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Açık Ders Kaynakları 30
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Akademik Çalışmalar 45375
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Sunumlar 42
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Temel Kayıtlar 2825
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Access status: Open Access ,
Design and simulation of a fault tolerant control system for the generic transport model under structural failure conditions
(Graduate School, 2026-06-22) Ünal, Muhammed Emre; Üstoğlu, İlker; 514221031; Defense Technologies
Commercial aviation safety has reached unprecedented levels in recent decades; however, Loss of Control In-flight (LOC-I) remains the single largest contributor to fatal accidents and hull losses in the transport sector. A significant portion of these accidents is precipitated by sudden structural failures—such as the detachment of vertical stabilizers, loss of control surfaces, or asymmetric wing damage—which drastically alter the aircraft's aerodynamic properties. Current generation Fly-by-Wire (FBW) systems predominantly utilize linear control laws, such as PID or LQR, with extensive gain scheduling. While these systems provide excellent performance within the nominal flight envelope, they lack the adaptability required to handle the severe non-linearities and dynamic coupling introduced by catastrophic structural damage. When the physical plant of the aircraft deviates significantly from the internal model used to design the controller, standard control loops often fail, leading to instability. This thesis addresses this critical gap by designing and validating a robust Fault Tolerant Flight Control (FTFC) system capable of recovering a transport aircraft from severe structural degradation. The research utilizes the NASA Generic Transport Model (GTM) as the primary simulation testbed. The GTM is a publicly available, high-fidelity simulational model derived from a dynamically scaled, twin-turbine research aircraft. It represents the non-linear aerodynamic characteristics of a typical commercial jet transport. This study leverages the GTM's validated aerodynamic database to simulate realistic responses to control surface deflections and structural asymmetries, providing a rigorous environment for testing fault-tolerant algorithms. The core contribution of this thesis is the implementation of an Incremental Nonlinear Dynamic Inversion (INDI) control strategy. Conventional Nonlinear Dynamic Inversion (NDI) attempts to linearize the aircraft dynamics by mathematically canceling out non-linear terms using an on-board aerodynamic model. However, NDI is highly sensitive to "model mismatch"—if the on-board model does not account for a missing flap or broken elevator, the inversion fails, potentially worsening the loss of control. INDI overcomes this limitation by adopting a sensor-based approach. Instead of relying on a stored model to estimate the total forces and moments acting on the aircraft, INDI utilizes high-frequency feedback of the angular acceleration (measured via IMU) and the current control surface positions. The control law computes the increment of control input required to achieve the desired change in acceleration over a discrete time step. By relying on immediate sensor measurements rather than a pre-computed model, INDI becomes inherently robust to model uncertainties and external disturbances. The controller essentially "learns" the new dynamics of the damaged aircraft in real-time without requiring complex online system identification algorithms. While the INDI controller stabilizes the rotational dynamics, ensuring the survival of the aircraft requires high-level decision-making. To achieve this, the study integrates the INDI inner loop with a logic-based Mission Supervisor. This module acts as an autonomous pilot, continuously monitoring the "Health Status" of the aircraft actuators and the "Energy State" defined by fuel, altitude, and range. Upon the detection of a failure, the Mission Supervisor executes a hierarchical decision process. It first categorizes the fault severity and then immediately overrides pilot or guidance inputs to impose strict safety limits. For asymmetric failures, bank angle is restricted to prevent spiral divergence. Subsequently, the system calculates the distance to the home base. If the aircraft is within a recoverable range, the Guidance module is switched to a "Return to Base" mode, directing the aircraft to a loiter waypoint. The proposed architecture was subjected to three specific, high-severity damage cases in a MATLAB/Simulink environment to validate its efficacy. The first scenario, Case 01, simulated the total loss of the rudder surface, representing a major lateral-directional asymmetry. The analysis focused on the controller's ability to maintain directional stability using only ailerons and potential differential thrust. The INDI controller successfully decoupled the lateral-directional dynamics, preventing the sideslip angle from exceeding critical limits during turning maneuvers. The second scenario, Case 04, represented the most critical failure mode: the instantaneous loss of the left wingtip. This severe structural failure created a massive rolling moment, a significant loss of lift on the port wing, and complex shifts in the aircraft's mass and center of gravity. Simulation results showed while the uncompensated open-loop dynamics failed to arrest the roll rate before the aircraft inverted before the aircraft inverted, the INDI controller sensed the un-modeled angular acceleration immediately and saturated the right ailerons to counter the torque. The Mission Supervisor successfully detected the lateral asymmetry, limited the bank angle to ten degrees, and stabilized the aircraft, proving the system's ability to handle catastrophic asymmetric lift and inertial cross-coupling. The final scenario, Case 05, tested the pitch authority limits through the loss of the left elevator. With half of the elevator surface missing, the aircraft's ability to flare for landing was compromised. The control allocation logic successfully redistributed the required pitch moment to the remaining right elevator. The analysis demonstrated that while the pitch response was sluggish, the system maintained sufficient authority to execute a safe approach and landing. In conclusion, the results of this study demonstrate that the integration of Incremental Nonlinear Dynamic Inversion with a logic-based Mission Supervisor provides a highly effective solution for LOC-I prevention. The INDI control law exhibits superior robustness to structural faults compared to model-based methods, while the Mission Supervisor ensures that the damaged aircraft is flown within a restricted, safe envelope. This architecture offers a promising pathway for the next generation of autonomous flight safety systems in commercial aviation.
