Advancing the Underactuated Grasping Capabilities of Single Actuator Prosthetic Hands

The last decade has seen significant advancements in upper limb prosthetics, specifically in the myoelectric control and powered prosthetic hand fields, leading to more active and social lifestyles for the upper limb amputee community. Notwithstanding the improvements in complexity and control of myoelectric prosthetic hands, grasping still remains one of the greatest challenges in robotics. Upper-limb amputees continue to prefer more antiquated body-powered or powered hook terminal devices that are favored for their control simplicity, lightweight and low cost; however, these devices are nominally unsightly and lack in grasp variety. The varying drawbacks of both complex myoelectric and simple body-powered devices have led to low adoption rates for all upper limb prostheses by amputees, which includes 35% pediatric and 23% adult rejection for complex devices and 45% pediatric and 26% adult rejection for body-powered devices [1]. My research focuses on progressing the grasping capabilities of prosthetic hands driven by simple control and a single motor, to combine the dexterous functionality of the more complex hands with the intuitive control of the more simplistic body-powered devices with the goal of helping upper limb amputees return to more active and social lifestyles. Optimization of a prosthetic hand driven by a single actuator requires the optimization of many facets of the hand. This includes optimization of the finger kinematics, underactuated mechanisms, geometry, materials and performance when completing activities of daily living. In my dissertation, I will present chapters dedicated to improving these subsystems of single actuator prosthetic hands to better replicate human hand function from simple control. First, I will present a framework created to optimize precision grasping – which is nominally unstable in underactuated configurations – from a single actuator. I will then present several novel mechanisms that allow a single actuator to map to higher degree of freedom motion and multiple commonly used grasp types. I will then discuss how fingerpad geometry and materials can better grasp acquisition and frictional properties within the hand while also providing a method of fabricating lightweight custom prostheses. Last, I will analyze the results of several human subject testing studies to evaluate the optimized hands performance on activities of daily living and compared to other commercially available prosthesis

Design and development of robust hands for humanoid robots

Design and development of robust hands for humanoid robot

Whole-Hand Robotic Manipulation with Rolling, Sliding, and Caging

Traditional manipulation planning and modeling relies on strong assumptions about contact. Specifically, it is common to assume that contacts are fixed and do not slide. This assumption ensures that objects are stably grasped during every step of the manipulation, to avoid ejection. However, this assumption limits achievable manipulation to the feasible motion of the closed-loop kinematic chains formed by the object and fingers. To improve manipulation capability, it has been shown that relaxing contact constraints and allowing sliding can enhance dexterity. But in order to safely manipulate with shifting contacts, other safeguards must be used to protect against ejection. “Caging manipulation,” in which the object is geometrically trapped by the fingers, can be employed to guarantee that an object never leaves the hand, regardless of constantly changing contact conditions. Mechanical compliance and underactuated joint coupling, or carefully chosen design parameters, can be used to passively create a caging grasp – protecting against accidental ejection – while simultaneously manipulating with all parts of the hand. And with passive ejection avoidance, hand control schemes can be made very simple, while still accomplishing manipulation. In place of complex control, better design can be used to improve manipulation capability—by making smart choices about parameters such as phalanx length, joint stiffness, joint coupling schemes, finger frictional properties, and actuator mode of operation. I will present an approach for modeling fully actuated and underactuated whole-hand-manipulation with shifting contacts, show results demonstrating the relationship between design parameters and manipulation metrics, and show how this can produce highly dexterous manipulators

