Nature grasping by a cable-driven under-actuated anthropomorphic robotic hand

Human hand is the best sample for humanoid robotic hand and a nature grasping is the final target that most robotic hands are pursuing. Many prior researches had been done in virtual and real for simulation the human grasping. Unfortunately, there is no perfect solution to duplicate the nature grasping of human. The main difficulty comes from three points. 1. How to 3D modelling and fabricate the real hand. 2. How actuated the robotic hand as real hand. 3. How to grasp objects in different shapes like human hand. To deal with these three problems and further to provide a partial solution for duplicate human grasping, this paper introduces our method to solve these problems from robotic hand design, fabrication, actuation and grasping plan. Our modelling progress takes only around 12 minutes that include 10 minutes of 3D scanning of a real human hand and two minutes for changing the scanned model to an articulated model by running our algorithm. Our grasping plan is based on the sampled trajectory and easy to implement for grasping different objects. Followed these steps, a seven DOF robotic hand is created and tested in the experiments

Pressure and angle sensors with optical fiber for instrumentation of the PrHand hand prosthesis

The principal cause of upper limb amputations is due to traumatism. The prosthesis is an assistive device to help in the activities of daily for the amputee person. However, one of the latest reports shows that in developing countries there are around 30 million people without assistive devices. This work presents the development of two kinds of sensors for the PrHand, an upper limb prosthesis based on compliant mechanism and soft-robotics. The sensors are made with polymeric optical fiber (POF), due to their flexibility and low cost, and the working principle is based on intensity variation. The angle sensors are used for monitoring the interphalangeal joint of the fingers, and for the assessment were made cycles of closing and opening each finger. On the other hand, the force sensors are located at the tip of three fingers to track the force made over the objects. Before encoring the sensors were evaluated making five cycles of compressing and decompressing each sensor. The results show a linear behavior between the angle and the voltage variation, one most remarkable angle sensor result was with a sensibility of 0.0357 V/° and an R2 of 99 % closing and 0.0483 V/° opening. In the case of the force sensor, a polynomial relation was found between the voltage changes and the pressure over the sensor; in some cases, the relation between voltage changes and pressure could be linear but that depends on the construction of the sensor. Regarding the obtained R2 of 99 %, its sensibility was 0.0361 V/N compression and 0.0368 V/N decompression. In conclusion, was successfully developed two kinds of sensors for the instrumentation of PrHand prosthesis. It is expected to use angle and sensor variables as input in algorithms of Machine Learning to improve the detection of objects. One aspect to improve is to control in a better way the sensor construction parameters due to the considerable influence over the sensor behavior

The Global Care Ecosystems of 3D Printed Assistive Devices

The popularity of 3D printed assistive technology has led to the emergence of new ecosystems of care, where multiple stakeholders (makers, clinicians, and recipients with disabilities) work toward creating new upper limb prosthetic devices. However, despite the increasing growth, we currently know little about the differences between these care ecosystems. Medical regulations and the prevailing culture have greatly impacted how ecosystems are structured and stakeholders work together, including whether clinicians and makers collaborate. To better understand these care ecosystems, we interviewed a range of stakeholders from multiple countries, including Brazil, Chile, Costa Rica, France, India, Mexico, and the U.S. Our broad analysis allowed us to uncover different working examples of how multiple stakeholders collaborate within these care ecosystems and the main challenges they face. Through our study, we were able to uncover that the ecosystems with multi-stakeholder collaborations exist (something prior work had not seen), and these ecosystems showed increased success and impact. We also identified some of the key follow-up practices to reduce device abandonment. Of particular importance are to have ecosystems put in place follow up practices that integrate formal agreements and compensations for participation (which do not need to be just monetary). We identified that these features helped to ensure multi-stakeholder involvement and ecosystem sustainability. We finished the paper with socio-technical recommendations to create vibrant care ecosystems that include multiple stakeholders in the production of 3D printed assistive devices

The Making of a 3D-Printed, Cable-Driven, Single-Model, Lightweight Humanoid Robotic Hand

Dexterity robotic hands can (Cummings, 1996) greatly enhance the functionality of humanoid robots, but the making of such hands with not only human-like appearance but also the capability of performing the natural movement of social robots is a challenging problem. The first challenge is to create the hand's articulated structure and the second challenge is to actuate it to move like a human hand. A robotic hand for humanoid robot should look and behave human like. At the same time, it also needs to be light and cheap for widely used purposes. We start with studying the biomechanical features of a human hand and propose a simplified mechanical model of robotic hands, which can achieve the important local motions of the hand. Then, we use 3D modeling techniques to create a single interlocked hand model that integrates pin and ball joints to our hand model. Compared to other robotic hands, our design saves the time required for assembling and adjusting, which makes our robotic hand ready-to-use right after the 3D printing is completed. Finally, the actuation of the hand is realized by cables and motors. Based on this approach, we have designed a cost-effective, 3D printable, compact, and lightweight robotic hand. Our robotic hand weighs 150 g, has 15 joints, which are similar to a real human hand, and 6 Degree of Freedom (DOFs). It is actuated by only six small size actuators. The wrist connecting part is also integrated into the hand model and could be customized for different robots such as Nadine robot (Magnenat Thalmann et al., 2017). The compact servo bed can be hidden inside the Nadine robot's sleeve and the whole robotic hand platform will not cause extra load to her arm as the total weight (150 g robotic hand and 162 g artificial skin) is almost the same as her previous unarticulated robotic hand which is 348 g. The paper also shows our test results with and without silicon artificial hand skin, and on Nadine robot