Access status: Metadata only ,
Influence of semolina cream addition on the bioaccessibility of polyphenols in walnut-filled pastry (Şöbiyet)
(Springer Science and Business Media LLC, 2025-03-30) Sena Bakir; Senem Kamiloglu; Tugba Ozdal; Esra Capanoglu; Gıda Mühendisliği Bölümü; Güven, Esra Çapanoğlu
Abstract Walnuts are widely consumed around the world, and are often used as a filling for pastries, especially in East Asia. In this study, a popular pastry called “şöbiyet” was examined to evaluate the interactions between semolina cream and walnuts. The phenolic profile, antioxidant activity, and in vitro bioaccessibility were analyzed. Samples containing 35% (W35%) and 20% (W20%) walnuts (w/w) were prepared with and without the addition of semolina cream. Total phenolic content (TPC) of undigested samples ranged from 417.6 ± 73.11 mg GAE 100 g −1 sample to 726.2 ± 21.66 mg GAE 100 g −1 sample. Although samples with added semolina cream showed higher TPC levels, the differences were not statistically significant (p 0.05). In contrast, total antioxidant activity (TAC) levels, as measured by the DPPH and CUPRAC assays, indicated that the addition of semolina cream significantly decreased antioxidant activity (p 0.05). A similar trend was observed in the in vitro bioaccessibility of individual phenolic compounds. In most cases, no significant differences were observed between samples with higher walnut content (W35%) regardless of whether they contained semolina cream (p 0.05). However, samples with lower walnut content (W20%) lost some of the phenolic compounds, TPC and TAC during intestinal digestion phase when semolina cream was added (p 0.05). Overall, the results highlighted that adjusting the walnut content and semolina cream composition in pastries can improve the bioaccessibility of polyphenols, suggesting potential applications in the development of functional foods with enhanced health benefits.
Access status: Metadata only ,
Biconservative Surfaces in Robertson–Walker Spaces
(Springer Science and Business Media LLC, 2025-03-29) Nurettin Cenk Turgay; Rüya Yeǧin Şen; Matematik Bölümü; Turgay, Nurettin Cenk
In this paper, we mainly focus on space-like PMCV surfaces in Robertson–Walker spaces. First, we derive certain geometrical properties of biconservative surfaces in the Robertson–Walker space \(L_1^n(f, c)\) of arbitrary dimension. Then, we get complete local classifications of PMCV surfaces in L₁⁴(f, 0), L₁⁵(f, 0) and L₁⁵(1, ± 1). Finally, we prove that a space-like PMCV biconservative surface in \(L_1^n(f, 0)\), n ≥ 6 lies on a totally geodesic submanifold with dimension either 4 or 5.
Access status: Metadata only ,
Recent progress in additive manufacturing of 7XXX aluminum alloys
(Springer Science and Business Media LLC, 2025-03-29) Varma Kvvssn; Muhammad Muteeb Butt; Hossein Laieghi; Zia Uddin; Elmas Salamci; Duck Bong Kim; Hüseyin Kizil; Metalurji ve Malzeme Müh.Böl.; Kızıl, Hüseyin
Abstract Additive manufacturing (AM) has emerged as a transformative technology for fabricating intricately tailored components, representing a paradigm shift in design versatility and material optimization. The fabrication of high-strength Al7XXX series alloys through this approach is attracting increasing interest due to their lightweight nature, exceptional mechanical properties, and corrosion resistance, making them essential for aerospace, automotive, and defense applications. Despite these advantages, manufacturing these alloys through AM remains challenging due to issues such as hot cracking, porosity, elemental evaporation, adhesion and bonding defects, and microstructural anisotropy. Recent studies have explored strategies to address these challenges, demonstrating successful fabrication and evaluating potential applications in advanced engineering. This review aims to report the current state of manufacturing techniques, categorizing them into solid-state and melting-based approaches while analyzing their processing mechanisms, challenges, and mechanical performance. Strategies for defect mitigation, including process optimization, post-processing treatments such as heat treatment and grain refinement, and novel alloy modifications, are critically reviewed. By consolidating recent advancements and identifying key challenges, this study establishes a foundation for future research, emphasizing defect control, microstructural stability, and industrial scalability for high-performance applications.
Access status: Metadata only ,
Türkiye’s Maritime Training and Education Institutes Non-Conformities Historical Evaluation by Grey Relation Analysis and Geographical Information System
(Galenos Yayinevi, 2025-03-28) Esat Güzel; Pelin Bolat; Temel Bilimler Bölümü; Bolat, Pelin
The main aim of the study is to determine an objective method for maritime training and education institutes quality assessment based on objective data. To achieve this, results of external audits carried out by independent evaluation are analysed using the Entropy Weighted Grey Relation Analysis method. In the final stage, results of Entropy Weighted Grey Relation Analysis method are demonstrated on QGIS, an open source Geographic Information System, thus Türkiye maritime training and education institutes non-conformities concentration and distribution maps are generated.