Finger Design Research Articles

Design and analysis of an underactuated anthropomorphic finger for upper limb prosthetics.

This paper presents the design of a linkage based finger mechanism ensuring extended range of anthropomorphic gripping motions. The finger design is done using a path-point generation method based on geometrical dimensions and motion of a typical index human finger. Following the design description, and its kinematics analysis, the experimental evaluation of the finger gripping performance is presented using the finger 3D printed prototype. The finger underactuation is achieved by utilizing mechanical linkage system, consisting of two crossed four-bar linkage mechanisms. It is shown that the proposed finger design can be used to design a five-fingered anthropomorphic hand and has the potential for upper limb prostheses development.

Design and simulation of an underactuated finger mechanism for LARM Hand

SUMMARYAn underactuated mechanism is presented as a new finger design for improving grasp adaptability of LARM Hand fingers. Underactuation is discussed as a feasible solution through several design structures for finger adaptability to shape and size of objects to be grasped. The proposed underactuated solution for a new LARM finger is characterized through simulation results in ADAMS environment for operation feasibility and performance.

Design and Development of Automatic Finger Inking Machine for Electoral Usage

Design and Development of Automatic Finger Inking Machine for Electoral Usage

P‐107: Investigation on the Flexoelectric Effect of LC in the Localized Area of FFS Pixel Structure

Due to the pixel size consideration, the finger design of FFS mode LCD pixel may different in the local area. In this paper, we discuss the flicker phenomenon and flexoelectric effect of LC in localized area of FFS mode Pixel.

Numerical Validation of a New Approach to Model Single Junction Low Concentration PV Cells under Non-Uniform Illumination

This study presents a numerical validation of a new approach to model single junction PV cell under non-uniform illumination for low-concentration solar collectors such as compound parabolic concentrators (CPC). The simulation is achieved by finite element modelling (FEM). To characterize the results, the model is simulated with five different non-uniform illumination profiles. The results indicate that increasing the non-uniformity of concentrated light will introduce more resistive losses and lead to a significant attenuation in the PV cell short-circuit current. The FEM modelling results are then used to validate the array modelling approach, in which a single junction PV cell is considered equivalent to a parallel-connected array of several cell splits. A comparison between the FEM and array modelling approaches shows good agreement. Therefore, the array modelling approach is a fast way to investigate the PV cell performance under non-uniform illumination, while the FEM approach is useful in optimizing design of fingers and bus-bars on a PV.

Reducing optical and resistive losses in graded silicon-germanium buffer layers for silicon based tandem cells using step-cell design

Si solar cells with a SiGe graded buffer on top are fabricated as the initial step in GaAsP/Si tandem cell fabrication. Using this structure, the impact of the SiGe buffer layer on the Si solar cells is characterized. To mitigate the impact of the narrow-bandgap SiGe on the electrical and optical characteristics of the Si sub-cell, a portion of the underlying Si is exposed using a step-cell design. The step-cell design is demonstrated to increase the Jsc of the SiGe/Si stack from 5 to 20 mA/cm2. The layout of the top mesa is shown to have an impact on the device characteristics with the finger design giving better results than the rectangular mesa with respect to fill factor and series resistance. In addition, utilizing the step-cell design increases overall spectral response of the bottom cell, with significant improvements in the short wavelength range.

Design and Testing of a Self-Adaptive Prosthetic Finger with a Compliant Driving Mechanism

In this paper, a novel underactuated prosthetic finger with a compliant driving mechanism is proposed. The underactuated finger is based on linkage mechanism and spring elements within the compliant driving mechanism. The proposed finger mechanism is able to obtain human-like operations. The feasibility of the mechanism is verified through suitable kinematic and static analysis. The structure parameters and the coefficient of the springs are calculated according to the requirements of human-like operations. Finally, we experimentally validate the reasonability of design results and demonstrate that the finger grasps objects in diverse ways.

