Innovative robot hand designs of reduced complexity for dexterous manipulation

This thesis investigates the mechanical design of robot hands to sensibly reduce the system complexity in terms of the number of actuators and sensors, and control needs for performing grasping and in-hand manipulations of unknown objects. Human hands are known to be the most complex, versatile, dexterous manipulators in nature, from being able to operate sophisticated surgery to carry out a wide variety of daily activity tasks (e.g. preparing food, changing cloths, playing instruments, to name some). However, the understanding of why human hands can perform such fascinating tasks still eludes complete comprehension. Since at least the end of the sixteenth century, scientists and engineers have tried to match the sensory and motor functions of the human hand. As a result, many contemporary humanoid and anthropomorphic robot hands have been developed to closely replicate the appearance and dexterity of human hands, in many cases using sophisticated designs that integrate multiple sensors and actuators---which make them prone to error and difficult to operate and control, particularly under uncertainty. In recent years, several simplification approaches and solutions have been proposed to develop more effective and reliable dexterous robot hands. These techniques, which have been based on using underactuated mechanical designs, kinematic synergies, or compliant materials, to name some, have opened up new ways to integrate hardware enhancements to facilitate grasping and dexterous manipulation control and improve reliability and robustness. Following this line of thought, this thesis studies four robot hand hardware aspects for enhancing grasping and manipulation, with a particular focus on dexterous in-hand manipulation. Namely: i) the use of passive soft fingertips; ii) the use of rigid and soft active surfaces in robot fingers; iii) the use of robot hand topologies to create particular in-hand manipulation trajectories; and iv) the decoupling of grasping and in-hand manipulation by introducing a reconfigurable palm. In summary, the findings from this thesis provide important notions for understanding the significance of mechanical and hardware elements in the performance and control of human manipulation. These findings show great potential in developing robust, easily programmable, and economically viable robot hands capable of performing dexterous manipulations under uncertainty, while exhibiting a valuable subset of functions of the human hand.Open Acces

Intelligent gripper design and application for automated part recognition and gripping

Intelligent gripping may be achieved through gripper design, automated part recognition, intelligent algorithm for control of the gripper, and on-line decision-making based on sensory data. A generic framework which integrates sensory data, part recognition, decision-making and gripper control to achieve intelligent gripping based on ABB industrial robot is constructed. The three-fingered gripper actuated by a linear servo actuator designed and developed in this project for precise speed and position control is capable of handling a large variety of objects. Generic algorithms for intelligent part recognition are developed. Edge vector representation is discussed. Object geometric features are extracted. Fuzzy logic is successfully utilized to enhance the intelligence of the system. The generic fuzzy logic algorithm, which may also find application in other fields, is presented. Model-based gripping planning algorithm which is capable of extracting object grasp features from its geometric features and reasoning out grasp model for objects with different geometry is proposed. Manipulator trajectory planning solves the problem of generating robot programs automatically. Object-oriented programming technique based on Visual C++ MFC is used to constitute the system software so as to ensure the compatibility, expandability and modular programming design. Hierarchical architecture for intelligent gripping is discussed, which partitions the robot’s functionalities into high-level (modeling, recognizing, planning and perception) layers, and low-level (sensing, interfacing and execute) layers. Individual system modules are integrated seamlessly to constitute the intelligent gripping system

