Design et développement d’un quadrirotor joueur de tennis de table avec des hélices inclinables

RÉSUMÉ Les bras manipulateurs joueurs de tennis de table les plus avancés sont chers et leur configuration requière beaucoup d’espace. On pourrait considérer l’utilisation de robots aériens pour exécuter cette tâche, mais la plupart des avions à décollage et atterrissage verticales (ADAV) ne sont pas suffisamment rapides pour reproduire des mouvements de frappes. L’objectif de la recherche présentée dans ce mémoire est de développer un nouveau type de robot aérien joueur de tennis de table. Un prototype de quadrirotor ayant des hélices inclinables est d’abord considéré pour permettre de suivre des trajectoires agressives. Le robot a besoin d’atteindre des vitesses de 3.5 m/s au point d’impact et de rester suffisamment léger pour être agile. Ensuite, pour obtenir de hautes performances sur ce requis, un contrôleur Itérative Linéaire Quadratique Régulateur (iLQR) qui suit des trajectoires ayant un snap minimum est implémenté. Le contrôle de la boucle interne est délégué à un microcontrôleur PX4 pour le tangage, le lacet et le roulis pour assurer une bonne robustesse et une haute fréquence. Cette approche est testée dans une simulation réaliste et ensuite le framework complet pour cette application est développer sur un ordinateur embarqué. Des résultats expérimentaux ont été obtenus avec des caméras de capture de mouvements donnant la position et le temps d’impact. Cette information est envoyée au quadrirotor par communication sans-fil et la trajectoire est exécutée immédiatement. Au meilleur de nos connaissances, il s’agit du premier robot aérien étant capable de retourner des balles de tennis de table lancées par un humain. Un taux de succès de 40% est obtenu sur les frappes avec le modèle réel du quadrirotor, significativement supérieur à ce qui était possible d’atteindre auparavant avec un quadrirotor.----------ABSTRACT State-of-art table tennis robot manipulators are expensive and their setup require a lot of space. One could consider using aerial robots for this task, but most vertical takeoff and landing (VTOL) vehicles are not fast enough to reproduce hitting motions. The objective of the research presented in this thesis is to develop a novel type of aerial robot tennis table player. A prototype of a quadrotor that uses tilting propellers is first considered to enable the possibility of aggressive trajectory tracking. The system needs to reach speeds up to 3.5 m/s at the position of impact and to remain light enough to be agile. Next, to obtain high performances for this requirement, an Iterative Quadratic Linear Controller (iLQR) method that follows minimum snap planned trajectories is implemented. Inner-loop control is delegated to a PX4 microcontroller for roll, pitch and yaw to ensure good robustness and high frequency. This approach is tested in a realistic simulation and then the complete software for this task is developed on an onboard computer. Experimental results have been conducted with a motion capture system to have the full state estimate of the system. The trajectory of the ball is also estimated by the motion capture system, giving the position and time of impact. This information is then sent to quadrotor wirelessly and the trajectory is executed immediately. To the best of our knowledge, this is the first aerial robot capable to return tennis table balls thrown by a human. Hitting rates of 40% are achieved with the real quadrotor, significantly better than what was possible before for a quadrotor

Primary versus Secondary Central Nervous System Melanoma: a Diagnostic Dilemma and Report of a Case

Malignant melanoma is a cancer of melanocytic origin, typically cutaneous. Despite recent advances, the prognosis is poor. Brain metastases occur in approximately 7-16% of cases and leptomeningeal metastases in 5-7%. Primary central nervous system (CNS) melanoma is rare, accounting for 1% of all melanoma cases and 0.07% of brain tumors. Methods: A 65-year old man presented with haemorrhagic venous infarction of the left temporal lobe, leading to reversible motor aphasia and right-sided hemiparesis. Brain magnetic resonance imaging also revealed peculiar supratentorial cerebral and meningeal lesions suggesting neoplasia or vasculitis. Ancillary tests were unremarkable, a brain biopsy was proposed, but the patient declined. After 1.5 years symptoms recurred and imaging studies found progression of lesions, with necrosis and surrounding vasogenic oedema. The patient finally agreed to a brain biopsy for conclusive diagnosis. Results: Histopathological and immunohistochemical assessment was consistent with malignant pigmented melanoma. There were no suspicious primary lesions, but the patient recounted having had a thoracic skin lump excised some years prior, allegedly benign, yet unavailable for second opinion. Conclusion: In suspicious CNS presentations, histopathological reevaluation of previously excised skin lesions is advised, especially if brain biopsy cannot be performed. Albeit rare, primary CNS melanoma should also be considered

ZINC-BASED DENTAL CEMENTS: PROPERTIES, APPLICATIONS, AND ADVANCEMENTS

Aim of the study Zinc-based dental cements have played a significant role in restorative dentistry for several decades. These cements, including zinc phosphate, zinc oxide-eugenol (ZOE), and zinc polycarboxylate, offer unique properties and have been utilized in various clinical applications. Material and methods We performed an extensive exploration of pertinent scientific literature to gather information for the present review. Systematic searches were executed in electronic databases, such as PubMed, Google Scholar, and Web of Science, targeting articles released from April. The scope of the search focused on articles written exclusively in the English language. The search encompassed a comprehensive set of keywords and their various combinations, including “zinc-based dental cements,” “properties,” “applications,” “advancements,” “biocompatibility,” “adhesion,” “mechanical strength,” “temporary restorations,” “luting agents,” “dental materials,” and “clinical outcomes.” Results zinc-based dental cements have demonstrated their significant potential as versatile materials in modern dentistry. Through a comprehensive exploration of their properties, applications, and advancements, it is evident that these cements offer a wide range of benefits for both practitioners and patients. Conclusions As research and development efforts persist, it is foreseeable that zinc-based dental cements will continue to evolve, further solidifying their role as integral components of successful dental treatments. With their ever-expanding applications and consistent improvements, these cements contribute significantly to the advancement of dental care, benefiting both practitioners and patients alike