Trends in the use of renewable energy sources to power buildings do not bypass objects for which maintaining a power supply is critical. This also applies to railway signal boxes. The aim of the research work was to t...
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Trends in the use of renewable energy sources to power buildings do not bypass objects for which maintaining a power supply is critical. This also applies to railway signal boxes. The aim of the research work was to test the multisource power supply system for a railway signal box with power electronic converter systems and a DC bus, built as part of the research project. The assumption for powering the railway signal box building was to use renewable sources, energy storage devices, and a 3 kV DC traction network as the second required power supply grid. Both power grids were connected by power electronic converters, and the power values of the converters were set based on the calculated power balance values using the values measured at the system nodes and the set constraints. The tests primarily tested the response of the power supply system to changes in load power and power generated by the photovoltaic source, as well as the charge level of the energy storage devices. The correctness of the control algorithm's operation was assessed based on the recorded power values in the power supply system nodes. The tests were carried out for 60 scenarios that covered all normal and emergency operating conditions. During the tests, delays in response to changes in the power supplied to the converters and the values of circular power flow between the power grid connections were recorded. The recorded delays ranged from 2 to about 50 s and the circular power flows did not exceed 1500 W. Based on the results of the tests, it was found necessary to improve the power measurement system in the power supply system nodes and to improve the quality of communication and the transmission time of measurement data transmission time.
This study aims to develop an accurate model of a charge equalization controller (CEC) that manages individual cell monitoring and equalizing by charging and discharging series-connected lithium-ion (Li-ion) battery c...
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This study aims to develop an accurate model of a charge equalization controller (CEC) that manages individual cell monitoring and equalizing by charging and discharging series-connected lithium-ion (Li-ion) battery cells. In this concept, an intelligent control algorithm is developed to activate bidirectional cell switches and control direct current (DC)-DC converter switches along with pulse width modulation (PWM) generation. Individual models of an electric vehicle (EV)-sustainable Li-ion battery, optimal power rating, a bidirectional flyback DC-DC converter, and charging and discharging controllers are integrated to develop a small-scale CEC model that can be implemented for 10 series-connected Li-ion battery cells. Results show that the charge equalization controller operates at 91% efficiency and performs well in equalizing both overdischarged and overcharged cells on time. Moreover, the outputs of the CEC model show that the desired balancing level occurs at 2% of state of charge difference and that all cells are operated within a normal range. The configuration, execution, control, power loss, cost, size, and efficiency of the developed CEC model are compared with those of existing controllers. The proposed model is proven suitable for high-tech storage systems toward the advancement of sustainable EV technologies and renewable source of applications.
Changes in the design of software algorithms for generating physical motion in flight simulators have typically been put forward on the grounds of improved motion cueing. Little attention hasbeen paid to more practica...
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This paper presents a new formation design that enables deployment of large distributed telescopes aligned with inertial targets in Earth orbit. To minimize propellant consumption, the proposed design uses a two-phase...
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This paper presents a new formation design that enables deployment of large distributed telescopes aligned with inertial targets in Earth orbit. To minimize propellant consumption, the proposed design uses a two-phase operations concept including observations and formation reconfigurations. During observations, a quasi-continuous control system negates the relative acceleration perpendicular to the line of sight, allowing the interspacecraft separation to passively drift. After each observation, a formation reconfiguration is performed to ensure proper alignment with the target at the start of the next observation. Absolute and relative orbits that minimize the total delta-v cost of a specified mission profile are derived in closed-form including effects of perturbations such as Earth oblateness. Additionally, a new stochastic model predictive control architecture is proposed that uses an optimal impulsive control algorithm to efficiently control the formation. The performance and value of the proposed formation design are demonstrated through high-fidelity simulations of a reference mission to image the exoplanet AEgir using a small starshade and telescope. The results of these simulations demonstrate both that the proposed formation design globally minimizes the delta-v cost of the mission and that the mission is feasible with current propulsion technologies.
In this study, an adaptive step size control algorithm incorporated in the continuation method (CM) is developed and combined with the filtered impulse function method based on aerostructural solvers and applied to tw...
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In this study, an adaptive step size control algorithm incorporated in the continuation method (CM) is developed and combined with the filtered impulse function method based on aerostructural solvers and applied to two aeroelastic analysis tasks concerned with modes tracking and parameter variation. The nonlinear limit cycle oscillation (LCO) of a NACA0012 airfoil with control surface free-play behavior is considered to illustrate how this adaptive step can achieve a balance between the stability, accuracy, and efficiency in the modes crossing region in modes tracking, the flutter point region in modes tracking, and the detrimental LCO region in parameter variation. It is shown that the computation time for modes tracking using this approach can be reduced by more than 65% while achieving almost the same estimate of the flutter speed as when using a fixed step size. The study also addresses a few unique and important phenomena in parameter variation such as modes jumping in the LCO curve that occur frequently using this adaptive step size algorithm. Furthermore, a combination of the modes tracking results to provide an estimate for the restart point for the CM solver to overcome the occurrence of possible extraneous solutions or divergence is proposed. The results of flutter analysis for linear structural system and nonlinear LCO analysis are validated against the results from experiments and the classical Theodorsen theory. The effect of viscous damping on the occurrence of detrimental LCO phenomena is also discussed and compared with the corresponding nondamping cases.
