Finger Mechanism Research Articles

Biomechanical analysis of force distribution in human finger extensor mechanisms.

The complexities of the function and structure of human fingers have long been recognised. The in vivo forces in the human finger tendon network during different activities are critical information for clinical diagnosis, surgical treatment, prosthetic finger design, and biomimetic hand development. In this study, we propose a novel method for in vivo force estimation for the finger tendon network by combining a three-dimensional motion analysis technique and a novel biomechanical tendon network model. The extensor mechanism of a human index finger is represented by an interconnected tendinous network moving around the phalanx's dorsum. A novel analytical approach based on the “Principle of Minimum Total Potential Energy” is used to calculate the forces and deformations throughout the tendon network of the extensor mechanism when subjected to an external load and with the finger posture defined by measurement data. The predicted deformations and forces in the tendon network are in broad agreement with the results obtained by previous experimental in vitro studies. The proposed methodology provides a promising tool for investigating the biomechanical function of complex interconnected tendon networks in vivo.

Research and Design of a Novel Tendon Driven Underactuated Multi-fingered Hand

For the dexterous hands, some features such as many actuator elements, complex control system and high cost make them difficult to be widely applied in a short time. Underactuated multi-fingered hands have the advantage of less actuators, simpler control system. So they can greatly cut down the complexity and cost of the hands under conditions of ensuring enough flexibility of grasping. A novel design program of the underactuated multi-fingered hand which has a tendon-pulley transmission is proposed. Following that, mechanical structure of the underactuated multi-fingered hand is designed. The methods of the joint springs are discussed. Pulley element's geometrical parameters which could affect the magnitude of the joint driving torque have a optimization analysis. Based on the analysis, an optimum design of the finger mechanism is proposed. Experimental study shows that the hand have a strong adaptive ability, and have a powerful grabing objects ability.

The Legionella pneumophila GTPase Activating Protein LepB Accelerates Rab1 Deactivation by a Non-canonical Hydrolytic Mechanism

GTPase activating proteins (GAPs) from pathogenic bacteria and eukaryotic host organisms deactivate Rab GTPases by supplying catalytic arginine and glutamine fingers in trans and utilizing the cis-glutamine in the DXXGQ motif of the GTPase for binding rather than catalysis. Here, we report the transition state mimetic structure of the Legionella pneumophila GAP LepB in complex with Rab1 and describe a comprehensive structure-based mutational analysis of potential catalytic and recognition determinants. The results demonstrate that LepB does not simply mimic other GAPs but instead deploys an expected arginine finger in conjunction with a novel glutamic acid finger, which forms a salt bridge with an indispensible switch II arginine that effectively locks the cis-glutamine in the DXXGQ motif of Rab1 in a catalytically competent though unprecedented transition state configuration. Surprisingly, a heretofore universal transition state interaction with the cis-glutamine is supplanted by an elaborate polar network involving critical P-loop and switch I serines. LepB further employs an unusual tandem domain architecture to clamp a switch I tyrosine in an open conformation that facilitates access of the arginine finger to the hydrolytic site. Intriguingly, the critical P-loop serine corresponds to an oncogenic substitution in Ras and replaces a conserved glycine essential for the canonical transition state stereochemistry. In addition to expanding GTP hydrolytic paradigms, these observations reveal the unconventional dual finger and non-canonical catalytic network mechanisms of Rab GAPs as necessary alternative solutions to a major impediment imposed by substitution of the conserved P-loop glycine.

Autonomous Pedestrian Push Button Activation by Outdoor Mobile Robot in Outdoor Environments

The authors have developed an outdoor mobile robot that has the ability to cross roads at an intersection or pedestrian crossing fully autonomously while traveling along sidewalks in an urban environment. This gives the robot the capability to travel longer and complex routes as the robot is able to cross a road and continue with its path. The developed robot has the unique ability to autonomously approach and activate the pedestrian push button with a mechanical finger. We first briefly describe the overall operation of such a road crossing robot. The rest of this paper then discusses in detail how the robot can meticulously navigate to and activate the pedestrian push button with the on-board finger. The contribution of this work is that although there are robots existing that perform precision docking or button activation, this robot is one of the few that can perform such an action in a real world outdoor environment that is completely unmodified. We prove this by deploying the robot in a real world road-crossing and it was successfully able to engage the pedestrian push button.

