Two-fingered Hand Research Articles

Prototype of robotic hand using two-fingered hand and rubber sheet for gripping nonuniform shaped objects

Prototype of robotic hand using two-fingered hand and rubber sheet for gripping nonuniform shaped objects

Grasping of arbitrary shape objects by a two-finger hand with an RGB-D hand-eye camera

Grasping of arbitrary shape objects by a two-finger hand with an RGB-D hand-eye camera

Erratum: “Torsional Stiffness Improvement of a Soft Pneumatic Finger Using Embedded Skeleton,” [ASME J. Mech. Rob. 12(1), p. 011016; DOI: 10.1115/1.4045227

Abstract Silicone-based pneumatic actuators are among the most widely used soft actuators in adaptable fingers. However, due to the soft nature of silicone, the performance of these fingers is highly affected by the low torsional stiffness, which may cause failure in grasping and manipulation. To address this problem, a compact design is proposed by embedding a rigid skeleton into a soft pneumatic finger. A finite element approach with an analytical model is used to evaluate the performance of the fingers both with and without the skeleton. Then, a series of experiments is performed to study the bending motion and rigidity of the fingers. The results reveal that the skeleton increases the torsional stiffness of the finger up to 300%. Furthermore, the consistency with the experimental data indicates the good precision of the proposed modeling method. Finally, a two-finger hand is designed to evaluate the performance of the reinforced finger in reality. The grasp experiments illustrate that the hybrid finger with the skeleton is highly adaptable and can successfully grasp and manipulate heavy objects. Thus, a potential approach is proposed to improve the torsional stiffness of silicone-based pneumatic fingers while maintaining adaptability.

Optimal Design and Redundancy Resolution of a Novel Robotic Two-Fingered Exoskeleton

This article deals with the optimal design and redundancy resolution of a seven DOF robotic two-fingered hand exoskeleton intended for rehabilitation purposes. The exoskeleton is designed to track the human digit motion accurately. As the human digit joint cannot be modeled by single revolute joint due to instantaneously varying center of rotation, a 4-bar mechanism is employed to model each phalanx of a finger. Optimal 4-bar linkages are designed by minimizing the error between the Cartesian trajectories of the human phalanx and those of the coupler points in respective 4-bar mechanisms. It is demonstrated that the designed 4-bar based exoskeleton can track the human digit motion accurately. Performance analysis of the developed device has been carried out by resolving its kinematic redundancy during a fine object translation motion by instantaneously optimizing manipulability measure.

Torsional Stiffness Improvement of a Soft Pneumatic Finger Using Embedded Skeleton

Abstract Silicone-based pneumatic actuators are among the most widely used soft actuators in adaptable fingers. However, due to the soft nature of silicone, the performance of these fingers is highly affected by the low torsional stiffness, which may cause failure in grasping and manipulation. To address this problem, a compact design is proposed by embedding a rigid skeleton into a soft pneumatic finger. A finite element approach with an analysical model is used to evaluate the performance of the fingers both with and without the skeleton. Then, a series of experiments is performed to study the bending motion and rigidity of the fingers. The results reveal that the skeleton increases the torsional stiffness of the finger up to 300%. Furthermore, the consistency with the experimental data indicates the good precision of the proposed modeling method. Finally, a two-finger hand is designed to evaluate the performance of the reinforced finger in reality. The grasp experiments illustrate that the hybrid finger with the skeleton is highly adaptable and can successfully grasp and manipulate heavy objects. Thus, a potential approach is proposed to improve the torsional stiffness of silicone-based pneumatic fingers while maintaining adaptability.

Toward Grasping Against the Environment: Locking Polygonal Objects Against a Wall Using Two-Finger Robot Hands

Caging offers a robust strategy for grasping objects with robot hands. This letter utilizes caging for locking polygonal objects against a wall using minimalistic two-finger robot hands. From the object's perspective, the wall and two-finger hand form an equivalent three-finger hand. The object is first caged by trapezoidal finger formations of the equivalent three-finger hand, and the hand is then closed until the object is locked against the wall in the desired grasp. The object can then be safely grasped and moved away from the wall, or it can be held fixed against it to be worked on by tools. This letter presents a novel and efficient caging-to-locking algorithm. While the equivalent hand's configuration space is four-dimensional, the algorithm uses the hand's two-dimensional contact space , which represents all contacts by two and three of the equivalent hand's fingers along the object boundary. The problem of computing the critical cage formation that allows the object to escape the equivalent hand is reduced to a search along a caging graph constructed incrementally in the equivalent hand's contact space. Starting from the desired locking grasp, the graph is searched for an escape path which passes through the critical cage formation. The technique is demonstrated with a detailed example.

