Researchers implement and analyze command governors for maneuver limiting in the most complex aircraft models available at Saab Aeronautics, surpassed only by real flight testing. The design is made for an aircraft mo...
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Researchers implement and analyze command governors for maneuver limiting in the most complex aircraft models available at Saab Aeronautics, surpassed only by real flight testing. The design is made for an aircraft model with nonlinear aerodynamics that also vary with speed and altitude, and the implementation is done in the Saab Aeronautics development simulator for the JAS 39 Gripen fighter aircraft. The ARES model is linearized around trimmed level flight at 25 different envelope points in the subsonic region. The short period dynamics is extracted from the linearized model and used for control law design.
Modeling of grinding workpiece surface topography is the foundational research about the service performance of the workpiece surface. In this paper, we focus on the real surface topography modeling of the grinding wh...
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Modeling of grinding workpiece surface topography is the foundational research about the service performance of the workpiece surface. In this paper, we focus on the real surface topography modeling of the grinding wheel and the digital generation method of the grinding workpiece surface based on the real surface of the grinding wheel. First of all, the grinding wheel surface is restructured based on the measured grinding wheel surface data after completing the filtering process and getting the characteristic parameters from the moving-average model to solve inaccuracy problem. According to the grinding kinematics, the motion trajectory equations of the abrasive grains are established. The surface topography of the workpiece is generated by the Boolean operation, and the optimization algorithm is used to solve the problem of large amounts of calculation and long operation time in the numerical modeling of 3D surface topography. Finally, the accuracy of the model is verified by comparing with the characteristic parameters of the groove and the roughness parameters of the experimental surface, which are the most important parameters in the surface topography.
The design and optimization of lifting surfaces on an aircraft is a difficult problem, and is typically performed using computational fluid dynamics, which is an expensive process. This paper demonstrates the capabili...
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This paper put forward a general framework for intelligent optimization/search based on benchmarking philosophy, and whose "intelligence" is mainly dependent on the organizing tactics rather than the probabi...
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This paper put forward a general framework for intelligent optimization/search based on benchmarking philosophy, and whose "intelligence" is mainly dependent on the organizing tactics rather than the probability rules of its operators. According to the guiding principles and the specific methods of benchmarking, it is easy to design efficient optimization/search algorithms for various complex problems in science, engineering, and management.
Newton-Raphson-based flying capacitor multilevel inverter modeling is investigated for capacitor voltage balancing. Without using voltage feedback, Newton-Raphson method determines the best switching pattern for maint...
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Newton-Raphson-based flying capacitor multilevel inverter modeling is investigated for capacitor voltage balancing. Without using voltage feedback, Newton-Raphson method determines the best switching pattern for maintaining nil mean current in all capacitors, hence minimizing the capacitor voltage fluctuation and eliminating certain harmonic orders. Flying capacitor multilevel inverter (FCMI) modeling is developed to work with the selective harmonic elimination (SHE) technique to obtain a programmable pulse generator for multilevel inverter commutation cell control. Theoretical results are verified by experiments and simulations for a flying capacitor four-level inverter. Results show that the proposed method does effectively eliminate a number of specific low order harmonics, and the output voltage is resulted in low total harmonic distortion and with balanced flying capacitors.
Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize its output power. A new MPPT system has been suggested for PV-DC motor pump system by designing two PI controllers. The first one is...
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Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize its output power. A new MPPT system has been suggested for PV-DC motor pump system by designing two PI controllers. The first one is used to reach MPPT by monitoring the voltage and current of the PV array and adjusting the duty cycle of the DC/DC converter. The second PI controller is designed for speed control of DC series motor by setting the voltage fed to the DC series motor through another DC/DC converter. The suggested design problem of MPPT and speed controller is formulated as an optimization task which is solved by artificial bee colony (ABC) to search for optimal parameters of PI controllers. Simulation results have shown the validity of the developed technique in delivering MPPT to DC series motor pump system under atmospheric conditions and tracking the reference speed of motor. Moreover, the performance of the ABC algorithm is compared with genetic algorithm for various disturbances to prove its robustness.