Variable density and viscosity, miscible displacements in horizontal Hele-Shaw cells. Part 2. Nonlinear simulations

AbstractDirect numerical simulations of the variable density and viscosity Navier–Stokes equations are employed, in order to explore three-dimensional effects within miscible displacements in horizontal Hele-Shaw cells. These simulations identify a number of mechanisms concerning the interaction of viscous fingering with a spanwise Rayleigh–Taylor instability. The dominant wavelength of the Rayleigh–Taylor instability along the upper, gravitationally unstable side of the interface generally is shorter than that of the fingering instability. This results in the formation of plumes of the more viscous resident fluid not only in between neighbouring viscous fingers, but also along the centre of fingers, thereby destroying their shoulders and splitting them longitudinally. The streamwise vorticity dipoles forming as a result of the spanwise Rayleigh–Taylor instability place viscous resident fluid in between regions of less viscous, injected fluid, thereby resulting in the formation of gapwise vorticity via the traditional, gap-averaged viscous fingering mechanism. This leads to a strong spatial correlation of both vorticity components. For stronger density contrasts, the streamwise vorticity component increases, while the gapwise component is reduced, thus indicating a transition from viscously dominated to gravitationally dominated displacements. Gap-averaged, time-dependent concentration profiles show that variable density displacement fronts propagate more slowly than their constant density counterparts. This indicates that the gravitational mixing results in a more complete expulsion of the resident fluid from the Hele-Shaw cell. This observation may be of interest in the context of enhanced oil recovery or carbon sequestration applications.

Design of the drive mechanism for an anthropomorphic robotic finger

Mechanisms may be used in the design of robotic fingers, in order to obtain drive systems which can be used for gripping or manipulating objects. In this work, a design methodology for a drive mechanism of an “anthropomorphic finger” is presented. The finger was previously developed by computational tools (CAD) at the UMNG-Colombia. The proposed methodology takes into account the mathematical relationships between the mechanical elements of the drive mechanism to carry out a dimensional synthesis, taking into account that the mechanism must fulfi ll the anthropometric characteristics of a human hand based on ten numerical positions (which were obtained from a previous UMNG work). Numerical simulation results and CAD modeling for the drive mechanism are presented. Finally, a discussion about results is included.

Liquid–vapour fronts in porous media: Multiplicity and stability of front positions

The mechanisms contributing to the stability and instability of the liquid–vapour front in a porous medium are analysed along a bifurcation curve with various combinations of thermal boundary conditions. In the first case, the boundaries above and below the layer of interest are assumed to be isothermal. It has been found that due to the competition between thermal and hydrostatic effects, the liquid–vapour interface may have multiple positions. A two-dimensional linear stability analysis of these basic states shows that the Rayleigh–Taylor mechanism is the dominant contributor to instability, but that there are circumstances under which the basic state may be stable. In the second case, a constant heat flux is imposed at the liquid boundary and a fixed temperature at the vapour boundary. It has been shown that the competition between the effects of cooling and the viscosity difference between the fluid phases causes multiple liquid–vapour front positions, whether or not gravity is considered. The stability analysis of such configurations has shown that along with the Rayleigh–Taylor (buoyancy-driven) mechanism, a Saffman–Taylor viscous fingering mechanism can also play an important rule in the transition to instability.

Exoskeleton Finger Rehabilitation Robot Dynamics Simulation Analysis

In this paper, an exoskeleton mechanical finger for rehabilitation has been designed. It has two finger knuckles which are driven by two cylinders separately. In the simulation process of ADAMS, the two cylinder driving stems are set different movement speeds and then the two finger-knuckles can be tracked as specific trajectories. The joint force and the torque curve of the exoskeleton mechanical finger at the point of the two knuckles can be got at different cylinder driving speeds.

Design and Dynamic Analysis of Mechanical Fingers Based on ProE

Mechanical fingers that imitates human fingers were designed, and kinematic analysis and dynamic analysis of them were conducted. By using bracing wire and expansion bracket, each section of the fingers could bend to 90 degrees, and torque exerted on the finger could be comparatively large. Through theoretical design and simulation analysis, it can obtain the same effect as fingers of an adult when clamping, enclasping and picking up an object.

