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Publisher: Elsevier   (Total: 3042 journals)

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Showing 1 - 200 of 3042 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 19, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 16, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 81, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 23, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 27, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 328, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription  
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 205, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 9, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 22, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 5, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 3)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 124, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 25, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 21, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 25, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 8, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 39, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 40, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 45, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 12)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 20, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 34, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 4)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 5, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 21, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 7, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 58)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 2, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 339, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 6, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 29, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 15)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 43, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 308, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 7, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 422, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 38, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 50, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 10, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 6)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 6, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 46, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 3)
American Heart J.     Hybrid Journal   (Followers: 47, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 44, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 34, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 30, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 24, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 44, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 179, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 54, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 2)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 23, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 23, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 33, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 53, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 5)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 2, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 38, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 160, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 10)
Anesthésie & Réanimation     Full-text available via subscription  
Anesthesiology Clinics     Full-text available via subscription   (Followers: 21, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 153, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Aerospace Science and Technology
  [SJR: 0.816]   [H-I: 49]   [308 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1270-9638
   Published by Elsevier Homepage  [3042 journals]
  • Surrogate modeling for the main landing gear doors of an airbus passenger
    • Authors: D. Viúdez-Moreiras; M. Martín; R. Abarca; E. Andrés; J. Ponsín; F. Monge
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): D. Viúdez-Moreiras, M. Martín, R. Abarca, E. Andrés, J. Ponsín, F. Monge
      Main Landing Gear Doors of commercial aircraft are affected by significant dynamic loads during flight, mainly due to the aerodynamic excitation. Thus, an accurate prediction early in the design results an important matter to select the optimal aerodynamic configuration. Therefore, a significant budget is invested by manufacturers in order to test the aerodynamic performance by means of wind tunnel and flight testing. However, the high cost associated to these tests restricts the number of test cases that can be performed. This paper presents a new surrogate model for the unsteady aerodynamics characterized by wind tunnel testing, in order to predict the aerodynamic effect in previously untested conditions, and in this way, to allow a first stage exploration of new areas in the design space, without the need of expensive wind tunnel or flight testing. Experimental results within the Main Landing Gear Doors of an Airbus Long Range Passenger Aircraft are presented, showing the benefits of this methodology.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.04.021
      Issue No: Vol. 68 (2017)
  • A health evaluation method of multicopters modeled by Stochastic Hybrid
    • Authors: Zhiyao Zhao; Quan Quan; Kai-Yuan Cai
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Zhiyao Zhao, Quan Quan, Kai-Yuan Cai
      For multicopters, failures may abort missions, crash multicopters, and moreover, injure or even kill people. In order to guarantee flight safety, a system of prognostics and health management should be designed to prevent or mitigate unsafe consequences of multicopter failures, where health evaluation is an indispensable module. This paper proposes a health evaluation method of multicopters based on Stochastic Hybrid System (SHS). In the SHS model, different working conditions (health statuses) of multicopters are modeled as discrete states, and system behaviors of different working conditions are modeled as continuous dynamics under discrete states. Then, the health of multicopters is quantitatively measured by a definition of health degree, which is a probability measure describing an extent of system degradation from an expected normal condition. On this basis, the problem of multicopter's health evaluation is transformed to a hybrid state estimation problem. In this case, a modified interacting-multiple-model algorithm is proposed to estimate the real-time distribution of hybrid state, and evaluate multicopter's health. Finally, a case study of multicopter with sensor anomalies is presented to validate the effectiveness of the proposed method.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.011
      Issue No: Vol. 68 (2017)
  • Inverse optical flow based guidance for UAV navigation through urban
    • Authors: Pooja Agrawal; Ashwini Ratnoo; Debasish Ghose
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Pooja Agrawal, Ashwini Ratnoo, Debasish Ghose
      The paper proposes a vision based guidance strategy for an unmanned aerial vehicle (UAV) navigating through urban canyons. The UAV has a single forward facing camera and relies on optical flow computed from the sequence of images captured by the camera. The steering command is inversely proportional to the optical flow difference between the two sides of the image. This leads to high turning and safe motion while directly facing an obstacle or a wall. Analysis is carried out for infinite and finite length obstacles to highlight the obstacle avoidance properties of the proposed strategy as compared to a widely used existing strategy. Realistic simulation studies with straight, L, and T shape canyons and combination of them show the viability of the proposed strategy while navigating through urban canyons.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.012
      Issue No: Vol. 68 (2017)
  • An axiomatic/asymptotic evaluation of best theories for isotropic metallic
           and functionally graded plates employing non-polynomic functions
    • Authors: S. Candiotti; J.L. Mantari; J. Yarasca; M. Petrolo; E. Carrera
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): S. Candiotti, J.L. Mantari, J. Yarasca, M. Petrolo, E. Carrera
      This paper presents Best Theory Diagrams (BTDs) constructed from various non-polynomial terms to identify best plate theories for metallic and functionally graded plates. The BTD is a curve that provides the minimum number of unknown variables necessary to obtain a given accuracy or the best accuracy given by a given number of unknown variables. The plate theories that belong to the BTD have been obtained using the Axiomatic/Asymptotic Method (AAM). The different plate theories reported are implemented by using the Carrera Unified Formulation (CUF). Navier-type solutions have been obtained for the case of simply supported plates loaded by a bisinusoidal transverse pressure with different length-to-thickness ratios. The BTDs built from non-polynomial functions are compared with BTDs using Maclaurin expansions. The results suggest that the plate models obtained from the BTD using non-polynomial terms can improve the accuracy obtained from Maclaurin expansions for a given number of unknown variables of the displacement field.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.003
      Issue No: Vol. 68 (2017)
  • Trustable UAV for higher level control architectures
    • Authors: Chimpalthradi R. Ashokkumar; George W.P. York; Scott Gruber
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Chimpalthradi R. Ashokkumar, George W.P. York, Scott Gruber
      Future unmanned air vehicles (UAVs) are expected to operate under the supervision of higher level control architectures that give instructions to engage and direct the UAV to perform a certain task. These instructions allow the UAV to make decisions along any point of its trajectory and then modify its flight path by using a sequence of reconfigurable controllers at the decision points. Assume that the UAV is flying with a transient and with a steady state contributing to a flight control mode (FCM) such as an altitude hold, an ascent and a descent mode when only longitudinal aircraft dynamics is considered. At the time of a decision, if the UAV bifurcates from its original (or parent) FCM in an effort to acquire a new (or a child) FCM and comply with a higher level instruction, then the UAV is said to be trustable. Mathematically, at the time of bifurcation where controller reconfiguration takes place, trustable UAV with the child trajectory must originate from a region where the stability regions of the parent and child trajectories intersect. In this paper, a procedure to reconfigure such FCMs and their controllers that develop the trustable UAV are presented. A three degree of freedom UAV is considered to illustrate the trustable UAV.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.013
      Issue No: Vol. 68 (2017)
  • Deployment analysis for space cable net structures with varying topologies
           and parameters
    • Authors: Rui Nie; Baiyan He; Lianhong Zhang; Yonggang Fang
      Pages: 1 - 10
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Rui Nie, Baiyan He, Lianhong Zhang, Yonggang Fang
      Cable net structures are widely used in space deployable devices. For truss-mesh reflector antennas, the cable net turns from a relaxed stage to a full tensioned state and forms a required functional surface during the deployment process. The deployment analysis of cable net structures is indispensable to the calculation of the deploying force, and meanwhile, it also provides valuable references for the cable net design. But unfortunately, at present there is still no effective way to analyze the deployment process of space cable net structures with varying topologies and parameters. In this paper, the parameterized deployment analysis for space cable net structures considering geometric nonlinearity, topological diversity and the cable's sag is presented. Firstly, the cable net is discretized into finite cable elements, and serial numbering rule is proposed to obtain the corresponding topological matrix. Then, governing equations are formulated and further assembled by matrix transformation theory, and trust-region algorithm is used to solve the system equations. In the calculating, the cable's stiffness is determined by its slack or tensional state, and the coupling between the deployment of trusses and the deformation of cable nets are considered by updating the coordinate values of boundary nodes in each time step. We use our method to analyze three case studies and the results agree with experiment data in previous literature. The elastic energies of cable nets during the deployment are calculated and the “self-stretching” process is discussed. The deployment analysis in this research is general for space cable net structures used in mesh reflector antennas.

