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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Modeling and Evaluation of a Finite Element Cervical Spinal Cord for Injury Assessment / Modellering och utvärdering av en finita elementmodell av cervikal ryggmärg för bedömning av skador.

Valle Olivera, Nicole January 2020 (has links)
Motor vehicles collisions and falls have gradually increase the risk for spinal cord injuries. An increased knowledge of the spinal behavior and its injury mechanisms can be used as preventive strategies. Total Human Model for Safety (THUMS) SAFER is used as a tool for injury prevention, however, there is a lack of studies that evaluate the spinal cord injuries. The aim of this thesis is to implement a cervical spinal cord into the THUMS model. The mesh element quality was modified and the spinal cord was further adjusted for a correct insertion into the THUMS. The strain of the posterior and anterior surface of the cervical spinal cord during a head flexion were analyzed against experiments. Subsequently, a comparison of the head kinematics in frontal collision of the THUMS with and without the cervical spinal cord was performed. A refinement of the mesh element quality for a suitable computational time was achieved. The strain evaluation of the the spinal cord showed the same behavior as in the experiment for the posterior surface but the results were contradictory for the anterior surface. The results of the head kinematics with and without spinal cord showed no good correlation with the experimental data. Moreover, the models exhibited a bigger difference between them during the extension of the head than flexion. A further improvement of the mesh element quality required smaller element size. Nonetheless, it is important to consider that computational time increases with a decrease of element size. Several factors were critical for the strain comparison, such as the lack of information for the calculation of the strain. The difference in head kinematics from the experiment may be due to the material properties of the neck skin and the lack of the active muscles. Moreover, the contact constraints in the model may result in the differences between the THUMS models. In general, the spinal cord has been refined to obtain a favorable computational time. The evaluations have indicated that further modifications in the neck skin and contact constraints are needed for a better resemblance with the human body. Likewise, further validations against experimental studies are suggested.
2

Reconstruction of Fall Injuries for Children of Different Ages / Rekonstruktion av fallskador hos barn av olika åldrar

Björgvinsdóttir, Linda January 2019 (has links)
The idea to use finite element (FE) models to reconstruct accidents for humans is becoming more popular the last years. They represent the human body very accurately and indicate well changes in shape, size and biomechanical properties. FE models are useful when looking at complex factors in the human body in a more systematic way and when the approach is too complicated for conventional setups. Positioned child models from PIPER were used in the process and then rotated in LS-PrePost according to impact points and impact velocities from a given literature data where information from witnessed fall accidents of children was given. The simulations were finally run in LS-Dyna and the purpose was to investigate if the resulting brain injuries were similar to the real life data. From the literature, the falling distance from lowest point of the body to the ground, the age of the child, gender, type of ground and results from CT scans were all known. To compare the results to the literature data, section cuts of the brain were taken at four locations with different time steps. Biomechanical injury predictors such as brain strain, acceleration, rotational angular acceleration and rotational angular velocity were observed and helped with the comparison. In total, 12 cases were reconstructed which ended as 22 simulations. Due to uncertainty regarding the falling height when the children fell from a swing, each swing case had 3 scenarios. Overall the comparison of predicted injury locations from LS-Dyna to real injury locations from CT scans indicated that 7 out of 12 cases compared relatively well. The comparison of a 23-month-old girl to the same case reconsructed with CRABI-18 showed similar outcomes of the angular acceleration and the angular velocity. The linear acceleration and HIC were however much higher with LS-Dyna. Comparison between the swing cases of a 10-, 12- and 13-year-old resulted in similar results for the 12- and 13 year-old girls but the 10 year boy had lower values for all biomechanical parameters except the angular velocity which was a bit higher. With more detailed information about real accidents and precise scaling of PIPER child models, reconstruction with LS-Dyna could be useful in the future to design safer playgrounds for children and to obtain injury criterion for children after fall incidents. / Användande av finita element (FE) modeller för att rekonstruera olyckor har blivit allt populärare de senaste åren. De representerar människokroppen mycket noggrant och indikerar väl förändringari form, storlek och biomekaniska egenskaper. FE-modeller är användbara när man tittar på komplexa faktorer i människokroppen på ett mer systematiskt sätt och när tillvägagångssättet är för komplicerat för konventionella metoder. PIPER barnmodellerna positionerades i enlighet med islagpunkter och islaghastigheter från en given databas där informationen från vittnade fallolyckor av barn gavs. Simuleringarna kördes slutligen i LS-Dyna och syftet var att undersöka om predikteringarna liknade de resulterande hjärnskadorna. Från databasen var fallhöjd från kroppens lägsta punkt till marken, barnets ålder, kön, typ av mark och resultat från CT skanningar kända. För att jämföra resultaten med litteraturdata togs sektionsavsnitt av hjärnan på fyra platser med olika tidspunkter. Biomekaniska skadeprediktorer såsom hjärntöjning, acceleration, vinkelacceleration och vinkelhastighet extraherades och användes i jämförelsen. Totalt, rekonstruerades 12 fallolyckor med totalt 22 simuleringar. På grund av osäkerhet om fallhöjden när barnen föll från en gunga, hade varje fall från gunga 3 scenarier/fallhöjder var. Sammantaget indikerar jämförelsen av förväntade skadepredikteringar från LS-Dyna till observerade skador från CT-skanningar att 7 av 12 fall korrelerade relativt bra. Jämförelsen av en 23 månader gammal tjej i samma fall som tidigare också rekonstruerades med en CRABI-18 docka visade liknande resultat av vinkelaccelerationen och vinkelhastigheten. Linjär acceleration och HIC var emellertid mycket högre med LS-Dyna simuleringarna. Jämförelse mellan fallen från gunga hos en 10-, 12-och 13-åring resulterade i liknande resultat för 12- och 13-åriga flickor, medan 10-åringen hade lägre värden för alla biomekaniska parametrar utom den vinkelhastighet som var lite högre. Med mer detaljerad information om verkliga olyckor och exakt uppskalning av PIPER barnmodeller kan rekonstruktion med LS-Dyna vara användbar i framtiden för att utforma säkrare lekplatser för barn och för att få skadeskala för barn efter fallhändelser.
3