Design and construction of an artificial finger based on SMA actuators

Shape Memory Alloy (SMA) wires are currently employed in robotics, as actuators of prosthetic limbs and medical equipment due to advantages such as reducing the size in the application, high power-to-weight ratio and elimination of complex transmission systems. In this paper, a new prosthetic finger is presented using SMA wire actuators. This robotic finger has been designed and modeled with three revolute joints and three SMA wires as the tendon in order to adduction each phalange of the finger and torsional springs to restore themto their original positions. The dynamic model of the finger has been simulated and validated in MATLAB/Simulation under different input voltages. By using this simulation, kinematic and kinetic of this finger have been analyzed. Also, by attention of the design goals, the mechanism of artificial finger is defined and has been developed in the Solid Works software. Based on simulation results, optimal choice of parameters and system features has been obtained and a prototype of finger has been built and tested.The results of practical experiments show that the designed artificial finger can achieve to the desired positions with high accuracy. Also, the results of practical tests confirm validity, high accuracy and authenticity of simulation model.

Design and Construction of an Artificial Finger based on SMA Actuators

Shape Memory Alloy (SMA) wires are currently employed in robotics, as actuators of prosthetic limbs and medical equipment due to advantages such as reducing the size in the application, high power-to-weight ratio and elimination of complex transmission systems. In this paper, a new prosthetic finger is presented using SMA wire actuators. This robotic finger has been designed and modeled with three revolute joints and three SMA wires as the tendon in order to adduction each phalange of the finger and torsional springs to restore themto their original positions. The dynamic model of the finger has been simulated and validated in MATLAB/Simulation under different input voltages. By using this simulation, kinematic and kinetic of this finger have been analyzed. Also, by attention of the design goals, the mechanism of artificial finger is defined and has been developed in the Solid Works software. Based on simulation results, optimal choice of parameters and system features has been obtained and a prototype of finger has been built and tested.The results of practical experiments show that the designed artificial finger can achieve to the desired positions with high accuracy. Also, the results of practical tests confirm validity, high accuracy and authenticity of simulation model.

Optimization of a Novel Anthropomorphic Three-Jointed Underactuated Finger Mechanism

A novel underactuated finger mechanism based on linkage and spring elements is proposed. The kinematic characteristic of the mechanism is analyzed to obtain the fingertip displacement and relationships between three joints. Considering the motion feature of human finger and actuation efficiency of the driving motor, the dimensional design of the finger mechanism is formulated as an optimization problem. The numerical simulation result shows that the finger mechanism can not only realize the anthropomorphic coupling motion, but also envelope objects with various shapes and sizes self-adaptively.

Kinematic Model of Anthropomorphic Robotics Finger Mechanisms

Research on Kinematic Model of Anthropomorphic robotics Finger mechanisms is being carried out to accommodate a variety of tasks such as grasping and manipulation of objects in the field of industrial applications, service robots, and rehabilitation robots. The first step in realizing a fully functional of anthropomorphic robotics Finger mechanisms is kinematic modeling. In this paper, a Kinematic Model of Anthropomorphic robotics Finger mechanism is proposed based on the biological equivalent of human hand where each links interconnect at the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints respectively. The Kinematic modeling was carried out using Denavit Hartenburg (DH) algorithm for the proposed of Kinematic Model of Anthropomorphic robotics Finger mechanisms. Index Terms— Anthropomorphic robot Finger, Modeling, Robotics, Simulation I. Introduction Among the vast applications of robotics, robotic assistance in human daily life and has been the major factor that contributes to its development. The focus on the anthropomorphism robotic limbs is currently undergoing a very rapid development. The creation of a multifingered anthropomorphic robotic hand is a challenge that demands innovative integration of mechanical, electronics, control and embedded software designs.

Kinematic Model of Anthropomorphic Robotics Finger Mechanisms

Kinematic Model of Anthropomorphic Robotics Finger Mechanisms

Structure-function analysis reveals a novel mechanism for regulation of histone demethylase LSD2/AOF1/KDM1b.