      PubDate: 2017-05-20T16:24:05Z
      DOI: 10.1016/j.ast.2017.05.008
      Issue No: Vol. 68 (2017)
  • Extreme aircraft maneuver under sudden lateral CG movement: Modeling and
    • Authors: Bijoy K. Mukherjee; Manoranjan Sinha
      Pages: 11 - 25
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Bijoy K. Mukherjee, Manoranjan Sinha
      Hitherto unaddressed issue of six degree-of-freedom transient dynamics during asymmetric ejection of stores with finite velocity, onboard a combat aircraft, is addressed and modeled from the first principle. Further, the effect of asymmetric center-of-gravity shift, post ejection of the store, on some complex high angle-of-attack maneuvers such as cobra and Herbst is also investigated. It is shown that the performance of the maneuvers drastically deteriorates when carried out with controller designed for the pre-ejection symmetric c . g . based dynamics. In order to improve the deteriorated performance, two new control schemes based on the standard sliding mode technique are proposed. The first sliding control is designed based on a simple ad-hoc model for the asymmetric dynamics, whereas the states are propagated using the exact model developed. It is shown that using this scheme the lost maneuver performance can be reasonably recovered. The second control scheme is formulated using an accurate asymmetric dynamics. This proposed control scheme almost completely recovers the original maneuver performance.

      PubDate: 2017-05-20T16:24:05Z
      DOI: 10.1016/j.ast.2017.04.030
      Issue No: Vol. 68 (2017)
  • Aerodynamic shape optimization of a transonic fan by an adjoint-response
           surface method
    • Authors: Xiao Tang; Jiaqi Luo; Feng Liu
      Pages: 26 - 36
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Xiao Tang, Jiaqi Luo, Feng Liu
      An adjoint-response surface method is developed to provide efficient surrogate model in a parametrized design space for aerodynamic optimization of turbomachinery blades. Our goal is to improve the adiabatic efficiency or equivalently reduce the entropy generation through blade row with a mass flow rate constraint. Firstly, an aerodynamic sensitivity analysis is conducted with a viscous adjoint method to find the suitable number of control points on the suction surface of the transonic NASA rotor 67. Then quadratic polynomial (QP) based response surfaces of 4, 6 and 8 parameters are examined to validate the advantages of the gradient-enhanced model. In the following 24-parameter aerodynamic design optimization case, a steepest descent optimization (SDO) based on adjoint gradient is conducted, then QP based response surface model is constructed using both the values of cost function and its adjoint gradients with respect to geometry control parameters. We present the geometric features, overall aerodynamic improvements and flow details of optimal designs given by SDO and gradient-enhanced response surface model (GERSM). The effects of blade reshaping on shock system, tip clearance flow and flow separation at hub are examined. Also, off-design performances are analyzed regarding both adiabatic efficiency and stall margin.

      PubDate: 2017-05-20T16:24:05Z
      DOI: 10.1016/j.ast.2017.05.005
      Issue No: Vol. 68 (2017)
  • Research on centrifugal compressor disk containment of auxiliary power
    • Authors: Conger Bai; Haijun Xuan; Zekan He; Yushen Zou; Guang Tang; Jin Tang
      Pages: 37 - 45
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Conger Bai, Haijun Xuan, Zekan He, Yushen Zou, Guang Tang, Jin Tang
      To investigate the centrifugal compressor disk containment of auxiliary power unit (APU) in gas turbine, research on specific compressor is conducted in combination of simulations and tests. Nonlinear explicit finite element analysis of tri-hub fragments impacting containment assembly is carried out using LS-DYNA. Impacting characteristics in each period are discussed. Strength of the outer cover, the back shroud and the connecting bolts between them is further studied through simulation. The results show that the fragments interact with the outer cover and the back shroud both in rotating plane and axial direction. The internal energy is mostly composed of the strain energy of the impeller. Insufficient strength of each component leads to an uncontained result. Potential failure modes are discussed. Verification tests on high-speed spin tester revealing both contained and uncontained cases have been conducted and showed that the outer cover, the back shroud and the connecting bolts between them all play a significant role to containment. Adequate strength of these components is essential. Otherwise the outer cover will detach away and the back shroud will be damaged.

      PubDate: 2017-05-20T16:24:05Z
      DOI: 10.1016/j.ast.2017.05.002
      Issue No: Vol. 68 (2017)
  • Robust finite time control algorithm for satellite attitude control
    • Authors: You Li; Dong Ye; Zhaowei Sun
      Pages: 46 - 57
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): You Li, Dong Ye, Zhaowei Sun
      Finite time controllers robust to inertia matrix uncertainty for satellite attitude stabilization control and attitude tracking control are developed in this paper. A three-stage finite sliding mode is constructed to improve system convergence rate. The singularity issue is solved by using the property of Euler Axis when it's paralleled to angular velocity. Based on this finite time sliding mode, finite time controller is developed to ensure the system state could reach the sliding mode in finite time. System inertia matrix uncertainty and disturbance torque is considered in this paper. The control torque constraint is also considered to ensure the norm of control torque does not exceed system upper bound. Finite time stability of the controller is proved and the controller performance is demonstrated by simulation results.

