Optimal control problems solved via swarm intelligence

Questa tesi descrive come risolvere problemi di controllo ottimo tramite swarm in telligence. Grande enfasi viene posta circa la formulazione del problema di controllo ottimo, in particolare riguardo a punti fondamentali come l’identificazione delle incognite, la trascrizione numerica e la scelta del risolutore per la programmazione non lineare. L’algoritmo Particle Swarm Optimization viene preso in considerazione e la maggior parte dei problemi proposti sono risolti utilizzando una formulazione differential flatness. Quando viene usato l’approccio di dinamica inversa, il problema di ottimo relativo ai parametri di trascrizione è risolto assumendo che le traiettorie da identificare siano approssimate con curve B-splines. La tecnica Inverse-dynamics Particle Swarm Optimization, che viene impiegata nella maggior parte delle applicazioni numeriche di questa tesi, è una combinazione del Particle Swarm e della formulazione differential flatness. La tesi investiga anche altre opportunità di risolvere problemi di controllo ottimo tramite swarm intelligence, per esempio usando un approccio di dinamica diretta e imponendo a priori le condizioni necessarie di ottimalitá alla legge di controllo. Per tutti i problemi proposti, i risultati sono analizzati e confrontati con altri lavori in letteratura. Questa tesi mostra quindi the algoritmi metaeuristici possono essere usati per risolvere problemi di controllo ottimo, ma soluzioni ottime o quasi-ottime possono essere ottenute al variare della formulazione del problema.This thesis deals with solving optimal control problems via swarm intelligence. Great emphasis is given to the formulation of the optimal control problem regarding fundamental issues such as unknowns identification, numerical transcription and choice of the nonlinear programming solver. The Particle Swarm Optimization is taken into account, and most of the proposed problems are solved using a differential flatness formulation. When the inverse-dynamics approach is used, the transcribed parameter optimization problem is solved assuming that the unknown trajectories are approximated with B-spline curves. The Inverse-dynamics Particle Swarm Optimization technique, which is employed in the majority of the numerical applications in this work, is a combination of Particle Swarm and differential flatness formulation. This thesis also investigates other opportunities to solve optimal control problems with swarm intelligence, for instance using a direct dynamics approach and imposing a-priori the necessary optimality conditions to the control policy. For all the proposed problems, results are analyzed and compared with other works in the literature. This thesis shows that metaheuristic algorithms can be used to solve optimal control problems, but near-optimal or optimal solutions can be attained depending on the problem formulation

Autonomous crater detection on asteroids using a fully-convolutional neural network

This paper shows the application of autonomous Crater Detection using the U-Net, a Fully-Convolutional Neural Network, on Ceres. The U-Net is trained on optical images of the Moon Global Morphology Mosaic based on data collected by the LRO and manual crater catalogues. The Moon-trained network will be tested on Dawn optical images of Ceres: this task is accomplished by means of a Transfer Learning (TL) approach. The trained model has been fine-tuned using 100, 500 and 1000 additional images of Ceres. The test performance was measured on 350 never before seen images, reaching a testing accuracy of 96.24%, 96.95% and 97.19%, respectively. This means that despite the intrinsic differences between the Moon and Ceres, TL works with encouraging results. The output of the U-Net contains predicted craters: it will be post-processed applying global thresholding for image binarization and a template matching algorithm to extract craters positions and radii in the pixel space. Post-processed craters will be counted and compared to the ground truth data in order to compute image segmentation metrics: precision, recall and F1 score. These indices will be computed, and their effect will be discussed for tasks such as automated crater cataloguing and optical navigation

Minimum-Fuel Control Strategy for Spacecraft Formation Reconfiguration via Finite-Time Maneuvers

This paper addresses the minimum-fuel spacecraft formation reconfiguration maneuver in J2 perturbed near-circular orbits. In this study, only the deputy is assumed to be maneuverable and capable of..

Granulocyte- and monocyte-platelet adhesion index in coronary and peripheral blood after extracorporeal circulation and reperfusion

Background: Neutrophil-granulocyte and mononuclear-cell functional changes occur during cardiopulmonary bypass and cardiovascular surgery. Leukocyte-platelet interaction, leading to generation of heterotypic co-aggregates, represents an amplification mechanism of local inflammatory response and tissue damage. Methods: Samples of 20 patients were drawn from coronary sinus before cardioplegia and after reperfusion, as well as from peripheral blood at 5 and 24 hours postoperatively. Granulocyte and monocyte expression of CD162, CD15s, CD18 and CD11b were quantified by flow cytometry at the different times. Parallel variations of leukocyte-platelet conjugates (percentages) and a derived (cell number-normalized) leukocyte-platelet adhesion index were measured using antibodies against CD45, CD14 and CD41a. The evaluation of platelet functional state was carried out using antibodies against CD62P (P-selectin) and PAC-1. Results: Monocyte and granulocyte cell number increased in coronary blood at reperfusion and in peripheral blood post-operatively. A different course characterized the changes of the leukocyte-platelet adhesion index with respect to the variations of circulating leukocyte-platelet co-aggregates . Leukocyte molecules expression showed no significant variations for CD15s on both leukocyte subsets, while a significant up-modulation for CD162 was observed on monocytes at 24 hours after extracorporeal circulation (P=0.0002), and for CD11b on granulocytes at 5 hours post-operatively (P=0.033). A loss of CD162 expression was observed at reperfusion (P=0.0038) on granulocytes, associated to a down-modulation of CD18 (P=0.0033) and CD11b (P=0.0184) in peripheral blood at 24 hours. No significant up-regulation of platelet activatory molecules was found at reperfusion, as well as post-operatively, when compared with the before-cardioplegia derived data. Conclusions: The variations of a normalized leukocyte-platelet adhesion index seem to reflect the leukocyte-platelet functional interaction more accurately than the measurements of cellular conjugates. The absence of platelet activation suggests that the leukocyte membrane modifications play a main role in controlling the formation and stability of heterotypic leukocyte-platelet co-aggregates after cardiac surgery with extracorporeal circulation

An Original Single-Body Synthetic Heart Valve: Feasibility Study And Prototype Realization

The research for durable, non-thrombogenic heart valve prostheses able to overcome the limits of biological and mechanical ones, promoted the development of synthetic valves. Their success has been hampered by lack of durability, due to calcification and thromboembolic complications. The aim of this work was to develop a prototype of a new elastomeric biocompatible valve, durable and free from calcification

A New Elastomeric Biomaterial for Arterial Diseases Applications

The covering of self-expandable stents (S-ESs) with elastic biocompatible membrane may avoid the atherosclerotic plaque prolapse between the stent struts into the lumen. In this work it is proposed a new elastomeric biomaterial, combined with a spray-technique, to realise a thin membrane for covering S-ESs. The membrane resulted adherent to metallic struts and able to follow stent deformation. The new biomaterial, an elastomeric silicone (polydimethylsiloxane PDMS) based poly(ether)urethane (PEtU/PDMS), deposited on the S-ESs by the spray-technique, showed in vitro good adhesion to metallic struts, even after deformation and recoil, and did not compromise its elastic behaviour. Capitalising on the good biocompatibility and low trombogenicity demonstrated by the material within previous studies it is expected that it can be used successfully for S-ESs covering for iliac-femoral applications

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements