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In caging, an object is geometrically confined by position-controlled robots and never escapes from the constraint. Caging has some advantages over conventional grasping, and its applications have been performed not only in 2D but also in 3D scenes with various actual robots. However, the conditions of complete caging are not always satisfied due to limited robot configuration. This paper studies...
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...
In this research, we demonstrated dexterous manipulation of sheet-like elastic objects, namely, playing cards, using a high-speed robot system. In particular, our goal was to achieve card throwing and card shooting towards a target object by using a high-speed multifingered robot hand and visual feedback based on a vision system. We discuss card grasping in the initial state by analyzing the motion...
ISR-Softhand is a novel under-actuated self contained anthropomorphic robotic hand which takes advantage of elastic joints and soft pads. The integrated compliance in the hand's joint allows for a very good adaptability to a wide range of objects. It can achieve the top ten grasps with highest frequency of usage by humans, with only three actuators.
Robotic prosthesis are usually intended as artificial device extensions replacing a missing part of a human body. A new approach regarding robotic limbs is presented here. A modular robot is used not only for replacing a missing part of the body but also as an extra-limb in order to enhance manipulation dexterity and enlarge the workspace of human beings. In this work, the model and control of an...
It is known that human controls muscles for hand poses in a coordinated manner and the coordination is referred to as a postural synergy. Using postural synergies, dexterous grasping tasks could be accomplished on a prosthetic hand via only a few (usually two) control inputs. Instead of implementing postural synergies digitally, this paper presents the design of a simple continuum mechanism for implementing...
This work aims to extend the application field of the constraint-based control framework called iTaSC (instantaneous task specification using constraints) toward manipulation tasks. iTaSC offers two advantages with respect to other methods: the ability to specify tasks in different spaces (and not only in Cartesian coordinates as for the Task Frame Formalism), and the treatment of geometric uncertainties...
In this paper, a method to derive the three predominant synergies and their temporal weights for planning grasps of the UB Hand IV (University of Bologna Hand, version IV) is proposed. The method adopted to define the postural synergies from experiments is based on the kinematic structure of the robotic hand and on the taxonomy of the grasps of common objects. The control strategy, exploiting postural...
This paper reports the integration of a kinematic model of the human hand during cylindrical grasping, with specific focus on the accurate mapping of thumb movement during grasping motions, and a novel, multi-degree-of-freedom assistive exoskeleton mechanism based on this model. The model includes thumb maximum hyper-extension for grasping large objects (∼>50mm). The exoskeleton includes a novel...
This paper investigates force accuracy of a human finger in three types of support conditions of an exoskeleton. The exoskeleton augments pinching force of a wearer's index finger in proportion to it based on surface electromyography. Three supporting manners of the pinching force are evaluated by switching a fingertip part of the exoskeleton. One is that the assistive force is applied to the wearer's...
In this paper we describe the hand of the humanoid iCub, an open source robotic platform funded by the European Commission. The principal design rationale was the necessity to supply the robot with sufficiently dexterous and sensorized hands in order to study complex skills such as manipulation. The final design has 9 actuators for each hand, 12 tactile sensors at each fingertip, 48 pressure sensors...
This paper formulates the dynamics of 5 degrees-of-freedom (DOFs) robotic hand that consists of an index finger and an opposable thumb like the human hand. This system has two geometrical constraints and five velocity constraints generated during the object manipulation task. The three of the velocity constraints are associated with the joint angles of the robot, and are combined to the proposed system...
In this paper, robot hand design aiming at application to a myoelectric prosthetic hand and recognition of finger operation via surface EMG are discussed. The robot hand with two fingers, thumb and index finger, was built to implement fundamental motions required in daily life, such as grasping and holding. The fingers are driven by the wire actuation system to imitate the human's tendon mechanism...
This paper proposes a tendon driven system with antagonistic pairs of polyarticular tendons to simulate a variable stiffness of a human fingertip. The stiffness of a robot finger should be adjusted according to a situation that includes large position errors or collisions, because it tolerates errors of object positions and dimensions in assembly task and absorbs collision energy in hitting or catching...
This paper proposes a novel control method for stable grasping using a multi-fingered hand-arm system with soft hemispherical finger tips. The proposed method is simple but easily achieves stable grasping of an arbitrary polyhedral object using an arbitrary number of fingers. Firstly, we formulate nonholonomic constraints between a multi-fingered hand-arm system and an object constrained by rolling...
This paper proposes a polyarticular tendon drive system to simulate a variable stiffness of a human fingertip. The stiffness determines displacement of the fingertip when an external force is affected to it. The stiffness should be adjusted not only according to measurement precision of object's dimensions in order to allow grasping position errors, but also according to tolerance of the assembly...
We have been developing a grip aid system using air cylinders to assist elderly who have weak grasping force to have daily living activities. The system is small and light weight. In this paper, mechanism to assist thumb, index, and middle fingers using one air cylinder for each finger, is proposed. And also control method of the device using a bending sensor to transfer their will to control the...
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