Journal articles: '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.

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Gohar Ali, Hina, and Ramon Vilanova Arbos. "Chattering Free Adaptive Sliding Mode Controller for Photovoltaic Panels with Maximum Power Point Tracking." Energies 13, no. 21 (October 30, 2020): 5678. http://dx.doi.org/10.3390/en13215678.

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Photovoltaic system is utilized to generate energy that relies upon the ecological conditions, for example, temperature, irradiance, and the load associated with it. Considering the non-linear component of photovoltaic (PV) array and the issue of low effectiveness because of the variable natural conditions, the Maximum Power Point Tracking (MPPT) method is required to extract the maximum power from the PV system. The adopted control is executed utilizing an Adaptive Sliding Mode Controller (ASMC) and the enhancement is actualized utilizing an Improved Pattern Search Method (IPSM). This work employs IPSM based optimization approach in order to command the underlying ASMC controller. The upper level decision determines the sliding surface for the adaptive controller. As a non-linear strategy, the stability of the adaptive controller is guaranteed by conducting a Liapunov analysis. On the practical side, MATLAB/Simulink is used as simulator for the controller implementation and coupling with PSIM in order to connect it with the PV system object of control. The simulation results validate that the proposed controller effectively improves the voltage tracking, system power with reduced chattering effect and steady-state error. The performance of the proposed control architectures is validated by comparing the proposals with that of the well-known and widely used Proportional Integral Derivative (PID) controller. That operated as a lower level controller for a Perturb & Observe (P&O) and Particle Swarm Optimization (PSO).

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Kochanek, K., B. Renard, P. Arnaud, Y. Aubert, M. Lang, T. Cipriani, and E. Sauquet. "A data-based comparison of flood frequency analysis methods used in France." Natural Hazards and Earth System Sciences 14, no. 2 (February 20, 2014): 295–308. http://dx.doi.org/10.5194/nhess-14-295-2014.

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Abstract. Flood frequency analysis (FFA) aims at estimating quantiles with large return periods for an extreme discharge variable. Many FFA implementations are used in operational practice in France. These implementations range from the estimation of a pre-specified distribution to continuous simulation approaches using a rainfall simulator coupled with a rainfall–runoff model. This diversity of approaches raises questions regarding the limits of each implementation and calls for a nation-wide comparison of their predictive performances. This paper presents the results of a national comparison of the main FFA implementations used in France. More accurately, eight implementations are considered, corresponding to the local, regional and local-regional estimation of Gumbel and Generalized Extreme Value (GEV) distributions, as well as the local and regional versions of a continuous simulation approach. A data-based comparison framework is applied to these eight competitors to evaluate their predictive performances in terms of reliability and stability, using daily flow data from more than 1000 gauging stations in France. Results from this comparative exercise suggest that two implementations dominate their competitors in terms of predictive performances, namely the local version of the continuous simulation approach and the local-regional estimation of a GEV distribution. More specific conclusions include the following: (i) the Gumbel distribution is not suitable for Mediterranean catchments, since this distribution demonstrably leads to an underestimation of flood quantiles; (ii) the local estimation of a GEV distribution is not recommended, because the difficulty in estimating the shape parameter results in frequent predictive failures; (iii) all the purely regional implementations evaluated in this study displayed a quite poor reliability, suggesting that prediction in completely ungauged catchments remains a challenge.

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Perozzi, Gabriele, Mohamed Radjeb Oudainia, Chouki Sentouh, Jean-Christophe Popieul, and Jagat Jyoti Rath. "Driver Assisted Lane Keeping with Conflict Management Using Robust Sliding Mode Controller." Sensors 23, no. 1 (December 20, 2022): 4. http://dx.doi.org/10.3390/s23010004.

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Lane-keeping assistance design for road vehicles is a multi-objective design problem that needs to simultaneously maintain lane tracking, ensure driver comfort, provide vehicle stability, and minimize conflict between the driver and the autonomous controller. In this work, a cooperative control strategy is proposed for lane-keeping keeping by integrating driving monitoring, variable level of assistance allocation, and human-in-the-loop control. In the first stage, a time-varying physical driver loading pattern is identified based on a relationship between lateral acceleration, road curvature, and the measured maximum driver torque. Together with the monitored driver state that indicates driver mental loading, an adaptive driver activity function is then formulated that replicates the levels of assistance required for the driver in the next stage. To smoothly transition authority between various modes (from manual to autonomous and vice versa) based on the generated levels of assistance, a novel higher-order sliding mode controller is proposed and closed-loop stability is established. Further, a novel sharing parameter (which is proportional to the torques coming from the driver and from the autonomous controller) is used to minimize the conflict. Experimental results on the SHERPA high-fidelity vehicle simulator show the real-time implementation feasibility. Extensive experimental results provided on the Satory test track show improvement in cooperative driving quality by 9.4%, reduction in steering workload by 86.13%, and reduced conflict by 65.38% when compared with the existing design (no sharing parameter). These results on the cooperative performance highlight the significance of the proposed controller for various road transportation challenges.

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Lee, Geonil, and Jae-il Jung. "Decentralized Platoon Join-in-Middle Protocol Considering Communication Delay for Connected and Automated Vehicle." Sensors 21, no. 21 (October 27, 2021): 7126. http://dx.doi.org/10.3390/s21217126.

