Finger Mechanism Research Articles

Myoelectric Hand Prosthesis Force Control Through Servo Motor Current Feedback

This paper presents the prehension force closed-loop control design of a mechanical finger commanded by electromyographic signal (EMG) from a patient's arm. The control scheme was implemented and tested in a mechanical finger prototype with three degrees of freedom and one actuator, driven by arm muscles EMG of normal volunteers. Real-time indirect estimation of prehension force was assessed by measuring the DC servo motor actuator current. A model of the plant comprising finger, motor, and grasped object was proposed. Model parameters were identified experimentally and a classical feedback phase-lead compensator was designed. The controlled mechanical finger was able to provide a more accurate prehension force modulation of a compliant object when compared to open-loop control.

Static and dynamic human flexor tendon–pulley interaction

The aim of the study was to investigate the influence of a preceding flexion or extension movement on the static interaction of human finger flexor tendons and pulleys concerning flexion torque being generated. Six human fresh frozen cadaver long fingers were mounted in an isokinetic movement device for the proximal interphalangeal (PIP) joint. During flexion and extension movement both flexor tendons were equally loaded with 40 N while the generated moment was depicted simultaneously at the fingertip. The movement was stopped at various positions of the proximal interphalangeal joint to record dynamic and static torque. The static torque was always greater after a preceding extension movement compared to a preceding flexion movement in the corresponding same position of the joint. This applied for the whole arc of movement of 0–105°. The difference between static extension and flexion torque was maximal 11% in average at about 83° of flexion. Static torque was always smaller than dynamic torque during extension movement and always greater than dynamic torque during flexion movement. The kind of preceding movement therefore showed an influence to the torque being generated in the proximal interphalangeal joint. The effect could be simulated on a mechanical finger device.

Adhesion control for injection overmolding of polypropylene with elastomeric ethylene copolymers

AbstractTwo types of random semicrystalline copolymers (ethylene–octene and ethylene–butene) were overmolded on a core polypropylene. Maximum solid–liquid interface temperature achieved for the overmolding injection process is used as the key parameter for adhesion control. The main bonding process is shown to be a Rouse‐type fingering mechanism that develops in short time scales. Normalized peel tests were conducted on overmolded samples to measure the resulting polypropylene copolymers' bonding strength. All the ethylene random copolymers used for this study give good adhesion to polypropylene in overmolding processes, provided the right range of interface temperature is reached. Adhesion strength can be easily controlled for efficient debonding and recycling of used overmolded parts. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Super under‐actuated multi‐fingered mechanical hand with modular self‐adaptive gear‐rack mechanism

PurposeThe purpose of this paper is to present recent work designing a mechanical robotic hand for self‐adaptive grasping, human‐like appearance, which can be used in a humanoid robot. Conventional robotic devices are relatively complex, large, cumbersome and difficult to be installed in a humanoid robot arm. Under‐actuated robot hands use less motors to drive more rotating joints, thus to simplify the mechanical structure, decrease the volume and weight and finally lower the difficulty of control and the cost.Design/methodology/approachA novel under‐actuated finger mechanism is designed, which is based on a gear‐rack mechanism, spring constraint and an active sleeve middle phalanx. The principle analyses of its self‐adaptive grasp and end power grasping are given. A new multi‐fingered hand named as TH‐3R Hand is designed based on the finger.FindingsThe design finger mechanism can be used in a robotic hand to make the hand obtain more degrees of freedom (DOF) with fewer actuators, and good grasping function of shape adaptation, decrease the requirement of control system. TH‐3R Hand has five fingers, 15 DOF. All fingers are similar. TH‐3R Hand has many advantages: it is simple in structure, light in weight, easy to control and low in cost. TH‐3R Hand can passively adapt different shapes and sizes of the grasped object. Experimental studies have demonstrated the self‐adaptation in grasping of the finger.Research limitations/implicationsThe implication of this research is that under‐actuated robotic hands are appropriate for the missions of grasping different objects. The limitation of the research to date is that issues of sensors, control, and communication have not yet been addressed.Practical implicationsKey technologies of the under‐actuated finger and TH‐3R Hand, with self‐adaptive grasping, human‐like appearance and low‐cost lightweight, are feasible. These technologies have the potential to make a significant impact.Originality/valueThese results present a self‐adaptive under‐actuated grasp concept and a humanoid robotic hand with under‐actuated gear‐rack mechanism.