      PubDate: 2017-05-20T16:24:05Z
      DOI: 10.1016/j.ast.2017.05.014
      Issue No: Vol. 68 (2017)
  • 3D grain burnback analysis using the partial interface tracking method
    • Authors: Wando Ki; Taeho Ko; Sangmin Kim; Woongsup Yoon
      Pages: 58 - 67
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Wando Ki, Taeho Ko, Sangmin Kim, Woongsup Yoon
      The evolution of multi-dimensional grains of solid rocket motor propellant was carried out using the partial interface tracking method. This method applies the Lagrangian approach to the axisymmetric area of the X–Y plane and the fin area of the Y–Z plane to analyze the multi-dimensional grain burnback. The Lagrangian approach is an effective way to simulate the axisymmetric or 2D shape of a grain, but it is difficult to determine the 3D shape using this method. Therefore, the partial interface tracking method was designed to solve this problem and to get solutions quickly. The grid data resulting from this method is generated in a standard file format, which makes it easy to check the grid shape through commercial modeling software. This method showed good agreement with previous literature and was effective for numerous different grains. Also, it was confirmed that the code can be applicable to the 0D flow field model.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.04.023
      Issue No: Vol. 68 (2017)
  • Design and structural analysis of unique structures under an internal
    • Authors: Brian Cranston; Mohammed AlGhofaily; Anthony Palazotto
      Pages: 68 - 76
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Brian Cranston, Mohammed AlGhofaily, Anthony Palazotto
      This paper details an experiment that was used to validate the frame deformation of three vacuums lighter than air vehicle finite element models composed of a frame with a skin covering. The experiment consisted of a simplified one directional loading to determine the behavior of a 3D printed frame, which was compared to a corresponding finite element model. A 3D printed icosahedron frame was loaded in compression using a mechanical testing machine to record the load versus displacement of the structure. It was discovered that the material properties of the printed structure were significantly lower than the quoted values from the manufacturer. The modulus property was extracted from the finite element model that best matched the experiment. The behavior of the frame from the experiment shows that the beams do buckle. The model matches the frame buckling and load retention. The feasibility of a vacuum lighter than air vehicle using an icosahedron, hexakis icosahedron, and celestial frame and skin were then analyzed since the method of analysis was proven through the experiment. The icosahedron showed failure due to material limits and the hexakis icosahedron showed definite feasibility using modern material properties.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.04.028
      Issue No: Vol. 68 (2017)
  • Mixing augmentation induced by a vortex generator located upstream of the
           transverse gaseous jet in supersonic flows
    • Authors: Lang-quan Li; Wei Huang; Li Yan
      Pages: 77 - 89
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Lang-quan Li, Wei Huang, Li Yan
      The mixing process plays a very important role in the engineering realization of the scramjet engine, and sufficient mixing between the incoming supersonic air and the fuel relates to improve the overall performance of the airbreathing hypersonic propulsion system. In the current study, the delta wing is placed in front of the injector to promote the mixing of fuel and supersonic crossflow, and the effects of the delta wing height and the jet-to-crossflow pressure ratio have been investigated numerically based on grid independency analysis and code validation. The obtained results predicted by the three-dimensional Reynolds-average Navier–Stokes (RANS) equations coupled with the two equation k – ω shear stress transport (SST) turbulence model show that the delta wing has a highly remarkable improvement on mixing characteristics such as mixing efficiency and fuel penetration depth. However, the delta wing also shows additional losses of stagnation pressure. In the case of higher values of delta wing height and jet-to-crossflow pressure ratio, higher penetration and more losses of stagnation pressure are shown. At the same time, the mixing efficiency decreases with the increase of the jet-to-crossflow pressure ratio irrespective of the height of the delta wing, and there is an optimum height of the delta wing for each jet-to-crossflow pressure ratio to achieve the maximization of rapid fuel–air mixing. In addition, the hydrogen content in the recirculation region between the orifice and the delta wing is a result of both the jet-to-crossflow pressure ratio and the height of the delta wing. In conclusion, the design of the flow field with the delta wing to realize objective comprehensive optimal performance is a multi-objective problem, and it should be solved by the multi-objective design optimization approach.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.016
      Issue No: Vol. 68 (2017)
  • Regression rate characteristics of hybrid rocket motor with helical grain
    • Authors: Hui Tian; Yuelong Li; Chengen Li; Xingliang Sun
      Pages: 90 - 103
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Hui Tian, Yuelong Li, Chengen Li, Xingliang Sun
      This paper concentrates on the fuel regression rate characteristics of hybrid rocket motor with helical grain and attempts to overcome the low regression rate shortcoming of conventional hybrid rocket motor. Both three-dimensional numerical simulations and lab-scale firing tests are conducted to analyze the regression behavior of solid helical fuel grain. Gaseous oxygen and polyethylene are utilized as the propellants. Head axial injection method and Laval nozzle are adopted in the motor. A steady numerical model based on pure-gas-phase reaction assumption is established. Flow field characteristics of the hybrid rocket motor with helical grain are identified through three-dimensional numerical simulations. Simulation results show that the helical structure can both increase turbulence kinetic energy and swirl number in the flow field. These two factors both contribute to the increase of the fuel regression rate. Geometric factors influencing the fuel regression rate are thread pitch, groove depth and groove width. Experimental results reveal that the fuel regression rate increases with the increase of the groove depth and the groove width. The thread pitch can also obviously influence the regression behavior of the helical grain. Overall, the helical grain can effectively increase the fuel regression rate of hybrid rocket motor.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.006
      Issue No: Vol. 68 (2017)
  • A new Multi-position calibration method for gyroscope's drift coefficients
           on centrifuge
    • Authors: Shi-ming Wang; Ni Meng
      Pages: 104 - 108
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Shi-ming Wang, Ni Meng
      In order to accurately calibrate the gyroscope's drift coefficients, the coordinate systems are established on precision centrifuge with counter-rotating platform, and the corresponding error sources of each coordinate system are analyzed. The precise input angular rate along each axis of gyroscope are derived by homogeneous transformation method and also the nominal input specific forces are given. The precise expression of each drift coefficient is provided combining with gyroscope's error model, input specific forces and angular rates of gyroscope at the 16-position. And the compensation for the identification results can be conducted by the expression. It can be shown that through simulation two coefficients are significantly influenced by centrifuge errors when using the 16-position calibration method, and centrifuge errors have no impacts on other coefficients, which proves that the method can effectively eliminate the impacts of centrifuge errors. Only several centrifuge errors should be considered in actual calibration such as the perpendicularity between the counter rotating platform's revolving axis and the working base, the wobbles of counter rotating platform, and the difference between the angular rate of counter rotating platform and the one of the main axis.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.001
      Issue No: Vol. 68 (2017)
  • Aircraft navigation based on differentiation–integration observer
    • Authors: Xinhua Wang; Lilong Cai
      Pages: 109 - 122
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Xinhua Wang, Lilong Cai
      In this paper, a generalized differentiation–integration observer is presented based on sensors selection. The proposed differentiation–integration observer can estimate the multiple integrals and high-order derivatives of a signal, synchronously. The parameters selection rules are presented for the differentiation–integration observer. The theoretical results are confirmed by the frequency–domain analysis. The effectiveness of the proposed observer is verified through the numerical simulations on a quadrotor aircraft: i) through the differentiation–integration observer, the attitude angle and the uncertainties in attitude dynamics are estimated synchronously from the measurements of angular velocity; ii) a control law is designed based on the observers to drive the aircraft to track a reference trajectory.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.007
      Issue No: Vol. 68 (2017)
  • An optimization-based procedure for self-generation of Re-entry Vehicles
    • Authors: Antonio Viviani; Luigi Iuspa; Andrea Aprovitola
      Pages: 123 - 134
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Antonio Viviani, Luigi Iuspa, Andrea Aprovitola
      In the present paper a multidisciplinary optimization procedure for the self-generation of re-entry vehicle shapes has been developed. The procedure relies on a novel parametric model of blended wing-body shapes which is used to create a re-entry configuration around a fixed volume. The flexibility of the model allows us to create lifting body or winged re-entry vehicle from an optimization procedure as monolithic bodies. Multidisciplinary analysis is performed with engineering methods valid in conceptual design. Results of shape optimization for a minimum mass configuration, performed for a Low Earth Orbit Re-entry mission, confirmed the suitability of the procedure by indicating a decrease of vehicle mass configuration that is obtained by reducing the wingspan parameter for a conceptual lifting body configuration.

      PubDate: 2017-05-26T02:02:20Z
      DOI: 10.1016/j.ast.2017.05.009
      Issue No: Vol. 68 (2017)
  • Dynamics of laminar separation bubble over NACA-0012 airfoil near stall
    • Authors: Jaber AlMutairi; Eltayeb ElJack; Ibraheem AlQadi
      Pages: 193 - 203
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Jaber AlMutairi, Eltayeb ElJack, Ibraheem AlQadi
      In this paper, we investigated the dynamics of laminar separation bubble over an airfoil near stall conditions. Large eddy simulation of flow around NACA-0012 airfoil was conducted at an angle of attack α = 11.5 ∘ for a Reynolds number Re c = 1.3 × 10 5 and Mach number M ∞ = 0.4 . A self-sustained low-frequency flow oscillation was observed and its life cycle was described and analyzed. The computed Strouhal number of the oscillation was in good agreement with the experimental data. The flow oscillation was due to quasi-periodic bursting and reforming of the laminar separation bubble. The size of the computed bubble was twice that of the experiment and resulted in 19 % difference between the computed and the experimental lift coefficients. The average of the maximum reverse velocity percentage inside the bubble, during attached phase, was 23.4 % . The characteristics of the transition in the separated shear layer changed through the low-frequency cycle in which the turbulent kinetic energy was maximum when the bubble is at its shortest length. Dynamic mode decomposition analysis of the computed flow identified two dominant modes; the low-frequency oscillation mode and a high frequency mode representing trailing-edge shedding. The reconstructed flow of the DMD modes produced two distinct events, i.e., (1) fully separated flow with intense shedding at the trailing-edge and (2) a fully attached flow with no apparent vortex shedding at the trailing-edge. The DMD results suggest a critical role of acoustic feedback from the trailing edge in promoting earlier transition and forcing the separated flow to reattach.

