The Anthropomorphic Hand Assessment Protocol (AHAP)

The progress in the development of anthropomorphic hands for robotic and prosthetic applications has not been followed by a parallel development of objective methods to evaluate their performance. The need for benchmarking in grasping research has been recognized by the robotics community as an important topic. In this study we present the Anthropomorphic Hand Assessment Protocol (AHAP) to address this need by providing a measure for quantifying the grasping ability of artificial hands and comparing hand designs. To this end, the AHAP uses 25 objects from the publicly available Yale-CMU-Berkeley Object and Model Set thereby enabling replicability. It is composed of 26 postures/tasks involving grasping with the eight most relevant human grasp types and two non-grasping postures. The AHAP allows to quantify the anthropomorphism and functionality of artificial hands through a numerical Grasping Ability Score (GAS). The AHAP was tested with different hands, the first version of the hand of the humanoid robot ARMAR-6 with three different configurations resulting from attachment of pads to fingertips and palm as well as the two versions of the KIT Prosthetic Hand. The benchmark was used to demonstrate the improvements of these hands in aspects like the grasping surface, the grasp force and the finger kinematics. The reliability, consistency and responsiveness of the benchmark have been statistically analyzed, indicating that the AHAP is a powerful tool for evaluating and comparing different artificial hand designs

Benchmarking anthropomorphic hands through grasping simulations

In recent decades, the design of anthropomorphic hands has been developed greatly improving both cosmesis and functionality. Experimentation, simulation, and combined approaches have been used in the literature to assess the effect of design alternatives (DAs) on the final performance of artificial hands. However, establishing standard benchmarks for grasping and manipulation is a need recognized among the robotics community. Experimental approaches are costly, time consuming, and inconvenient in early design stages. Alternatively, computer simulation with the adaptation of metrics based on experimental benchmarks for anthropomorphic hands could be useful to evaluate and rank DAs. The aim of this study is to compare the anthropomorphism of the grasps performed with 28 DAs of the IMMA hand, developed by the authors, using either (i) the brute-force approach and grasp quality metrics proposed in previous works or (ii) a new simulation benchmark approach. The new methodology involves the generation of efficient grasp hypotheses and the definition of a new metric to assess stability and human likeness for the most frequently used grasp types in activities of daily living, pulp pinch and cylindrical grip, adapting the experimental Anthropomorphic Hand Assessment Protocol to the simulation environment. This new simulation benchmark, in contrast to the other approach, resulted in anthropomorphic and more realistic grasps for the expected use of the objects. Despite the inherent limitations of a simulation analysis, the benchmark proposed provides interesting results for selecting optimal DAs in order to perform stable and anthropomorphic grasps

Grasping Ability and Motion Synergies in Affordable Tendon-Driven Prosthetic Hands Controlled by Able-Bodied Subjects

Affordable 3D-printed tendon-driven prosthetic hands are a rising trend because of their availability and easy customization. Nevertheless, comparative studies about the functionality of this kind of prostheses are lacking. The tradeoff between the number of actuators and the grasping ability of prosthetic hands is a relevant issue in their design. The analysis of synergies among fingers is a common method used to reduce dimensionality without any significant loss of dexterity. Therefore, the purpose of this study is to assess the functionality and motion synergies of different tendon-driven hands using an able-bodied adaptor. The use of this adaptor to control the hands by means of the fingers of healthy subjects makes it possible to take advantage of the human brain control while obtaining the synergies directly from the artificial hand. Four artificial hands (IMMA, Limbitless, Dextrus v2.0, InMoov) were confronted with the Anthropomorphic Hand Assessment Protocol, quantifying functionality and human-like grasping. Three subjects performed the tests by means of a specially designed able-bodied adaptor that allows each tendon to be controlled by a different human finger. The tendon motions were registered, and correlation and principal component analyses were used to obtain the motion synergies. The grasping ability of the analyzed hands ranged between 48 and 57% with respect to that of the human hand, with the IMMA hand obtaining the highest score. The effect of the subject on the grasping ability score was found to be non-significant. For all the hands, the highest tendon-pair synergies were obtained for pairs of long fingers and were greater for adjacent fingers. The principal component analysis showed that, for all the hands, two principal components explained close to or more than 80%of the variance. Several factors, such as the friction coefficient of the hand contact surfaces, limitations on the underactuation, and impairments for a correct thumb opposition need to be improved in this type of prostheses to increase their grasping stability. The principal components obtained in this study provide useful information for the design of transmission or control systems to underactuate these hands