A Numerical Simulation for Design and Operation of an Underactuated Finger Mechanism for LARM Hand

A simulation procedure for an underactuated finger mechanism is proposed for design purposes as based on the kinematics and statics analysis of mechanism operation. A reachable space is proposed and simulated to describe the range and capability to adaptively grasp objects with various shapes and sizes. A numerical example is reported as a result that has been simulated through a specific code with MATLAB program. Results are discussed for a proper design of a new finger mechanism for the LARM (Laboratory of Robotics and Mechatronics) Hand. Results show that the proposed design of a new underactuated finger mechanism can provide human-like grasping operation, and it can be embedded within the finger body with a human-sized mechanical design during the whole motion of grasp operation.

Effect of A and B Metal Ion Site Occupancy on Conformational Changes in an RB69 DNA Polymerase Ternary Complex

Rapid chemical quench assays, as well as equilibrium and stopped-flow fluorescence experiments, were performed with an RB69 DNA polymerase (RB69 pol)-primer-template (P/T) complex containing 2-aminopurine (dAP) and a metal exchange-inert Rh(III) derivative of a deoxynucleoside triphosphate (Rh.dTTP). The objective was to determine the effect of catalytic metal ion (A site) occupancy on the affinity of an incoming Rh.dTTP for the RB69 pol-P/T binary complex and on the rate of the conformational change induced by Rh.dTTP binding. With Ca(2+) in the A site, the affinity of the incoming Rh.dTTP for the RB69 pol-P/T binary complex and the conformational change rate can be determined in the absence of chemistry. When Mg(2+) was added to a ternary complex containing Rh.dTTP opposite dAP, the templating base, nucleotidyl transfer occurred, but the rate of product formation was only one-tenth of that found with Mg.dTTP, as determined by rapid chemical quench assays. Rates of conformational change subsequent to formation of a ternary complex, in the absence of chemistry, were estimated from the rate of change in dAP fluorescence with an increase in the Rh.dTTP concentration. We have shown that there is an initial rapid quenching of dAP fluorescence followed by a second phase of dAP quenching, which has nearly the same rate as that of dTMP incorporation, as estimated from rapid chemical quench experiments. We have also demonstrated that the affinity of Rh.dTTP for occupancy of the B metal ion site is dependent on the presence of Ca(2+). However, a saturating Rh.dTTP concentration in the absence of Ca(2+) results in full quenching of dAP fluorescence, whereas a saturating Ca(2+) concentration in the absence of Rh.dTTP gives only partial quenching of dAP fluorescence. The implications of these results for the mechanism of Fingers closing, metal ion binding, and base selectivity are discussed.

Geometric Optimization of Three-Phalanx Prosthesis Underactuated Fingers using Particles Swarm Algorithm

Problem statement: One are now interested to investigate the optimum design procedure for a finger driving mechanism to have a good configuration of the finger for its utilization in hand prosthesis. A Geometric Optimization of Three-Phalanx Prosthesis Underactuated Fingers (TPPUF) based on a Particle Swarm Optimization (PSO) was presented. Approach: Firstly, a numerical evaluation of the human-like motion was obtained by using an anthropomorphic finger mechanism. Secondly, the dimensional design of a finger driving mechanism had been formulated as a multi-objective optimization problem by using evaluation criteria for fundamental characteristics that were associated with finger motion, grasping equilibrium and force transmission. Results: Testing results indicated that the proposed PSO gives high-quality result and shorter computation time compared with genetic algorithm. Conclusion: Using the PSO Algorithm with the Matlab-software, it is possible to identify all the necessary parameters of the mathematical models.

Kinetic and Thermodynamic Basis of Guanine Nucleotide Exchange on the Rab Ypt1p by the Membrane Tethering Complex TRAPPI

