The second part is devoted to the space discretization and the implementation of the scheme. A second-order cell-centred finite volume scheme on staggered grids is applied for the spatial discretization. The implementation of the numerical scheme has been performed using a Fortran 90 code and using the PetsC and MPI library The last part of the manuscript is devoted to numerical simulations. In the Rayleigh-Taylor instability configuration, we perform simulations by varying the yield stress, and describing the evolution of the interface and the localization of the rigid zones. In the dambreak configuration, we use Stick-Slip boundary conditions and we compare our results to the existing literature
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Nouri, Ahmed Saïd. "Généralisation du régime glissant et de la commande à structure variable : applications aux actionneurs classiques et à muscles artificiels." Toulouse, INSA, 1994. http://www.theses.fr/1994ISAT0003.
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De nombreux systemes dynamiques (exemple: robot) presentent, en plus des perturbations exterieures, des non linearites et des perturbations parametriques, le recours a des commandes robustes est donc souhaitable. Une solution reside dans la commande a structure variable. En effet, lorsque le regime glissant est atteint, la dynamique du systeme boucle est plongee dans celle du systeme reduit et libre, d'ou l'independance vis a vis des perturbations exterieures et parametriques. L'auteur propose une generalisation de la surface de glissement permettant pour le systeme a commander d'une part, la validation du modele presume issu de l'identification et d'autre part, la determination du degre relatif: les deux methodologies sont presentees et testees en simulation et experimentation. L'auteur etudie ensuite trois types de commande a structure variable appliquees a un systeme monovariable (axe de robot mu par un moteur a courant continu ou par un moteur a muscles artificiels). Une structure variable generalisee dite dynamique: la discontinuite appliquee sur la derivee la plus elevee permet une diminution du phenomene de broutement; les premiers resultats d'experimentation de cette loi de commande sont obtenus. Une structure variable classique (ou statique): l'auteur propose une nouvelle methodologie de calcul de la commande equivalente en fonction de l'entree du modele de reference et du gain statique du systeme etudie. Une structure variable adaptative avec modele de reference et utilisant seulement la description externe du systeme: l'auteur degage l'aspect multisurface de glissement et etablit une methode de calcul des parametres de reglage basee sur la notion du regime glissant. Pour chaque loi de commande, un tableau de synthese du correcteur est propose et des resultats de simulation et d'experimentation sont donnes. La robustesse de ces trois algorithmes est comparee en simulation (par rapport a une dynamique non modelisee) et en experimentation (variation de la charge manipulee). Le temps de reponse de ces trois algorithmes est pratiquement le meme
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Khan, Abdul Kareem. "Electrostaticanalisys the Ras active site." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7161.
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La preorganització electrostàtica del centre actiu s'ha postulat com el mecanisme genèric de l'acció dels enzims. Així, alguns residus "estratègics" es disposarien per catalitzar reaccions interaccionant en una forma més forta amb l'estat de transició, baixant d'aquesta manera el valor de l'energia dactivació g cat. S'ha proposat que aquesta preorientació electrostática s'hauria de poder mostrar analitzant l'estabilitat electrostàtica de residus individuals en el centre actiu.Ras es una proteïna essencial de senyalització i actúa com un interruptor cel.lular. Les característiques estructurals de Ras en el seu estat actiu (ON) són diferents de les que té a l'estat inactiu (OFF). En aquesta tesi es duu a terme una anàlisi exhaustiva de l'estabilitat dels residus del centre actiu deRas en l'estat actiu i inactiu.
The electrostatic preorganization of the active site has been put forward as the general framework of action of enzymes. Thus, enzymes would position "strategic" residues in such a way to be prepared to catalyze reactions by
interacting in a stronger way with the transition state, in this way decreasing the activation energy g cat for the catalytic process. It has been proposed that
such electrostatic preorientation should be shown by analyzing the electrostatic stability of individual residues in the active site.
Ras protein is an essential signaling molecule and functions as a switch in the
cell. The structural features of the Ras protein in its active state (ON state) are different than those in its inactive state (OFF state). In this thesis, an exhaustive analysis of the stability of residues in the active and inactive Ras active site is performed.
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Hung, Bing-Shian, and 洪秉賢. "Study of Motion Stability Simulation and Control of Variable Centroid Vehicle." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/45479941526753864648.
