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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

Dynamic movement primitives andreinforcement learning for adapting alearned skill

Lundell, Jens January 2016 (has links)
Traditionally robots have been preprogrammed to execute specific tasks. Thisapproach works well in industrial settings where robots have to execute highlyaccurate movements, such as when welding. However, preprogramming a robot isalso expensive, error prone and time consuming due to the fact that every featuresof the task has to be considered. In some cases, where a robot has to executecomplex tasks such as playing the ball-in-a-cup game, preprogramming it mighteven be impossible due to unknown features of the task. With all this in mind,this thesis examines the possibility of combining a modern learning framework,known as Learning from Demonstrations (LfD), to first teach a robot how toplay the ball-in-a-cup game by demonstrating the movement for the robot, andthen have the robot to improve this skill by itself with subsequent ReinforcementLearning (RL). The skill the robot has to learn is demonstrated with kinestheticteaching, modelled as a dynamic movement primitive, and subsequently improvedwith the RL algorithm Policy Learning by Weighted Exploration with the Returns.Experiments performed on the industrial robot KUKA LWR4+ showed that robotsare capable of successfully learning a complex skill such as playing the ball-in-a-cupgame. / Traditionellt sett har robotar blivit förprogrammerade för att utföra specifika uppgifter.Detta tillvägagångssätt fungerar bra i industriella miljöer var robotar måsteutföra mycket noggranna rörelser, som att svetsa. Förprogrammering av robotar ärdock dyrt, felbenäget och tidskrävande eftersom varje aspekt av uppgiften måstebeaktas. Dessa nackdelar kan till och med göra det omöjligt att förprogrammeraen robot att utföra komplexa uppgifter som att spela bollen-i-koppen spelet. Medallt detta i åtanke undersöker den här avhandlingen möjligheten att kombinera ettmodernt ramverktyg, kallat inläraning av demonstrationer, för att lära en robothur bollen-i-koppen-spelet ska spelas genom att demonstrera uppgiften för denoch sedan ha roboten att själv förbättra sin inlärda uppgift genom att användaförstärkande inlärning. Uppgiften som roboten måste lära sig är demonstreradmed kinestetisk undervisning, modellerad som dynamiska rörelseprimitiver, ochsenare förbättrad med den förstärkande inlärningsalgoritmen Policy Learning byWeighted Exploration with the Returns. Experiment utförda på den industriellaKUKA LWR4+ roboten visade att robotar är kapabla att framgångsrikt lära sigspela bollen-i-koppen spelet
2

Learning Multi-step Dual-arm Tasks From Demonstrations

Natalia S Sanchez Tamayo (9156518) 29 July 2020 (has links)
Surgeon expertise can be difficult to capture through direct robot programming. Deep imitation learning (DIL) is a popular method for teaching robots to autonomously execute tasks through learning from demonstrations. DIL approaches have been previously applied to surgical automation. However, previous approaches do not consider the full range of robot dexterous motion required in general surgical task, by leaving out tooltip rotation changes or modeling one robotic arm only. Hence, they are not directly applicable for tasks that require rotation and dual-arm collaboration such as debridement. We propose to address this limitation by formulating a DIL approach for the execution of dual-arm surgical tasks including changes in tooltip orientation, position and gripper actions.<br><br>In this thesis, a framework for multi-step surgical task automation is designed and implemented by leveraging deep imitation learning. The framework optimizes Recurrent Neural Networks (RNNs) for the execution of the whole surgical tasks while considering tooltip translations, rotations as well as gripper actions. The network architecture proposed implicitly optimizes for the interaction between two robotic arms as opposed to modeling each arm independently. The networks were trained directly from the human demonstrations and do not require to create task specific hand-crafted models or to manually segment the demonstrations.<br><br>The proposed framework was implemented and evaluated in simulation for two relevant surgical tasks, the peg transfer task and the surgical debridement. The tasks were tested under random initial conditions to challenge the robustness of the networks to generalize to variable settings. The performance of the framework was assessed using task and subtask success as well as a set of quantitative metrics. Experimental evaluation showed favorable results for automating surgical tasks under variable conditions for the surgical debridement, which obtained a task success rate comparable to the human task success. For the peg transfer task, the framework displayed moderate overall task success. Quantitative metrics indicate that the robot generated trajectories possess similar or better motion economy that the human demonstrations.

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