The effect of feedback flow control on the wake of a circular cylinder at a Reynolds number of 100 is investigated in direct numerical simulation. The control approach uses a low-dimensional model based on proper orth...
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The effect of feedback flow control on the wake of a circular cylinder at a Reynolds number of 100 is investigated in direct numerical simulation. The control approach uses a low-dimensional model based on proper orthogonal decomposition (POD). The controller applies linear proportional, and differential feedback to the estimate of the first POD mode. The range of validity of the POD model is explored in detail. Actuation is implemented as displacement of the cylinder normal to the flow. It is demonstrated that the threshold peak amplitude below which the control actuation ceases to be effective is in the order of 5% of the cylinder diameter. The closed-loop feedback simulations explore the effect of both fixed-phase and variable-phase feedback on the wake. Whereas fixed-phase feedback is effective in reducing drag and unsteady lift, it fails to stabilize this state once the low drag state has been reached. Variable-phase feedback, however, achieves the same drag and unsteady lift reductions while being able to stabilize the flow in the low drag state. In the low drag state, the neat wake is entirely steady, whereas the far wake exhibits vortex shedding at a reduced intensity. A drag reduction of 15% of the drag was achieved, and the unsteady lift force was lowered by 90%.
Sloshing of liquid fuel has significant implications in the accurate control of the spacecraft. Rapid simulation of the force and moment exerted by liquid against the spacecraft is rather important for the dynamics an...
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Sloshing of liquid fuel has significant implications in the accurate control of the spacecraft. Rapid simulation of the force and moment exerted by liquid against the spacecraft is rather important for the dynamics and control of the spacecraft. Fast numerical simulation models, especially those capable of dealing with violent liquid sloshing in the lunar soft-landing spacecraft with fluid merging and splitting, are required for real-time control algorithms. For this purpose, a modified smoothed particle hydrodynamics method, namely, noninertial smoothed particle hydrodynamics (NI-SPH), is proposed. In this method, noninertial coordinate system is used to derive transient external excitations to liquid. Meanwhile, the linear and angular momentum theorems of the particle system are adopted to calculate the force and moment exerted by liquid against the spacecraft, which avoids the accuracy loss of the integration of pressures. Furthermore, parallelization based on OpenMP is used to speed up the simulation. To show the accuracy and efficiency, results from the NI-SPH method are compared with those obtained by traditional computational fluid dynamics software, for several 3D liquid sloshing cases.
In the framework of a statistical model of an adaptive optics system (AOS) of phase conjugation, three algorithms based on an integrated mathematical approach are considered, each of them intended for minimisation of ...
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In the framework of a statistical model of an adaptive optics system (AOS) of phase conjugation, three algorithms based on an integrated mathematical approach are considered, each of them intended for minimisation of one of the following characteristics: the sensor error (in the case of an ideal corrector), the corrector error (in the case of ideal measurements) and the compensation error (with regard to discreteness and measurement noises and to incompleteness of a system of response functions of the corrector actuators). Functional and statistical relationships between the algorithms are studied and a relation is derived to ensure calculation of the mean-square compensation error as a function of the errors of the sensor and corrector with an accuracy better than 10 %. Because in adjusting the AOS parameters, it is reasonable to proceed from the equality of the sensor and corrector errors, in the case the Hartmann sensor is used as a wavefront sensor, the required number of actuators in the absence of the noise component in the sensor error turns out 1.5 - 2.5 times less than the number of counts, and that difference grows with increasing measurement noise.
Vibration energy harvesting (VeH) techniques by means of intentionally designed mechanisms have been used in the last decade for frequency bandwidth improvement under excitation for adequately high-vibration amplitude...
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Vibration energy harvesting (VeH) techniques by means of intentionally designed mechanisms have been used in the last decade for frequency bandwidth improvement under excitation for adequately high-vibration amplitudes. Oil, gas, and water are vital resources that are usually transported by extensive pipe networks. Therefore, wireless self-powered sensors are a sustainable choice to monitor in-pipe system applications. The mechanism, which is intended for water pipes with diameters of 2-5 inches, contains a piezoelectric beam assembled to the oscillating body. A novel U-shaped geometry of an underwater energy harvester has been designed and implemented. Then, the results have been compared with the traditional circular cylinder shape. At first, a numerical study has been carried at Reynolds numbers Re = 3000, 6000, 9000, and 12,000 in order to capture as much as kinetic energy from the water flow. Consequently, unsteady Reynolds Averaged Navier-Stokes (URANS)-based simulations are carried out to investigate the dynamic forces under different conditions. In addition, an Adaptive Differential Evolution (JADE) multivariable optimization algorithm has been implemented for the optimal design of the harvester and the maximization of the power extracted from it. The results show that the U-shaped geometry can extract more power from the kinetic energy of the fluid than the traditional circular cylinder harvester under the same conditions.
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