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碩士大葉大學
機械與自動化工程學系
98
The objective for this study is to establish the simulation and evaluation mehtodlogy for Variable Centroid Vehicle (VCV) motion stability control system. VCV drive and handling and ride performance parameters such as longitudinal and lateral acceleration, yaw and roll rate and side slip angle can be calculated and compared under different dynamic simulation conditions. The roll rate was assessed with other appropriate control strategies and controllers’ settings to assure the VCV can be operating for safe and stable control condition. In this study, object-oriented simulation program Simulink was used to construct the modules including the VCV longitudinal and lateral motion. VCV driving and braking torque management, lateral force and normal force control model, wheel models, were tested and validated by commercial vehicle simulation program CarSim under the same driving conditions. VCV center of gravity hight and the length of wheelbase become time-varing input parameters for stability control system. VCV dynamic performance correlations between these two input parameters and the outputs from vehicle stability control system can be observed and vehicle stablilty can be improved by integrated consideration of traction and braking control to reduce the oversteer and rollover dangerous conditions. The wheel traction slip and brake skid effects under different centroid hight and wheel base were simulated and the lateral acceleration, yaw rate performance were also be evaluated at the same conditions. By Hardware-in-Loop,(HIL) technology, the software simulation controller parameters can be converted to real vehicle control signals through CAN bus so that the optimized location of VCV centroid be adjusted to the more safe and stable operating position.
Books on the topic "Variable stability simulator"
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Sobczyk, Eugeniusz Jacek. Uciążliwość eksploatacji złóż węgla kamiennego wynikająca z warunków geologicznych i górniczych. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN, 2022. http://dx.doi.org/10.33223/onermin/0222.
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Hard coal mining is characterised by features that pose numerous challenges to its current operations and cause strategic and operational problems in planning its development. The most important of these include the high capital intensity of mining investment projects and the dynamically changing environment in which the sector operates, while the long-term role of the sector is dependent on factors originating at both national and international level. At the same time, the conditions for coal mining are deteriorating, the resources more readily available in active mines are being exhausted, mining depths are increasing, temperature levels in pits are rising, transport routes for staff and materials are getting longer, effective working time is decreasing, natural hazards are increasing, and seams with an increasing content of waste rock are being mined. The mining industry is currently in a very difficult situation, both in technical (mining) and economic terms. It cannot be ignored, however, that the difficult financial situation of Polish mining companies is largely exacerbated by their high operating costs. The cost of obtaining coal and its price are two key elements that determine the level of efficiency of Polish mines. This situation could be improved by streamlining the planning processes. This would involve striving for production planning that is as predictable as possible and, on the other hand, economically efficient. In this respect, it is helpful to plan the production from operating longwalls with full awareness of the complexity of geological and mining conditions and the resulting economic consequences. The constraints on increasing the efficiency of the mining process are due to the technical potential of the mining process, organisational factors and, above all, geological and mining conditions. The main objective of the monograph is to identify relations between geological and mining parameters and the level of longwall mining costs, and their daily output. In view of the above, it was assumed that it was possible to present the relationship between the costs of longwall mining and the daily coal output from a longwall as a function of onerous geological and mining factors. The monograph presents two models of onerous geological and mining conditions, including natural hazards, deposit (seam) parameters, mining (technical) parameters and environmental factors. The models were used to calculate two onerousness indicators, Wue and WUt, which synthetically define the level of impact of onerous geological and mining conditions on the mining process in relation to: —— operating costs at longwall faces – indicator WUe, —— daily longwall mining output – indicator WUt. In the next research step, the analysis of direct relationships of selected geological and mining factors with longwall costs and the mining output level was conducted. For this purpose, two statistical models were built for the following dependent variables: unit operating cost (Model 1) and daily longwall mining output (Model 2). The models served two additional sub-objectives: interpretation of the influence of independent variables on dependent variables and point forecasting. The models were also used for forecasting purposes. Statistical models were built on the basis of historical production results