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Workspace optimization of a rotationalparallel platform for use in a laparoscopictraining tool
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Arbetsytsoptimering av en rotationel parallelplattform för användning till ett träningsverktyginom Laparoskopi (Swedish)
Abstract [sv]

Projektets mål var att optimisera och konstruera en rotationell parallel platform för användninginom träning för laparoskopi. Optimeringen baserades på fyra variabler; aktuator placering,aktuator vinkel, bottenben längd och toppbens längd. Optimeringens mål var att maximeraplatformens arbetsvolym. Två optimeringar utfördes, en baserad på translationell arbetsvolymoch en baserad på rotationell arbetsvolym.En mjukvarumodell av en rotationell platform utvecklades som ett objekt i Matlab. Detta tillät ettenkelt sätt att ändra variabler på platformen, utvärdera platformen baserat på nya variabler samtenkelt visualisera ändringarna.För att utvärdera volymerna av arbetsområdet utvecklades en algoritm som hittar kanterna avplatformens arbetsvolym. Denna algoritm anses vara betydligt effektivare än tidigare rutnätsmetoder som ofta använts för detta syfte. För att utvärdera rotationella arbetsvolymenutvecklades ett nytt mått som kallas angular agility där arean av en yta runt varje rotationsaxelvid noll grader beräknas. Detta implementerades då en komplett rotationsvolym kalkyl i allamöjliga positioner ansågs vara för tidskrävande.Plattformen optimerades med hjälp av en genetisk algoritm som implementerades i Matlab. Alloptimering utfördes med en population av 100 plattformer, mutation av -10 – 10 mm och graderoch en minimal förbättring med 2 procent per iteration.Den translationsoptimerade platformen ger en arbetsvolym som är 630% större änoriginalplatformen. Den rotationsoptimerade platformen ger en rotationsvolym som är 77%större än originalplatformen.Test av den translationsoptimerade platformen påvisade fel i originalkoden för platformen somåtgärdades. Efter åtgärdningen påvisade tester att mjukvarumodellen och den konstrueradeplatformen överrensstämde väl.All kod som skrevs under projektet är tillgänglig med bifogas ej i rapporten på grund avmändgen kod som producerades.

Abstract [en]

The goal of this project was to optimize and construct a rotational parallel platform for use intraining of Laparoscopic surgery. The optimization was based on four variables; actuatorposition, actuator angle, bottom leg length and top leg length. The goal of the optimization wasto maximize the platforms workspace volume. Two optimizations were performed, one based ontranslational workspace volume and one based on rotational workspace volume.A software model of a rotational parallel platform was developed as an object in Matlab. Thisallowed for a simple way of changing variables of the platform, evaluate the platform based onthe new variables and a simple way of visualizing the changes.To evaluate the volumes of the workspace, an edge search algorithm was developed that findsthe edges of the workspace of the platform. This algorithm is very adaptable and is deemed to besignificantly more efficient than conventional grid based searches which are often used for thispurpose. To evaluate the rotational workspace volume a new measure was developed; angularagility. The area of a surface around each of the rotational axes at zero degrees is measured. Thiswas implemented since a complete rotational volume evaluation in all edge positions of theworkspace is too time inefficient for optimization.The platform was optimized with the help of a genetic algorithm that was implemented inMatlab. All optimization was performed with a population of 100 platforms, a mutation rate of -10 – 10 mm and degrees and a minimum improvement rate of 2 percent per iteration.The translational optimized platform gives a workspace volume which is 630% larger than theoriginal platform. The rotational optimized platform gives a rotational volume that is 77% largerthan the original platform.Initial tests of the translational optimized platform revealed faults in the original code for theexisting platform. After adjusting the code further testing showed close relation between thesoftware model and the constructed platform.All code written during the project is available but is not included in the report due to the volumeof code produced.

Place, publisher, year, edition, pages
2012. , 52 p.
Series
MMK 2012:68 MDA 427
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-146642OAI: oai:DiVA.org:kth-146642DiVA: diva2:724356
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Available from: 2015-03-06 Created: 2014-06-12 Last updated: 2015-03-06Bibliographically approved

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