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A force control based strategy for extrinsic in-hand object manipulation through prehensile-pushing primitives
KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
En styrningskontrollbaserad strategi för yttre handhantering av objekt genom prehensile-pushing primitives (Swedish)
Abstract [en]

Object manipulation is a complex task for robots. It often implies a compromise between the degrees-of-freedom of hand and its fingers have (dexterity) and its cost and complexity in terms of control. One strategy to increase the dexterity of robotic hands with low dexterity is called extrinsic manipulation and its principle is to exploit additional accelerations on the object caused by the effect of external forces. We propose a force control based method for performing extrinsic in-hand object manipulation, with force-torque feedback. For this purpose, we use a prehensile pushing action, which consists of pushing the object against an external surface, under quasistatic assumptions. By using a control strategy, we also achieve robustness to parameter uncertainty (such as friction) and perturbations, that are not completely captured by mathematical models of the system. The force control strategy is performed in two different ways: the contact force generated by the interaction between the object and the external surface is controlled using an admittance controller, while an additional control of gripping force applied by the gripper on the object is done through a PI controller. A Kalman filter is used for the estimation of the state of the object, based on force-torque measurements of a sensor at the wrist of the robot. We validate our approach by conducting experiments on a PR2 robot, available at the Robotics, Perception, and Learning lab at KTH Royal Institute of Technology.

Abstract [sv]

Att greppa och manipulera objekt är en komplex uppgift för robotar. Det innebär ofta en kompromiss mellan hand och fingrars frihetsgrader (fingerfärdighet) mot reglersystemets kostnad och komplexitet. Extrinsic manipulation är en strategi för att öka fingerfärdigheten hos robothänder, och dess princip är att utnyttja accelerationer på objektet som orsakas av yttre krafter. Vi föreslår en metod baserad på att reglerakraft för hantering av objekt i handen, genom en återkoppling av kraftmomentet. För detta ändamål använder vi en prehensile pushing action, där objektet puttas mot en yta, under kvasistiska antaganden. Genom att använda en reglerstrategi får vi en robusthet mot parametrars osäkerhet (som friktion) och störningar, vilka inte beskrivs av systemets model. Kraftkontrollstrategin utförs på två olika sätt: kraften mellan objektet och den yttre ytan styrs med en admittance controller medan en ytterligare styrning av applicerad gripkraft på objektet görs med en PI-reglerare. Ett Kalman filter används för att estimera objektets tillstånd, baserat på mätningar av kraftmoment via en sensor vid robotens handled. Vi utvärderar vårt tillvägagångssätt genom att utföraexperiment på en PR2-robot vid KTHs Robotics, Perception och Learning Lab.

Place, publisher, year, edition, pages
2017.
Keyword [en]
Force-control, object manipulation, extrinsic manipulation, estimation, prehensile-pushing, grasp
National Category
Robotics
Identifiers
URN: urn:nbn:se:kth:diva-220136OAI: oai:DiVA.org:kth-220136DiVA, id: diva2:1166702
Presentation
2017-12-01, 523, Teknikringen 14, Stockholm, 10:00 (English)
Supervisors
Examiners
Available from: 2017-12-21 Created: 2017-12-15 Last updated: 2017-12-21Bibliographically approved

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CiteExportLink to record
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Citation style
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