of selected seven Polish mines. On the basis of variability of geological and mining conditions at 120 longwalls, the influence of individual parameters on longwall mining between 2010 and 2019 was determined. The identified relationships made it possible to formulate numerical forecast of unit production cost and daily longwall mining output in relation to the level of expected onerousness. The projection period was assumed to be 2020–2030. On this basis, an opinion was formulated on the forecast of the expected unit production costs and the output of the 259 longwalls planned to be mined at these mines. A procedure scheme was developed using the following methods: 1) Analytic Hierarchy Process (AHP) – mathematical multi-criteria decision-making method, 2) comparative multivariate analysis, 3) regression analysis, 4) Monte Carlo simulation. The utilitarian purpose of the monograph is to provide the research community with the concept of building models that can be used to solve real decision-making problems during longwall planning in hard coal mines. The layout of the monograph, consisting of an introduction, eight main sections and a conclusion, follows the objectives set out above. Section One presents the methodology used to assess the impact of onerous geological and mining conditions on the mining process. Multi-Criteria Decision Analysis (MCDA) is reviewed and basic definitions used in the following part of the paper are introduced. The section includes a description of AHP which was used in the presented analysis. Individual factors resulting from natural hazards, from the geological structure of the deposit (seam), from limitations caused by technical requirements, from the impact of mining on the environment, which affect the mining process, are described exhaustively in Section Two. Sections Three and Four present the construction of two hierarchical models of geological and mining conditions onerousness: the first in the context of extraction costs and the second in relation to daily longwall mining. The procedure for valuing the importance of their components by a group of experts (pairwise comparison of criteria and sub-criteria on the basis of Saaty’s 9-point comparison scale) is presented. The AHP method is very sensitive to even small changes in the value of the comparison matrix. In order to determine the stability of the valuation of both onerousness models, a sensitivity analysis was carried out, which is described in detail in Section Five. Section Six is devoted to the issue of constructing aggregate indices, WUe and WUt, which synthetically measure the impact of onerous geological and mining conditions on the mining process in individual longwalls and allow for a linear ordering of longwalls according to increasing levels of onerousness. Section Seven opens the research part of the work, which analyses the results of the developed models and indicators in individual mines. A detailed analysis is presented of the assessment of the impact of onerous mining conditions on mining costs in selected seams of the analysed mines, and in the case of the impact of onerous mining on daily longwall mining output, the variability of this process in individual fields (lots) of the mines is characterised. Section Eight presents the regression equations for the dependence of the costs and level of extraction on the aggregated onerousness indicators, WUe and WUt. The regression models f(KJC_N) and f(W) developed in this way are used to forecast the unit mining costs and daily output of the designed longwalls in the context of diversified geological and mining conditions. The use of regression models is of great practical importance. It makes it possible to approximate unit costs and daily output for newly designed longwall workings. The use of this knowledge may significantly improve the quality of planning processes and the effectiveness of the mining process.
Book chapters on the topic "Variable stability simulator"
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Hamel, Peter G. "Variable Stability Aircraft and In-Flight Simulators." In In-Flight Simulators and Fly-by-Wire/Light Demonstrators, 33–71. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-53997-3_5.
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Wei, Lisheng, Ming Jiang, and Minrui Fei. "Stability Analysis and Numerical Simulation for a Class of Multi-variable Networked Control Systems." In Lecture Notes in Computer Science, 442–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11842-5_61.
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Derouich, Mohamed. "Dengue Fever." In Handbook of Research on Systems Biology Applications in Medicine, 809–24. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-076-9.ch044.
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Dengue fever is a re-emergent disease affecting more than 100 countries. Its incidence rate has increased fourfold since 1970 with nearly half the world’s population now at risk. In the chapter, a mathematical model with immunization is proposed to simulate the succession of 2 epidemics with variable human populations. Stability of the equilibrium points is carried out and simulation is given for different parameters settings.
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Kumar Behara, Ramesh, and Kavita Behara. "Simulation Analysis of DFIG Integrated Wind Turbine Control System." In Wind Turbines - Advances and Challenges in Design, Manufacture and Operation [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103721.