Coupled and Self-Adaptive Under-Actuated Finger With a Novel S-Coupled and Secondly Self-Adaptive Mechanism

This paper presents a novel under-actuated (UA) finger with first coupled and secondly self-adaptive (COSA) grasping mode. COSA fingers can adaptively grasp objects with different sizes and shapes while its motions during grasping are anthropopathic. Until now there are two COSA mechanisms available and they are both direct parallel combinations of coupled mechanism and self-adaptive mechanism. These kind of direct combinations lead to complex mechanical structure and high power consumption. This paper proposes a novel single-route transmission mechanism for COSA grasping mode, S-coupled and directly self-adaptive (CDSA) mechanism for short. Compared with available COSA mechanisms, the S-CDSA mechanism has simpler structure and higher grasping force. Design of 2-joint S-CDSA finger is introduced in this paper. Force analysis for 2-joint S-CDSA finger is given. Furthermore, a 2-joint S-CDSA finger is manufactured. The force analysis and experimental results show that the novel S-CDSA mechanism is effective.

IPMC-Actuated Compliant Mechanism-Based Multifunctional Multifinger Microgripper

Over the past few decades, the Electro Active Polymer (EAPs) has become quite useful for vast applications in the field of robotic and bio-mimetic. Ionic Polymer Metal Composite (IPMC) is one of the EAPs which holds an excellent bending property at low actuation voltage resulting high force output; thus, it is capable of doing work as good as human finger tip when the same is employed as an actuator for micromanipulation. In the present investigation, a four-fingered micro gripper under the actuation of IPMC has been addressed. The microgripper consists of four fingers made of Polydimethyl Siloxane and each finger has three notches. The novelty of this gripping device is in its multifunction operation. It can manipulate microobject less than 1 mm diameter as well as macro object within the diameter of 10 mm. This finger design is compliant in nature. The development of micropart handling devices and allied research is a highly challenging task. The principle on which the gripper operates and its fabrication process are explained in detail in this article. It involves miniature part handling, integration, and assembly operation.

HIT prosthetic hand based on tendon-driven mechanism

An underactuated finger structure actuated by tendon-driven system is presented. Kinematics and static analysis of the finger is done, and the results indicate that the prosthetic finger structure is effective and feasible. Based on the design of finger, a prosthetic hand is designed. The hand is composed of 5 independent fingers and it looks more like humanoid. Its size is about 85% of an adult’s hand and weights about 350 g. Except the thumb finger, each finger is actuated by one DC motor, gear head and a tendon, and has three curling/extension joints. The thumb finger which is different from other existing prostheses is a novel design scheme. The thumb finger has four joints including three curling/extension joints and a joint which is used to realize the motion of the thumb related to the palm, and these joints are also driven by one DC motor, harmonic drive and a tendon. The underactuation and adaptive curling/extension motion of the finger are realized by joint torsion springs. A high-powered chip of digital signal processing (DSP) is the main part of the electrical system which is used for the motors control, data collection, communication with external controlling source, and so on. To improve the reliability of the hand, structures and sensors are designed and made as simply as possible. The hand has strong manipulation capabilities that have been verified by finger motion and grasping tests and it can satisfy the daily operational needs and psychological needs of deformities.

Analysis of Coordinated Motions of Humanoid Robot Fingers Using Interphalangeal Joint Coordination

In this study, we analyse the coordinated motions of humanoid robot fingers using an interphalangeal joint coordination. For this purpose, four humanoid robot fingers with different sizes have been considered. A biomimetic interphalangeal joint coordination (IJC) formulation based on the grasp configuration of human fingers has been presented for humanoid robot fingers. The usefulness of the specified IJC formulation for human-like finger motion has been verified through comparative demonstrations. As a result, a proper coordination of humanoid robot fingertips can be achieved by applying our IJC formulation. Also the IJC formulation can be used to design of humanoid robot fingers.