Strategies towards large-scale 3D printing without size constraints

Three-dimensional (3D) printing has been profoundly changing the production mode of traditional industries. However, this technique is usually limited to metre-scale fabrication, which prevents large-scale 3D printing (LS3DP) applications such as the manufacturing of buildings, aircraft, ships, and rockets. LS3DP faces great challenges, particularly, it not only requires confronting problems not yet solved by conventional 3D printing, such as the inability to print functional structures due to limitations by single-material manufacturing, but also needs to overcome the size effect limitation of large-scale printing. Here, we systematically review the state of the art in the integration of materials and technologies in LS3DP. We also demonstrate some disruptive engineering cases of LS3DP in the field of construction. The challenges and strategies for overcoming size constraints to achieve LS3DP of functional structures are discussed, including multifunctional 3D printing processes from nano- to large-scale and large-scale 4D printing processes, diverse printable materials and sustainable structures, horizontal and vertical size-independent printers, collaborative and intelligent control of the entire process, and extreme environment printing. These strategies can provide tremendous opportunities for the fully automated, intelligent, and unmanned production of these different material megastructures and internal multiscale multifunctional components such as buildings/structures, aerospace vehicles, and marine equipment

Open-Source TIG-Based Metal 3D-Printing

Metal 3-D printing has been relegated to high-cost proprietary high-resolution systems and low-resolution low-cost metal inert gas (MIG) systems. In order to provide a path to high-resolution, low-cost, metal 3-D printing, this manuscript proposes a new open source metal 3-D printer design based around a low-cost tungsten inert gas (TIG) welder coupled to a commercial open source self replicating rapid prototyper. Optimal printing parameters for the machine are acquired using a novel computational intelligence software. TIG has many advantages over MIG, such as having a low heat input, clean beads, and the potential for both high-resolution prints as well as insitu alloying of complex geometries. The design can be adapted to most RepRap-class systems and has a basic yet powerful free and open source software (FOSS) package for the characterization of the 3-D printer. This system can be used for fabricating custom metal scientific components and tools, near net-shape structural metal component rapid prototyping, adapting and depositing on existing metal structures, and is deployable for in-field prototyping for appropriate technology applications

Diseño y construcción de una prótesis mecánica para amputación transmetacarpal controlada por muñón flexible y cables para una persona adulta

La investigación se centró en el diseño y construcción de una prótesis mecánica para amputación transmetacarpal controlada por muñón flexible y cables, para mejorar la capacidad de realizar actividades cotidianas de los usuarios. Se realizó una amplia investigación de la anatomía y biomecánica de la mano, así como de las necesidades y expectativas de los usuarios, utilizando un enfoque interdisciplinario que combina la ingeniería, la biomecánica, la psicología y la ergonomía. El desarrollo del proyecto comenzó con un análisis de las necesidades del usuario y la definición del alcance de la prótesis. Luego se procedió al prototipado utilizando tecnología de barrido mediante nube de puntos y se plasmaron las demandas del usuario en un prototipo. Se realizó un estudio CAE para validar el diseño y la selección de materiales de cada una de las partes de la prótesis, utilizando TPU y PLA debido a su resistencia y biocompatibilidad con la piel. Se evaluó la funcionalidad de la prótesis mediante un protocolo de pruebas bajo la norma AHAP y se obtuvieron resultados satisfactorios con un 60% de satisfacción según la norma. La prótesis presentó una buena capacidad de agarre a bajo costo en comparación con las prótesis existentes en el mercado y puede ser mejorada aumentando la capacidad de carga, incrementando el número de hilos y rediseñando las articulaciones. En conclusión, la investigación logró diseñar y construir una prótesis mecánica que mejora la capacidad de realizar actividades cotidianas de los usuarios con amputación transmetacarpal. El enfoque interdisciplinario y la utilización de tecnología de vanguardia permitieron validar el diseño y se logró una buena capacidad de agarre a bajo costo. La prótesis tiene potencial para ser mejorada y puede ser una solución accesible para las personas que requieren este tipo de dispositivos.The research focused on the design and construction of a mechanical prosthesis for transmetacarpal amputation controlled by a flexible stump and cables, to improve the ability of users to perform daily activities. Extensive research into the anatomy and biomechanics of the hand, as well as the needs and expectations of users, was conducted using an interdisciplinary approach combining engineering, biomechanics, psychology and ergonomics. The development of the project began with an analysis of the user's needs and the definition of the scope of the prosthesis. Prototyping was then carried out using point cloud scanning technology and the user's demands were captured in a prototype. A CAE study was carried out to validate the design and selection of materials for each part of the prosthesis, using TPU and PLA due to their resistance and biocompatibility with the skin. The functionality of the prosthesis was evaluated through a test protocol under the AHAP standard and satisfactory results were obtained with 60% satisfaction according to the standard. The prosthesis presented a good gripping capacity at a low cost compared to existing prostheses on the market and can be improved by increasing the load capacity, increasing the number of threads and redesigning the joints. In conclusion, the research managed to design and build a mechanical prosthesis that improves the ability to perform daily activities of users with transmetacarpal amputation. The interdisciplinary approach and the use of state-of-the-art technology allowed the design to be validated and good gripping capacity was achieved at low cost. The prosthesis has the potential to be improved and can be an accessible solution for people who require this type of device