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Recently, scientists and academics are discovering progressive improvements in the arena of wind power technology economically and reliably, allowing them to produce electricity focusing on renewable energy resources. Wind turbines (WT) using the Doubly Fed Induction Generators (DFIGs) have attracted particular attention because of their advantages such as variable speed constant frequency (VSCF) operation, independent control capabilities for maximum power point tracking (MPPT), active and reactive power controls, and voltage control strategy at the point of common coupling (PCC). When such resources have to be integrated into the existing power system, the operation becomes more challenging, particularly in terms of stability, security, and reliability. A DFIG system with its control strategies is simulated on MATLAB software. This entails the rapid control prototype testing of grid-connected, variable speed DFIG wind turbines to investigate the WT’s steady-state and dynamic behavior under normal and disturbed wind conditions. To augment the transient stability of DFIG, the simulation results for the active and reactive power of conventional controllers are compared with the adaptive tracking, self-tuned feed-forward PI controller model for optimum performance. Conclusive outcomes manifest the superior robustness of the feed-forward PI controller in terms of rising time, settling time, and overshoot value.
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Savin, Sergei. "ZMP-Based Trajectory Generation for Bipedal Robots Using Quadratic Programming." In Advances in Computational Intelligence and Robotics, 266–85. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-5225-9924-1.ch007.
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In this chapter, the problem of trajectory generation for bipedal walking robots is considered. A number of modern techniques are discussed, and their limitations are shown. The chapter focuses on zero-moment point methods for trajectory generation, where the desired trajectory of that point can be used to allow the robot to keep vertical stability if followed, and presents an instrument to calculate the desired trajectory for the center of mass for the robot. The chapter presents an algorithm based on quadratic programming, with an introduction of a slack variable to make the problem feasible and a change of variables to improve the numeric properties of the resulting optimization problem. Modern optimization tools allow one to solve such problems in real time, making it a viable solution for trajectory planning for the walking robots. The chapter shows a few results from the numerical simulation made for the algorithm, demonstrating its properties.
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Nadweh, Safwan Mhrez, and Ola Ahmad Khaddam. "Power Quality and Stability Analysis of Variable-Speed Drive Systems (VSDS)." In Handbook of Research on Smart Power System Operation and Control, 387–411. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8030-0.ch017.
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This chapter introduces an analysis of power quality of variable-speed drive systems (VSDS). In this chapter, several issues have been discussed as VSDS in terms of cost and effectiveness, VSDS control loops (open loop, closed loop), and power quality in VSDS. Harmonics standards and harmonics in VSDS were discussed in this chapter in addition to highlighting the effects of harmonics on power factor, crest factor, and other power quality specifications. The solutions used to mitigate the harmonics in VSDS were discussed in detail. Finally, simulation of the conventional VSDS model and VSDS with one harmonic mitigation solution in order to clarify the usefulness of using this solution on power quality specifications were discussed.
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Theodoridis, Dimitris C., Yiannis S. Boutalis, and Manolis A. Christodoulou. "High Order Neuro-Fuzzy Dynamic Regulation of General Nonlinear Multi-Variable Systems." In Artificial Higher Order Neural Networks for Modeling and Simulation, 134–61. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-2175-6.ch007.
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The direct adaptive dynamic regulation of unknown nonlinear multi variable systems is investigated in this chapter in order to address the problem of controlling non-Brunovsky and non-square systems with control inputs less than the number of states. The proposed neuro-fuzzy model acts as a universal approximator. While with the careful selection of a Lyapunov-like function, the authors prove the stability of the proposed control algorithm. Weight updating laws derived from the Lyapunov analysis assure the boundedness of the closed-loop signals incorporating the well-known modified parameter hopping. In addition, the proposed algorithm shows robustness when facing modelling errors, and therefore, the state trajectories present uniform ultimate boundedness. The proposed dynamic controller proved to control those general nonlinear systems, which are difficult or even impossible to control with other algorithms. Simulation results on well-known benchmark problems demonstrate the applicability and effectiveness of the method.
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Gorbachev, Sergey, Boris Gusev, Victor Kuzin, Shengli Xie, and Dong Yue. "Leader-Follower Consensus of Fractional-Order Multi-Agent Systems Using Adaptive Fuzzy control." In Hybrid Methods of Big Data Analysis and Applications, 271–94. Creosar Publishing, 2022. http://dx.doi.org/10.57118/creosar/978-1-915740-01-4_13.
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This part studies the leader-follower consensus (LFC) issue of fractional-order multi-agent systems (FOMASs) with nonlinear or linear function. Firstly, a fractional Lyapunov method is proposed to prove the stability of the FOMAS. Secondly, based on a sliding mode control method, when the follower dynamics is linear, a controller is devised to realize this uniform tracking question. Thirdly, when the follower has a nonlinear dynamic function satisfying the Lipschitz condition, it is verified that the devised controller is still reasonable. Fourthly, suppose that the dynamics of the followers are unknown, an adaptive fuzzy variable structure controller is devised to guarantee the consistency of the FOMAS. Finally, noting that the proposed conditions for stability and consensus are easy to verify, simulation calculations are written to expound the adaptability of control scheme.