Development of a tendon-driven robotic finger for an anthropomorphic robotic hand

Our paper proposes a tendon-driven robotic finger based on an anatomical model of a human finger and a suitable method for its analysis. Our study aims to realize an anthropomorphic robotic hand that has the same characteristics and dexterity as that of a human hand, and it also aims to identify the advantages of the human musculoskeletal structure for application to the design and control of robot manipulators. When designing an anthropomorphic robotic hand, several devices are required to apply the human finger structure to a tendon-driven robotic finger. Reasons for this include that one of the human finger muscles, namely, the lumbrical muscle, is situated between tendons, which is an unfavorable configuration for the tendon-driven mechanism. Second, unlike a standard pulley used in a tendon-driven mechanism, some moment arms of the human finger change nonlinearly according to the joint angle. In our robotic finger design, we address these difficulties by rearranging its tendons and develop a mechanism to change the moment arm. We also propose a method to analyze and control this robotic fingers coordinating joints using non-stretch branching tendons based on the human extensor mechanism with a virtual tendon Jacobian matrix and the advantage is that this constraint virtually reduces the degrees-of-freedom (DOF) of the mechanism. Further, we build a prototype to confirm its motion using this method. In addition, we show that the state with the reduced DOF can be lost by external forces acting on the mechanism, and this condition can be changed manually by adjusting the tendon forces. This makes it possible to control the virtual DOFs to satisfy the requirements of the task. Finally, we discuss the benefits from anthropomorphic structures including the tendon arrangement, which mimic the human lumbrical muscle, and the above mentioned mechanism with non-linear moment arms from the perspective that there are two states of DOFs. These insights may provide new perspectives in the design of robotic hands.

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.

Behavioral Modeling of a CMOS–MEMS Nonlinear Parametric Resonator

Predictive design of nonlinear microelectromechanical systems featuring parametric resonance provides motivation to refine mixed MEMS/analog behavioral composable modeling and simulation methodologies. Toward this end, a schematic of a canonical parametric resonator testbed is built with primitive beam, plate, and gap models from a MEMS Verilog-AMS library along with a macro model of a non-interdigitated comb with electrostatic spring coefficients extracted from finite element analysis. A CMOS-MEMS parametric resonator for validation experiments exploits the well known non-interdigitated finger design to create a voltage-controlled spring constant as the parametric stimulus. Behavioral modeling and the analytic perturbation solutions are validated by optical vibration measurements matching to 0.2% and 2.1%, respectively.

Artificial Biometric Finger Driven by Shape‐Memory Alloy Wires

This paper presents the design and testing of an artificial finger based partly on biomechanics. The prototype was manufactured in acrylonitrile butadiene styrene plastic using a rapid prototyping three-dimensional printer. The flexing of the finger was realized by Ni-Ti shape-memory alloy (SMA) wires with diameters of 0.3 mm, activated by resistive heating. The results obtained show the new prototype to be superior in performance, mainly in terms of angles of rotation of the phalanges, compared with some SMA fingers discussed in the literature.

Anthropomorphic tendon-driven robotic hands can exceed human grasping capabilities following optimization

How functional versatility emerges in vertebrate limbs in spite of their anatomical complexity is a longstanding question. In particular, fingers are actuated by numerous muscles pulling on tendons following intricate paths. In contrast, the tendon-driven robotic hands with intuitive tendon routings preferred by roboticists for their ease of analysis and control do not perform at the level of their biological counterparts. Thus there is much debate on whether and how the anatomy of the human hand contributes to grasp capabilities. These parallel questions in biology and robotics arise partly because it is unclear how the number and routing of tendons offer functional benefits. We use a novel computational approach that analyzes tendon-driven systems and quantifies grasp quality to compare the precision grasp capabilities of thousands of robotic index finger and thumb designs vs. the capabilities measured in human hands. Our exhaustive search finds that neither the symmetrical designs sometimes preferred by roboticists nor randomly generated designs approach the grasp capabilities of the human hand (they are on average 73% weaker). However, optimizing for anatomically plausible asymmetry in joint centers, tendon routings, and maximal tendon tensions produces designs that can exceed the human hand by 13–45%, and outperform the preferred robotic designs by up to 435%. Thus, the grasp capabilities of prosthetic or anthropomorphic hands can be greatly improved by judiciously altering design parameters, at times in counter-intuitive ways. Moreover we conclude that, in addition to its other capabilities, the human hand’s anatomy is very advantageous for precision grasp as it greatly outperforms numerous alternative robotic designs.