Design and experiment of a universal two-fingered hand with soft fingertips based on jamming effect

The goal of robotic manipulators is to grasp objects of irregular shapes with better precision and efficiency. Universal grippers developed in recent years are designed with excessive complexity or lower resistance to damage. In this paper, we propose the idea of a universal parallel-fingered hand with soft fingertips based on jamming effect, in which negative pressure and particle flow are utilized to achieve variable stiffness. Then we set up a whole pick-and-place experiment system to evaluate the operational performance in the real serving situations. The results indicate that for most rigid objects, our prototype with soft fingertips, the stiffness of which is over the threshold to bear maximum task load after jamming, can demonstrate higher grasping stability than rigid ones, reduce around 40% motor drive power consumption and have a higher load capacity compared with the rigid-fingertip prototype under stable grasping, and have a relatively better operating precision of ± 0.62 mm compared to most of previous soft grippers when placing objects with equal weight. The findings can facilitate to improve the grasping precision of mechanical hands with soft fingertips.

Towards Ultra Low-Cost Myoactivated Prostheses.

In developing countries, due to the high cost involved, amputees have limited access to prosthetic limbs. This constitutes a barrier for this people to live a normal life. To break this barrier, we are developing ultra-low-cost closed-loop myoactivated prostheses that are easy to maintain manufacture and that do not require electrodes in contact with the skin to work effectively. In this paper, we present the implementation for a simple but functional hand prosthesis. Our simple design consists of a low-cost embedded microcontroller (Arduino), a wearable stretch sensor (adapted from electroresistive bands normally used for “insulation of gaskets” against EM fields), to detect residual muscle contraction as direct muscle volumetric shifts and a handful of common, not critical electronic components. The physical prosthesis is a 3D printed claw-style two-fingered hand (PLA plastic) directly geared to an inexpensive servomotor. To make our design easier to maintain, the gears and mechanical parts can be crafted from recovered materials. To implement a closed loop, the amount of closure of prosthesis is fed back to the user via a second stretch sensor directly connected to claw under the form of haptic feedback. Our concept design comprised of all the parts has an overall cost below AUD 30 and can be easily scaled up to more complicated devices suitable for other uses, i.e., multiple individual fingers and wrist rotation.

Posture Control of a Grasped Object by Two-fingered Hand with Round-belt Twist Mechanism

Posture Control of a Grasped Object by Two-fingered Hand with Round-belt Twist Mechanism

Solution Structure of the Cuz1 AN1 Zinc Finger Domain: An Exposed LDFLP Motif Defines a Subfamily of AN1 Proteins.

Zinc binding domains are common and versatile protein structural motifs that mediate diverse cellular functions. Among the many structurally distinct families of zinc finger (ZnF) proteins, the AN1 domain remains poorly characterized. Cuz1 is one of two AN1 ZnF proteins in the yeast S. cerevisiae, and is a stress-inducible protein that functions in protein degradation through direct interaction with the proteasome and Cdc48. Here we report the solution structure of the Cuz1 AN1 ZnF which reveals a compact C6H2 zinc-coordinating domain that resembles a two-finger hand holding a tri-helical clamp. A central phenylalanine residue sits between the two zinc-coordinating centers. The position of this phenylalanine, just before the penultimate zinc-chelating cysteine, is strongly conserved from yeast to man. This phenylalanine shows an exceptionally slow ring-flipping rate which likely contributes to the high rigidity and stability of the AN1 domain. In addition to the zinc-chelating residues, sequence analysis of Cuz1 indicates a second highly evolutionarily conserved motif. This LDFLP motif is shared with three human proteins—Zfand1, AIRAP, and AIRAP-L—the latter two of which share similar cellular functions with Cuz1. The LDFLP motif, while embedded within the zinc finger domain, is surface exposed, largely uninvolved in zinc chelation, and not required for the overall fold of the domain. The LDFLP motif was dispensable for Cuz1's major known functions, proteasome- and Cdc48-binding. These results provide the first structural characterization of the AN1 zinc finger domain, and suggest that the LDFLP motif may define a sub-family of evolutionarily conserved AN1 zinc finger proteins.

Evaluation of quality of partial caging by a planar two-fingered hand

In partial caging, an object is partially constrained by robots and is able to escape from there. Although complete caging ensures the hand never releases the confined object, insufficient degrees of freedom of robots does not often satisfy the conditions for caging. Partial caging, however, can be accomplished even by robots having such mechanical restriction. We consider a case that an object moves in the semi-closed region formed by a planar robot hand with two fingers, as an example of partial caging in two-dimensional space. Then the parameters of fingers: joint angles interfere in the object motion to escape from the hand through the gap between the fingertips. Some simulation results show differences of difficulty of escaping according to arrangement of fingers, and factors interfering in the difficulty are analyzed. Additionally, we also evaluate ease of entering the hand through the gap and define an ability index of robot hand for partial caging with the above two evaluation scores. Then a high index score indicates that the hand assumed to be able to capture objects easily and confine it without any finger motion. It can be utilized for mechanical design and controlling strategies of robots in capturing objects.

ユニバーサル多指ハンド：ジャミング効果を利用したソフトグリッパ

This paper presents a simple and compact universal two-fingered hand with soft finger-tips with jamming effect. To grasp several kinds of object, high-DoF fingered hand, multi-gripper device etc. has been developed. We adopt jamming effect device for a finger-tip to fit various object shape. We develop a two-fingered hand with jamming effect device and test it to compare with rigid finger-tip hand.