Augmentation de performance des doigts sous-actionnés par actionnement multiple

RÉSUMÉ Les préhenseurs font partie des éléments critiques en robotique, notamment lorsqu’ils sont amenés à saisir des objets de formes et de grandeurs différentes. L’utilisation typique d’un actionneur pour chaque degré de liberté (DDL) constitue un système complexe nécessitant généralement l’utilisation de plusieurs capteurs et d’algorithmes de contrôle évolués. Les concepts sous-actionnés, pour leur part, ne nécessitent généralement pas ces éléments. Ils suscitent donc un intérêt grandissant et font l’objet de plus en plus d’études, le coût et le poids devenant des enjeux inévitables. La plupart des mécanismes sous-actionnés n’utilisent pas plus d’un actionneur agissant sur les mêmes DDL. Pour les doigts sous-actionnés, sujet de ce mémoire, l’utilisation d’un seul actionneur peut limiter les performances. L’objectif de la présente étude est de quantifier les avantages de l’actionnement multiple, c’est-à-dire l’utilisation de plusieurs actionneurs. Deux cas sont étudiés. Le premier porte sur l’amélioration des performances du point de vue de la saisie d’objets. Le deuxième porte sur le contrôle de la trajectoire de fermeture, c’est-à-dire le mouvement libre du doigt sans qu’il y ait contact avec un objet. Dans le premier cas, l’amélioration des performances de la prise englobante, c’est-à-dire enveloppant l’objet en maximisant le nombre de contacts, est évaluée pour différentes combinaisons d’actionneurs, après une optimisation de la géométrie pour chacune d’entre elles. Deux architectures sont étudiées, une pour laquelle un maximum de trois couples d’actionnement sont distribués à l’intérieur du mécanisme, et l’autre pouvant accueillir deux actionneurs dans la paume. Pour la première, une amélioration marquée de la performance est observée, alors que pour la deuxième, la différence est plutôt modeste. Dans le deuxième cas, l’architecture comportant deux actionneurs dans la paume est optimisée pour obtenir deux trajectoires de fermeture différentes. L’actionnement du doigt par un des actionneurs occasionne une trajectoire analogue à une prise englobante alors que l’utilisation du second en occasionne une pour laquelle la phalange distale demeure perpendiculaire à la paume. Un prototype de ce doigt ayant le comportement escompté est présenté. À la lumière de cette étude, il est clair qu’il y a avantage à utiliser plusieurs actionneurs sur un doigt sous-actionné, que ce soit pour améliorer les performances de la saisie d’objets ou pour permettre le contrôle de la trajectoire de fermeture.----------ABSTRACT Grippers are one of the critical elements in robotics, especially when they get to grasp differently shaped and sized objects. Typical use of one actuator per degree of freedom (DOF) leads to complex mechanisms generally needing many sensors and advanced control algorithms. However in most cases, underactuated designs do not need those components. Therefore, underactuated grippers are the focus of a growing number of works as cost and weight become inescapable issues. Most underactuated mechanisms use no more than one actuator for a set of DOF. As for underactuated fingers, topic of this work, using a single actuator can limit their performance. The main objective of this work is to quantify the advantages of multiple drive actuation, i.e., using several actuators. Two cases are studied. The first focuses on grasp performance augmentation. The second one is about motion control. In the first study case, grasp performance augmentation is assessed for various combinations of actuators, geometry being optimized for each one. Two architectures are studied, one for which a maximum of three torques inputs are distributed throughout the mechanism, and another able to accommodate two actuators in the palm. For the first one, a significant performance amelioration is observed, while for the second one, the difference is modest. In the second study case, the architecture using two actuators in the palm is optimized in order to obtain two distinct closing motions. Driving the finger with one actuator leads to a enveloping grasp like motion, while using the second one leads to a pinch grasp preshaping, i.e., a closing motion for which the distal phalanx remains perpendicular to the palm. A prototype showing the expected behaviour is presented. In the light of this study, it is clear that using several actuators on an underactuated finger is an advantage, whether it be for grasp performance augmentation or to allow motion control

ReHand - a portable assistive rehabilitation hand exoskeleton

This dissertation presents a synthesis of a novel underactuated exoskeleton (namely ReHand2) thought and designed for a task-oriented rehabilitation and/or for empower the human hand. The first part of this dissertation shows the current context about the robotic rehabilitation with a focus on hand pathologies, which influence the hand capability. The chapter is concluded with the presentation of ReHand2. The second chapter describes the human hand biomechanics. Starting from the definition of human hand anatomy, passing through anthropometric data, to taxonomy on hand grasps and finger constraints, both from static and dynamic point of view. In addition, some information about the hand capability are given. The third chapter analyze the current state of the art in hand exoskeleton for rehabilitation and empower tasks. In particular, the chapter presents exoskeleton technologies, from mechanisms to sensors, passing though transmission and actuators. Finally, the current state of the art in terms of prototype and commercial products is presented. The fourth chapter introduces the concepts of underactuation with the basic explanation and the classical notation used typically in the prosthetic field. In addition, the chapter describe also the most used differential elements in the prosthetic, follow by a statical analysis. Moreover typical transmission tree at inter-finger level as well as the intra- finger underactuation are explained . The fifth chapter presents the prototype called ReHand summarizing the device description and explanation of the working principle. It describes also the kinetostatic analysis for both, inter- and the intra-finger modules. in the last section preliminary results obtained with the exoskeleton are shown and discussed, attention is pointed out on prototype’s problems that have carry out at the second version of the device. The sixth chapter describes the evolution of ReHand, describing the kinematics and dynamics behaviors. In particular, for the mathematical description is introduced the notation used in order to analyze and optimize the geometry of the entire device. The introduced model is also implemented in Matlab Simulink environment. Finally, the chapter presents the new features. The seventh chapter describes the test bench and the methodologies used to evaluate the device statical, and dynamical performances. The chapter presents and discuss the experimental results and compare them with simulated one. Finally in the last chapter the conclusion about the ReHand project are proposed as well as the future development. In particular, the idea to test de device in relevant environments. In addition some preliminary considerations about the thumb and the wrist are introduced, exploiting the possibility to modify the entire layout of the device, for instance changing the actuator location