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Cooperative driving is an essential component of intelligent transport systems (ITSs). It promises greater safety, reduced accidents, efficient traffic flow, and fuel consumption reduction. Vehicle platooning is a representative service model for ITS. The principal sub-systems of platooning systems for connected and automated vehicles (CAVs) are cooperative adaptive cruise control (CACC) systems and platoon management systems. Based on vehicle state information received through vehicle-to-vehicle (V2V) communication, the CACC system allows platoon vehicles to maintain a narrower safety distance. In addition, the platoon management system using V2V communications allows vehicles to perform platoon maneuvers reliably and accurately. In this paper, we propose a CACC system with a variable time headway and a decentralized platoon join-in-middle maneuver protocol with a trajectory planning system considering the V2V communication delay for CAVs. The platoon join-in-middle maneuver is a challenging research subject as the research must consider the requirement of a more precise management protocol and lateral control for platoon safety and string stability. These CACC systems and protocols are implemented on a simulator for a connected and automated vehicle system, PreScan, and we validated our approach using a realistic control system and V2V communication system provided by PreScan.

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Heidari, M., S. H. Hejazi, and S. M. Farouq Ali. "Steam-Assisted Gravity-Drainage Performance With Temperature-Dependent Properties—A Semianalytical Approach." SPE Journal 22, no. 03 (October 20, 2016): 902–11. http://dx.doi.org/10.2118/175036-pa.

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Summary Steam-assisted gravity drainage (SAGD) is one of the successful in-situ thermal-recovery methods for oil-sands production. In this paper, we provide a simple semianalytical model that can accurately analyze an SAGD project with variable properties. In particular, we investigate the effect of temperature-dependent properties such as thermal conductivity, heat capacity, and rock density on SAGD performance. The proposed model sequentially solves the transient nonlinear heat-transfer equation coupled with the continuity equation with Kirchhoff's transformation and the heat integral method (HIM). A criterion for timestep selection is defined on the basis of the Courant and Péclet numbers to guarantee the stability of the sequential technique. The results illustrate that the temperature-dependent physical properties affect temperature distributions ahead of steam chamber which consequently have a significant impact on the cumulative oil production and oil-production rate. Moreover, the results show that the temperature profile ahead of the steam chamber changes with time and space, and a 2D transient assumption for SAGD modeling is necessary. The semianalytical model runs in a small fraction of numerical-simulator runtime, yet it provides reasonable results. Thus, it has the potential to be used as a tool for quick SAGD evaluations.

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Nurlan, Zhanserik, Tamara Zhukabayeva, and Mohamed Othman. "EZ-SEP: Extended Z-SEP Routing Protocol with Hierarchical Clustering Approach for Wireless Heterogeneous Sensor Network." Sensors 21, no. 4 (February 3, 2021): 1021. http://dx.doi.org/10.3390/s21041021.

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Wireless sensor networks (WSN) are networks of thousands of nodes installed in a defined physical environment to sense and monitor its state condition. The viability of such a network is directly dependent and limited by the power of batteries supplying the nodes of these networks, which represents a disadvantage of such a network. To improve and extend the life of WSNs, scientists around the world regularly develop various routing protocols that minimize and optimize the energy consumption of sensor network nodes. This article, introduces a new heterogeneous-aware routing protocol well known as Extended Z-SEP Routing Protocol with Hierarchical Clustering Approach for Wireless Heterogeneous Sensor Network or EZ-SEP, where the connection of nodes to a base station (BS) is done via a hybrid method, i.e., a certain amount of nodes communicate with the base station directly, while the remaining ones form a cluster to transfer data. Parameters of the field are unknown, and the field is partitioned into zones depending on the node energy. We reviewed the Z-SEP protocol concerning the election of the cluster head (CH) and its communication with BS and presented a novel extended mechanism for the selection of the CH based on remaining residual energy. In addition, EZ-SEP is weighted up using various estimation schemes such as base station repositioning, altering the field density, and variable nodes energy for comparison with the previous parent algorithm. EZ-SEP was executed and compared to routing protocols such as Z-SEP, SEP, and LEACH. The proposed algorithm performed using the MATLAB R2016b simulator. Simulation results show that our proposed extended version performs better than Z-SEP in the stability period due to an increase in the number of active nodes by 48%, in efficiency of network by the high packet delivery coefficient by 16% and optimizes the average power consumption compared to by 34.

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Sebastián, Rafael. "Review on Dynamic Simulation of Wind Diesel Isolated Microgrids." Energies 14, no. 7 (March 24, 2021): 1812. http://dx.doi.org/10.3390/en14071812.

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Wind diesel isolated microgrids (WDIMs) combine wind turbine generators (WTGs) with diesel generators (DGs) to supply electricity to remote consumers. WDIMs are low-inertia isolated power systems where large system frequency and voltage variations occur. WDIM dynamic modeling allows short-term simulations to be performed and detailed electrical variable transients to be obtained so that the WDIM power quality and stability can be tested. This paper presents a literature review about WDIM dynamic simulation. The review classifies articles according to factors such as the different WDIM operation modes (diesel only, wind–diesel and wind only) simulated, the types of WTGs used in the WDIM (constant- and variable-speed types), or the use of different short-term energy storage technologies (batteries, ultracapacitors, flywheels) to improve the WDIM power quality, stability and reliability. Papers about the dynamic simulation of related isolated microgrids are also reviewed. Finally, as an example of WDIM dynamic simulation, a WDIM with one WTG, one DG, load and a discrete dump load (DL) is modeled and simulated. The WDIM response to variations of wind speed and load consumption is shown by graphs of the main electrical variables. The simulations show how the DL is used to improve the WDIM stability and reliability.

