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    Aircraft performance optimization using fish-like locomotion

    , Article AIAA Atmospheric Flight Mechanics Conference and Exhibit ; 2008 ; 9781563479458 (ISBN) Pourtakdoust, S. H ; Mortazavi, S. H ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2008
    Abstract
    In this article, an optimal maneuver structure is proposed to improve the cruise fuel consumption performance of a transport category aircraft. The maneuver is taken by analogy to the natural phenomena of fish movement in the water. By using fish-like locomotion and implementing it on a transport category aircraft, better performance economy has been realized in cruise flight. The maneuver structure and the required control actions are extracted using optimal control theory. The power required during a specified cruise time span is taken as the merit function in the optimal control formulation. The cost savings associated with this type of optimized periodic maneuver during cruise is... 

    An extension of ant colony system to continuous optimization problems

    , Article 4th International Workshop on Ant Colony Optimization and Swarm Intelligence, ANTS 2004, Brussels, 5 September 2004 through 8 September 2004 ; Volume 3172 LNCS , 2004 , Pages 294-301 ; 03029743 (ISSN); 3540226729 (ISBN); 9783540226727 (ISBN) Pourtakdoust, S. H ; Nobahari, H ; Sharif University of Technology
    Springer Verlag  2004
    Abstract
    A new method for global minimization of continuous functions has been proposed based on Ant Colony Optimization. In contrast with the previous researches on continuous ant-based methods, the proposed scheme is purely pheromone-based. The algorithm has been applied to several standard test functions and the results are compared with those of two other meta-heuristics. The overall results are compatible, in good agreement and in some cases even better than the two other methods. In addition the proposed algorithm is much simpler, which is mainly due to its simpler structure. Also it has fewer control parameters, which makes the parameter settings process easier than many other methods. © 2004... 

    A new hybrid approach for dynamic continuous optimization problems

    , Article Applied Soft Computing Journal ; Volume 12, Issue 3 , 2012 , Pages 1158-1167 ; 15684946 (ISSN) Karimi, J ; Nobahari, H ; Pourtakdoust, S. H ; Sharif University of Technology
    2012
    Abstract
    A new hybrid approach for dynamic optimization problems with continuous search spaces is presented. The proposed approach hybridizes efficient features of the particle swarm optimization in tracking dynamic changes with a new evolutionary procedure. In the proposed dynamic hybrid PSO (DHPSO) algorithm, the swarm size is varied in a self-regulatory manner. Inspired from the microbial life, the particles can reproduce infants and the old ones die. The infants are especially reproduced by high potential particles and located near the local optimum points, using the quadratic interpolation method. The algorithm is adapted to perform in continuous search spaces, utilizing continuous movement of... 

    An adaptive unscented Kalman filter for quaternion-based orientation estimation in low-cost AHRS

    , Article Aircraft Engineering and Aerospace Technology ; 2007 , Pages 485-493 ; 00022667 (ISSN) ; Volume 79, Issue 5 Pourtakdoust, S. H ; Ghanbarpour Asl, H ; Sharif University of Technology
    2007
    Abstract
    Purpose - This paper aims to develop an adaptive unscented Kalman filter (AUKF) formulation for orientation estimation of aircraft and UAV utilizing low-cost attitude and heading reference systems (AHRS). Design/methodology/approach - A recursive least-square algorithm with exponential age weighting in time is utilized for estimation of the unknown inputs. The proposed AUKF tunes its measurement covariance to yield optimal performance. Owing to nonlinear nature of the dynamic model as well as the measurement equations, an unscented Kalman filter (UKF) is chosen against the extended Kalman filter, due to its better performance characteristics. The unscented transformation of the UKF is shown... 

    A deep learning approach for the solution of probability density evolution of stochastic systems

    , Article Structural Safety ; Volume 99 , 2022 ; 01674730 (ISSN) Pourtakdoust, S. H ; Khodabakhsh, A. H ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    Derivation of the probability density evolution provides invaluable insight into the behavior of many stochastic systems and their performance. However, for most real-time applications, numerical determination of the probability density evolution is a formidable task. The latter is due to the required temporal and spatial discretization schemes that render most computational solutions prohibitive and impractical. In this respect, the development of an efficient computational surrogate model is of paramount importance. Recent studies on the physics-constrained networks show that a suitable surrogate can be achieved by encoding the physical insight into a deep neural network. To this aim, the... 

    Dynamic modeling and structural reliability of an aeroelastic launch vehicle

    , Article Advances in Aircraft and Spacecraft Science ; Volume 9, Issue 3 , 2022 , Pages 263-M278 ; 2287528X (ISSN) Pourtakdoust, S. H ; Khodabaksh, A. H ; Sharif University of Technology
    Techno-Press  2022
    Abstract
    The time-varying structural reliability of an aeroelastic launch vehicle subjected to stochastic parameters is investigated. The launch vehicle structure is under the combined action of several stochastic loads that include aerodynamics, thrust as well as internal combustion pressure. The launch vehicle's main body structural flexibility is modeled via the normal mode shapes of a free-free Euler beam, where the aerodynamic loadings on the vehicle are due to force on each incremental section of the vehicle. The rigid and elastic coupled nonlinear equations of motion are derived following the Lagrangian approach that results in a complete aeroelastic simulation for the prediction of the... 