      PubDate: 2017-05-31T02:08:11Z
      DOI: 10.1016/j.ast.2017.05.015
      Issue No: Vol. 68 (2017)
  • Improvement of Min–Max limit protection in aircraft engine control:
           An LMI approach
    • Authors: Amin Imani; Morteza Montazeri-Gh
      Pages: 214 - 222
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Amin Imani, Morteza Montazeri-Gh
      Current aircraft engine control logic employs a Min–Max selector structure. This structure must provide desired thrust and prevent the engine from exceeding any safety or operational limits. Careful analysis shows that there is no assurance for traditional Min–Max algorithm with linear compensators to protect output limits in transient regime, while limit violation can cause serious damages and even lead to loss of engine. In this paper, according to analysis outcomes, a strategy is presented to design linear regulators of Min–Max selector control to improve transient limit protection. For this objective, the isolated limitation loops are designed overshoot/undershoot-free to reduce the possibility of limit violation during activeness of the individual limit regulator. Despite the success of this approach, it is observed that some outputs influenced by engine acceleration or deceleration exceed their limits when other loop regulators are active. To overcome this problem, the limit values of these outputs are considered in controller design process of other loops using state feedback method and a set of linear matrix inequalities (LMIs). Simulation results show that the proposed approach effectively decreases the possibility of transient limit violation and can improve Min–Max limit protection in aircraft engine control.

      PubDate: 2017-05-31T02:08:11Z
      DOI: 10.1016/j.ast.2017.05.017
      Issue No: Vol. 68 (2017)
  • Reliability-based design optimization of rotating FGM cylindrical shells
           with temperature-dependent probabilistic frequency constraints
    • Authors: Naser Safaeian Hamzehkolaei; Mahmoud Miri; Mohsen Rashki
      Pages: 223 - 239
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Naser Safaeian Hamzehkolaei, Mahmoud Miri, Mohsen Rashki
      In this study, the reliability-based design optimization (RBDO) of rotating functionally graded cylindrical shells (FGCSs) subjected to temperature dependent probabilistic frequency constraints is investigated. The uncertain parameters such as FG material properties and the shell thermo-mechanical loads are considered as random variable in RBDO. To decrease model uncertainty, the effect of initial thermal stresses are efficiently included in elasticity-based vibration equations of the shell and the powerful differential quadrature method (DQM) is employed to accurately determine the shell frequency parameters. An efficient RBDO framework based on the hybrid weighted average simulation method (WASM) and DQM together with the particle swarm optimization (PSO) method is then presented for design optimization of the FGCSs. A key feature of proposed hybrid DQ-WASM-PSO is that only one simulation run is required for WASM during entire optimization process of the FGCS, even if the distribution type of input variables and/or the system target reliability level be changed. The influence of temperature rise, temperature-dependence of FGM properties, annular velocity, PDFs of the random variables, and convection heat transfer coefficient of the shell inside fluid on the RBDO results are carried out. Parametric study indicates that exact evaluation of the initial thermal stresses, temperature-dependence of the FGM properties and convection heat transfer coefficient have considerable effect on optimization results.

      PubDate: 2017-05-31T02:08:11Z
      DOI: 10.1016/j.ast.2017.05.004
      Issue No: Vol. 68 (2017)
  • Separation control using quasi-radial wall jets
    • Authors: Khodayar Javadi; Majid Hajipour
      Pages: 240 - 251
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Khodayar Javadi, Majid Hajipour
      In this paper, flow separation control over a NACA 4415 wing section using arrays of discrete quasi-radial wall jets is numerically investigated. This novel flow control method is studied under conditions which the wing section angle of attack is α = 18 degrees and Reynolds number based on chord length is R e c = 550000 . Contours of mean streamwise velocity indicated that quasi-radial wall jets cover wing surface rapidly. Therefore, arranging them in a spanwise row can be an effective way in adding momentum to the near wall fluid particles. According to the results, if blowing parameters of the jets be chosen correctly, arrays of quasi-radial wall jets would lead to considerable decrease in wake region extent and would bring enhancement of wing aerodynamic performance (up to 46% increment of lift coefficient). Moreover, investigation of streamlines and velocity vectors reveals the presence of two helical vortices on both edges of quasi-radial wall jets. These vortices, which form due to interactions between external stream and spanwise velocity component of jets, generate mixing in the surrounding fluid. It could be said that besides momentum addition, quasi-radial wall jets in an external stream act like vortex generators.

      PubDate: 2017-06-05T11:11:24Z
      DOI: 10.1016/j.ast.2017.04.012
      Issue No: Vol. 68 (2017)
  • Introduction of full flight dynamic stability constraints in aircraft
           multidisciplinary optimization
    • Authors: J. Mieloszyk; T. Goetzendorf-Grabowski
      Pages: 252 - 260
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): J. Mieloszyk, T. Goetzendorf-Grabowski
      Obtaining satisfactory flight dynamic characteristics for an aircraft within the design process is a mandatory task required by the flight law regulations. In the classical approach dynamic stability analyses are done at the end of the design process, when most aircraft properties are already known. Possible changes of the dynamic properties can influence the whole project and force a redesign. This reason has caused a number of researchers and industry representatives to try to incorporate the dynamic analysis earlier in the design process. This demanding task has often been executed with a number of simplifications, limited to a single wing or analysis of only the longitudinal flight dynamic stability modes. The new presented approach goes much further. The article presents a successful attempt to include all dynamic modes of motion (longitudinal and lateral) into the analysis taking stability criteria as constraints. The numerical optimization process is fully automated and based on parallel processing, making the computations very efficient. Moreover, a complete aircraft in an innovative boxwing configuration is optimized with the dynamic stability constraints, which has not been achieved ever before.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.024
      Issue No: Vol. 68 (2017)
  • Collision avoidance of Coulomb spacecraft formations using multi-mode hall
    • Authors: Ting Wang
      Pages: 261 - 268
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Ting Wang
      A great number of abandoned satellites and satellite constellations that cannot maintain their precise positions by orbital control are wandering in geostationary Earth orbits, and these represent significant collision risk with functioning satellites. Collision avoidance for a Coulomb satellite formation (CSF) is a major problem that remains to be solved. However, internal Coulomb forces cannot alter the inertial momentum of the CSF center of mass. Thus, collision avoidance cannot be implemented employing purely Coulomb-based control. In this paper, multi-mode Hall thrusters are proposed to supply CSF propulsion in collision avoidance. To avoid plume contamination between close-proximity satellites in a CSF, the low-thrust mode of the Hall thruster is initially employed to gradually transform a close-proximity CSF to a formation with an appropriate security distance between nearby satellites. The security distance is selected to avoid the impact of plume contamination while employing the high-thrust mode of the Hall thruster to maneuver the CSF around an obstacle. Both stages apply optimal control based on a linear quadratic regulator. Subsequently, a CSF may be reconfigured to its initial formation. Meanwhile, the satellites maintain their original charges throughout the entire process. Simulations are employed to verify the effectiveness of the proposed scheme.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.021
      Issue No: Vol. 68 (2017)
  • A robust optimization approach for airport departure metering under
           uncertain taxi-out time predictions
    • Authors: Mayara Condé Rocha Murça
      Pages: 269 - 277
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Mayara Condé Rocha Murça
      Airports are critical elements in the air transportation system in terms of traffic flow management. The high volume of operations along with the constraining airside capacity can exacerbate surface congestion and lead to increased flight delays and costs, especially during peak times. Surface traffic optimization is an alternative for alleviating congestion. However, the high level of uncertainty in actual operations can compromise the effectiveness of optimal policies. This paper presents a robust optimization approach for metering aircraft departures under uncertainty in the taxi-out process. A mixed integer linear programming model for runway sequencing and scheduling that incorporates uncertainty sets for the taxi-out time is proposed in order to dynamically determine an optimal and robust sequence and schedule of aircraft release from the gate. Actual operational data from Brasilia International Airport in Brazil is used to evaluate the effectiveness of departure metering at this airport. An assessment of benefits and trade-offs of introducing robustness is performed based on stochastic simulation of departure performance under different control strategies. The robust optimization approach shows positive impacts in protecting against uncertainty as it reduces runway delays and taxi-out times and increases takeoff time predictability.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.020
      Issue No: Vol. 68 (2017)
  • Pilot induced oscillation suppression controller design via nonlinear
           optimal output regulation method
    • Authors: Anh Tuan Tran; Noboru Sakamoto; Yoshimitsu Kikuchi; Koichi Mori
      Pages: 278 - 286
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Anh Tuan Tran, Noboru Sakamoto, Yoshimitsu Kikuchi, Koichi Mori
      This paper proposes a controller design method for preventing pilot-induced-oscillation (PIO) based on nonlinear optimal output regulation theory and center stable manifold method. The type of PIO considered is due to actuator rate limiting and the proposed controller assures C ⁎ handling quality by the optimal control when actuator works in the linear region. The simulation result shows that the proposed nonlinear controller has better tracking performance in comparison with the linear optimal output regulation controller. The robustness of the designed controller against parametrization error, noise and time-delay is also verified.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.010
      Issue No: Vol. 68 (2017)
  • Corrigendum to “Waypoint constrained guidance for entry vehicles”
           [Aerosp. Sci. Technol. 52 (2016) 52–61]
    • Authors: Zixuan Liang; Qingdong Li; Zhang Ren
      First page: 287
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Zixuan Liang, Qingdong Li, Zhang Ren

