ETD

Archivio digitale delle tesi discusse presso l'Università di Pisa

Tesi etd-06292015-160141


Tipo di tesi
Tesi di laurea magistrale
Autore
TRIGILI, EMILIO
URN
etd-06292015-160141
Titolo
Study and development of a soft semi-active rotational joint for wearable robotics
Dipartimento
INGEGNERIA DELL'INFORMAZIONE
Corso di studi
INGEGNERIA BIOMEDICA
Relatori
relatore Dott. Vitiello, Nicola
relatore Dott. Cianchetti, Matteo
relatore Dott. Cempini, Marco
relatore Prof.ssa Laschi, Cecilia
Parole chiave
  • variable stiffness
  • soft robotics
  • soft joint
  • granular jamming
  • wearable robotics
Data inizio appello
17/07/2015
Consultabilità
Non consultabile
Data di rilascio
17/07/2085
Riassunto
In recent times, wearable robotics has rapidly gained increasing consideration in medical field: powered exoskeletons can work in close contact with the human body, to provide assistance for daily-living activities, but also as powerful tools for rehabilitation. A key challenge in their design is the kinematic compliance toward the addressed body segments, so that the exoskeleton and the human joint axes maintain alignment while moving. If this requirement is not satisfied, undesired residual forces will load the human articulations. Currently, this problem is tackled with the addition of passive degrees of freedom, lending additional motions in the robotic joint, to self-compensate the misalignments. Nonetheless, this leads to a more complex, bulky and heavier structure, limiting the robot's wearability.
In this work we developed a soft rotational joint aiming to replace or improve the self-aligning mechanism design. In particular, we evaluated its ability to sustain axial loads while transmitting a torque. Since the soft joint has not inherently the same strength as its rigid counterpart, granular jamming is employed to increase its stiffness. Its design was explored by testing two different membrane materials, and two different contact surfaces between the granular materials. The performances of the prototype were evaluated testing the soft-joint assembled in parallel to a cable-actuated revolute joint, emulating a flexion-extension motion. The experimental setup included an Instron testing machine, to control the cable tension and displacement, and a mono-axial load cell to evaluate the force unloaded through the soft joint during the flexion arc of motion.
The results show that the soft joint is actually able to absorb a substantial part of the applied axial load, without affecting the execution of the movement, with a behavior that is strongly dependent on the type of membrane and grain used and slightly dependent on the velocity of rotation.
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