Pattern recognition-based real-time myoelectric control for anthropomorphic robotic systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Mechatronics at Massey University, Manawatū, New Zealand

All copyrighted Figures have been removed but may be accessed via their source cited in their respective captions.Advanced human-computer interaction (HCI) or human-machine interaction (HMI) aims to help humans interact with computers smartly. Biosignal-based technology is one of the most promising approaches in developing intelligent HCI systems. As a means of convenient and non-invasive biosignal-based intelligent control, myoelectric control identifies human movement intentions from electromyogram (EMG) signals recorded on muscles to realise intelligent control of robotic systems. Although the history of myoelectric control research has been more than half a century, commercial myoelectric-controlled devices are still mostly based on those early threshold-based methods. The emerging pattern recognition-based myoelectric control has remained an active research topic in laboratories because of insufficient reliability and robustness. This research focuses on pattern recognition-based myoelectric control. Up to now, most of effort in pattern recognition-based myoelectric control research has been invested in improving EMG pattern classification accuracy. However, high classification accuracy cannot directly lead to high controllability and usability for EMG-driven systems. This suggests that a complete system that is composed of relevant modules, including EMG acquisition, pattern recognition-based gesture discrimination, output equipment and its controller, is desirable and helpful as a developing and validating platform that is able to closely emulate real-world situations to promote research in myoelectric control. This research aims at investigating feasible and effective EMG signal processing and pattern recognition methods to extract useful information contained in EMG signals to establish an intelligent, compact and economical biosignal-based robotic control system. The research work includes in-depth study on existing pattern recognition-based methodologies, investigation on effective EMG signal capturing and data processing, EMG-based control system development, and anthropomorphic robotic hand design. The contributions of this research are mainly in following three aspects: Developed precision electronic surface EMG (sEMG) acquisition methods that are able to collect high quality sEMG signals. The first method was designed in a single-ended signalling manner by using monolithic instrumentation amplifiers to determine and evaluate the analog sEMG signal processing chain architecture and circuit parameters. This method was then evolved into a fully differential analog sEMG detection and collection method that uses common commercial electronic components to implement all analog sEMG amplification and filtering stages in a fully differential way. The proposed fully differential sEMG detection and collection method is capable of offering a higher signal-to-noise ratio in noisy environments than the single-ended method by making full use of inherent common-mode noise rejection capability of balanced signalling. To the best of my knowledge, the literature study has not found similar methods that implement the entire analog sEMG amplification and filtering chain in a fully differential way by using common commercial electronic components. Investigated and developed a reliable EMG pattern recognition-based real-time gesture discrimination approach. Necessary functional modules for real-time gesture discrimination were identified and implemented using appropriate algorithms. Special attention was paid to the investigation and comparison of representative features and classifiers for improving accuracy and robustness. A novel EMG feature set was proposed to improve the performance of EMG pattern recognition. Designed an anthropomorphic robotic hand construction methodology for myoelectric control validation on a physical platform similar to in real-world situations. The natural anatomical structure of the human hand was imitated to kinematically model the robotic hand. The proposed robotic hand is a highly underactuated mechanism, featuring 14 degrees of freedom and three degrees of actuation. This research carried out an in-depth investigation into EMG data acquisition and EMG signal pattern recognition. A series of experiments were conducted in EMG signal processing and system development. The final myoelectric-controlled robotic hand system and the system testing confirmed the effectiveness of the proposed methods for surface EMG acquisition and human hand gesture discrimination. To verify and demonstrate the proposed myoelectric control system, real-time tests were conducted onto the anthropomorphic prototype robotic hand. Currently, the system is able to identify five patterns in real time, including hand open, hand close, wrist flexion, wrist extension and the rest state. With more motion patterns added in, this system has the potential to identify more hand movements. The research has generated a few journal and international conference publications