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Shukla, Hiramani, Srete Nikolovski, More Raju, Ankur Singh Rana, and Pawan Kumar. "SMES-GCSC Coordination for Frequency and Voltage Regulation in a Multi-Area and Multi-Source Power System with Penetration of Electric Vehicles and Renewable Energy Sources." Energies 16, no. 1 (December 26, 2022): 251. http://dx.doi.org/10.3390/en16010251.

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Frequency, tie-line power, and the terminal voltages of synchronized generators must all be kept within prescribed limits to ensure the stability of an interconnected power grid through combined automatic generation control (AGC) and automatic voltage regulator (AVR) loops. Thermal power plants, electric vehicles, and renewable energy sources—including solar and wind, geothermal, and solar thermal power plants—form the two-area integrated power system in present research. A new cascade controller named the cascaded proportional integral derivative (PID) and fractional-order PID (CPID-FOPID) controller is proposed for the first time, whose performance is compared with the PID and FOPID controller. The results show that the proposed cascade controller outperforms PID and FOPID in delivering superior dynamic characteristics, including short settling times and low oscillation amplitudes. A new metaheuristic algorithm named the coot algorithm was applied to optimize the parameters of these controllers. The suggested controller outperforms FOPID in the combined AGC and AVR problem under uncertain conditions (random load disturbance, variable input of solar irradiation, and wind power). Robustness of the controller is tested with significant variation in the turbine time constant of the thermal and geothermal power plant. In this study, authors also investigated the best possible coordination between the superconducting magnetic energy storage (SMES) and gate-controlled series capacitor (GCSC) devices to control both voltage and frequency simultaneously. The effect of communication time to the power system is analyzed in this study. Additionally, the obtained results are satisfactorily validated using OPAL-RT real-time digital simulator.

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Prakash, A. Om, and R. Narmatha Banu. "Feature-Reduced Stability Analysis of Islanded Photovoltaic Microgrid Inverters." International Journal of Photoenergy 2022 (November 21, 2022): 1–15. http://dx.doi.org/10.1155/2022/7225179.

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A smart grid environment is prone to data explosion while controlling a microgrid system. Islanded Microgrid’s stability analysis involves a large number of system state variables thus consuming more computational memory due to parallel connected inverter dynamics. Parallel inverters generate reference voltage and frequency using droop controllers, unlike grid-connected inverters where the primary grid provides the reference voltage and frequency. This paper develops feature-reduced stability analysis of the parallel inverters thus reducing the computational memory of its stability analysis. Principal component analysis being a feature extraction technique is applied to reduce the number of variables determining stability. MATLAB is used to develop the average model of a parallel inverter with an LCL filter and a three-phase AC load. Evaluation of the stability analysis using the state variable analysis with the virtual resistance method is simulated. Simulation validates stability analysis of the model with reduced state variables. An average model developed using MATLAB and PCA carried out using Python clearly indicated the validation of the dimensionality reduction in the stability analysis. The reduced number of variables is validated for a stable range of the parallel inverter droop controller. Both cases validated the dimensionality reduction in the stability analysis of parallel inverters.

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Yang, Xiao Hong, and Chun Chen. "Modeling and Simulation of Variable-Pitch Wind Power Generation System." Advanced Materials Research 724-725 (August 2013): 568–71. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.568.

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in this work, a model for variable-pitch wind power generation controller system is set up. The model is simulated under MATLAB / Simulink environment. The simulation result shows that adding adjustable variable-pitch wind turbine can significantly improves the stability of the generator speed and output power. This work can provide a reference for correlative study on wind power generation system.

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Hayati, Sajad, Mohammad Hajaliakbari, Yalda Rajabi, and Sajad Rasaee. "Chatter reduction in slender boring bar via a tunable holder with variable mass and stiffness." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, no. 12 (March 1, 2017): 2098–108. http://dx.doi.org/10.1177/0954405417690554.

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In this study, a new strategy is presented to increase the machining stability due to chatter suppression for boring and turning machining processes. The proposed approach is based on varying the position of stability lobes via changing mechanical properties of the tool body such as the mass and stiffness. Because of the shape of stability lobe diagrams, having a tool with a tunable stability lobe diagram can be useful to alter an unstable condition to a stable condition. For this purpose, a structure for the tool body is designed that is consisted of a hollow body with a core as a tunable screw inside it. As the core gets in or out, it changes the mass and stiffness of the tool body that leads to change the position of stability lobe diagram. In order to study the effect of designed structure on stability, the structure is simulated using a validated finite element time domain model. The time domain simulation shows a considerable improvement in stability of process. The strategy is experimentally applied to the process via modulation of the tool structure in the machining process to validate the simulation results. The experimental results have a high coincidence with theory and show a good improvement in stability.