Open-Loop Precision Grasping With Underactuated Hands Inspired by a Human Manipulation Strategy

In this paper, we demonstrate an underactuated finger design and grasping method for precision grasping and manipulation of small objects. Taking inspiration from the human grasping strategy for picking up objects from a flat surface, we introduce the flip-and-pinch task, in which the hand picks up a thin object by flipping it into a stable configuration between two fingers. Despite the fact that finger motions are not fully constrained by the hand actuators, we demonstrate that the hand and fingers can interact with the table surface to produce a set of constraints that result in a repeatable quasi-static motion trajectory. Even when utilizing only open-loop kinematic playback, this approach is shown to be robust to variation in object size and hand position. Variation of up to 20° in orientation and 10 mm in hand height still result in experimental success rates of 80% or higher. These results suggest that the advantages of underactuated, adaptive robot hands can be carried over from basic grasping tasks to more dexterous tasks.

Finite element analysis of the effect on employing thermal through vias and heat fingers to increase heat transfer to fluid in calorimetric flow sensors

Measurement results of a robust silicon calorimetric flow sensor with a 25μm thick silicon dioxide membrane with thermal silicon vias have been compared with results obtained from three-dimensional Finite Element Analysis (FEA). Based on the fabricated device, the sensor has been further developed to include heat-exchanging fingers extending down into the integrated flow channel for increased heat transfer. Using FEA, different designs of the fingers have been compared with respect to signal strength, sensitivity, power consumption and pressure loss in the channel at flow rates from 0 to about 650sccm. Using heat fingers, the sensor signal was improved by a factor of five. The sensor signal, i.e. the temperature difference between downstream and upstream elements, was more than 60°C when the central heater was heated 300°C above room temperature, which was comparable to a thin-membrane device modeled. The maximum sensitivity using the finger design was about 1.4°Csccm−1, and the maximum power consumption was almost 700mW, which is considerably higher than for thin-membrane sensors. A figure of merit used for evaluation, was the ratio of signal strength to power consumption. The results show that the device design is a promising concept that is suitable in systems requiring robust monolithically integratable flow sensors.

Assisted design of linkage‐driven adaptive soft fingers

PurposeAdaptive grippers are versatile end effectors that mechanically adapt their shapes to the objects they seize, allowing for soft and delicate grasps while still allowing for strong contact forces if needed and therefore they are well suited for industrial applications. The purpose of this paper is to present a software‐oriented approach to design optimal architectures of linkage‐driven adaptive (often a.k.a underactuated) fingers with three degrees of freedom.Design/methodology/approachThe user of the software presented in this paper can design planar underactuated fingers following defined constraints. The software uses an algorithm able to compute the internal and contact forces generated, respectively, in and by the finger, it is also capable of automating the design of non‐straight links to eliminate mechanical interferences, and includes results from a topological synthesis to generate all possible architectures. The mechanisms are evaluated for many criteria such as the volume of their workspaces, stability, force isotropy, stiffness of their grasps, and compactness.FindingsThis article introduces 11 new designs of underactuated fingers for four different usages, and many of these variants are good candidates for a physical realization. One of the interesting results of this work is the recurrence of S3 variants coupled with torque amplifiers or closely resembling designs using many unrelated performance criteria.Originality/valueThis paper is the first, to the best of the authors' knowledge, to investigate the systematic design of underactuated fingers driven by linkages considering not one but dozens of mechanical architectures.

Design and control of an IPMC artificial muscle finger for micro gripper using EMG signal

This paper presents the design and control of an ionic polymer metal composite (IPMC) based artificial finger for micro gripper. In this work, IPMC based micro finger is actuated by controlled electromyography (EMG) signal. The EMG signal is taken from human index finger via EMG sensor. This signal is pre-amplified before transferring to IPMC for achieving the large bending behavior of IPMC. The bio-mimetic actuation behavior of IPMC is studied by movement of index finger muscles through long tendons. The stability analysis of EMG signal from human index finger is carried out by providing the PID control system. Experimentally, it is observed that IPMC finger can hold the load up to 100mg when IPMC finger is activated through EMG via human muscles and an IPMC based micro gripper is demonstrated.