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Boulkroune, Abdesselem, and Amina Boubellouta. "Fuzzy Control-Based Synchronization of Fractional-Order Chaotic Systems With Input Nonlinearities." In Advanced Synchronization Control and Bifurcation of Chaotic Fractional-Order Systems, 261–88. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-5418-9.ch009.
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This chapter addresses the fuzzy adaptive controller design for the generalized projective synchronization (GPS) of incommensurate fractional-order chaotic systems with actuator nonlinearities. The considered master-slave systems are with different fractional-orders, uncertain models, unknown bounded disturbances, and non-identical form. The suggested controller includes two keys terms, namely a fuzzy adaptive control and a fractional-order variable structure control. The fuzzy logic systems are exploited for approximating the system uncertainties. A Lyapunov approach is employed for determining the parameter adaptation laws and proving the stability of the closed-loop system. At last, simulation results are given to demonstrate the validity of the proposed synchronization approach.
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Prasad, Sumer Chand. "Double Fed Induction Generator Control for Wind Power Generation." In Applications of Artificial Intelligence in Electrical Engineering, 144–57. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2718-4.ch009.
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Doubly-fed induction generator wind turbines are largely developed due to their variable speed feature. The response of wind turbines to grid disturbance is an important issue, especially since the rated power of the wind turbine is increased; therefore, it is important to study the effect of grid disturbances on the wind turbine. In the chapter, the characteristics of the doubly-fed induction generator during wind speed fluctuation are studied. MATLAB/Simulink software has been used to observe the characteristics of wind turbines during wind speed fluctuation. Simulation results of the doubly-fed induction generator wind turbine system show improved system stability during wind speed variation. Power electronics converters used in the DFIG system are the most sensitive parts of the variable speed wind turbines with regards to system disturbances. To protect from excessive current, the DFIG system is equipped with an over-current and DC voltage overload protection system that trips the system under abnormal conditions.
Conference papers on the topic "Variable stability simulator"
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Scamps, Alexander, and P. Gibbens. "Development of a Variable Stability Flight Simulator as a Research/Education Tool." In AIAA Modeling and Simulation Technologies Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-5753.
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Mirza, Abdullah, Marinus M. van Paassen, T. J. Mulder, and Max Mulder. "Simulator Evaluation of a Medium-Cost Variable Stability System for a Business Jet." In AIAA Scitech 2019 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-0370.
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Heidari, Mohammad Reza, and Terry Wayne Stone. "Development of a Thermal Stability Method for Phase Appearance and Disappearance Handling in Thermal Compositional Simulators." In SPE Reservoir Simulation Conference. SPE, 2021. http://dx.doi.org/10.2118/203912-ms.
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Abstract Thermal compositional simulators rely heavily on multicomponent, multiphase flash calculations for a variety of reasons, including reservoir and wellbore initialization, phase appearance and disappearance, and property calculation. In a mass variable formulation, an isenthalpic flash is used for phase split computation, phase saturation update, component mole fraction update in different phases, and temperatures. A natural variable formulation utilizes an isothermal flash mainly for phase appearance and disappearance as well as computation of component mole fractions in appearing phases. Multiphase multicomponent isothermal flash calculations cannot be performed in narrow boiling systems which are very common in the simulation of thermal EOR operations such as Steam-Assisted Gravity Drainage (SAGD) or Steam Flooding (SF). In a narrow boiling point system, pressure and temperature are not linearly independent, and an isothermal flash will fail. In addition, flash calculations are computationally expensive, and reservoir simulators use different techniques to perform them as little as possible. A new thermal stability check has been developed that can be used in thermal compositional simulators and replaces an isothermal flash calculation. The new stability check quickly determines the phase state of a fluid sample and can be used as an initial guess for mole fraction of a phase appearing in the next simulation cycle. In this method, primary variables of the simulator are used as input for the stability check immediately after the nonlinear solver update so that computation of global mole fractions is not required. The new stability check can also be used in separator and isenthalpic flash calculations to determine the phase state of a fluid. An algorithm is provided, covering all different transitions of phase states in a thermal compositional simulator. The proposed algorithm is significantly faster than a flash calculation and saves simulation time spent in this calculation, hence the overall speed up is case dependent. The new stability check is simple, computationally inexpensive, and robust. It can be used for multicomponent and single-component systems, and we tested it rigorously against real field and synthetic models. The new thermal stability check always predicts the number of phase states correctly and never fails. In this paper, we demonstrate a thermal compositional simulation that is run without performing a single flash calculation.