TRAPPI is a multiprotein tethering complex involved in mediating the initial interaction of endoplasmic reticulum (ER)-derived vesicles at the cis-Golgi, that serves as a guanine nucleotide exchange factor (GEF) for the Rab GTPase, Ypt1p. Activation of Ypt1p by TRAPPI is required for membrane fusion, and thus the mechanism of nucleotide exchange by TRAPPI is a crucial step of regulation in vesicular transport. A minimal complex of five proteins (Bet5p, Trs23p, Trs31p, and 2 copies of Bet3p) is required for GEF activity, suggesting a complex interaction between TRAPPI and Ypt1p.The large majority of GEFs accelerate nucleotide exchange from G-proteins by inserting a glutamate finger wedge into the nucleotide binding pocket. We recently solved the crystal structure of nucleotide-free Ypt1p in complex with TRAPPI, which revealed the absence of the canonical glutamate finger and suggested a novel mechanism of GEF activity by TRAPPI.In this study, we measured the rate and equilibrium constants for nucleotide and TRAPPI binding to Ypt1p. Nucleotide binding is accelerated ∼30-fold and dissociation more than three orders of magnitude, suggesting that the nucleotide binding site is more accessible in the presence of TRAPPI. Analysis of various mutant TRAPPI complexes, a Ypt1 mutant defective in nucleotide binding, and the Mg2+-dependence of exchange do not support a glutamate finger mechanism, and favor nucleotide exchange through a novel mechanism in which TRAPPI accelerates nucleotide dissociation by opening the nucleotide binding site through interactions with switch I and II. Thermodynamic linkage analysis indicates that TRAPPI binds nucleotide-free Ypt1 with greater affinity than Ypt1 with bound nucleotide. However, this increased stability cannot account for the >1000-fold increase in the rate of nucleotide exchange, indicating that GEF activity of TRAPPI is under kinetic control.

A Computational Design Method for a Shape Memory Alloy Wire Actuated Compliant Finger

This paper presents a computational method to design a compliant finger for robotic manipulations. As traditional mechanical fingers require bulky electromagnetic motors and numerous relative moving parts to achieve dexterous motion, we propose a class of fingers; the manipulation of which relies on finger deflections. These compliant fingers are actuated by shape memory alloy (SMA) wires that exhibit high work-density, frictionless, and quiet operations. The combination of compliant members with embedded SMA wires makes the finger more compact and lightweight. Various SMA wire layouts are investigated to reduce their response time while maintaining sufficient output force. The mathematical models of finger deflection caused by SMA contraction are then derived along with experimental validations. As finger shapes are essential to the range of deflected motion and output force, we find its optimal initial shapes through the use of a shape parametrization technique. We further illustrate our method by designing a humanoid finger that is capable of three-dimensional manipulation. Since compliant fingers can be fabricated monolithically, we expect the proposed design method to be utilized for applications of various scales.

Design Considerations for an Underactuated Robotic Finger Mechanism

A design approach is presented in this paper for underactuation in robotic finger mechanisms. The characters of underactuated finger mechanisms are introduced as based on linkage and spring systems,The feature of self-adaptive enveloping grasp by underactuated finger mechanisms is discussed with feasible in grasping unknown objects. The design problem of robotic fingers is analyzed by looking at many aspects for an optimal functionality. Design problems and requirements for underactuated mechanisms are formulated as related to human-like robotic fingers. In particular,characteristics of finger mechanisms are analyzed and optimality criteria are summarized with the aim to formulate a general design algorithm. A general multi-objective optimization design approach is applied as based on a suitable optimization problem by using suitable expressions of optimality criteria. An example is illustrated as an improvement of finger mechanism in Laboratory of Robotics and Mechatronics (LARM) Hand. Results of design outputs and grasp simulations are reported with the aim to show the practical feasibility of the proposed concepts and computations.

ON MOTION GENERATION OF WATT I MECHANISMS FOR MECHANICAL FINGER DESIGN

This work formulates and demonstrates a motion generation method for the synthesis of a particular type of planar six-bar mechanism-the Watt I mechanism. The Watt I mechanism is essentially a “stacked” four-bar mechanism (having two closed loops and a single degree of freedom). Extending the planar motion generation method of Suh and Radcliffe [11] to incorporate relative motion between moving pivots, Watt I mechanisms are synthesized to simultaneously approximate two groups of prescribed rigid-body poses for simultaneous dual motion generation capability. The example included demonstrates the synthesis of a finger mechanism to achieve a prescribed grasping pose sequence.

Designing an underactuated mechanism for a 1 active DOF finger operation

In this paper a novel finger mechanism with 1 active DOF is proposed for an underactuated operation. The underacuation mechanism design is based on spring elements within the mechanism structure. The feasibility of the mechanism is verified through suitable kinematic and static analysis to give performance characteristics. The finger mechanism is able to obtain a human-like grasping operation and it can be embedded within the finger body with human-size mechanical design. The proposed finger mechanism is presented also as obtained from a synthesis procedure which is based on the analyzed characteristics. A design solution is proposed and tested through numerical simulation.

Experimental Tests on Feasible Operation of a Finger Mechanism in the LARM Hand#

The feasibility and efficiency of a finger mechanism in the LARM Hand have been verified through experimental tests in terms of both operation performance and design characteristics. In this paper, we have reported how to carry out an experimental evaluation of mobility and stiffness characteristics of the finger mechanism in the LARM Hand. Results of laboratory tests show the soundness of the testing procedure and feasibility of the finger mechanism design.