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Chen, Wuwei, Rongyun Zhang, Linfeng Zhao, Hongbo Wang, and Zhenya Wei. "Control of chaos in vehicle lateral motion using the sliding mode variable structure control." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 4 (February 6, 2018): 776–89. http://dx.doi.org/10.1177/0954407017753529.

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A 3-degree of freedom (DOF) nonlinear model including yaw, lateral, and roll motions was constructed, and a numerical simulation of chaotic behavior was performed using the Lyapunov exponent method. The vehicle motion is complex, manifesting double-periodic, quasi-periodic, and chaotic phases, which negatively affects the vehicle lateral stability. To control this chaotic behavior, a controller was designed based on the sliding mode variable structure control (SM-VSC) method. To decrease chattering and further improve lateral stability of the vehicle under extreme operating conditions, the adaptive power reaching law was realized by using a fuzzy control method. The performance of the SM-VSC system was simulated by using Matlab/simulink. The simulation results including the uncontrol, SM-VSC control, and adaptive-reaching SM-VSC control were compared, which demonstrated that the adaptive-reaching SM-VSC control method is more effective in suppressing the chaotic phase of the vehicle lateral motion. The approach proposed in this paper can significantly improve a vehicle’s lateral stability under extreme operating conditions.

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Xia, Ja Kuan, Shi Xuan Lu, Shuang Mao, and Wei Huang. "Rotational Speed Control of Wind Power Generation Systems with Variable-Speed and Variable-Pitch." Applied Mechanics and Materials 130-134 (October 2011): 3190–94. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.3190.

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A robust controller of wind turbine pitch angle is designed by using the quantitative feedback theory based on the analysis of wind power system model in this paper. The controller design methodology is to select the system parameters quantitatively at different wind speed disturbances in order to optimize the response time and the output stability. Theoretical analysis and simulation results demonstrate that the controller can control the speed stability of wind power system with strong robustness to uncertain disturbances of the system parameters when the wind speed fluctuates randomly.

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Cong, Qian, Xiaojie Shi, Ju Wang, Yu Xiong, Bo Su, Wei Xu, Hai Liu, Kuiyue Zhou, Lei Jiang, and Weijun Tian. "Stability Study and Simulation of Quadruped Robots with Variable Parameters." Applied Bionics and Biomechanics 2022 (January 19, 2022): 1–9. http://dx.doi.org/10.1155/2022/9968042.

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Walking stability is one of the key problems restricting the development of quadruped robots. Two new kinds of variable parameter quadruped robots with high stability were proposed. The two groups of variable parameter models were applied to quadruped robots with the full elbow joint or elbow joint for front legs and knee joint for back legs, respectively, and the stability of their linear motion under different variable parameters was deeply studied by Recurdyn. The quadruped robots with elbow joint for front legs and knee joint for back legs displayed good antijamming ability to lateral impact. According to the rigid-flexible simulation experiment, the largest force occurred in the knee joint during the movement of the quadruped robot. This provided a theoretical basis for the design of real quadruped robots.

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Cao, Ziyang, Hua Li, Zhen Yin, and Wei Liu. "Analysis and Prediction of Micromilling Stability with Variable Tool Geometry." Advances in Mechanical Engineering 6 (January 1, 2014): 870782. http://dx.doi.org/10.1155/2014/870782.

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Micromilling can fabricate miniaturized components using micro-end mill at high rotational speeds. The analysis of machining stability in micromilling plays an important role in characterizing the cutting process, estimating the tool life, and optimizing the process. A numerical analysis and experimental method are presented to investigate the chatter stability in micro-end milling process with variable milling tool geometry. The schematic model of micromilling process is constructed and the calculation formula to predict cutting force and displacements is derived. This is followed by a detailed numerical analysis on micromilling forces between helical ball and square end mills through time domain and frequency domain method and the results are compared. Furthermore, a detailed time domain simulation for micro end milling with straight teeth and helical teeth end mill is conducted based on the machine-tool system frequency response function obtained through modal experiment. The forces and displacements are predicted and the simulation result between variable cutter geometry is deeply compared. The simulation results have important significance for the actual milling process.

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Eduardo Tarifa, Enrique, Eleonora Erdmann, Demetrio Humana, María Soledad Vicente, Luis Rodolfo Cari, and Lorgio Mercado Fuentes. "Gas transport network analysis." Ingeniería e Investigación 27, no. 3 (September 1, 2007): 89–97. http://dx.doi.org/10.15446/ing.investig.v27n3.14849.

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Growing demand for natural gas necessarily leads to demands for increased transport network capacity. This can be done by increasing the capacity of already installed gas pipelines and optimising operating conditions. Greater knowledge (know-how) regarding the process is thus needed and may be applied by following the procedure outlined in this work. The proposed method concerns studying a gas network by using simulation tools; it has been used for studying a transport network in Argentina. The proposed method has the following stages: 1) system analysis (identifying parameters, disturbances, manipulated variables, state variables and output variables), 2) stationary simulation, 3) dynamic simulation and 4) case studies (analysing sensitivity, stability and controllability). Once a system’s critical variables have been identified then stationary simulation allows the amount of gas and its pressure to be determined for each sink, in several scenarios. These results can be used for designing suitable operational procedure for such cases. Dynamic simulation describes a system’s stationary state and how the state of the process evolves. Such additional information allows refining previously-designed procedures and also makes dynamic simulation an excellent tool for operator training. Two alternatives were analysed for stationary simulation: an HYSYS simulator and traditional Excel spreadsheet calculations. Predicted stationary states were similar by both methods. The sensitivity of the most relevant system variables was then studied; the HYSYS simulator was used for dynamic simulation in all cases. System sensitivity and dynamics were determined, such information being required for making improvements to network installations and operational procedures and thereby proving the procedure’s worth.