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Denoual, Thomas, Jean-François Petiot, Franck Mars, and Andras Kemeny. "Predicting the Subjective Evaluation of Drivers in a Driving Simulator During Loss of Adherence." In ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82511.
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This paper investigates the possibility of using objective indicators to predict the subjective evaluation of a driver in a simulator. Situations of loss of adherence (LOA) were controlled and modulated in intensity and duration on a static and on a dynamic simulator (with and without a motion base). Multiple regression analyses were performed using the subjective evaluation of participants as the dependent variable, and the objective physical variables of the interaction driver/vehicle as the independent variables. The results assigned the most contributive variables to the accuracy of the model’s prediction for each subjective item, lateral acceleration and yaw rate for “control feeling” for instance. They also underlined the consistency of our approach and the influence of motion rendering on the perception of LOA intensity. A similar method could be used to evaluate the perception of various configurations of electronic stability control (ESC) systems.
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Lavretsky, Eugene. "Design, Analysis, and Flight Evaluation of a Primary Control System with Observer-Based Loop Transfer Recovery and Direct Adaptive Augmentation for The Calspan Variable Stability Simulator Learjet-25B Aircraft." In AIAA Scitech 2019 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-1081.
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Ersal, Tulga, Mark Brudnak, Ashwin Salvi, Jeffrey L. Stein, Zoran Filipi, and Hosam K. Fathy. "Development of an Internet-Distributed Hardware-in-the-Loop Simulation Platform for an Automotive Application." In ASME 2009 Dynamic Systems and Control Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/dscc2009-2709.
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This paper summarizes efforts to integrate, for the first time, two geographically-dispersed hardware-in-the-loop simulation setups over the Internet in an observer-free way. The two setups are the engine-in-the-loop simulation setup at the University of Michigan (UM) in Ann Arbor, MI, USA, and the driver-in-the-loop ride motion simulator at the US Army Tank-Automotive Research, Development and Engineering Center (TARDEC) in Warren, MI, USA. The goal of this integration is to increase the fidelity of experiments and to enable concurrent engineering. First, a model-based simulation of the setup is utilized to analyze the effects of variable delay, an intrinsic characteristic of the Internet, on the integrated system, particularly in terms of stability, robustness, and transparency. Then, experiments with the actual hardware are presented. The conclusion is that the two pieces of hardware can indeed be integrated over the Internet without relying on observers in a stable and subjectively transparent manner, even if the nominal delay is increased by four times.
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Abdelhafiz, Mostafa Magdy, Joachim Magdy Oppelt, and Luiz Adolfo Hegele. "Thermal Analysis of the Wellbore System During Drilling Operations Using an Improved Drilling Simulator." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211721-ms.
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Abstract Prediction of the wellbore fluids and formation temperatures during well construction is an essential step for efficient drilling operation. This work presents the applications of an improved comprehensive drilling simulator for predicting the wellbore system temperature during the drilling process. A fully transient numerical model of the wellbore temperature is developed for drilling and geothermal production applications. The model describes the dynamic behaviour of the thermal state of the wellbore during circulation, drilling and static conditions. The developed model is successfully implemented with the commercial virtual drilling simulator through an application programming interface (API) provided by the simulator. The model is capable to predict the temperature of the wellbore fluids, drill string, casing, cement, and rock formation with variable properties in real-time. This implementation allows the coupling of the thermal model with other physical models, which leads to more advanced and realistic simulations. The model is assessed and validated through a direct comparison with field data. The data is acquired during the drilling of a geothermal well located in the Hanover area in Germany. The results showed a good agreement between the predicted outlet fluid temperature and the measured one. Furthermore, an analysis of the effect of various parameters on the wellbore system temperature is performed. These parameters include drilling parameters such as weight on bit, bit and drill string rpm, circulation rate and drilling rate, in addition to the wellbore geometry parameters such as wellbore radius, casing and drill string sizes. This analysis showed the impact of these parameters on the wellbore temperature profile including the critical areas such as the casing setting point and bottom hole assembly. This information may lead to enhancing the wellbore stability by monitoring the thermal stresses, especially in high-temperature wells. Moreover, predicting the drill bit temperature can result in increasing the lifetime of the bit by adjusting the operating conditions to keep the bit temperature within the specified range. Based on these results, the enhanced drilling simulator with the transient temperature model showed to be a suitable tool for effective well planning.