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.018
      Issue No: Vol. 68 (2017)
  • Aircraft stall phenomenon analysis using nonlinearity index theory
    • Authors: Daniel P. Tapolcai; Ashraf Omran; Brett Newman
      Pages: 288 - 298
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Daniel P. Tapolcai, Ashraf Omran, Brett Newman
      Stalling has been understood to be an important nonlinear process in the behavior of the motion of flight vehicles. Nonlinearity index theory is presented herein as a gauge to understand and measure the nonlinearity of aircraft under given operating conditions. Traditionally, linear theory has been relied upon for analysis of stalling and the phenomena related to it in order to correlate the significance of stall to flight behavior and overall general flight safety. However, for complex flight vehicles involving post-stall regimes, in some cases linear theory has been shown to be misleading in its given approaches. The nonlinearity index is given here as a means by which the overall linearity of the system can be evaluated, and is used to discern the accuracy and conclusions of the traditional methods of linear analysis. This theory is applied to a nonlinear pitch-plunge aircraft model and exposes behavior undetected by the traditional approach.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.04.008
      Issue No: Vol. 68 (2017)
  • Integral backstepping sliding mode control for quadrotor helicopter under
           external uncertain disturbances
    • Authors: Zhenyue Jia; Jianqiao Yu; Yuesong Mei; Yongbo Chen; Yuanchuan Shen; Xiaolin Ai
      Pages: 299 - 307
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Zhenyue Jia, Jianqiao Yu, Yuesong Mei, Yongbo Chen, Yuanchuan Shen, Xiaolin Ai
      In this paper, a novel nonlinear control strategy along with its simulation for a quadrotor helicopter is proposed. The normal 6-DOF dynamic model of the quadrotor based on the Newton–Euler formula as well as the model with external uncertain disturbances are established. Considering the underactuated and strongly coupled characteristics of quadrotor helicopter, we design a nonlinear control method by using integral backstepping combined with the sliding mode control (integral BS-SMC) to stabilize the quadrotor attitude and to accomplish the task of trajectory tracking. The designed controllers based on the hierarchical control scheme can be divided into rotational controller and translational controller and their stability are validated by the Lyapunov stability theorem. By means of the proposed controllers, the chattering phenomenon and discontinuousness of control inputs faced by traditional sliding mode control (SMC) can be avoided. The feasibility of the control approach presented in this paper is verified by the simulations under different scenarios. The results show that the nonlinear control method not only has a better tracking performance than others but also has a higher robustness when unknown disturbances occur.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.022
      Issue No: Vol. 68 (2017)
  • Optimization of discrete cavities in a centrifugal compressor to enhance
           operating stability
    • Authors: Sang-Bum Ma; Kwang-Yong Kim
      Pages: 308 - 319
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Sang-Bum Ma, Kwang-Yong Kim
      In order to improve the operating stability of a centrifugal compressor, discrete cavities are introduced just upstream of the impeller and optimized for further improve the operating stability. Aerodynamic analysis is performed using a commercial code, ANSYS-CFX 15.0, to solve three-dimensional Reynolds-averaged Navier–Stokes equations with a shear stress transport turbulence model. The stall margin of the centrifugal compressor is used as the objective function, and three geometric parameters associated with the shape of the discrete cavities (the width and angle of the cavity port, and the axial distance between cavities) were selected as design variables. The Latin hypercube sampling method is used to compose the design space with 27 design points, and a radial basis neural network model is constructed as a surrogate model of the objective function. The optimization results show that the stall margin of the centrifugal compressor with the optimum discrete cavities is improved by 15.4% compared to the compressor without cavity.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.029
      Issue No: Vol. 68 (2017)
  • Numerical studies for performance improvement of a variable geometry dual
           mode combustor by optimizing deflection angle
    • Authors: Shuo Feng; Juntao Chang; Yuanshi Zhang; Chenlin Zhang; Youyin Wang; Wen Bao
      Pages: 320 - 330
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Shuo Feng, Juntao Chang, Yuanshi Zhang, Chenlin Zhang, Youyin Wang, Wen Bao
      As part of our efforts to study the effect of the deflection angle on combustor performance of a variable geometry dual mode combustor, the flow field characteristics and mechanisms of the combustor performance loss, which comprised of compression loss, combustion heat addition loss and expansion loss, were investigated in the variable geometry dual mode combustor numerically with a Mach number of 3, a divergence ratio of 1.76, a fuel equivalence ratio of 0.6, and a deflection angle ranging from 8° to 16°. Numerical results indicated that the total pressure recovery coefficient and combustion efficiency increased with the deflection angle and there was a maximum to be obtained at the deflection angle of 12° due to the interaction between the dominant shock resulted by combustion heat release and the additional shock caused by the wedge system. Irreversible entropy generation loss was analyzed specifically in this paper to clarify and describe the combustor performance loss for the variable geometry dual mode combustor. Moreover, thrust-to-drag ratio was utilized to assess the effect of the deflection angle on combustor performance. By taking into account the flow field characteristics and combustor performance characteristics, the high combustor performance of a variable geometry dual mode combustor can be improved by selecting and optimizing the deflection angle.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.025
      Issue No: Vol. 68 (2017)
  • Robust weighted fusion Kalman estimators for systems with multiplicative
           noises, missing measurements and uncertain-variance linearly correlated
           white noises
    • Authors: Xuemei Wang; Wenqiang Liu; Zili Deng
      Pages: 331 - 344
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Xuemei Wang, Wenqiang Liu, Zili Deng
      For linear discrete time-varying and time-invariant multisensor uncertain systems with multiplicative noises, missing measurements and uncertain-variance linearly correlated white noises, by introducing the fictitious noises to compensate the stochastic uncertainties, the system under consideration can be converted into one with only uncertain noise variances. According to the minimax robust estimation principle, based on the worst-case system with conservative upper bounds of uncertain noise variances, the four robust weighted state fusion time-varying and steady-state Kalman estimators (predictor, filter, smoother) are presented respectively. They include the three fusers weighted respectively by matrices, scalar and diagonal matrices and a new modified covariance intersection (CI) fuser. They are designed in a unified framework, such that the filters and smoothers are designed based on the predictors. By the Lyapunov equation approach, their robustness is proved in the sense that for all admissible uncertainties, their actual estimation error variances are guaranteed to have the corresponding minimal upper bounds. The convergence in a realization between the robust fused time-varying and steady-state Kalman estimators for the time-varying and time-invariant systems are proved by the dynamic error system analysis (DESA) method. Their accuracy relations are also proved. A simulation example applied to uninterruptible power system (UPS) shows the effectiveness of the proposed results.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.023