The PrHand: Functional Assessment of an Underactuated Soft-Robotic Prosthetic Hand

Functional tests aim to compare the functionality of a prosthesis with a human hand. The main objective of this work is to present and evaluate an affordable prosthesis (PrHand) built with soft robotic technologies and novel joints based on compliant mechanisms. Two functional tests have been selected in this work. The first is the AHAP protocol, which evaluates how the prosthesis performs eight different grips; three variables are considered: grasping, maintaining, and grasping ability score (GAS). The results were 69.03% with 57.77% in grasping and 80.28% in maintaining. The second test is the AM-ULA, which evaluates the prosthesis by performing 23 Activities of Daily Living. PrHand prosthesis had a score of 2.5 over 4.0. The functionality of the PrHand prosthesis has similar results to other prostheses evaluated in the literature. The comparison with the human hand was 69%. PrHand presents a promising solution for amputees in developing countries regarding cost and functionalit

Effect of the Thumb Orientation and Actuation on the Functionality and Performance of Affordable Prosthetic Hands: Obtaining Design Criteria

The advent of 3D printing technologies has enabled the development of low-cost prosthetic underactuated hands, with cables working as tendons for flexion. Despite the particular relevance to human grasp, its conception in prosthetics is based on vague intuitions of the designers due to the lack of studies on its relevance to the functionality and performance of the device. In this work, some criteria for designers are provided regarding the carpometacarpal joint of the thumb in these devices. To this end, we studied four prosthetic hands of similar characteristics with the motion of abduction/adduction of the thumb resolved in three different ways: fixed at a certain abduction, coupled with the motion of flexion/extension, and actuated independently of the flexion/extension. The functionality and performance of the hands were assessed for the basic grasps using the Anthropomorphic Hand Assessment Protocol (AHAP) and a reduced version of the Southampton Hand Assessment Procedure (SHAP). As a general rule, it seems desirable that thumb adduction/abduction is performed independently of flexion/extension, although this adds one degree of control. If having this additional degree of control is beyond debate, coupled flexion/extension and adduction/abduction should be avoided in favour of the thumb having a fixed slight palmar abduction.This research was supported by the Spanish MINECO, AEI, and ERDF under Grant DPI2017-89910-R; the MICIN/AEI/10.13039/501100011033 for the project PID2020-118021RB-I00; the Generalitat Valenciana under Grant GV/2018/125; and the Universitat Jaume I under Grant UJI-B2017-70

A fabric-based soft hand exoskeleton for assistance: the ExHand Exoskeleton

INTRODUCTION: The rise of soft robotics has driven the development of devices for assistance in activities of daily living (ADL). Likewise, different types of actuation have been developed for safer human interaction. Recently, textile-based pneumatic actuation has been introduced in hand exoskeletons for features such as biocompatibility, flexibility, and durability. These devices have demonstrated their potential use in assisting ADLs, such as the degrees of freedom assisted, the force exerted, or the inclusion of sensors. However, performing ADLs requires the use of different objects, so exoskeletons must provide the ability to grasp and maintain stable contact with a variety of objects to lead to the successful development of ADLs. Although textile-based exoskeletons have demonstrated significant advancements, the ability of these devices to maintain stable contact with a variety of objects commonly used in ADLs has yet to be fully evaluated. MATERIALS AND METHODS: This paper presents the development and experimental validation in healthy users of a fabric-based soft hand exoskeleton through a grasping performance test using The Anthropomorphic Hand Assessment Protocol (AHAP), which assesses eight types of grasping with 24 objects of different shapes, sizes, textures, weights, and rigidities, and two standardized tests used in the rehabilitation processes of post- stroke patients. RESULTS AND DISCUSSION: A total of 10 healthy users (45.50 ± 14.93 years old) participated in this study. The results indicate that the device can assist in developing ADLs by evaluating the eight types of grasps of the AHAP. A score of 95.76 ± 2.90% out of 100% was obtained for the Maintaining Score, indicating that the ExHand Exoskeleton can maintain stable contact with various daily living objects. In addition, the results of the user satisfaction questionnaire indicated a positive mean score of 4.27 ± 0.34 on a Likert scale ranging from 1 to 5

Evaluación y comparación de manos protésicas de impresión 3D mediante el Anthropomorphic Hand Assessment Protocol (AHAP)

