Development of system for localisation of a planar robot using optical sensors

164 σ.Η παρούσα εργασία διαπραγματεύεται την ανάπτυξη πρωτότυπου συστήματος προσδιορισμού θέσης και προσανατολισμού ενός σώματος, χρησιμοποιώντας οπτικούς αισθητήρες laser και κατάλληλο αλγόριθμο ελαχιστοποίησης της επίδρασης του θορύβου. Το σύστημα αυτό θα ενσωματωθεί στο διαστημικό ρομπότ του διαστημικού εξομοιωτή σε τρεις κατάλληλες θέσεις. Οι συσκευές αυτές είναι ουσιαστικά οι αισθητήρες που βρίσκονται σε μια πολύ κοινή κατασκευή, τα ποντίκια των ηλεκτρονικών υπολογιστών (Η/Υ). Έχουν την δυνατότητα να δίνουν τη στοιχειώδη μετατόπιση του συστήματος στο οποίο είναι προσαρτημένες σε δύο άξονες. Προϋπόθεση είναι να βρίσκονται σε πολύ μικρή απόσταση από την επιφάνεια κίνησης και η ύπαρξη μικροελεγκτή για την επικοινωνία του εκάστοτε αισθητήρα με άλλα υποσυστήματα. Δεδομένου ότι κατά την στοιχειώδη μετακίνηση σε δύο άξονες ο κάθε αισθητήρας δίνει δύο τιμές, ο κεντρικός υπολογιστής του ρομπότ λαμβάνει συνολικά τρία ζεύγη τιμών. Για την εύρεση της θέσης και του προσανατολισμού του χρειάζονται πρακτικά τρεις τιμές, ή αλλιώς οι τιμές από δύο μόνο αισθητήρες. Για αυτό τον λόγο, ένας κατάλληλος αλγόριθμος επεξεργάζεται τις τιμές, και χρησιμοποιώντας διάφορους μαθηματικούς τρόπους βρίσκει τις ζητούμενες τιμές. Για την εξέταση όλων των παραπάνω, αναπτύχθηκε ένα πειραματικό σύστημα επικοινωνίας μεταξύ του επιλεγμένου αισθητήρα και του επιλεγμένου μικροελεγκτή, ενώ η επικοινωνία έγινε με την βοήθεια του πρωτοκόλλου SPI (Serial Peripheral Interface) που απαντάται όλο και συχνότερα σε μικροσυσκευές ευρείας κατανάλωσης. Ο τρόπος διασύνδεσης αναφέρεται αναλυτικά και τα αποτελέσματα δείχνουν την ευκολία χειρισμού του πρωτοκόλλου. Ταυτόχρονα με το υλικό μέρος, αναπτύχθηκε και μοντέλο του συστήματος, για να αποτελεί τη βάση στην οποία θα μπορούν να δοκιμαστούν διάφοροι αλγόριθμοι ελαχιστοποίησης θορύβου. Για την καλύτερη μοντελοποίηση του θορύβου έγιναν σχετικά πειράματα για την εύρεση της στατιστικής του. Τέλος δοκιμάστηκαν κάποιοι πρώτοι αλγόριθμοι, τα αποτελέσματα των οποίων αναφέρονται αναλυτικά.The present work negotiates the development of an original system for the determination of position and orientation of body, using optical sensors with laser and a suitable algorithm for the minimization of the effects of measurement noise. This system will be incorporated in the space robot of the space simulator at three suitable points of it. These appliances are substantially the sensors that can be found in a very common manufacture, the mice of personal computers (PCs). They have the ability of giving the elementary translation of system on which they are, in two axes. A condition for their proper use is to have a very small distance from the surface of movement and the existence of a microcontroller for the interconnection between each sensor and other subsystems. Since at the elementary translation in two axes, each sensor gives two values, the central computer of robot receives in total three pairs of measurements. To determine the position and its orientation, the system needs practically three values, or differently the measurements from only two sensors. For this reason, a suitable algorithm processes the measurements, and using various mathematic ways finds the asked values. For the examination of the above, it was developed an experimental system of communication between the selected sensor and the selected microcontroller, while the communication between them was created with the use of the SPI protocol (Serial Peripheral Interface), a protocol that gains a widespread use in mass consumption devices. The interconnection is analyzed analytically and the results show the ease of handling this protocol. Simultaneously with the hardware part, it was also developed a model of the system, in order to create the base, on which various algorithms for minimization of noise will be tested. For the better modeling of noise, experiments for the determination of its statistics have been taken place. Finally a number of basic algorithms were tested and their results are reported analytically.Ιωσήφ Σ. Παρασκευά