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Kouno, Susumu. "A Sensitivity Variable Tactile Sensor with Self-Tuner." Journal of Robotics and Mechatronics 18, no. 1 (February 20, 2006): 83–88. http://dx.doi.org/10.20965/jrm.2006.p0083.

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We propose an approach for changing tactile sensor gain based on how much force is imparted to the sensor, so the sensor maintains a wide dynamic range. Assuming a strain-gauge-based tactile sensor, we propose a DC current approach with stability guaranteed. We provide two theorems - saturation condition giving gain leading to saturation, and stability condition giving gain leading to instability. We demonstrate experimental results and simulation results.

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Panayotova, I. N. "COEFFICIENT STABILITY OF OPERATOR‐DIFFERENCE SCHEMES WITH TIME VARIABLE OPERATORS." Mathematical Modelling and Analysis 3, no. 1 (December 15, 1998): 152–59. http://dx.doi.org/10.3846/13926292.1998.9637098.

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The problem of the coefficient stability for operator‐ difference schemes with variable operator is investigated. A priori coordinated estimates in the L 2‐norm are obtained for differential‐operator equations and operator‐difference schemes. Estimates in the energy space HA for coefficient stability and stability with respect to the right-hand side and the initial data are proved under more strong assumptions for operator's perturbation.

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FANG, Wei, Tianlin QIU, Deshang LI, and Haowei WANG. "Configuration system design and longitudinal flight simulation verification of variable stability helicopter." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 40, no. 1 (February 2022): 118–24. http://dx.doi.org/10.1051/jnwpu/20224010118.

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For in-flight simulation of variable stability helicopter, how to have the ability to change a wide range of response characteristics and ensure flight safety is an important design problem. This paper proposes configuration design technology of the variable stability helicopter, which purpose is to safely change steady-state and dynamic response characteristics of the variable stability helicopter, and make the pilot feel good or poor helicopter response characteristics. The configuration control system of the variable stability helicopter is designed theoretically, and the configuration switch logic is studied from the perspective of flight safety. The numerical simulation test of the longitudinal configuration control law was carried out, and the configuration control law and configuration switch logic were added to the ground closed-loop test to verify. The results show that the expected response characteristics of the helicopter are obtained by applying the configuration system design technology.

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Gu, Bei, and H. Harry Asada. "Co-Simulation of Algebraically Coupled Dynamic Subsystems Without Disclosure of Proprietary Subsystem Models." Journal of Dynamic Systems, Measurement, and Control 126, no. 1 (March 1, 2004): 1–13. http://dx.doi.org/10.1115/1.1648307.

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A method for simultaneously running a collection of dynamic simulators coupled by algebraic boundary conditions is presented. Dynamic interactions between subsystems are simulated without disclosing proprietary information about the subsystem models, as all the computations are performed based on input-output numerical data of encapsulated subsystem simulators coded by independent groups. First, this paper describes a system of interacting subsystems with a causal conflict as a high-index, Differential-Algebraic Equation (DAE), and develops a systematic solution method using Discrete-Time Sliding Mode control. Stability and convergence conditions as well as error bounds are analyzed by using nonlinear control theory. Second, the algorithm is modified such that the subsystem simulator does not have to disclose its internal model and state variables for solving the overall DAE. The new algorithm is developed based on the generalized Kirchhoff Laws that allow us to represent algebraic boundary constraints as linear equations of the subsystems’ outputs interacting to each other. Third, a multi-rate algorithm is developed for improving efficiency, accuracy, and convergence characteristics. Numerical examples verify the major theoretical results and illustrate features of the proposed method.

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Scholten, Pepijn A., Marinus M. van Paassen, Q. Ping Chu, and Max Mulder. "Variable Stability In-Flight Simulation System Based on Existing Autopilot Hardware." Journal of Guidance, Control, and Dynamics 43, no. 12 (December 2020): 2275–88. http://dx.doi.org/10.2514/1.g005066.

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TAN, MAN-CHUN, YAN ZHANG, WEN-LI SU, and YU-NONG ZHANG. "EXPONENTIAL STABILITY ANALYSIS OF NEURAL NETWORKS WITH VARIABLE DELAYS." International Journal of Bifurcation and Chaos 20, no. 05 (May 2010): 1541–49. http://dx.doi.org/10.1142/s0218127410026691.

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Some sufficient conditions to ensure the existence, uniqueness and global exponential stability of the equilibrium point of cellular neural networks with variable delays are derived. These results extend and improve the existing ones in the literature. Two illustrative examples are given to demonstrate the effectiveness of our results.