      Issue No: Vol. 68 (2017)
  • A study on the unsteady conjugate heat transfer of hot gas valve
    • Authors: Kyungwook Lee; Seonuk Heo; Sejin Kwon; Jongkwang Lee
      Pages: 362 - 369
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Kyungwook Lee, Seonuk Heo, Sejin Kwon, Jongkwang Lee
      Numerical simulations of a hot gas valve were conducted in this study to establish an analysis method. The far-field effect was also checked to select a computational domain. The existence of the far-field did not affect flow and temperature characteristics. The grid sensitivity was checked by varying the grid number from 25,000 to 120,000. The thrusts were similar according to the number of grid. However, differences in temperature distribution were observed. Three turbulence models were adopted to determine the influence of turbulence on thrust and temperature distribution: Spalart–Allmaras, RNG k – ε , and k – ω SST. The thrusts of the hot gas valve were similar in all simulation cases. However, an approximately 2% deviation in temperature distribution was observed at an operating pressure of 128 atm. Time step size and iteration were selected for the unsteady analysis. The analysis was conducted using only an S–A turbulent model and a valve grid. No significant difference was found. Hence, the time step size was set as 10 μs, and 50 iterations were performed. The unsteady analysis was conducted by increasing the time step size throughout the four sections considering the operating time of the hot gas valve. The time step size was increased when the quantitative result reached within 5% difference in each section. The flow, pressure, and temperature fields in the flow area reached the steady state with within 5% difference at 8 ms, 100 ms, and 5.5 s, respectively. The three fields in the flow area reached the steady state at 10 s from the operating time of the hot gas valve. However, an approximately 7% difference in temperature field was observed in the solid area. The calculation time was reduced by approximately 130 times compared to the existing calculation method.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.026
      Issue No: Vol. 68 (2017)
  • Pressure rising slope variation accompanying with combustion mode
           transition in a dual-mode combustor
    • Authors: Chenlin Zhang; Juntao Chang; Shuo Feng; Jicheng Ma; Junlong Zhang; Wen Bao
      Pages: 370 - 379
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Chenlin Zhang, Juntao Chang, Shuo Feng, Jicheng Ma, Junlong Zhang, Wen Bao
      Direct-connect experiment with equivalence ratio linear increasing in a dual-mode combustor with a strut is conducted at free stream Mach number of 2.0. Based on the pressure histories on side wall, pressure rising slope variation accompanying with combustion mode transition is found and discussed. The pressure rising has different slopes vary as equivalence ratio linearly increasing. Meanwhile, this characteristic of pressure slope variation leads to the change of combustor thrust. By analyzing the combustion heat release zone and the geometric configuration combustor, a typical simplified geometric model is proposed and studied by using numerical simulation. The phenomenon of the pressure rising slope variation is obtained and explained by the shock train movement in numerical simulation. In the process of shock train movement, a normal shock is established at thermal throat to make the airflow of throat position reach critical state, which could limit the mass flow rate of the supersonic mainstream. Further, inviscid and isentropic flow analysis is employed to illustrate the variation of pressure rising resulted from the occurrence of a normal shock wave. The analysis indicates that the cross-sectional area of mainstream is bounded by the subsonic boundary layer plays a key role to alter the pressure rising slope.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.034
      Issue No: Vol. 68 (2017)
  • Finite element modeling and pyroshock response analysis of separation nuts
    • Authors: Xixiong Wang; Zhaoye Qin; Jifeng Ding; Fulei Chu
      Pages: 380 - 390
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Xixiong Wang, Zhaoye Qin, Jifeng Ding, Fulei Chu
      Separation nuts are widely used as release devices to fasten and separate substructures of launching systems in aerospace applications. High shock transient response is generated during the separation of release devices, which tends to cause damage to the nearby micro mechanism and hardware. The purpose of this article is to predict the shock response of separation nut and find out the sensitive parameters for shock response. In this article, the explicit dynamics method hydrocodes is adopted to model the separation nuts, upon which the pyroshock response is investigated. Firstly, the separation mechanism of the nuts is introduced. Then, a FE model for the separation nuts is developed using hydrocodes software ANSYS/Autodyn, which is validated by comparing the simulation results with the pyroshock test data in shock response spectrum (SRS). Finally, the effects of the preload level and the amount of explosive on the pyroshock response are discussed. The simulation results demonstrate that decreasing the preload level is a more efficient way to reduce the pyroshock received by the spacecraft.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.028
      Issue No: Vol. 68 (2017)
  • Static response and free vibration of functionally graded carbon
           nanotube-reinforced composite rectangular plates resting on
           Winkler–Pasternak elastic foundations
    • Authors: Nguyen Dinh Duc; Jaehong Lee; T. Nguyen-Thoi; Pham Toan Thang
      Pages: 391 - 402
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Nguyen Dinh Duc, Jaehong Lee, T. Nguyen-Thoi, Pham Toan Thang
      In the present article, static response and free vibration of functionally graded carbon nanotube reinforced composite (FG-CNTRC) rectangular plate resting on Winkler–Pasternak elastic foundations using an analytical approach are studied. The rectangular plates are reinforced by single-walled carbon nanotubes (SWCNTs) which are assumed to be graded through the thickness direction with four types of distributions. The mathematical model of the FG-CNTRC plate is developed based on the first-order shear deformation plate theory (FSDT) and Hamilton principle. By using Navier solution, the governing equations are solved to obtain the central deflection and the natural frequency parameters. Several examples are verified to have higher accuracy than those from the previous method in the literature. Also, the effects of different parameters on static response and natural frequency of FG-CNTRC plate are highlighted by solving numerous examples. Finally, these new results may serve as benchmarks for future investigations.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.032
      Issue No: Vol. 68 (2017)
  • A potential game approach to multiple UAV cooperative search and
    • Authors: Pei Li; Haibin Duan
      Pages: 403 - 415
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Pei Li, Haibin Duan
      In this paper, we developed a game theoretic formulation for multiple unmanned aerial vehicle (UAV) cooperative search and surveillance. The cooperative search problem is decomposed into three sequential tasks: coordinated motion, sensor observation, and cooperative information fusion. Firstly, the coordinated motion is designed as a multi-player potential game with constrained action sets. Then the binary log-linear learning is adopted to perform motion control, which guarantees optimal coverage. Then a consensus based fusion algorithm is introduced to construct the probability map to guide the following coordinated motion. Finally, simulations are performed to validate the effectiveness of our proposed approach. The modular framework enables the separate design of utility functions and learning algorithms, which offers a flexible way to accommodate different global objectives and underlying physical constraints.