    Aerodynamic shape optimization of unguided projectiles using Ant Colony Optimization and Genetic Algorithm

    , Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 2 , 2006 , Pages 698-706 ; 9781604232271 (ISBN) Nobahari, H ; Nabavi, S. Y ; Pourtakdoust, S. H ; Sharif University of Technology
    2006
    Abstract
    The problem of aerodynamic shape optimization of unguided projectiles has been investigated. Two stochastic optimization methods have been applied to solve the problem. These include a Genetic Algorithm (GA) and the recently developed Continuous Ant Colony System (CACS), which is based on the well-known Ant Colony Optimization meta-heuristic. The objective function is defined as the summation of normal force coefficients over a set of given flight conditions. An engineering code (EC) is used to calculate the normal force coefficients over the flight conditions. The obtained results of CACS+EC are compared with those of GA+EC, as well as the results of a previous work (GA +AeroDesign). The... 

    Performance of a novel heat based model for spacecraft attitude estimation

    , Article Aerospace Science and Technology ; Volume 70 , 2017 , Pages 317-327 ; 12709638 (ISSN) Labibian, A ; Alikhani, A ; Pourtakdoust, S. H ; Sharif University of Technology
    2017
    Abstract
    This paper presents a novel heat based measurement model for attitude determination (AD) using temperature data via two filtering techniques. Within the space environment, the Sun and Earth are considered as the major sources of external radiation that affect satellite surface temperature. In order to perform the required AD task, the satellite surface temperatures are related to its attitude via a proposed heat model (HM), assuming that the satellite navigational data is available. The proposed HM relates the net heat flux of three satellite orthogonal surfaces to its attitude. Filtering implementation of the proposed HM using the Unscented Kalman Filter (UKF) for AD is the key contribution... 

    Covariance-based multiple-impulse rendezvous design

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 55, Issue 5 , 2019 , Pages 2128-2137 ; 00189251 (ISSN) Shakouri, A ; Kiani, M ; Pourtakdoust, S. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    A novel trajectory design methodology is proposed in the current work to minimize the state uncertainty in the crucial mission of spacecraft rendezvous. The trajectory is shaped under constraints utilizing a multiple-impulse approach. State uncertainty is characterized in terms of covariance, and the impulse time as the only effective parameter in uncertainty propagation is selected to minimize the trace of the covariance matrix. Furthermore, the impulse location is also adopted as the other design parameter to satisfy various translational constraints of the space mission. Efficiency and viability of the proposed idea have been investigated through some scenarios that include constraints on... 

    A new shape-based multiple-impulse strategy for coplanar orbital maneuvers

    , Article Acta Astronautica ; Volume 161 , 2019 , Pages 200-208 ; 00945765 (ISSN) Shakouri, A ; Kiani, M ; Pourtakdoust, S. H ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    A new shape-based geometric method (SBGM) is proposed for generation of multi-impulse transfer trajectories between arbitrary coplanar oblique orbits via a heuristic algorithm. The key advantage of the proposed SBGM includes a significant reduction in the number of design variables for an N-impulse orbital maneuver leading to a lower computational effort and energy requirement. The SBGM generates a smooth transfer trajectory by joining a number of confocal elliptic arcs such that the intersections share common tangent directions. It is proven that the well-known classic Hohmann transfer and its bi-elliptic counterpart between circular orbits are special cases of the proposed SBGM. The... 

    Reliability analysis of composite anisogrid lattice interstage structure

    , Article Mechanics Based Design of Structures and Machines ; 2020 Raouf, N ; Davar, A ; Pourtakdoust, S. H ; Sharif University of Technology
    Bellwether Publishing, Ltd  2020
    Abstract
    Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and... 

    Design of a supervisory controller for CLOS guidance with lead angle

    , Article Aircraft Engineering and Aerospace Technology ; Volume 78, Issue 5 , 2006 , Pages 395-406 ; 00022667 (ISSN) Nobahari, H ; Alasty, A ; Pourtakdoust, S. H ; Sharif University of Technology
    2006
    Abstract
    Purpose - The purpose of this paper is to propose a supervisory command-to-line-of-sight guidance law with lead angle which keeps the missile flight within the tracking beam. Design/methodology/approach - A nonlinear supervisory controller is designed and coupled with the main sliding mode controller in the form of an additional control signal. The supervisory control signal is activated when the beam angle constraint goes to be violated. Initially a supervisory controller is designed using nonlinear control theory. Subsequently the main tracking controller is designed using sliding mode approach which forces the missile to fly along the desired line-of-sight. The stability of the... 

