Grasping with Soft Hands

Abstract

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.

Hand synergies: Integration of robotics and neuroscience for understanding the control of biological and artificial hands

“…Through the observation of human hand operations, it can be easily realized how fundamental in everyday grasping the role of hand compliance to adapt fingers to the shape of the surrounding objects is. Since the shape of soft hands is determined by the forces exchanged with the objects in contact, objects and environmental constraints can be profitably exploited to functionally shape the hand and to go beyond its nominal kinematic limits by exploiting structural softness [175,176], substantially changing the classical manipulation planning paradigm. Due to their simplicity, compliance and robustness, hands developed following the soft synergy approach represent an ideal platform for the development of novel prostheses, thus opening interesting perspectives in robotic rehabilitation.…”

Incrementality and Hierarchies in the Enrollment of Multiple Synergies for Grasp Planning

“…Finding a valuable strategy for grasp success and quality in terms of contact force by changing the hand/object relative configuration represents a key topic for planning and control of robotic hands. This is particularly true considering soft adaptable robotic hands where the importance of hand/object relative pose is crucial to fully take advantage from end-effector adaptability in shaping around different items [33]. This motivates our investigation for different hand poses.…”

Model-Based Grasping of Unknown Objects from a Random Pile

“…The underlying geometric idea is similar, however, in that they rely on the shortest distance from any of the contact forces to the boundary of its friction cone, a process that resembles the computation of the distance from the set of external wrenches E to the boundary of the set of mapped available contact forces C . We should also cite the net force index used by Bonilla et al [35]. It consists in measuring the amount of internal force within the grasp beyond the weight of the object, with the objective of minimising this value.…”