Comunicació presentada a la IX Reunión del Capítulo Español de la Sociedad Europea de Biomecánica (ESB 2019)El diseño y fabricación de prótesis por impresión 3D ha tenido un importante crecimiento en los últimos años debido a su bajo coste y su mayor accesibilidad1. Organizaciones como Enabling the future (e-NABLE)2 trabajan por todo el mundo para facilitar este tipo de prótesis a niños y usuarios con pocos recursos. El problema de estas prótesis es que han sido creadas para cubrir una necesidad de la manera más fácil y rápidamente posible, sin analizar y mejorar su funcionalidad para realizar actividades de la vida diaria (ADLs). Esto en parte se debe a que el aumento de los diseños no ha ido acompañado de un desarrollo paralelo de métodos objetivos que evalúen su funcionamiento. Su evaluación se basa en protocolos o cuestionarios diseñados específicamente3. Pocos son los trabajos4,5 que han utilizado protocolos más ampliamente conocidos en el ámbito de la mano humana como el Box and Block test o el SHAP. El Anthropomorphic Hand Assessment Protocol (AHAP)6 es un benchmark definido por los autores mediante el cual se mide la capacidad manipulativa de manos artificiales antropomorfas mediante la realización de 26 tareas. El AHAP permite cuantificar de manera numérica tanto el antropomorfismo como la funcionalidad de las prótesis a través del Grasping Ability Score (GAS). El objetivo del presente estudio es comparar diferentes prótesis fabricadas mediante impresión 3D a través de su GAS y destacar las dificultades que presentan para realizar los agarres más comunes en las ADLs

Design and Development of an Open-Source ADL-Compliant Prosthetic Arm for Transradial Amputees

Transradial amputation is traumatic – leading to the amputee having a limited ability to perform activities of daily living (ADLs). Below-elbow prostheses are prescribed. The high cost associated with prostheses results in many amputees in low-to-middleincome countries relying on government subsidised devices, which are cosmetic rather than functional, or none at all. Open-source prostheses have the potential to increase the accessibility of functional prosthetic arms, but at present are not optimised to assist the dominant hand in performing bimanual ADLs. The aim of this study is thus to design and experimentally validate an open-source prosthetic arm that is functionally optimised for the performance of ADLs in the unilateral transradial amputee population. The ADL arm is functional open-source below-elbow prosthesis. This device is bodypowered; featuring a hand terminal device with thumb abduction and adduction, and wrist pronation and supination functionality. Elbow flexion of the residual limb is used to actuate the terminal device. The prosthesis requires no existing prosthetic hardware; and the majority of parts can be 3D printed. The ADL arm is designed to reliably perform the grasps required by the non-dominant hand in two-handed ADL activities. Device validation includes functional and simulated-use components. The functional assessment uses the Anthropomorphic Hand Assessment Protocol (AHAP); while the simulated-use assessment involves a practical ADL verification, and a usability assessment using healthy volunteer participants. The AHAP gives as result a grasping ability score (GAS) and partial GAS for ten grasp types associated with ADLs. The GAS represents the percentage of healthy limb function achievable by the prosthesis. The overall GAS of the ADL arm is found to be 68 %. The ADL arm achieved a partial GAS of greater than 75 % for four of five bimanual ADL grasps. A major design flaw resulted in a partial GAS of 33.3 % for the lateral pinch grasp type. The performance in this grasp, as well as others, would be greatly improved by the inclusion of a mechanism to lock the distal joint of the digits in extension during grasp. In this way, the hand would be better able to apply force to an object with the pads of the digits. Simulated-use validation of the ADL arm is performed on healthy participants using the designed bypass socket. The ADL assessment involves the completion of 86 ADL and instrumental ADL tasks; scored using the designed self-report questionnaire. The participant could perform all but seven tasks independently, and the perceived difficulty for tasks requiring the prosthesis was low overall. Seven healthy volunteers are used to assess the system usability. Participants performed a number of tasks and then completed the system usability scale (SUS). The perceived usability of the device is found to increase with increased device familiarity, yielding an overall score of 84.29. This result indicates that participants found the experience with the device to be ‘good' overall. In conclusion, the ADL arm is functionally competent and has proven its ability to assist in the performance of ADLs in a simulated-use environment; using healthy participants. A number of design modifications are recommended to overcome the limitations of the current design, which should be tested in the transradial amputee population to corroborate the results obtained in this study