      PubDate: 2017-06-10T11:15:04Z
      DOI: 10.1016/j.ast.2017.05.031
      Issue No: Vol. 68 (2017)
  • A new adaptive finite time nonlinear guidance law to intercept maneuvering
    • Authors: Vahid Behnamgol; Ahmad Reza Vali; Ali Mohammadi
      Pages: 416 - 421
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Vahid Behnamgol, Ahmad Reza Vali, Ali Mohammadi
      A new adaptive nonlinear guidance law for homing missiles to intercept maneuvering targets in terminal phase is proposed. This guidance law generates smooth acceleration commands and is able to stabilize the relative lateral velocity in a desired finite time. The proposed guidance law uses bounds of the target acceleration and jerk and is consisting of two adaptive terms. It is proved that the first adaptive term of the proposed guidance law converges to the target acceleration normal to the line of sight. Finite time stability of the guidance loop is proved by using Lyapunov stability theorem. Numerical simulations are performed to illustrate the proposed guidance law potential.

      PubDate: 2017-06-14T11:16:46Z
      DOI: 10.1016/j.ast.2017.05.033
      Issue No: Vol. 68 (2017)
  • Discrete event simulation of long-duration space station operations for
           rapid evaluation
    • Authors: Kun-Peng Lin; Meng-Li Wang; Yuan Hong; Yang Yang; Jia-Xin Zhou
      Pages: 454 - 464
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Kun-Peng Lin, Meng-Li Wang, Yuan Hong, Yang Yang, Jia-Xin Zhou
      A long term space station operational scenario involves a large number of on-orbit missions, however, for their successful implementation they require various logistics missions to be performed. Logistics missions are triggered by on-orbit missions and there are complex interactions between different missions. Based on the computational efficiency afforded by event-based simulation, Discrete Event Simulation (DES) is used to model diverse on-orbit and logistics missions holistically within an integrated scenario and schematize it as a discrete system. It helps to quickly evaluate the physical feasibility and performance effectiveness of complex space station operations. Moreover, operational uncertainty is introduced into the DES model, comprising launch delays of visiting vehicles and onboard emergencies hazarding the safeties of space station or astronauts. Monte Carlo simulation is adopted to help in stochastic analyses and five measurable metrics are further defined to quantify the impact of uncertainty on nominal scenarios. The proposed DES model and associated metrics are demonstrated with both nominal and contingency operations. Simulation results indicate that such an approach is effective and efficient in simulating space station operations and able to support the top-level mission design of China's future space station program.

      PubDate: 2017-06-20T07:41:29Z
      DOI: 10.1016/j.ast.2017.05.037
      Issue No: Vol. 68 (2017)
  • Dynamic stability of rolling missile with proportional navigation & PI
           autopilot considering parasitic radome loop
    • Authors: Duo Zheng; Defu Lin; Xinghua Xu; Song Tian
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Duo Zheng, Defu Lin, Xinghua Xu, Song Tian
      The dynamic stability of coning motion for a radar homing rolling missile is studied in this paper, and the parasitic radome loop is considered and introduced into the guidance system of the radar homing rolling missile. A mathematical model with complex summation considering the parasitic radome loop is proposed, and the sufficient and necessary conditions for the dynamic stability of the coning motion for the rolling missile are analytically derived by using the stability criterion of third-order characteristic equation with complex coefficients. Numerical simulations with different parameters are conducted to demonstrate the effectiveness of the proposed stability condition. The stability condition proposed in this paper can be used in the guidance and control system design of a radar homing rolling missile while considering the parasitic radome loop.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.036
      Issue No: Vol. 67 (2017)
  • Performance based multidisciplinary design optimization of morphing
    • Authors: Frederico Afonso; José Vale; Fernando Lau; Afzal Suleman
      Pages: 1 - 12
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Frederico Afonso, José Vale, Fernando Lau, Afzal Suleman
      The aeronautical industry is currently facing contradictory aircraft design requirements. There is a need to increase speed and capacity while minimizing the environmental impact. Novel configurations and morphing solutions are being proposed to address these requirements. In order to achieve the optimal aircraft configuration or the best morphing solution for a given mission, it is necessary to explore Multidisciplinary Design Optimization (MDO) solutions during the conceptual design phase. To this end, a MDO framework is proposed for conceptual design and analysis of new aircraft configurations, including the capability to analyze and quantify the effect of morphing wing solutions on aircraft performance. To illustrate the versatility and capabilities of the MDO tool, the design of a morphing wingtip on a conventional aircraft for two different flight conditions is assessed based on a reference model transport aircraft. Also, the performance of a morphing bending and twist control applied to a reference joined-wing configuration to improve lateral-directional stability is quantified. The results obtained show a significant reduction in fuel consumption when introducing a wingtip, although an incremental and negligible reduction was verified when enabling the wingtip with morphing capabilities. A considerable increase in yaw authority was achieved for the joined-wing model with the bending-twist morphing wingtip, however this morphing concept was not able to reach the same roll authority as conventional ailerons.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.029
      Issue No: Vol. 67 (2017)
  • CFD-based aeroelastic reduced-order modeling robust to structural
           parameter variations
    • Authors: Maximilian Winter; Florian M. Heckmeier; Christian Breitsamter
      Pages: 13 - 30
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Maximilian Winter, Florian M. Heckmeier, Christian Breitsamter
      This article deals with the development of two efficient computational-fluid-dynamics (CFD) based models for the computation of unsteady aerodynamic motion-induced forces. In contrast to established reduced-order modeling (ROM) approaches, which are generally fixed to a given set of structural eigenmodes, the proposed methods can be applied for variable mode shapes. Hence, the generated aerodynamic models remain valid to some extent even if mass and stiffness variations within the underlying finite-element (FE) model are considered. In this way, additional computationally demanding CFD computations are avoided once the model has been obtained. Under this premise, two modeling frameworks robust to structural parameter variations are developed, while so-called basis modes are employed to approximate arbitrary mode shapes. Firstly, a time-domain ROM originating from linear system identification principles (SI-ROM) is presented and, secondly, a frequency-domain approach based on a small disturbance CFD solver (SD-ROM) is proposed. Moreover, two different strategies for the basis mode generation are evaluated. The first method is based on a local approximation using radial basis functions, whereas the second method uses two-dimensional Chebyshev polynomials in order to yield a global approximation of the structural grid deformations. Both novel ROM approaches combined with the two basis mode construction techniques are demonstrated and assessed regarding their efficiency and accuracy. The results in terms of the well-known AGARD 445.6 wing configuration demonstrate that the proposed methods can reproduce the unsteady aerodynamic forces accurately, while the computational effort is significantly reduced. Moreover, generic modifications with respect to the FE model are considered to indicate the potential of the new methods regarding aircraft aeroelastic design and optimization.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.030
      Issue No: Vol. 67 (2017)
  • Local and asymmetrical potential field approach to leader tracking problem
           in rigid formations of fixed-wing UAVs
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Cezary Kownacki, Leszek Ambroziak
      The paper presents a novel approach to a position control problem in rigid formations of nonholonomic unmanned aerial vehicles (UAVs), such as fixed-wing aircrafts. In the most known approaches of artificial potential fields applied in swarm robotics, it is assumed that the potential fields usually reach a zero or minimal magnitude at desired positions of UAVs in the formation, i.e. a steady state, since they are usually defined as a spherical function of positions errors. This is not feasible for fixed-wing UAVs, which have limited turn radius and minimum flight speed securing them against a substantial loss of lift force. Therefore, at the stationary state of the formation, UAV should reach speed and heading angle of a reference point defined as a real or virtual formation leader. To achieve this, a new asymmetrical local potential field is proposed in the paper. It will steer UAV in the formation flight in the way that makes its airspeed and heading angle asymptotically tending to the airspeed and the heading of the leader, according to the decrement of its position error. This guarantees both a precision of position tracking and stability of flight of each UAV as well as entire formation. Moreover a simplicity of this approach allows implementing it easily into real UAVs.

      PubDate: 2017-06-27T07:52:54Z
  • Adaptive control of hypersonic vehicles based on characteristic models
           with fuzzy neural network estimators
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Yafei Chang, Tiantian Jiang, Zhiqiang Pu
      Strong uncertainties and time-variations of hypersonic vehicles during the reentry phase pose huge challenges to their control system design. This paper addresses a novel adaptive output feedback control scheme based on characteristic models with fuzzy neural network estimators to guarantee the stable and accurate attitude tracking for the hypersonic vehicle, which is subject to unknown time-varying aerodynamics. By characteristic modeling, the time-varying uncertainties are integrated into several characteristic parameters to be estimated online, which inherit the time-variation property from the aerodynamics. And then the characteristic model-based adaptive control law is constructed, while the fuzzy neural network estimators are designed to estimate the time-varying characteristic parameters. The control performances including the property of estimators and the attitude tracking error are also analyzed. At last, the effectiveness of the proposed adaptive control scheme is illustrated by several representative simulations.

