5 research outputs found
Advanced Flight Control Design and Evaluation: An application of time delayed Incremental Backstepping
No full textThe sensor-based approach of Incremental Backstepping is applied to flight control law design in this research project. It allows the usage of the same control law on different types of aircraft without the need for redesign. Apart from full state availability, the derivation of Incremental Backstepping assumes instantaneous control action. Due to actuator lags and delays, the implementation of control commands cannot necessarily be considered instantaneous. This mitigates the stability guarantee provided by Lyapunov theory. Therefore, a novel technique to estimate the time delay margins of the Incremental Backstepping controlled systems is proposed in the thesis. This provides an important stability measure for possible certification and widens the application range of Incremental Backstepping. This simple, yet effective, Lyapunov-based control technique shows positive robustness properties with respect to model uncertainties, unknown parameters, external disturbances and time delay effects. It is applied to the DA 42 aircraft as a (pilot-in-the-loop) rate controller in the scope of this thesis. The implementation requires measurements of the aircrafts angular accelerations and control surface deflections. If the latter is not available, it is shown that filters can still be used in the control system. However, the usage of filters mitigates the highly favorable robustness properties of the closed-loop system. Moreover, a controller evaluation strategy is proposed. It rates the performance and stability properties of the Incremental Backstepping controlled system in terms of the flight control system requirements. Evaluation of the Incremental Backstepping controller shows allowable input multiplicative uncertainties of up to 40% of the nominal value at the worst-case excitation frequency for a controller update rate of 100Hz. When no reference shaping is applied, the handling qualities of the incremental rate controller show to be less desirable than that of a conventional linear controller designed specifically for the DA 42. However, it is possible to improve handling characteristics by reference shaping. Furthermore, the handling characteristics of the incremental controller remain fairly constant along the flight envelope and in adverse flight conditions.Guidance, Control & NavigationControl and Operations (C&O) - Control and Simulation Division (C&S)Aerospace Engineerin
Aflsuiting Grevelingen: Noordelijk Sluitgat: Rapport modelonderzoek
No full textIn een detailmodel is een vergelijkend onderzoek naar de vormgeving van de sluitgaten uitgevoerd, waarbij van een bepaalde keuze voor de lengte van de verdediging is uitgegaan, n.l. aan weerszijden 80 m gemeten uit de drempelas. De ontgronding is hierbij als criterium genomen. Het onderzoek is uitgevoerd voor eb, daar hierbij de grootste snelheden in de sluitgaten zijn te verwachten.Of de uit het onderzoek gevolgde gunstigste oplossing bij de gekozen verdedigingslengte aanvaardbaar iss zal afhangen van de in het prototype te verwachten ontgrondingen. Hiertoe is het noodzakelijk een voorspelling te doen. voor de tijdschaal van de ontgronding. Aan de hand van een vergelijking tussen de in het Veerse G-at opgetreden ontgrondingen en die in een model hiervan, is getracht voor een niet samengetrokken drie-dimensionaal model enig inzicht in de, aan de hand van een twee dimensionaal onderzoek bepaalde9 formule voor de tijdschaal te verkrijgen. Tenslotte is voor verschillende drempelcombinaties in de beide sluitgaten een onderzoek ingesteld naar de aantasting van de grindbestorting, die als afdekking van de verdediging op de Krammerplaat is toegepast.Deltawerken, Grevelinge
Microcatheter tracking in thrombectomy procedures: A finite-element simulation study