Mesure tactile proprioceptive pour des doigts sous-actionnés

RÉSUMÉ La préhension et la manipulation d’objets par des robots deviennent de plus en plus répandues dans divers domaines, et ce, pour de multiples applications. L’utilisation de robots permet d’améliorer la répétabilité, la rapidité et la précision lors de certaines tâches, et ce, comparativement aux performances d’un opérateur humain. De plus, un robot peut également être conçu pour accomplir certaines tâches qu’une personne ne pourrait effectuer, que ce soit au niveau de la force nécessaire ou du manque d’espace pour manoeuvrer. Des robots peuvent également plus aisément fonctionner dans des environnements hostiles. Tout comme pour l’être humain, la rétroaction tactile est particulièrement utile et même inévitable pour effectuer certaines tâches. Il faut toutefois souligner qu’il s’agit d’un thème de recherche où l’on est encore bien loin d’avoir atteint les performances humaines. Pour s’en approcher, de nombreuses et diverses technologies de capteurs tactiles existent, mais chacune comporte ses défauts. Ainsi, bien qu’il existe actuellement des solutions technologiques pour donner une rétroaction sensorielle à un robot ou à son opérateur, ces dernières s’avèrent généralement coûteuses, présentent différents défauts au niveau de la sensibilité et ne sont pas toujours adaptées à certaines utilisations. Dans l’optique de trouver une alternative efficace aux technologies conventionnelles de détection et de mesure tactiles, la présente thèse se concentre sur la possibilité d’utiliser la raideur inhérente du mécanisme de transmission d’un doigt sous-actionné. En effet, les doigts et les mains sous-actionnés sont de plus en plus communément utilisés pour leur simplicité propre et leur capacité à saisir et à s’adapter à la forme d’objet de manière purement mécanique sans schéma de commande complexe ou de nombreux actionneurs. Contrairement aux mécanismes pleinement actionnés, les doigts sous-actionnés, communément appelés adaptatifs, comportent des éléments passifs pour contraindre leur mouvement avant le contact, tout en permettant d’obtenir une prise stable sans développer des forces de contact trop élevées initialement. Les doigts sous-actionnés étant généralement dépourvus d’actionneurs à l’intérieur du doigt lui-même, les seuls capteurs déjà présents sont typiquement situés à l’unique actionneur. Toutefois, en analysant et traitant en temps réel les données de ces capteurs internes, également appelés proprioceptifs, il est possible d’extraire une panoplie d’informations sur ce qui se passe au niveau des phalanges. Ce principe est donc utilisé pour obtenir des algorithmes de détection tactile pouvant être utilisés sur différents systèmes, tels qu’une pince compliante et un préhenseurs à membrures.----------ABSTRACT Robotic hands have become more and more prevalent in many fields. They have replaced human operators in many repetitive applications where robots become more precise and efficient. Moreover, robotic graspers can lift heavier loads and accomplish maneuvers a human could not. They can also manipulate objects in hostile environments where it would be dangerous for humans. Therefore, a lot of work has been done in recent years to improve their capabilities such as their speed, dexterity, strength, and versatility. However, current robotic manipulators lack the sensory feedback of their human counterparts. Indeed, haptic and tactile feedbacks are still very limited in current devices, which may be a problem, because tactile sensing is deemed nearly mandatory for a large number of applications. Conventional tactile sensors, which are usually applied on the external surface of a robot, are generally used, but they can also be costly, insensitive to some dynamic phenomena, and not adequate to some applications. To solve these issues, many authors have worked on finding alternatives to standard tactile sensors. This thesis fits in this current trend by focusing on the possibility of using the internal stiffness of underactuated fingers to design a virtual tactile sensor. This technique is referred to as proprioceptive tactile sensing. It is applied here to underactuated robotics fingers, which are becoming prevalent in many fields. Underactuated mechanisms, sometimes referred to as self-adaptive, are particularly interesting because of their intrinsic ability to mechanically adapt themselves to the shape of an object without complex control laws and as low as only one actuator. As they have by definition less actuators, they generally have no sensor in the finger’s mechanism itself. Instead of adding new sensors, it is possible to take advantage of the sensors already present, such as the ones at the actuator. Therefore, in this thesis, only data provided by sensors at the actuator is used. Since a oneto-one relationship exists between the contact location and the instantaneous stiffness of the mechanism, it is possible to compute one from the other. Therefore, with the measurements from sensors at the actuator, it is possible to estimate the point of contact. To this aim, a complete model is proposed and experimental data is provided. Different algorithms were tested successfully on a compliant biocompatible gripper and a 2-DOF linkage-driven finger. Finally, an optimization procedure is presented with the aim of finding the optimal parameters of the transmission mechanism to improve the sensitivity of the virtual tactile sensor. The data presented in this thesis demonstrate the robustness of the proposed proprioceptive tactile sensing (PTS) technique