Grasp Planning and Tendon-driven Design of Two-fingered Hand Based on Grasp Matrix

Grasp Planning and Tendon-driven Design of Two-fingered Hand Based on Grasp Matrix

3P2-R02 二指ハンドによるIn-handケージングマニピュレーションの計画と実行(ロボットハンドの機構と把持戦略(2))

3P2-R02 二指ハンドによるIn-handケージングマニピュレーションの計画と実行(ロボットハンドの機構と把持戦略(2))

Assemblable Hand for Laparoscopic Surgery with Phased Array and Single-Element Ultrasound Probes

During laparoscopic surgery, large internal organs should often be manipulated while being internally visualized. For this purpose, we study an assemblable two-fingered hand implemented with an ultrasound probe. The fingers are separately introduced into the abdominal cavity through small incisions and are assembled into a hand sufficiently large to grasp or manipulate the large organ. Two types of ultrasound probes are employed; a phased array probe of a commercially available ultrasound diagnosis system, and a single-element probe. Using the latter probe, the hand is assembled through 12 mm trocars and is assessed in an in vivo experiment. Ultrasound echo sensing is found to retrieve diagnostic information regarding specific internal organs. It also visualizes the finger and its back during grasping, which can improve the safety of hand grasping and manipulation. Furthermore, ultrasound echo sensing can assist the measurement of the relative position and orientation of the two grasping fingers.

3D two-fingered caging for two types of objects: sufficient conditions and planning

Caging is a method to capture an object geometrically by robots. Position-controlled robots can make the object inescapable from the robot formation. Moreover less number of mobile robots or a robot hand with low degrees of freedom can constrain the object with considering concavity of the object. In this paper, we propose two types of caging: ring-type and waist-type, which both can be accomplished by a two-fingered hand. We derive sufficient conditions for caging of the two types and construct RRT-based motion planner for caging by a robotic arm/hand system. In motion planning, we find one of final configurations that satisfy the sufficient conditions and produce a path of robot configuration to the goal. With object recognition using AR picture markers, we can acquire geometrical information of objects and plan robot motion for caging. We show some experimental results of planning and execution of planned caging motion for four objects.

Developmental Process of a Chopstick-Like Hybrid-Structure Two-Fingered Micromanipulator Hand for 3-D Manipulation of Microscopic Objects

The development of a chopstick-like two-fingered micromanipulator based on a hybrid mechanism is presented. The microhand consists of two 3-prismatic-revolute-spherical (PRS) parallel modules connected serially in a mirror image style. Each module has a long glass pipette as an end effector. The development process consists of three phases. In the first phase, analysis and mathematical modeling, a novel solution of the inverse kinematics problem (IKP) of a 3-revolute-prismatic-spherical (RPS) parallel module, is derived and applied with proper modification to the case of 3-PRS of the proposed mechanism. The solution is extended to the two-fingered hybrid mechanism of the microhand. In the optimization and design phase, the optimization of the chosen design parameters of a theoretical 3-PRS parallel module is carried out using two approaches: discretization method and genetic algorithms. Based on the optimal design parameters, a CAD model of the 3-PRS finger module is built, and a complementary optimization step using the ANSYS Workbench program is carried out to determine suitable characteristics of the pin flexure hinge. Finally, the total CAD model of the two-fingered hand is built. In the realization and implementation phase, the description of the hardware system of the two-fingered microhand prototype is presented. The program description, calibration method, practical Jacobian matrices, practical workspace, and error analysis of the prototype are discussed.

2A2-M04 2本指マイクロハンドにおける先端位置合わせ自動化手法の開発

2A2-M04 2本指マイクロハンドにおける先端位置合わせ自動化手法の開発

Performance Evaluation of Teleoperation for Manipulating Micro Objects Using Two-Fingered Micro Hand

We developed a dexterous micromanipulation system consisting of a two-fingered micro hand, an autofocusing optical microscope, an image processor, and user interfaces. The micro hand has 6 degrees of freedom (DOF), 3 DOF each for two fingers that work similar to a thumb and forefinger or chopsticks. This hand grasps, moves, rotates and releases micron-scale objects. In teleoperation mode, the user controls hand motion with a joystick or keyboard while observing the microscope image on a TV monitor. We evaluate teleoperation performance for manipulating micron-scale objects. Several types of motion command methods proposed include a keyboard or joystick as operation device, and position or rate command modes. The tasks experimentally evaluated are picking, grasping, moving, and releasing micron-size objects, i.e., a glass grain in air and a yeast cell in liquid. These are compared in positioning accuracy and task execution time.

Experimental study of coordinated control of multifingered hands with the kinetostatic filtering method

For the coordinated control of multifingered robot hands it is important to simultaneously control both the position of a target object and the force exerted on it. In particular, the 'internal force' which does not affect the motion of the object should be controlled in order not to break it. This paper proposes an extension of the 'kinetostatic filtering method' by using a pseudo-inverse of the Jacobian. In addition, a new control signal is introduced for posture control of the fingertips. Experiments with a two-fingered hand are conducted to verify the capacity of the proposed controller and to show the transient response of it.