Ανάπτυξη εφαρμογών σε όλα τα δυνατά περιβάλλοντα προγραμματισμού του ρομπότ Katana-Neuronics / Applications development under various programming environments of the robot Katana-Neuronics

Καραστεργίου, Βασιλική, Τσιλομήτρου, Ουρανία 20 October 2010 (has links)
Σκοπός της παρούσας διπλωματικής εργασίας είναι ο προγραμματισμός και ο έλεγχος του ρομποτικού βραχίονα Katana s400 6M90 της εταιρίας Neuronics AG σε διάφορα περιβάλλοντα. Ο ρομποτικός βραχίονας έχει προγραμματιστεί στο περιβάλλον της γλώσσας C++, της γλώσσας C, του Matlab και του Labview. Βασικό στόχο αποτέλεσε η δημιουργία προγραμμάτων, τα οποία θέτουν τον ρομποτικό βραχίονα σε εκτέλεση βασικών λειτουργιών και κινήσεων. Τα προγράμματα αυτά δημιουργήθηκαν στο περιβάλλον της γλώσσας C++ και του Matlab. Προγράμματα για πιο σύνθετες λειτουργίες υλοποιήθηκαν στο περιβάλλον προγραμματισμού της γλώσσας C και του Labview. Στα προγράμματα αυτά συμπεριλαμβάνεται και ο έλεγχος του ρομπότ μέσω κάρτας ψηφιακών εισόδων/εξόδων (IOs), που είναι ενσωματωμένη στην βαθμίδα ελέγχου του ρομπότ. Επιπλέον, πραγματοποιήθηκε έλεγχος μέσω εφαρμογών TCP/IP, μέσω των οποίων δίνεται η δυνατότητα προγραμματισμού του ρομπότ από κάποια απομακρυσμένη θέση. Επιπρόσθετο στόχο αποτέλεσε η ανάπτυξη εφαρμογής, στην οποία χρησιμοποιήθηκε PLC για τον έλεγχο του ρομπότ σε συνδυασμό με μια μεταφορική ταινία, η οποία χρησιμοποιήθηκε για τη μεταφορά αντικειμένων. Κατά την εφαρμογή αυτή, το ρομπότ ελέγχθηκε μέσω της κάρτας ψηφιακών εισόδων/εξόδων. Τέλος, πραγματοποιήθηκε ορθή και αντίστροφη κινηματική ανάλυση και ορισμός του χώρου εργασίας του ρομποτικού βραχίονα. / The purpose of the present graduation study is the programming and control of the robotic arm Katana s400 6M90G, which belongs to the corporation Neuronics AG, under various softwares. The robotic arm has been programmed under a C++ and a C–based software, and under the development environments of Matlab and LabView. The main purpose was the creation of programs, which set the robot in mode of execution of main movements and functions. These programs were created in the environments of C++ and Matlab. Programs for more complex functions were created in the environment of C and LabView. These programs, also, include control via digital inputs/outputs (IOs) card, which is set in the control board of the robot. Moreover, control via TCP/IP applications has been accomplished, through which the user has the ability to program the robot while using a remote pc. An additional purpose was the development of an application, in which a plc and a conveyor were used. In this application, the robot was controlled via the digital inputs/outputs (IOs) card. Finally, direct kinematics and inverse kinematics analysis are presented, such as robot’s workspace definition.

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