LSD2/AOF1/KDM1b catalyzes demethylation of mono- and di-methylated H3K4 and plays an important role in transcriptional regulation and genomic imprinting. Here, we report the high-resolution crystal structures of apo-LSD2 and LSD2 in complex with a peptide that mimics H3K4me2. Three structural domains of LSD2, namely, the novel N-terminal zinc finger, the centrally located SWIRM domain, and the C-terminal oxidase domain, closely pack together to form a boot-shaped structure. The active site cavity in the oxidase domain is large enough to accommodate several residues of the histone H3 tail and cannot discriminate between the different states of H3K4 methylation. The N-terminal zinc-finger domain, composed of a novel C4H2C2-type zinc finger and a specific CW-type zinc finger, is required for demethylase activity and, surprisingly, the binding of cofactor flavin adenine dinucleotide (FAD). In fact, a relay of extensive interactions through the zinc finger-SWIRM-oxidase domains is required for LSD2 demethylase activity and the binding of FAD. These results reveal a novel mechanism for the zinc finger and SWIRM domains in controlling LSD2 demethylase activity and provide a framework for elucidating the regulation and function of LSD2.

DEVELOPMENT OF MULTI-FINGERED ROBOTIC HAND WITH COUPLED AND DIRECTLY SELF-ADAPTIVE GRASP

This paper presents a coupled and directly self-adaptive underactuated (CDSA) grasp mode, which has hybrid functions: coupled grasp and directly self-adaptive grasp. A novel multi-pulley-belt finger mechanism with springs is designed based on CDSA grasp mode. Compared with traditional coupled underactuated fingers or directly self-adaptive underactuated fingers, the grasp process of the new finger is more humanoid and its stability is better. Force analysis and size optimization rules of the finger are given. A multi-fingered robotic hand, CDSA hand, based on the CDSA finger is developed, whose control system adopts a digital signal processor (DSP) circuit module with a keyboard as its communication interface. The CDSA hand has five fingers, six DC motors, and 15 joint DOF, nine of which are CDSA joint DOF. The appearance and actions of CDSA hand imitate human hand, whose size is 1.5 times of human hand. CDSA hand weighs 1.6 kg and can grasp objects up to 0.5 kg. Simulation and experimental results show that CDSA hand is able to realize CDSA grasp mode effectively.

Single degree-of-freedom exoskeleton mechanism design for thumb rehabilitation.

This paper presents the kinematic design of a spatial, 1-degree-of-freedom closed linkage to be used as an exoskeleton for thumb motion. Together with an already-designed finger mechanism, it forms a robotic device for hand therapy. The goal for the exoskeleton is to generate the desired grasping and pinching path of the thumb with one degree of freedom, rather than using a system actuating all its joints independently. In addition to the path of the thumb, additional constraints are added in order to control the position and size of the exoskeleton, reducing physical and sensory interference with the user.

The Effect of Conservative Management in Extensor Plus Finger After Partial Amputation to the Ulnar Digits—A Case Report

The extensor plus finger after partial amputation of ulnar digits can affect the functions of the hand. The therapist intricate knowledge of intrinsic and extrinsic mechanism of fingers and creative approach in therapy would solve the puzzle when managing complex problem (extensor plus finger). Here we study a case of extensor plus finger after partial amputation of ulnar digits, its mechanism, and our experience with conservative management in managing extensor plus finger.

Robot Finger Module With Multidirectional Adjustable Joint Stiffness

This paper describes a novel finger mechanism that enables a robot to perform a gentle and dexterous motion. This finger contains three joints, in which the proximal (PIP) and distal intraphalangeal (DIP) joints are coupled rigidly, and the metacarpophalangeal (MP) joint has a multidirectional passive compliance that is adjustable as in humans. In the MP joint, two kinds of silicone-rubber cushions (A-SRC and B-SRC) are placed between a motor-driven disk and an output link. A-SRC plays three roles: 1) transmission of the rotational motion from the motor to the output link by the friction force between the surface of A-SRC and the motor-driven disk; 2) absorption of external forces from multiple directions by its elastic deformation; and 3) sensing the directions and magnitudes of external forces with the change in inside pressure. B-SRC adjusts the characteristics of joint compliance by pressing A-SRC against the motor-driven disk. We investigate the basic performance of this finger module through several experiments.

1P1-J03 全方向駆動ローラ付指機構による対象物の操り動作(ロボットハンドの機構と把持戦略(3))

1P1-J03 全方向駆動ローラ付指機構による対象物の操り動作(ロボットハンドの機構と把持戦略(3))