Grasping with Soft Hands

Despite some prematurely optimistic claims, the ability of robots to grasp general objects in unstructured environments still remains far behind that of humans. This is not solely caused by differences in the mechanics of hands: indeed, we show that human use of a simple robot hand (the Pisa/IIT SoftHand) can afford capabilities that are comparable to natural grasping. It is through the observation of such human-directed robot hand operations that we realized how fundamental in everyday grasping and manipulation is the role of hand compliance, which is used to adapt to the shape of surrounding objects. Objects and environmental constraints are in turn used to functionally shape the hand, going beyond its nominal kinematic limits by exploiting structural softness. In this paper, we set out to study grasp planning for hands that are simple - in the sense of low number of actuated degrees of freedom (one for the Pisa/IIT SoftHand) - but are soft, i.e. continuously deformable in an infinity of possible shapes through interaction with objects. After general considerations on the change of paradigm in grasp planning that this setting brings about with respect to classical rigid multi-dof grasp planning, we present a procedure to extract grasp affordances for the Pisa/IIT SoftHand through physically accurate numerical simulations. The selected grasps are then successfully tested in an experimental scenario

Grasp and Manipulation Analysis for Synergistic Underactuated Hands Under General Loading Conditions

In dexterous grasping, the development of simple but practical hands with reduced number of actuators, designed to perform some manipulation tasks, is both attractive and challenging. To carefully synthesize inter- and intra-finger couplings a rigorous way to establish grasping and manipulation properties of an underactuated hand is of paramount importance. In this paper, we propose a general approach to characterize the structural properties of underactuated hands focusing on their kinematic and force analysis. A complete kinostatic characterization of a given grasp (pure squeeze, spurious squeeze, kinematic grasp displacements and so on) is introduced. The analysis is quasi-static but it is not limited to rigid-body motions, encompassing also essential elastic motions, statically indeterminate configurations, and pre-loaded initial conditions. The introduction of generalized compliance at contacts and in the actuation mechanism is included, as it is an essential feature of safe and dependable modern hands. Efficient algorithms to characterize the system behavior are presented and applied in two different numerical examples

Velvet Fingers: A Dexterous Gripper with Active Surfaces.

The design of grasping and manipulation systems is one of the most investigated topics in recent robotic and automation engineering. It is a process that has to take into account many development possibilities and to face different trade offs, as that between application possibilities and design complexity. In this work we present the design of a novel end-effector that merges the essential mechanics and control simplicity of underactuated devices, together with the high levels of manipulability usually featured in dexterous robotic hands. To obtain this enhancement, the proposed gripper considers the possibility offered by active surfaces, i.e. engineered contact surfaces able to simulate different levels of friction and to apply tangential thrust to the contacted object. The actual dexterity enhancement is evaluated by an analytical manipulability analysis and some examples of in hand manipulations and grasps are taken into account. A mechanical solution is presented, which implements the proposed idea through the adoption of one DoF active surfaces mounted on the fingers. The proposed solution presents a manipulability index one order of magnitude higher than common grippers

HANDS.DVI: A DeVice-Independent Programming and Control Framework for Robotic HANDS

The scientific goal of HANDS.DVI consists of developing a common framework to programming robotic hands independently from their kinematics, mechanical construction, and sensor equipment complexity. Recent results on the organization of the human hand in grasping and manipulation are the inspiration for this experiment. The reduced set of parameters that we effectively use to control our hands is known in the literature as the set of synergies. The synergistic organization of the human hand is the theoretical foundation of the innovative approach to design a unified framework for robotic hands control. Theoretical tools have been studied to design a suitable mapping function of the control action (decomposed in its elemental action) from a human hand model domain onto the articulated robotic hand co-domain. The developed control framework has been applied on an experimental set up consisting of two robotic hands with dissimilar kinematics grasping an object instrumented with force sensors

HANDS.DVI: A DeVice-Independent programming and control framework for robotic

Abstract. The scientific goal of HANDS.DVI consists of developing a common framework to programming robotic hands independently from their kinematics, mechanical construction, and sensor equipment complexity. Recent results on the organization of the human hand in grasping and manipulation are the inspiration for this experiment. The reduced set of parameters that we effectively use to control our hands is known in the literature as the set of synergies. The synergistic organization of the human hand is the theoretical foundation of the innovative approach to design a unified framework for robotic hands control. Theoretical tools have been studied to design a suitable mapping function of the control action (decomposed in its elemental action) from a human hand model domain onto the articulated robotic hand co-domain. The developed control framework has been applied on an experimental set up consisting of two robotic hands with dissimilar kinematics grasping an object instrumented with force sensors