No full textBackground and objective: Mechanical thrombectomy is a minimally invasive procedure that aims at removing the occluding thrombus from the vasculature of acute ischemic stroke patients. Thrombectomy success and failure can be studied using in-silico thrombectomy models. Such models require realistic modeling steps to be effective. We here present a new approach to model microcatheter tracking during thrombectomy. Methods: For 3 patient-specific vessel geometries, we performed finite-element simulations of the microcatheter tracking (1) following the vessel centerline (centerline method) and (2) as a one-step insertion simulation, where the microcatheter tip was advanced along the vessel centerline while its body was free to interact with the vessel wall (tip-dragging method). Qualitative validation of the two tracking methods was performed with the patient's digital subtraction angiography (DSA) images. In addition, we compared simulated thrombectomy outcomes (successful vs unsuccessful thrombus retrieval) and maximum principal stresses on the thrombus between the centerline and tip-dragging method. Results: Qualitative comparison with the DSA images showed that the tip-dragging method more realistically resembles the patient-specific microcatheter-tracking scenario, where the microcatheter approaches the vessel walls. Although the simulated thrombectomy outcomes were similar in terms of thrombus retrieval, the thrombus stress fields (and the associated fragmentation of the thrombus) were strongly different between the two methods, with local differences in the maximum principal stress curves up to 84%. Conclusions: Microcatheter positioning with respect to the vessel affects the stress fields of the thrombus during retrieval, and therefore, may influence thrombus fragmentation and retrieval in-silico thrombectomy
Revolutionary poetics of a nomadic educational machine
No full textW artykule zostaje poddana analizie praca nomadycznej maszyny edukacyjnej. Podniesiono przede wszystkim wątek jest auto-nie-reprezentacji. Wskazano na konieczność uwzględnienia specyfiki silnika tejże maszyny, zwłaszcza w kontekście głosu i jego relacji z tym, co ludzkie i racjonalne. Poetyka nomadycznej maszyny edukacyjnej jest nie tylko sposobem ujawniania się i zakrywania, ale stanowi praktykę oporową. Autor, starając się zarysować budowę tego elementu silnika maszyny i jego pracę, rozważania teoretyczne odnosi do empirycznego materiału, zapomnianych historii opowiadanych przez zbuntowane wielości.In this paper the work of a nomadic educational machine is analyzed. The topic of non-self-representation has been raised primarily. The necessity of taking into account the specifics of the engine of this machine has been emphasized, especially in the context of the voice and its relationship with what is human and rational. Poetics of a nomadic educational machine is not only a way of coming out and covering, but it is also the practice of resistance. The author, trying to outline the structure of this engine component and its work, theoretically refers to the empirical material, forgotten stories told by the rebellious multiplicity.
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Spatial Distribution and Chemical Composition of Road Dust in Two High-Altitude Latin American Cities
No full textRoad dust (RD) resuspension is one of the main sources of particulate matter in cities with adverse impacts on air quality, health, and climate. Studies on the variability of the deposited PM10 fraction of RD (RD10) have been limited in Latin America, whereby our understanding of the central factors that control this pollutant remains incomplete. In this study, forty-one RD10 samples were collected in two Andean cities (Bogotá and Manizales) and analyzed for ions, minerals, and trace elements. RD10 levels varied between 1.8–45.7 mg/m2, with an average of 11.8 mg/m2, in Bogotá and between 0.8–26.7 mg/m2, with an average of 5.7 mg/m2, in Manizales. Minerals were the most abundant species in both cities, with a fraction significantly larger in Manizales (38%) than Bogotá (9%). The difference could be explained mainly by the complex topography and the composition of soil derived from volcanic ash in Manizales. The volcanic activity was also associated with SO4−2 and Cl−. Enrichment factors and principal component analysis were conducted to explore potential factors associated to sources of RD10. Elements such as Cu, Pb, Cr, Ni, V, Sb, and Mo were mainly associated with exhaust and non-exhaust traffic emissions.The authors are grateful for the financial support provided by ECOPETROL and CORPOCALDAS. The authors’ viewpoint does not necessarily reflect the official opinion of their institutions. We thank our students from CLIMA Research Group and Hydraulic Engineering and Environmental Research Group who developed the field campaigns. In addition, we would like to thank Universidad Nacional de Costa Rica, who supported the chemical analysis of the road dust samples. The author Guilherme M. Pereira acknowledges the Brazilian foundation Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, São Paulo Research Foundation; Grants nos. 2019/01316-8 and 2018/07848-9).Peer reviewe