    Design of a supervisory controller for CLOS guidance with lead angle

    , Article AIAA Guidance, Navigation, and Control Conference 2005, San Francisco, CA, 15 August 2005 through 18 August 2005 ; Volume 4 , 2005 , Pages 3083-3095 ; 1563477378 (ISBN); 9781563477379 (ISBN) Nobahari, H ; Alasty, A ; Pourtakdoust, S. H ; Sharif University of Technology
    2005
    Abstract
    This paper proposes a supervisory Command to Line-of-Sight (CLOS) guidance law with lead angle. The proposed scheme guarantees the missile to fly within the beam, when there is a beam angle constraint. In this regard a supervisory controller is coupled with a main Sliding Mode Controller (SMC). The supervisory control signal is activated when the beam constraint goes to be violated. First the supervisory controller is designed based on a recent idea on how the states of a nonlinear system with local stable controller can be controlled to stay within the domain of attraction. Then a sliding mode controller is designed, as the main tracking controller, to force the missile to fly along the... 

    Reliability analysis of composite anisogrid lattice interstage structure

    , Article Mechanics Based Design of Structures and Machines ; Volume 50, Issue 9 , 2022 , Pages 3322-3330 ; 15397734 (ISSN) Raouf, N ; Davar, A ; Pourtakdoust, S. H ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and... 

    A modified unsteady-nonlinear aeroelastic model for flapping wings

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2022 ; 09544100 (ISSN) Pourtakdoust, S. H ; Zare, H ; Bighashdel, A ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is... 

    A modified unsteady-nonlinear aeroelastic model for flapping wings

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 237, Issue 4 , 2023 , Pages 751-768 ; 09544100 (ISSN) Pourtakdoust, S. H ; Zare, H ; Bighashdel, A ; Sharif University of Technology
    SAGE Publications Ltd  2023
    Abstract
    A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is... 

    An analytical approach in dynamic calibration of strain gauge balances for aerodynamic measurements

    , Article IEEE Sensors Journal ; Volume 18, Issue 9 , May , 2018 , Pages 3572-3579 ; 1530437X (ISSN) Bighashdel, A ; Zare, H ; Pourtakdoust, S. H ; Sheikhy, A. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Strain gauge balances (SGBs) are efficient and accurate means of static force measurement. However, due to their inherent elastic characteristics, they lack desired performance when used in dynamic loading conditions. In this paper, a novel technique is presented that remedies their inherent weakness in measuring dynamic periodic forces. The proposed method produces a correction factor to compensate the measured loading in dynamic situations. For this purpose, first an analytical investigation is performed to determine the structural dynamic behavior of a typical SGB system via the modal approach. This analytical investigation leads to identification of the structural interference effects... 

    On-line orbit and albedo estimation using a strong tracking algorithm via satellite surface temperature data

    , Article IEEE Transactions on Aerospace and Electronic Systems ; 9 December , 2020 Nasihati Gourabi, F ; Kiani, M ; Pourtakdoust, S. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    The Earth albedo factor (EAF) is a major required parameter for the thermal analysis of low Earth orbit (LEO) satellites. Satellites receive variable albedo radiation as they orbit around the Earth that is heavily dependent on the Earth's local terrain as well as the instantaneous cloud coverage. However, for satellite thermal balancing and control analysis, a constant mean EAF is usually taken based on the orbital parameters that could potentially introduce erroneous results. Recent advances in temperature-based orbit estimation (TBOE) algorithms have revealed a significant sensitivity concerning EAF giving rise to the idea of its on-line estimation for added accuracy. In this sense, a... 

    Satellite pose estimation using Earth radiation modeled by artificial neural networks

    , Article Advances in Space Research ; Volume 70, Issue 8 , 2022 , Pages 2195-2207 ; 02731177 (ISSN) Nasihati Gourabi, F ; Kiani, M ; Pourtakdoust, S. H ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    The thermal energy received by each surface of an Earth-orbiting satellite strongly depends on its position and orientation. In this sense, simultaneous orbit and attitude estimation (SOAE) using the surface temperature data has been focused in the present study. The Earth infrared (IR) radiation and the Earth's top-of-atmosphere (TOA) albedo are two key sources of radiation affecting the satellite surface temperature rate. The Earth's radiation information has been monitored for the past two decades by the Clouds and the Earth's Radiant Energy System (CERES) project, producing a comprehensive set of Earth radiation budget (ERB) data for climate, weather and applied science research. The... 

    Optimal approach to halo orbit control

    , Article AIAA Guidance, Navigation, and Control Conference and Exhibit 2003, Austin, TX, 11 August 2003 through 14 August 2003 ; 2003 ; 9781563479786 (ISBN); 9781624100901 (ISBN) Rahmani, A ; Jalali, M. A ; Pourtakdoust, S. H ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2003
    Abstract
    Three-dimensional orbits in the vicinity of the collinear libration points of the Sun-Earth/Moon barycenter system are currently being considered for use with a number of missions planed for 2000 and beyond. Since such libration point trajectories are, in general, unstable, spacecraft moving on these paths must use some form of trajectory control to remain close to their nominal orbit. In this paper, circular restricted three body problem is reviewed and a numerical method to control spacecrafts on periodic halo orbits around L1 and L2 collinear points of the Sun-Earth/Moon barycenter system is investigated. The control approach is based on the optimal control theory and implements variation...