Abstract
To match the richness and complexity of the sensory and motor functionalities of a human hand with a robust and economically reasonable robotic device remains one of the hardest challenges in the field. Previous work has explored the possibility to exploit insight from neuroscientific results on postural correlation patterns (synergies) taming the sensorimotor complexity of hands. The postural synergy model has been recently extended to account for grasp force control through a model of “soft synergies” which incorporate hand compliance. In this paper we propose a first translation of such principles in the design of a robot hand. It so turns out that the implementation of the soft synergy model in an effective design is not obvious. The solution proposed in this paper rests on ideas coming from under-actuated hand design. We give a synthesis method to realize a desired set of soft synergies through the principled design of adaptive under-actuated mechanisms, which we call the method of adaptive synergies. This approach leads to the design and implementation of a prototype modular hand capable of accommodating an arbitrary number of synergies. The effectiveness of the design is shown in grasping simulations and experiments.
Highlights
Neurosciences studies suggest that the brain uses the hand as an organized and ordered ensemble
In particular the behavior of an adaptive synergy hand can match that of a soft synergy hand as long as E = K and fsolves
Equation (16) gives an effective method to implement the behavior of a soft synergy hand on the hardware of an adaptive synergy hand
Summary
Neurosciences studies suggest that the brain uses the hand as an organized and ordered ensemble. The software synergy approach of [3] faces the problem by constraining the motion of each finger when it comes in contact with the grasped object, while a parallel actuation system, realized with memoryshape alloys, was proposed in [6] by the same authors of [4] to integrate the (rigid) hardware synergy they implemented before An improvement over the former solutions is the introduction of soft synergies. The prototype comprehends interchangeable phalanx modules, which can be connected in series, and a stack of distribution mechanisms, in order to be customized and expanded It can be mechanically set-up to implement up to four adaptive synergies on fingers with an adjustable number of DOFs. Functionality of the prototype is demonstrated in some grasping simulations and experiments with some differently shaped objects (see Fig. 1).
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