      PubDate: 2017-06-27T07:52:54Z
  • Reduced basis methods for structurally nonlinear Joined Wings
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Nick Teunisse, Luciano Demasi, Paolo Tiso, Rauno Cavallaro
      There is currently a large interest towards unconventional aircraft configurations. According to many experts, only revolutionary concepts can meet the demands of a sustainable aviation. Within this scenario, studies and investigations on innovative aircraft layouts have been flourished: Blended Wing Body, Joined Wings and Box Wings are relevant examples of configurations departing from the traditional monoplane. Joined Wings are characterized by strong geometric nonlinear effects, whose complexity is enhanced by the over-constrained layout and the intrinsic relevant bending-torsion coupling. Thus, the application of standard linear analysis tools of routine use in the aerospace industry is neither acceptable nor practical: the preliminary design phase needs a large number of simulations that have to be computationally fast and at the same time preserve an acceptable level of accuracy/fidelity. For this reason, reduced order models are particularly relevant for the design of these systems. However, several reduced order methods applied in the past to Joined Wings did not provide satisfactory accuracy and reliability. The poor performance is mainly due to the very early onset of nonlinear effects, even at very moderate deflections. This work provides an assessment, and an algorithm enhancement when needed, of several existing techniques aimed to build an effective reduction basis for model order reduction. In particular, Vibration Modes, Modal Derivatives, Ritz Vectors, Static Modes, Trial Solutions and Corrections Vectors are critically examined when applied to a representative JW configuration. The results indicate that Ritz Vectors and Modal Derivatives provide excellent accuracy of the reduced solution when compared with the full order solution. Specifically, a drastic increase in the performance of the reduced order model is noticed when ab-initio information regarding Modal Derivatives are included. This highlights and confirms the relevance of nonlinearities even at the early deformation stages. Hence, taking into account nonlinearities since the early design phases seems to be an unavoidable necessity for Joined Wings. As a consequence, efficient and reliable reduced order modeling might play an essential role in the design of such innovative configurations.

      PubDate: 2017-06-27T07:52:54Z
  • Evaluation of free vibration and bending analysis of laminated composite
           and sandwich plates using non-polynomial zigzag models: C0 Finite element
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Suganyadevi Sarangan, B.N. Singh
      The present work deals with prediction of bending and free vibration analysis of laminated composite and sandwich plates using non-polynomial zigzag theories inline with C 0 finite element formulation. The assumed mathematical model is the combination of zigzag parameters and non-polynomial shear strain functions with constant variation of transverse displacement. It represents continuous form of out-plane stresses and parabolic variation across the plate thickness. Moreover, improved form of in-plane responses also achieved. The mathematical model is layer independent and consist of less number of unknowns like in the case of first order theory. Hence, the present theory required less computational efforts. Higher mode shapes of frequencies are obtained for the multilayered sandwich plates and composite plates. By ranging the geometrical parameters, loading conditions, material properties and boundary conditions the numerical examples are carried out to establish the superiority of the current zigzag models than the available results.

      PubDate: 2017-06-27T07:52:54Z
  • Stabilization of rigid body attitude motion with time-delayed feedback
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Ehsan Samiei, Amit K. Sanyal, Eric A. Butcher
      A continuous nonlinear full-state time-delayed feedback control scheme is designed within the framework of geometric mechanics to stabilize the rigid body attitude motion, which is subject to an unknown constant time delay in feedback measurement. The attitude kinematics is globally described on the matrix Lie group S O ( 3 ) of rigid body rotations. A Morse–Lyapunov–Krasovskii functional is utilized to guarantee the asymptotic stability of the system, which yields the control gain matrices via linear matrix inequality stability conditions. In light of this result, a delayed feedback control scheme is also designed for the planar rotational motion to examine the almost global asymptotic stability of the system in the presence of an unknown time delay in feedback measurement. Simulations are performed for the proposed control schemes based on the discretized models of the controlled systems and the performance of the proposed controllers are evaluated by employing large maneuvers.

      PubDate: 2017-06-27T07:52:54Z
  • Wing shape and dynamic twist design of bio-inspired nano air vehicles for
           forward flight purposes
    • Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): M. Hassanalian, G. Throneberry, A. Abdelkefi
      The wing shape and kinematics of flapping wing nano air vehicles play a crucial role in the effectiveness of the system. Optimizing these design parameters allows for greater endurance during flight due to a reduction in the needed aerodynamic power. In this study, seven insects' wings are considered in order to investigate which wing shape requires less amount of aerodynamic power for forward flight missions. A strip theory model is employed and verified for two types of birds, namely, Jack Daw, and Mew Gull. Then, this aerodynamic theory is utilized to model and optimize the kinematics of the seven wings with a particular investigation on the impacts of the dynamic twist on the performance of bio-inspired nano air vehicles. Each wing is divided into strips that are individually analyzed and integrated over the full wingspan to determine the needed aerodynamic power and propulsive efficiency. The use of this modified strip theory is beneficial because it includes the unsteady aerodynamic effects and the possible change in the wings' dimensions. A parametric study is then carried out to determine the optimum wing shape and associated dynamic twist of the flapping wing nano air vehicle when considering two scenarios. In the first scenario, the wingspan for all considered seven wing shapes is considered the same. As for the second scenario, the seven wing shapes are considered with same wing surface. The results show that for same wingspan and wing surface, the bio-inspired honeybee and bumblebee wing shapes have the optimum performances, respectively. The performed analysis gives guidelines on the optimum design of flapping wing nano air vehicles for forward flight applications.

      PubDate: 2017-06-27T07:52:54Z
  • Aircraft engine health prognostics based on logistic regression with
           penalization regularization and state-space-based degradation framework
    • Authors: Jianbo
      Abstract: Publication date: September 2017
      Source:Aerospace Science and Technology, Volume 68
      Author(s): Jianbo Yu
      Engine health prognostics is critical to ensure reliability and safety of aircraft operations due to the provision of various health decision information. In this studying, a prognostics system is developed based on logistic regression (LR) and state-space-model (SSM) for engine health assessment and prediction. In this system, a health indicator based on logistic probability (LP) inferred from a variable set of sensor signals selected by LR with penalization regularization (LRPR) is used to characterize engine health states. LP is capable of offering a failure probability for the monitored engine, which has intuitive explanation related to its health state. A data-model-fusion method is developed for the engine health prognostics task accomplished by integration of LR and particle filtering (PF). Bayesian state estimations, on the basis of the engine health changes modeled by a baseline LR, are implemented to sequentially update the current health state and then to predict the future health propagation of engines. The prognostics system is applied to a gas turbine on the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) test-bed developed by NASA. The experimental results indicate the potential applications of the proposed system as an effective tool for engine health prognostics.

      PubDate: 2017-06-10T11:15:04Z
  • A comparison of PIV and interferometric Rayleigh scattering measurements
           in the near field of underexpanded sonic jets
    • Authors: Kemal
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Kemal Bülent Yüceil
      Velocity measurements were made in the near field of underexpanded sonic air jets using particle image velocimetry (PIV), interferometric Rayleigh scattering and total pressure tubes. Shadowgraph technique was also used to visualize the shock waves generated due to underexpansion in the near field of the jets. The two main objectives were to study the effect of underexpansion ratio on the flow structure and to determine the suitability of the PIV technique in high-speed flows with shock waves. The jets were produced by a convergent nozzle connected to a settling chamber. Different underexpansion conditions were obtained by changing the chamber (jet total) pressure against the atmospheric ambient. Jet exit-to-ambient pressure ratios ranged between 1 and 20.32 corresponding to fully-expanded jet Mach numbers between 1 and 3.03, respectively. The PIV measurements of the streamwise and transverse velocities in the near field up to ten nozzle diameters were made, from which distributions of mean velocities, turbulence intensities and turbulent shear stress were obtained. In order to check the accuracy of the PIV measurements (particularly, the particle lag effects) an interferometric Rayleigh scattering technique was also used to obtain the streamwise velocity for certain jet conditions. Additionally, some pressure measurements were made using a total pressure tube to provide a comparison with the two optical techniques. In general, the PIV method provided good velocity data in the jet near field and allowed the identification of flow structures and their respective locations such as shock waves, expansion regions, slip lines and shear layers. However, when compared to the Rayleigh scattering data, the effect of particle inertia was evident in certain locations in the jets. This effect was most dramatic just downstream of the Mach disk (barrel shock) in the case of highly underexpanded jets.

      PubDate: 2017-04-09T17:08:29Z
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Heriot-Watt University
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