1P1-C14 腹腔内組立式3指5自由度ハンド(第2報) : 指駆動機構の改良とIn Vivo実験による評価(手術支援ロボティクス・メカトロニクス)

1P1-C14 腹腔内組立式3指5自由度ハンド(第2報) : 指駆動機構の改良とIn Vivo実験による評価(手術支援ロボティクス・メカトロニクス)

인간손의 동작과 모양을 모방한 휴머노이드 로봇손 설계

A specialized anthropomorphic robot hand which can be attached to the biped humanoid robot MAHRU-R in KIST, has been developed. This built-in type hand consists of three fingers and a thumb with total four DOF(Degrees of Freedom) where the finger mechanism is well designed for grasping typical objects stably in human's daily activities such as sphere and cylinder shaped objects. The restriction of possible motions and the limitation of grasping objects arising from the reduction of DOF can be overcome by reflecting a typical human finger's motion profile to the design procedure. As a result, the developed hand can imitate not only human hand's shape but also its motion in a compact and efficient manner. Also this novel robot hand can perform various human hand gestures naturally and grasp normal objects with both power and precision grasping capability.

1A1-A12 把持面全体に触覚を実装可能なロボットフィンガー機構とその実現(ロボットハンドの機構と把持戦略)

Tactile sensors are necessary for robotic hand to achieve manipulation under complex environment, such as we often exploit the inner surface even on our hand/finger joints to manipulate edgy objects (e.g. a string). Unfortunately, conventional robotic hands/fingers have no tactile sensors on the hand/finger joints because of limitation of their mechanism. In this paper, we propose a novel mechanism of robotic finger which eases implementation of tactile sensors on the joints; i.e. it allows us to implement tactile sensors seamlessly on the finger surface. We experiment our finger mechanism and show its capability of sensing an edgy object; it is sufficient to be used for manipulation.

複合遊星ギアを用いたロボットフィンガの新機構

This paper presents a new mechanism for artificial fingers. It enables adduction/abduction of the MP joint in addition to the synergetic flexion/extension of the DIP, PIP and MP joints. The key mechanism is the newly invented double planetary gear system (DPGS) that allows three DOF motions of the finger in a compact placement of all actuators in a palm. The DPGS receives two input torques; one is an active torque coming from DC-motors, which drives solar gears, the other is a passive torque around the carrier of the planetary gears generated by a spring. This active/passive hybrid actuation enables to grip unknown shape objects with no sensory feedback. This paper describes the kinematics and the kinetics of the newly developed mechanism followed by the kinetics of pinching the object by two-fingers. It also shows the results of a couple of experiments. Additionally, we show a new mechanical design aiming for constructing a multi-fingered hand.

2A1-H06 示指の腱駆動モデルの動作シミュレーション(ワイヤ駆動系の機構と制御)

The index finger of human has already been modeled anatomically. This anatomical model has one problem in the tendon driven system. It is difficult for the index finger to produce both the torque in the negative direction at the PIPjoint and the torque in the positive direction at the MPjoint. The problem was solved using a new model of the index finger proposed in this study. In the new model, one extensor tendon was added at the MP joint. The computed simulation showed that the new model can produce any torque at three joints of the index finger. The new model is thus useful to investigate the control mechanism of the index finger.

1A1-A10 多指多関節ユニバーサルロボットハンドの開発(ロボットハンドの機構と把持戦略)

A multi-fingered universal robot hand has been developed in order to construct the platform of humanoid hand study. The special feature of the hand is a miniaturized friction generation mechanism that is installed in the joint driving mechanism. This design has a good effect on sustaining a large external force by a small finger mechanism with a singular point posture.

1A1-A06 低バックラッシュ立体カム関節を用いた人間型ロボットハンド機構の開発 : 指の関節機構の試作と評価(ロボットハンドの機構と把持戦略)

In this paper, we discribe a prototype finger mechanism of an anthropomorphic robot hand with 3D-cam joints. In the previous development, a finger joint is driven by a motor through wires and gears or by compressed air through tubes and so on. These actuation methods, however, have some problems; such as creeping a wire, requirement of large space for an air-compressor, and backlash of gears, which are difficult to solve. The 3D-cam joint we developed has a benefit of extremely low backlash and an ability of self-adjustment for easily assembling a joint structure.