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Wei, Li Sheng, Ming Jiang, Qi Gong Chen, and Min Rui Fei. "H-Infinity Robust Control Methodology of Multi-Variable NCSs." Advanced Materials Research 97-101 (March 2010): 2373–76. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.2373.

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This note investigates H-infinity robust controller design for uncertain multi-variable networked control systems with disturbance. The complete mathematical model is derived. And the sufficient condition for asymptotical stability is analyzed by using 2nd Lyapunov stability theory combined with free-weighting matrices techniques. The existence of such a controller is given in terms of the solvability of linear matrix inequalities. The efficacy and feasibility of the proposed methods is shown by presenting simulation results.

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Zhan, Huashui. "On the Solutions of a Porous Medium Equation with Exponent Variable." Discrete Dynamics in Nature and Society 2019 (August 1, 2019): 1–15. http://dx.doi.org/10.1155/2019/9290582.

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The paper studies the initial-boundary value problem of a porous medium equation with exponent variable. How to deal with nonlinear term with the exponent variable is the main dedication of this paper. The existence of the weak solution is proved by the monotone convergent method. Moreover, according to the different boundary value conditions, the stability of weak solutions is studied. In some special cases, the stability of weak solutions can be proved without any boundary value condition.

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35

Abuelma'atti, Muhammad Taher, and Muhammad Haroon Khan. "On the Stability of Resistively Variable Capacitors Using General Impedance Converters." Active and Passive Electronic Components 18, no. 2 (1995): 129–35. http://dx.doi.org/10.1155/1995/39168.

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The stability of three recently proposed circuits for realizing resistively variable capacitors is studied. It is shown that the circuits may oscillate for practical values of active and passive components. Simulation and experimental results are included.

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GIOVANGIGLI, V., and B. GRAILLE. "ASYMPTOTIC STABILITY OF EQUILIBRIUM STATES FOR AMBIPOLAR PLASMAS." Mathematical Models and Methods in Applied Sciences 14, no. 09 (September 2004): 1361–99. http://dx.doi.org/10.1142/s0218202504003659.

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We investigate a system of partial differential equations modeling ambipolar plasmas. The ambipolar — or zero current — model is obtained from general plasmas equations in the limit of vanishing Debye length. In this model, the electric field is expressed as a linear combination of macroscopic variable gradients. We establish that the governing equations can be written as a symmetric form by using entropic variables. The corresponding dissipation matrices satisfy the null space invariant property and the system of partial differential equations can be written as a normal form, i.e. in the form of a symmetric hyperbolic–parabolic composite system. By properly modifying the chemistry source terms and/or the diffusion matrices, asymptotic stability of equilibrium states is established and decay estimates are obtained. We also establish the continuous dependence of global solutions with respect to vanishing electron mass.

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Dong, Jian, Bin He, Chenghong Zhang, and Gang Li. "Open-Closed-Loop PD Iterative Learning Control with a Variable Forgetting Factor for a Two-Wheeled Self-Balancing Mobile Robot." Complexity 2019 (August 8, 2019): 1–11. http://dx.doi.org/10.1155/2019/5705126.

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A novel iterative learning control (ILC) algorithm for a two-wheeled self-balancing mobile robot with time-varying, nonlinear, and strong-coupling dynamics properties is presented to resolve the trajectory tracking problem in this research. A kinematics model and dynamic model of a two-wheeled self-balancing mobile robot are deduced in this paper, and the combination of an open-closed-loop PD-ILC law and a variable forgetting factor is presented. The open-closed-loop PD-ILC algorithm adopts current and past learning items to drive the state variables and input variables, and the output variables converge to the bounded scope of their desired values. In addition, introducing a variable forgetting factor can enhance the robustness and stability of ILC. Numerous simulation and experimental data demonstrate that the proposed control scheme has better feasibility and effectiveness than the traditional control algorithm.

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Park, Junho, and Youngjin Choi. "Input-to-State Stability of Variable Impedance Control for Robotic Manipulator." Applied Sciences 10, no. 4 (February 13, 2020): 1271. http://dx.doi.org/10.3390/app10041271.

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Variable impedance control has been required to perform a variety of interactive tasks in contact with environments. In some cases, the time-varying stiffness matrix of the impedance model can be used to achieve high performance for uneven contact tasks. In the paper, two sufficient conditions are proposed to ensure the input-to-state stability (ISS) irrespective of time-varying stiffness. Furthermore, the update rule of the stiffness is also suggested in such a way that the asymptotic stability is guaranteed under certain region conditions. Even when the update rule is not applied, the ISS is at least assured. In other words, the error is always bounded only if the external force/torque is bounded. In detail, two sufficient conditions offer the lower bound of stiffness and the upper bound of its time derivative. Simulation results show that the ISS of variable impedance control is achieved if the proposed sufficient conditions are satisfied. Also, we can confirm the asymptotic behavior in the simulation when the stiffness is updated according to the given rule.

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Zhang, Qiang, Xiaopeng Wei, and Jin Xu. "On Global Exponential Stability of Discrete-Time Hopfield Neural Networks with Variable Delays." Discrete Dynamics in Nature and Society 2007 (2007): 1–9. http://dx.doi.org/10.1155/2007/67675.