An Investigation into Validated Task-Based Evaluation Methods for Upper-Limb Prostheses

Despite significant mechatronic advancements in prosthetic hands, achieving the functionality of a biological extremity remains far from realized. For the development of next generation prosthetics and improved patient outcomes, standardized, reliable, and validated task-based evaluation measures are essential. A task-based approach, entailing the manipulation of physical objects with prostheses, directly assesses patient performance in real-time and offersnumerous benefits. Task-based assessments aid clinical decision-making, allowing clinicians to choose the best prosthetic device or strategy for individual patients and enables precise tracking of patient progress, highlighting treatment effectiveness or the need for adjustments. These measures also provide objective data for cost justification in insurance and public health systems, enhancing transparency among stakeholders, including researchers, clinicians, patients, and regulatory bodies. Finally, the standardization of task-based measures facilitates consistent comparisons across different prosthetic devices and control systems, promoting iterative improvement and innovation. Thus, properly implemented standardized evaluation measures are fundamental to the advancement of upper-limb prosthetics.This thesis critically examines currently available task-based evaluation methods forupper-limb prosthetic technologies, highlighting the gap between the rapid advancement of prosthetic devices and the development of standardized assessment protocols. First, a comprehensive literature review, published in Frontiers in Robotics and AI, revealed that only 25 assessments for upper-limb prostheses have been validated since 1948, highlighting many researchers’ reliance on non-standardized tests that may not have rigorously established validity and not fully address the diverse interests of clinical and research communities. This research then applies theory to practice by using one of the highest rated currently available methods, the Anthropomorphic Hand Assessment Protocol (AHAP), to compare three open-source 3D-printed prosthetic hands with three commercially produced ones. This analysis, currently under review in BMC Biomedical Engineering, illustrates the practical challenges and advancements in prosthetic evaluation and paves the way for a more in-depth discussion on enhancing assessment methodologies. Finally, an online survey about task-based functional measures was conducted to understand and gather insights from diverse practitioners who interact with individuals prescribed upper-limb prostheses. The findings from this survey will influence future task-based evaluation methods and will be presented at the MyoElectric Control Conference in August 2024. This thesis not only provides insights into existing evaluation methods but also pinpoints areas for enhancement, significantly contributing to the development of effective and universally accepted evaluation techniques for upper-limb prostheses

Design of a mechanical system for underactuation of hand prostheses

Treball Final de Grau en Enginyeria Mecànica. Codi: EM1047. Curs acadèmic: 2021/2022The project has been developed working with the Biomechanics and Ergonomics research group in the framework of the UNIQUE-HAND project that has as final objective the creation of viable artificial hands valid as prostheses for individuals and also as robotic hands for industry, as well as the improvement of aesthetics of prior designs, allowing people to wear their prostheses with more confidence and trying the designs to go unnoticed. As mentioned above, the specific objective of this FDP is to design a mechanical underactuation system that improves weak points of previous developments and tries to reproduce as faithfully as possible the different hand grasps used by healthy people during activities of daily living. This mechanical system must be designed in order to be manufactured using the fused deposition modelling (FDM) 3D printing technique [2] and will be fitted into a completely new designed hand prototype which houses this underactuation system, the design of which is also reflected in this paper. The design of the prosthesis includes fingers, joints, returning system, flexion system, abduction and adduction of the thumb and palmar structure of the hand. This new system will be tested in the laboratory by carrying out two essays, one of them will be a grasping test and the other will be the water bottle test (WBT) that will be explained further in the paper and the other will be the Anthropomorphic Hand Assessment Protocol (AHAP) [3]. The presented design is based on differential mechanisms, such as pulleys and whiffletree mechanisms and will be explained in further detail later on. The design of the prosthetic hand has been based on the scan of a real human hand and then modified in order to adapt the different proportions and finger orientations, as well as the different mechanisms that allow the flexion and extension of the hand as mentioned above. The actuation of the different cables that allow the movement of the hand will be obtained by using a bowden cable together with a harness and triceps cuff system and the prosthesis will be located just below the tested subject hand, thus allowing a more natural behaviour when making grasps. This project contains the design of the underactuation mechanical system and its manufacture using a 3D printer. Furthermore, there are details about the assembly process and the different components of the design. Eventually, there is an explanation of the tests that will be carried out, which will determine the performance of the system, and the obtained results from these tests