Anthropomorphism Index of Mobility for Artificial Hands

The increasing development of anthropomorphic artificial hands makes necessary quick metrics that analyze their anthropomorphism. In this study, a human grasp experiment on the most important grasp types was undertaken in order to obtain an Anthropomorphism Index of Mobility (AIM) for artificial hands. The AIM evaluates the topology of the whole hand, joints and degrees of freedom (DoFs), and the possibility to control these DoFs independently. It uses a set of weighting factors, obtained from analysis of human grasping, depending on the relevance of the different groups of DoFs of the hand. The computation of the index is straightforward, making it a useful tool for analyzing new artificial hands in early stages of the design process and for grading human-likeness of existing artificial hands. Thirteen artificial hands, both prosthetic and robotic, were evaluated and compared using the AIM, highlighting the reasons behind their differences. The AIM was also compared with other indexes in the literature with more cumbersome computation, ranking equally different artificial hands. As the index was primarily proposed for prosthetic hands, normally used as nondominant hands in unilateral amputees, the grasp types selected for the human grasp experiment were the most relevant for the human nondominant hand to reinforce bimanual grasping in activities of daily living. However, it was shown that the effect of using the grasping information from the dominant hand is small, indicating that the index is also valid for evaluating the artificial hand as dominant and so being valid for bilateral amputees or robotic hands

Assessment of the use of preliminary concepts test and rubrics in practical learning at university

Comunicació presentada al ICERI 2019 12th annual International Conference of Education, Research and Innovation (Seville, Spain. 11-13 November, 2019).The high number of students and teachers in the laboratory practices of the course Theory of Machines and Mechanisms, shared by several engineering degrees at Universitat Jaume I, makes the teaching planning and evaluation challenging. Some issues were observed in past years, such as differences in the student knowledge of basic concepts, underpreparation before practical classes, poor quality of the written reports, absence of common objective assessment criteria among teachers and low success rate. That led us to the implementation of an action for educational improvement during the academic year 2018-2019. The aim was to improve the students' level of training before attending laboratory practices, to standardize the evaluation among teachers and to involve students in the process of assessment in order to improve learning outcomes and the quality of the reports delivered. The improvement action included, on one side, carrying out an initial evaluation with a diagnostic test. The results of this test were used to estimate the basic knowledge of the students and proposing specific tutorial sessions in order to unify their level of knowledge. This method should increase the students involvement and improve the success while performing the laboratory practices. On the other side, rubrics were created in order to standardize the correction criteria. These rubrics were also made public to the students, before the classes, in an attempt to improve the quality of their reports. In addition, for some of the reports the students were asked to self-assess their own reports following the public rubric. The results indicate that teachers found the rubrics useful for objective and fair evaluation. However, the standard deviation across teachers has not been apparently reduced with respect to the previous year by the use of them, although the differences in the student cohort have to be taken into account. The effect on grades of the factors teacher and session, as well as their interaction, was significant (p<.05) according to the ANOVA tests, as already was prior to the application of the action. It was also found that the student grades in the practical classes did not improved significantly. A low implication in the preparation before classes and a low tutorial attendance were observed in the collective of students, possible explaining in part the discrete improvements obtained. The self-assessment improved the grades on average where it was applied. We concluded that the involvement of both students and teachers is necessary to promote learning quality using these techniques

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

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

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

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

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

Affordable 3D-printed tendon prosthetic hands: Expectations and benchmarking questioned

The popularization of 3D-printing has allowed enhancing affordable prostheses for persons with amputations in developing countries, yet manufacturers are not subjected to any control from any medical regulatory authority. Adopted evaluation protocols seem to cherish optimistic expectations. A reduced performance test, derived from the Southampton Hand Assessment Procedure and two bench tests, to evaluate the mechanical advantage in the fingers and the slip resistance, are proposed to assess affordable tendon-driven devices. Ultimately, five models amongst those most commonly found in the scientific literature and the Internet have been evaluated. Three subjects participated with the aid of an able-bodied adaptor. The reduced test of performance provides consistent results but with a more direct interpretation of the failed patterns of prehension. All these models create far more expectations than the results deliver. With the supplementary material provided, an affordable benchmarking can be established with this reduced performance test and the two bench tests. They can lead to improved designs, prescriptions and regulations

Methods for the design and evaluation of anthropomorphic artificial hands

The objective of this thesis is to contribute to the definition of applicable methods during the design process of artificial hands in order to obtain more anthropomorphic and functional designs, as well as to define metrics and protocols that help evaluate these aspects. The proposed methods are focused on the mechanical design of any anthropomorphic hand, both in the prosthetic and robotic fields, although in this thesis greater emphasis has been placed on hands designed for 3D printing, given its growing popularity and accessibility and its potential impact on society. Most of the developments and proposals made are based on biomechanical aspects obtained from the analysis of the human hand. In this thesis, the evaluation of the degree of anthropomorphism of artificial hands has been approached from three complementary perspectives: experimentation, definition of analytical indexes and simulation by means of models.El objetivo de esta tesis es el de contribuir a la definición de métodos aplicables durante el proceso de diseño de manos artificiales con el fin de obtener diseños más antropomorfos y funcionales, así como definir métricas y protocolos que ayuden a evaluar estos aspectos. Los métodos propuestos están enfocados al diseño mecánico de cualquier mano antropomorfa, tanto en el ámbito protésico como en el robótico, si bien en esta tesis se ha hecho un mayor énfasis en manos orientadas a la fabricación mediante impresión 3D, dado su creciente auge y accesibilidad y por su potencial impacto en la sociedad. Gran parte de los desarrollos y propuestas realizados están basados en aspectos biomecánicos obtenidos del análisis de la mano humana. En esta tesis la evaluación del grado de antropomorfismo de las manos artificiales se ha abordado desde tres perspectivas complementarias: experimentación, definición de índices analíticos y simulación mediante modelos

Diseño, construcción y evaluación experimental de una mano antropomórfica accionada por cable

[ES] El objetivo del Trabajo Fin de Máster consiste en diseñar, construir y evaluar experimentalmente una mano antropomórfica accionada por cable. La mano se deberá diseñar para ser fabricada utilizando tecnología de impresión 3D y se empleará en laboratorio para evaluación experimental de las capacidades prensiles de una mano artificial. La mano tendrá cinco dedos, del mismo modo que una mano humana y tendrá 6 grados de libertad, cada uno accionado con un cable y retorno por sistemas elásticos. El pulgar se accionará con 2 grados de libertad, uno para flexión y otro para abducción y el resto de dedos con 1 grado de libertad de flexión. El accionamiento de los cables que mueven la mano se realizará con los dedos de un operador humano, de modo que dicho operador pueda utilizar la mano mecánica como una prolongación de su propia mano, para agarrar una variedad de objetos en ensayos de laboratorio. El dispositivo de accionamiento incluirá sensores que permitan medir y registrar en un ordenador los movimientos de cada cable durante los ensayos de laboratorio de agarre de objetos. El análisis de las correlaciones entre movimientos de cada cable permitirá analizar las sinergias empleadas enLlop Harillo, I. (2016). Diseño, construcción y evaluación experimental de una mano antropomórfica accionada por cable. http://hdl.handle.net/10251/72201.TFG