Towards a Standardized Grasping and Refuelling On-Orbit Servicing for GEO Spacecraft

Exploitation of space must benefit from the latest advances in robotics. On-orbit servicing is a clear candidate for the application of autonomous rendezvous and docking mechanisms. However, during the last three decades most of the trials took place combining extravehicular activities (EVAs) with telemanipulated robotic arms. The European Space Agency (ESA) considers that grasping and refuelling are promising near-mid-term capabilities that could be performed by servicing spacecraft. Minimal add-ons on spacecraft to enhance their serviceability may protect them for a changing future in which satellite servicing may become mainstream. ESA aims to conceive and promote standard refuelling provisions that can be installed in present and future European commercial geostationary orbit (GEO) satellite platforms and scientific spacecraft. For this purpose ESA has started the ASSIST activity addressing the analysis, design and validation of internal provisions (such as modifications to fuel, gas, electrical and data architecture to allow servicing) and external provisions (such as integrated berthing fixtures with peripheral electrical, gas, liquid connectors, leak check systems and corresponding optical and radio markers for cooperative rendezvous and docking). This refuelling approach is being agreed with European industry (OHB, Thales Alenia Space) and expected to be consolidated with European commercial operators as a first step to become an international standard; this approach is also being considered for on-orbit servicing spacecraft, such as the SpaceTug, by Airbus DS. This paper describes in detail the operational means, structure, geometry and accommodation of the system. Internal and external provisions will be designed with the minimum possible impact on the current architecture of GEO satellites without introducing additional risks in the development and commissioning of the satellite. Endeffector and berthing fixtures are being designed in the range of few kilos and linear dimensions around 15cm. A central mechanical part is expected to perform first a soft docking followed by a motorized retraction ending during a hard docking phase using aligning pins. Mating and de-mating will be exhaustively analysed to ensure robustness of operations. Leakage-free valves would allow for the transfer of fuel to the serviced spacecraft. The validation of the ASSIST system through dedicated environmental tests in a vacuum chamber together with dynamic testing using an air-bearing table will allow for the demonstration of concept feasibility and its suitability for becoming a standard of the on-orbit space industry

FabSpaces at ImageCLEF 2017 - Population Estimation (Remote) Task

International audienceThe paper summarizes the participation of the 6 FabSpaces to the population estimation (remote) pilot task at ImageCLEF 2017 Lab. FabSpace 2.0 is an open-innovation network for geodata-driven innovation that aims at improving universities contribution to the socioeconomic and environmental performance of societies. In the framework of the ImageCLEF Lab, the 6 FabSpaces participated although only four of them succeeded in submitting a run. This paper summarizes their participations. For each FabSpace, we present the local organization to participate to the CLEF Lab, the participants and their work. We conclude this paper with some lessons we learned from this participation

Pancreatic surgery outcomes: multicentre prospective snapshot study in 67 countries

Background: Pancreatic surgery remains associated with high morbidity rates. Although postoperative mortality appears to have improved with specialization, the outcomes reported in the literature reflect the activity of highly specialized centres. The aim of this study was to evaluate the outcomes following pancreatic surgery worldwide.Methods: This was an international, prospective, multicentre, cross-sectional snapshot study of consecutive patients undergoing pancreatic operations worldwide in a 3-month interval in 2021. The primary outcome was postoperative mortality within 90 days of surgery. Multivariable logistic regression was used to explore relationships with Human Development Index (HDI) and other parameters.Results: A total of 4223 patients from 67 countries were analysed. A complication of any severity was detected in 68.7 percent of patients (2901 of 4223). Major complication rates (Clavien-Dindo grade at least IIIa) were 24, 18, and 27 percent, and mortality rates were 10, 5, and 5 per cent in low-to-middle-, high-, and very high-HDI countries respectively. The 90-day postoperative mortality rate was 5.4 per cent (229 of 4223) overall, but was significantly higher in the low-to-middle-HDI group (adjusted OR 2.88, 95 per cent c.i. 1.80 to 4.48). The overall failure-to-rescue rate was 21 percent; however, it was 41 per cent in low-to-middle-compared with 19 per cent in very high-HDI countries.Conclusion: Excess mortality in low-to-middle-HDI countries could be attributable to failure to rescue of patients from severe complications. The authors call for a collaborative response from international and regional associations of pancreatic surgeons to address management related to death from postoperative complications to tackle the global disparities in the outcomes of pancreatic surgery (NCT04652271; ISRCTN95140761)