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Konopczynski, Michael Robert, and Anna Helene Petitt. "The Practical Design of a Carbon Storage Injection Well Completion Using In-Line Flow Control Devices to Maintain Injection Stability." In SPE Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210651-ms.
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Abstract While depleted oil and gas fields can provide important storage capacity for Carbon Capture and Storage (CCS), injection of carbon dioxide into extremely pressure depleted hydrocarbon fields can be problematic due to the phase change of CO2 that can cause flow instability and result in adverse physical phenomena, such as the cooling associated with the latent heat of vaporization and Joule-Thomson cooling which could damage the completion equipment, reduce the hydrostatic head of CO2 and make it difficult to inject carbon dioxide. Thus far, most completion solutions to this problem have focused on multi-string designs, either parallel or concentric, using flow conduit friction to maintain sufficient back pressure to prevent CO2 flashing. These methods can restrict the amount of carbon dioxide which can be injected and/or are costly or technically prohibitive. An alternative solution is proposed using variable, autonomous or surface-controlled, flow control devices strategically placed in the injection tubing string to provide stepwise pressure drops with depth. This paper builds on the CCS simulator examined in SPE-209705 (Petitt and Konopczynski, 2022) by comparing three case studies modelled by altering the aperture of the wellhead choke and the inline control devices to maintain the CO2 in liquid form. These real-life scenarios were modelled with a variety of injection and reservoir pressures thus mimicking the varying conditions over the life of a well. Using a purpose-designed CCS wellbore flow simulator that honors the thermodynamics and heat transfer of CO2 injection, we have modelled the flow performance of CCS well completions with multiple downhole flow control devices placed at strategic depths, the size and number of devices chosen to achieve the desired pressure distribution and CO2 injection rate. The modelling shows that the multi-flow control device concept can maintain the carbon dioxide in a dense phase over anticipated operating conditions and provides a greater injection rate capacity and turndown range than multi-string solutions inside the same casing size. Depleted reservoirs and restricted CO2 injection rates require the greatest number of flow control devices, while maximum injection rates at maximum reservoir pressures require the fewest number of devices, introducing the potential for completion designs that permit retrieval of the in-line devices with minimal intervention as the reservoir is charged through project life.
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Pan, Huanquan, and Hamdi A. Tchelepi. "Compositional Flow Simulation Using Reduced-Variables and Stability-Analysis Bypassing." In SPE Reservoir Simulation Symposium. Society of Petroleum Engineers, 2011. http://dx.doi.org/10.2118/142189-ms.
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Ketelheun, Anja, Clemens Olbricht, Frederik Hahn, and Johannes Janicka. "Premixed Generated Manifolds for the Computation of Technical Combustion Systems." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59940.
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Large eddy simulations (LES) show a good prediction accuracy at a decent computational cost for the simulation of combustion processes in complex geometries. However, the large grids required make the direct solution of detailed reaction kinetics impracticable. Therefore, the chemical reactions can be tabulated in a pre-processing step using detailed chemistry with one-dimensional laminar steady flamelets. These flamelets can be either non-premixed or premixed and are stored based on controlling variables like mixture fraction and reaction progress parameter, for example. In this work, a progress variable approach (PVA) using premixed flamelets was adopted to generate a manifold defined by mixture fraction and reaction progress variable. Since the computation of the flamelets is only feasible between flammability limits, the data outside these limits has to be extrapolated to obtain the complete manifold for all chemical states. The extrapolation influences the stability of the LES and its prediction quality and so four different extrapolation schemes were studied. A probability density function (PDF) model was applied to account for subgrid scale variances. Two methods of modeling the joint PDF of mixture fraction and progress variable in terms of their statistical dependence were investigated. Some results of a bluff body configuration comparing the PDF modeling approaches are shown. The results demonstrated that a diffusion flame can be simulated with both the progress variable approach based on premixed flamelets and classic non-premixed flamelets without progress variable.