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Global exponential stability of a class of discrete-time Hopfield neural networks with variable delays is considered. By making use of a difference inequality, a new global exponential stability result is provided. The result only requires the delay to be bounded. For this reason, the result is milder than those presented in the earlier references. Furthermore, two examples are given to show the efficiency of our result.

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WU, XIAOFENG, YI ZHAO, and SHENG ZHOU. "LAG SYNCHRONIZATION OF CHAOTIC LUR'E SYSTEMS VIA REPLACING VARIABLES CONTROL." International Journal of Bifurcation and Chaos 15, no. 02 (February 2005): 617–35. http://dx.doi.org/10.1142/s021812740501220x.

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In this paper, we propose a method to research lag synchronization of the identical master-slave chaotic Lur'e systems via replacing variables control with time delay. By means of absolute stability theory, we prove two types of sufficient conditions for the lag synchronization: Lur'e criterion and frequency domain criterion. Based on the criteria, we suggest an optimization scheme to design the control variables. Applying the scheme to general Chua's circuits, we obtain the parameter ranges in which the master-slave Chua's circuits laggingly synchronize or not by varied single-variable control. Finally, we cite the examples by illustration of the results.

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Zang, Liguo, Shaoqing Yang, Chongyou Wu, Xingyu Wang, and Fei Teng. "Design and kinematics analysis of coordinated variable wheel-track walking mechanism." International Journal of Advanced Robotic Systems 17, no. 4 (July 1, 2020): 172988142093057. http://dx.doi.org/10.1177/1729881420930577.

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Wheeled walking mechanism has the advantages of high mobility and low rolling resistance, but it is easy to sink and slip when working in soft and muddy terrain. Tracked walking mechanism has the advantages of high passability and stability, but it has the problems of difficult steering and slow walking speed. In order to make the walking mechanism possess a combination of passability, stability, and mobility, a coordinated variable wheel-track walking mechanism was designed. The coordinated variable triangle track can change the landing area through the deformation structure to improve the ability of the walking mechanism to adapt to different terrains. The kinematics equation of the wheel-track walking mechanism was established, and the front wheel steering angle equation during motion was derived. Based on RecurDyn software, the motion simulation of the walking mechanism was carried out under the conditions of straight walking and turning on the flat ground, climbing hillsides, and crossing ditches. The simulation results show that the coordinated variable wheel-track walking mechanism has the mobility of wheeled walking mechanism and the passability and stability of the tracked walking mechanism. The stability and climbing ability of the wheel-track walking mechanism was better when the coordinated variable triangle track in the stretch state, and the mobility and steering ability was better in the contraction state.

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Jiang, Rui Min, Jun Zhou, and Jian Guo Guo. "A Variable Structure Attitude Control System Design Based on Finite Time Stability." Applied Mechanics and Materials 446-447 (November 2013): 1141–45. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.1141.

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A variable structure attitude control system design method that guarantees the finite-time stability is proposed for hypersonic vehicle attitude control. According to the characteristics of the hypersonic vehicle longitudinal attitude model, it is considered to comprise attack angle control loop and angular rate control loop. The attack angle controller and pitch angular rate controller based on variable structure control are designed respectively which ensure the finite-time stability. The finite-time stability of the whole attitude control system has been proved .The simulation results illustrated that the proposed attitude controller has good rapidity and robustness.

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NICHOLS, JOSEPH W., PETER J. SCHMID, and JAMES J. RILEY. "Self-sustained oscillations in variable-density round jets." Journal of Fluid Mechanics 582 (June 14, 2007): 341–76. http://dx.doi.org/10.1017/s0022112007005903.

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The stability properties of round variable-density low-Mach-number jets are studied by means of direct numerical simulation (DNS) and linear stability analysis. Fully three-dimensional DNS of variable-density jets, with and without gravity, demonstrate that the presence of buoyancy causes a more abrupt transition to turbulence. This effect helps to explain differences between normal gravity and microgravity jet diffusion flames observed in the laboratory.The complete spectrum of spatial eigenmodes of the linearized low-Mach-number equations is calculated using a global matrix method. Also, an analytic form for the continuous portion of this spectrum is derived, and used to verify the numerical method. The absolute instability of variable-density jets is confirmed using Brigg's method, and a comprehensive parametric study of the strength and frequency of this instability is performed. Effects of Reynolds number, the density ratio of ambient-to-jet fluid (S1), shear-layer thickness and Froude number are considered. Finally, a region of local absolute instability is shown to exist in the near field of the jet by applying linear stability analysis to mean profiles measured from DNS.

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Yuli Asmi, Rahman, Agus Siswanto, and Irwan Mahmudi. "Stability issues in presence variable distributed generation into radial distribution network." MATEC Web of Conferences 218 (2018): 01005. http://dx.doi.org/10.1051/matecconf/201821801005.

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Related to environmental issues resulting from the use of traditional energy sources, drive usage of renewable energy is increasing. Changes in the structure of the network will certainly affect the changes in voltage stability. In this paper, discuss the impact of the stability after distributed generation penetration whose its output intermittent relatively. The simulation based PSAT software and tested into IEEE 30 bus system. Observation of voltage deviation and SVSI-index on some load buses in conditions before and after integration of wind generation. Load condition is a very determining factor of bus voltage stability index. This relates to the active power and reactive power needs that must be injected by DG penetration.