Design and Analysis of a Body-Powered Underactuated Prosthetic Hand

As affordable and efficient 3-D printers became widely available, researchers are focusing on developing prosthetic hands that are reasonably priced and effective at the same time. By allowing anyone with a 3-D printer to build their body powered prosthetic hands, many people could build their own prosthetic hand. However, one of the major problems with the current designs is the user must bend and hold their wrist in an awkward position to grasp an object. The primary goal of this thesis is to present the design process and analysis of a mechanical operated, underactuated prosthetic hand with a novel ratcheting mechanism that locks the finger automatically at a desired position. The prosthetic hand is composed of the following components: a frame for the hand and forearm, ratcheting mechanism, finger mount, rack, pawl and stopper for ratchet, cable, springs, rigidly supporting finger and a compliant finger. The compliant finger was manufactured using shape deposition manufacturing. The joints of the finger were made using PMC 780, polyurethane material, and the finger pads were made of Polydimethylsiloxane(PDMS). To estimate how a compliant finger behaves on the actual system with the ratcheting mechanism and how much force is required to operate this finger, the preshaping analysis was conducted. The preshaping analysis data was verified by loading and unloading weights to the tendon cable and taking pictures of the finger each time the cable force was varied. Then, the pictures were processed using MATLAB image processing tools to calculate joint angles. Additionally, the contact force analysis was performed to determine the effects of the contact location and finger joint angles on the magnitude of contact force given the tension of the cable. Using the contact force analysis, it would be possible to estimate how much load the hand can hold. Finally, the hand was tested to hold various shapes of objects to prove how well it can grasp. Based on the experiment, the hand had a higher success rate of grasping objects that are lightweight (less than 500g) and cylindrical or circular shaped

Design of the passive joints of underactuated modular soft hands for fingertip trajectory tracking

In this letter, we propose a method to design tendon-driven underactuated hands whose fingertips can track a predefined trajectory, when actuated. We focus on passively compliant hands composed of deformable joints and rigid links. We first introduce a procedure to determine suitable joints stiffness and tendon routing, then a possible realization of a robotic underactuated finger is shown. The kinematic and kinetostatic analysis of a tendon-driven robotic finger is necessary to define the overall stiffness values of the finger joints. A structural analysis of the element constituting each passive joint allowed to define a relation between the stiffness and joint's main dimensional and material properties. We validated the proposed framework both in simulation and with experiments using the robotic Soft-SixthFinger as a case study. The Soft-SixthFinger is a wearable robot for grasping compensation in patients with a paretic hand. We demonstrated that different fingertip trajectories can be achieved when joint stiffness and tendon routing are properly designed. Moreover, we demonstrated that the device is able to grasp a wider set of objects when a specific finger flexion trajectory is designed. The proposed framework is general and can be applied to robotic hands with an arbitrary number of fingers and joints per finger. The modular approach furthermore allows the user to easily customize the hand according to specific tasks or trajectories

Design and Implement Towards Enhanced Physical Interactive Performance Robot Bodies

In this thesis, it will introduce the design principle and implement details towards enhanced physical interactive performance robot bodies, which are more specically focused on under actuated principle robotic hands and articulated leg robots. Since they both signicantly function as the physical interactive robot bodies against external environment, while their current performance can hardly satisfy the requirement of undertaking missions in real application. Regarding to the enhanced physical interactive performances, my work will emphasis on the three following specific functionalities, high energy efficiency, high strength and physical sturdiness in both robotics actuation and mechanism. For achieving the aforementioned targets, multiple design methods have been applied, rstly the elastic energy storage elements and compliant actuation have been adopted in legged robots as Asymmetrical Compliant Actuation (ACA), implemented for not only single joint but also multiple joints as mono and biarticulation congurations in order to achieve higher energy effciency motion. Secondly the under actuated principle and modular nger design concept have been utilized on the development of robotic hands for enhancing the grasping strength and physical sturdiness meanwhile maintaining the manipulation dexterity. Lastly, a novel high payload active tuning Parallel Elastic Actuation (PEA) and Series Elastic Actuation (SEA) have been adopted on legged robots for augmenting energy eciency and physical sturdiness. My thesis contribution relies on the novel design and implement of robotics bodies for enhancing physical interactive performance and we experimentally veried the design effectiveness in specic designed scenario and practical applications