Reports on the topic "Variable stability simulator"
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Financial Stability Report - Second Semester of 2020. Banco de la República de Colombia, March 2021. http://dx.doi.org/10.32468/rept-estab-fin.sem2.eng-2020.
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The Colombian financial system has not suffered major structural disruptions during these months of deep economic contraction and has continued to carry out its basic functions as usual, thus facilitating the economy's response to extreme conditions. This is the result of the soundness of financial institutions at the beginning of the crisis, which was reflected in high liquidity and capital adequacy indicators as well as in the timely response of various authorities. Banco de la República lowered its policy interest rates 250 points to 1.75%, the lowest level since the creation of the new independent bank in 1991, and provided ample temporary and permanent liquidity in both pesos and foreign currency. The Office of the Financial Superintendent of Colombia, in turn, adopted prudential measures to facilitate changes in the conditions for loans in effect and temporary rules for rating and loan-loss provisions. Finally, the national government expanded the transfers as well as the guaranteed credit programs for the economy. The supply of real credit (i.e. discounting inflation) in the economy is 4% higher today than it was 12 months ago with especially marked growth in the housing (5.6%) and commercial (4.7%) loan portfolios (2.3% in consumer and -0.1% in microloans), but there have been significant changes over time. During the first few months of the quarantine, firms increased their demands for liquidity sharply while consumers reduced theirs. Since then, the growth of credit to firms has tended to slow down, while consumer and housing credit has grown. The financial system has responded satisfactorily to the changes in the respective demands of each group or sector and loans may grow at high rates in 2021 if GDP grows at rates close to 4.6% as the technical staff at the Bank expects; but the forecasts are highly uncertain. After the strict quarantine implemented by authorities in Colombia, the turmoil seen in March and early April, which was evident in the sudden reddening of macroeconomic variables on the risk heatmap in Graph A,[1] and the drop in crude oil and coal prices (note the high volatility registered in market risk for the region on Graph A) the local financial markets stabilized relatively quickly. Banco de la República’s credible and sustained policy response played a decisive role in this stabilization in terms of liquidity provision through a sharp expansion of repo operations (and changes in amounts, terms, counterparties, and eligible instruments), the purchases of public and private debt, and the reduction in bank reserve requirements. In this respect, there is now abundant aggregate liquidity and significant improvements in the liquidity position of investment funds. In this context, the main vulnerability factor for financial stability in the short term is still the high degree of uncertainty surrounding loan quality. First, the future trajectory of the number of people infected and deceased by the virus and the possible need for additional health measures is uncertain. For that reason, there is also uncertainty about the path for economic recovery in the short and medium term. Second, the degree to which the current shock will be reflected in loan quality once the risk materializes in banks’ financial statements is uncertain. For the time being, the credit risk heatmap (Graph B) indicates that non-performing and risky loans have not shown major deterioration, but past experience indicates that periods of sharp economic slowdown eventually tend to coincide with rises in non-performing loans: the calculations included in this report suggest that the impact of the recession on credit quality could be significant in the short term. This is particularly worrying since the profitability of credit establishments has been declining in recent months, and this could affect their ability to provide credit to the real sector of the economy. In order to adopt a forward-looking approach to this vulnerability, this Report presents several stress tests that evaluate the resilience of the liquidity and capital adequacy of credit institutions and investment funds in the event of a hypothetical scenario that seeks to simulate an extreme version of current macroeconomic conditions. The results suggest that even though there could be strong impacts on the credit institutions’ volume of credit and profitability under such scenarios, aggregate indicators of total and core capital adequacy will probably remain at levels that are above the regulatory limits over the horizon of a year. At the same time, the exercises highlight the high capacity of the system's liquidity to face adverse scenarios. In compliance with its constitutional objectives and in coordination with the financial system's security network, Banco de la República will continue to closely monitor the outlook for financial stability at this juncture and will make the decisions that are necessary to ensure the proper functioning of the economy, facilitate the flow of sufficient credit and liquidity resources, and further the smooth operation of the payment systems. Juan José Echavarría Governor