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LIANG, JINLING, JINDE CAO, and JAMES LAM. "CONVERGENCE OF DISCRETE-TIME RECURRENT NEURAL NETWORKS WITH VARIABLE DELAY." International Journal of Bifurcation and Chaos 15, no. 02 (February 2005): 581–95. http://dx.doi.org/10.1142/s0218127405012235.

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In this paper, some global exponential stability criteria for the equilibrium point of discrete-time recurrent neural networks with variable delay are presented by using the linear matrix inequality (LMI) approach. The neural networks considered are assumed to have asymmetric weighting matrices throughout this paper. On the other hand, by applying matrix decomposition, the model is embedded into a cooperative one, the latter possesses important order-preserving properties which are basic to our analysis. A sufficient condition is obtained ensuring the componentwise exponential stability of the system with specific performances such as decay rate and trajectory bounds.

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Saber, Fatima Ezzahra, Mohamed Ouahi, and Abdelmjid Saka. "Estimation of Steering Wheel Angle and Vehicle Lateral State from Measured Lateral Forces." International Journal of Engineering Research in Africa 39 (November 2018): 14–31. http://dx.doi.org/10.4028/www.scientific.net/jera.39.14.

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This paper introduces a method to estimate the lateral dynamics parameters,which are valuable to the development of more complex and powerful driver assistance system. In the assumption of measured lateral forces, three state observer methods are designed to simultaneously estimate the steering angleas unknown input and vehicle lateral state variables. The stability conditionsof such observers are derived in terms of Linear Matrix Inequalities (LMI). Simulation results through Matlab/Simulink software based on data of the CALLAS vehicle simulator is used to evaluate the performance of observersbased on Unknown Input Observer (OEI).

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Zhang, Yue, Kuanquan Wang, Yongfeng Yuan, Dong Sui, and Henggui Zhang. "Effects of Maximal Sodium and Potassium Conductance on the Stability of Hodgkin-Huxley Model." Computational and Mathematical Methods in Medicine 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/761907.

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Hodgkin-Huxley (HH) equation is the first cell computing model in the world and pioneered the use of model to study electrophysiological problems. The model consists of four differential equations which are based on the experimental data of ion channels. Maximal conductance is an important characteristic of different channels. In this study, mathematical method is used to investigate the importance of maximal sodium conductanceg-Naand maximal potassium conductanceg-K. Applying stability theory, and takingg-Naandg-Kas variables, we analyze the stability and bifurcations of the model. Bifurcations are found when the variables change, and bifurcation points and boundary are also calculated. There is only one bifurcation point wheng-Nais the variable, while there are two points wheng-Kis variable. The (g-Na, g-K) plane is partitioned into two regions and the upper bifurcation boundary is similar to a line when bothg-Naandg-Kare variables. Numerical simulations illustrate the validity of the analysis. The results obtained could be helpful in studying relevant diseases caused by maximal conductance anomaly.

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SHERRATT, THOMAS N., and GILBERT ROBERTS. "The Stability of Cooperation Involving Variable Investment." Journal of Theoretical Biology 215, no. 1 (March 2002): 47–56. http://dx.doi.org/10.1006/jtbi.2001.2495.

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LOU, XUYANG, and BAOTONG CUI. "GLOBAL EXPONENTIAL STABILITY CONDITIONS FOR DELAYED PARABOLIC NEURAL NETWORKS WITH VARIABLE COEFFICIENTS." International Journal of Bifurcation and Chaos 17, no. 12 (December 2007): 4409–15. http://dx.doi.org/10.1142/s0218127407020063.

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In this paper, we present a class of delayed parabolic neural networks (DPNN) with variable coefficients. Some sufficient conditions for the global exponential stability of the DPNN with variable coefficients are derived by a method based on delay differential inequality. The method, which does not make use of Lyapunov functionals, is simple and effective for the stability analysis of DPNN with variable coefficients.

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Xu, Kelu, Ning Xie, Chengmin Wang, and Xudong Shi. "Modeling and Simulation of Variable Speed Variable Frequency Electrical Power System in More Electric Aircraft." Open Electrical & Electronic Engineering Journal 11, no. 1 (April 17, 2017): 87–98. http://dx.doi.org/10.2174/1874129001711010087.

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The More Electric Aircraft (MEA), Variable Speed Variable Frequency (VSVF) and Electrical Power System (EPS) has lager generating capacity and higher energy efficiency than the conventional Constant Speed Constant Frequency EPS, but the generators of MEA have to working as redundant power supplies to improve the power supply reliability, instead of parallel power supply. To study the steady state operation and power source change strategies under different fault conditions of VSVF EPS, the integrated structure of VSVF EPS is firstly illustrated and operating principles of components are theorized. The key components including variable frequency generators, Bus Power Control Unit, rectifiers and other supplementary elements are then simulated to build a comprehensive VSVF EPS model on the platform of Simulink and the power source change strategies are realized by logic units. Finally, the stability analysis in terms of normal operation is carried out in case studies and power source exchange strategies in different situations are summarized. The results show that the model proposed by the paper can be used to simulate MEA VSVF EPS and analyze its whole operational process effectively and efficiently.

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Journal articles on the topic 'Variable stability simulator'

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