This paper proposes a novel two-stage Energy Management System (EMS) that is suitable for smallscale grid-connected electrical systems, such as smart homes and buildings, encompassing renewable generators and electric...
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This paper proposes a novel two-stage Energy Management System (EMS) that is suitable for smallscale grid-connected electrical systems, such as smart homes and buildings, encompassing renewable generators and electrical storage. In such systems, forecast errors of renewable generation and energy demand profiles result in a significant uncertainty on the power exchanged between the end users and the utility grid. The proposed EMS reduces such demand uncertainty and the electricity bill for end users, at the same time. The main novelty of the proposed technique is that it does not require any change in pricing plans or user's habits, differently from classical Demand Side Management schemes. Moreover, thanks to the increased predictability of the exchanged power, utility providers are facilitated in managing the wholesale risk, for example by designing appropriate pricing schemes. The proposed EMS is based on an optimization algorithm. It starts from profiles of renewable generation and load demand, which are obtained by a forecasting method based on suitably chosen and trained Artificial Neural Networks. Furthermore, it has been designed to be suitable for an embedded implementation on low-performance processing platforms. The proposed EMS has been validated using datasets coming from monitoring campaigns. The considered case study is a smart home with an annual energy consumption of about 4500 kWh. It encompasses a grid-connected electrical distribution power plant with a 3 kW photovoltaic generator and a 4.6 kWh battery electrical storage system. The results obtained for a sample month demonstrate the effectiveness of the approach. As a matter of fact, the demand uncertainty is only 4.75% against a cumulative forecast error of 10.35% expressed as normalized root mean square error. At the same time, the end user's cash flow is 2.43% higher than the income obtained without an EMS. (C) 2017 Elsevier B.V. All rights reserved.
An effective performance-matching design framework for solid rocket motor tailored toward satisfying various thrust-performance requirements is presented in this research paper through an innovative and specialized ge...
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An effective performance-matching design framework for solid rocket motor tailored toward satisfying various thrust-performance requirements is presented in this research paper through an innovative and specialized general-design approach developed to evaluate the general-design parameters. During the general-design stage, a combination of grain web and area ratio is selected as the design variables to be adjusted to obtain the general parameters. Based on the general parameters obtained, a grain-design stage incorporates the level-set method and simulates solid-propellant evolution and internal ballistic analysis, thereby obtaining the thrust performance. Grain-design effectiveness is determined by how closely the designed solid-rocket-motor performance matches and compares to a prespecified thrust curve. An efficient sequential-field-approximate-optimization algorithm is proposed and used to minimize the average rms error between the desired and designed thrusts. Validation of the proposed design framework is carried out by evaluating motor cases possessing different thrust requirements, and results obtained highlight the proposed framework as a practical and efficient strategy for solid-rocket-motor designs.
This communication presents a simple and useful technique to suppress the radiation sidelobe levels (SLLs) of reflector antennas by embedding reflecting elements around the edge boundary. Due to the fact that sidelobe...
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This communication presents a simple and useful technique to suppress the radiation sidelobe levels (SLLs) of reflector antennas by embedding reflecting elements around the edge boundary. Due to the fact that sidelobes mainly arise from the edge diffractions, the reflecting elements can alter the phase distribution of induced currents along the edge boundary, and therefore reduce the sidelobes through the destructive cancellation of fields radiated from these elements. The desired phases are found through the implementation of pattern synthesis technique such as genetic algorithm to optimize the SLLs. This technique of edge current phase alternation may be employed, in conjunction with using a tapered feed radiation to illuminate the reflector, to control both amplitudes and phases of edge currents. Thus, the edge diffraction mechanism may be better controlled to optimize SLLs. In this communication, both resonant and nonresonant types of metallic elements are implemented and compared to illustrate their characteristics of radiations in SLL suppression. This technique is particularly useful to suppress the SLLs within a local angular region. Numerical results based on the method of moment analysis are presented to validate the feasibility.
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