Kinematic Analysis of Multi-Fingered, Anthropomorphic Robotic Hands

The ability of stable grasping and fine manipulation with the multi-fingered robot hand with required precision and dexterity is playing an increasingly important role in the applications like service robots, rehabilitation, humanoid robots, entertainment robots, industries etc.. A number of multi-fingered robotic hands have been developed by various researchers in the past. The distinct advantages of a multi-fingered robot hand having structural similarity with human hand motivate the need for an anthropomorphic robot hand. Such a hand provides a promising base for supplanting human hand in execution of tedious, complicated and dangerous tasks, especially in situations such as manufacturing, space, undersea etc. These can also be used in orthopaedic rehabilitation of humans for improving the quality of the life of people having orthopedically and neurological disabilities. The developments so far are mostly driven by the application requirements. There are a number of bottlenecks with industrial grippers as regards to the stability of grasping objects of irregular geometries or complex manipulation operations. A multi-fingered robot hand can be made to mimic the movements of a human hand. The present piece of research work attempts to conceptualize and design a multi-fingered, anthropomorphic robot hand by structurally imitating the human hand. In the beginning, a brief idea about the history, types of robotic hands and application of multi-fingered hands in various fields are presented. A review of literature based on different aspects of the multi-fingered hand like structure, control, optimization, gasping etc. is made. Some of the important and more relevant literatures are elaborately discussed and a brief analysis is made on the outcomes and shortfalls with respect to multi-fingered hands. Based on the analysis of the review of literature, the research work aims at developing an improved anthropomorphic robot hand model in which apart from the four fingers and a thumb, the palm arch effect of human hand is also considered to increase its dexterity. A robotic hand with five anthropomorphic fingers including the thumb and palm arch effect having 25 degrees-of-freedom in all is investigated in the present work. Each individual finger is considered as an open loop kinematic chain and each finger segment is considered as a link of the manipulator. The wrist of the hand is considered as a fixed point. The kinematic analyses of the model for both forward kinematics and inverse kinematic are carried out. The trajectories of the tip positions of the thumb and the fingers with respect to local coordinate system are determined and plotted. This gives the extreme position of the fingertips which is obtained from the forward kinematic solution with the help of MATLAB. Similarly, varying all the joint iv angles of the thumb and fingers in their respective ranges, the reachable workspace of the hand model is obtained. Adaptive Neuro-Fuzzy Inference System (ANFIS) is used for solving the inverse kinematic problem of the fingers. Since the multi-fingered hand grasps the object mainly through its fingertips and the manipulation of the object is facilitated by the fingers due to their dexterity, the grasp is considered to be force-closure grasp. The grasping theory and different types of contacts between the fingertip and object are presented and the conditions for stable and equilibrium grasp are elaborately discussed. The proposed hand model is simulated to grasp five different shaped objects with equal base dimension and height. The forces applied on the fingertip during grasping are calculated. The hand model is also analysed using ANSYS to evaluate the stresses being developed at various points in the thumb and fingers. This analysis was made for the hand considering two different hand materials i.e. aluminium alloy and structural steel. The solution obtained from the forward kinematic analysis of the hand determines the maximum size for differently shaped objects while the solution to the inverse kinematic problem indicates the configurations of the thumb and the fingers inside the workspace of the hand. The solutions are predicted in which all joint angles are within their respective ranges. The results of the stress analysis of the hand model show that the structure of the fingers and the hand as a whole is capable of handling the selected objects. The robot hand under investigation can be realized and can be a very useful tool for many critical areas such as fine manipulation of objects, combating orthopaedic or neurological impediments, service robotics, entertainment robotics etc. The dissertation concludes with a summary of the contribution and the scope of further work

Investigation and development of a flexible gripper with adaptable finger geometry

Das zuverlässige und schonende Greifen ist ein Hauptanliegen bei der Entwicklung von neuartigen Greifvorrichtungen. Je größer die Kontaktfläche zwischen dem Greifer und dem Greifobjekt ist, desto schonender und zuverlässiger ist der Greifvorgang. Um dieses Ziel zu erreichen wurden in den letzten Jahrzehnten zahlreiche Untersuchungen zu adaptiven passiven Greifern durchgeführt. Ein neuer Forschungszweig im Bereich selbstadaptiver Greifer sind Greifer mit nachgiebigen blattfederartigen Greifelementen (Greiferfinger) Die Funktionsweise basiert auf dem elastischen Ausknicken der Greifelemente infolge einer translatorische Antriebsbewegung Die vorliegende Arbeit konzentriert sich auf die Verbesserung des Greifvorgangs, indem die Kontaktlänge zwischen den blattfederartigen Greiferfingern und dem zu greifenden Objekt deutlich erhöht wird. Um diese Aufgabenstellung zu lösen, muss eine geeignete Greifergeometrie für ein gegebenes Greifobjekt berechnet werden. Die gezielte Berechnung der erfoderlichen Greifergeometrie für ein bekanntes Greifobjekt ist nicht möglich. Daher wurde als Lösungsansatz die umkehrte Richtung gewählt. Für eine definierte Greifgeometrie wird die Gestalt des dazu passenden “idealen” Greifobjektes ermittelt und anschließend mit der Gestalt zu greifenden Objektes verglichen. Bei Gestaltabweichungen wird die Greifergeometrie iterative verändert, bis seine geeignete Greifergeometrie gefunden wurde. Im Rahmen der vorliegenden Arbeit wird zunächst die Ermittlung des “idealen” Greifobjektes behandelt. Es wurde ein Algorithmus entwickelt, der für eine vorgegebene Greifergeometrie die Gestalt eines runden bzw. elliptischen Objektes ermittelt. Der Algorithmus verwendet als Eingabedaten die Biegelinien der elastisch ausgeknickten Greiffinger unter Berücksichtigung unterschiedlicher Randbedingungen. Als Ausgabedaten liefert der Algorithmus die Gestalt des passenden Greifobjektes zurück. Für quadratische bzw. rechteckige sowie für dreieckige Objekte wurden unterschiedliche Greifgeometrien untersucht. Außerdem wird für quadratische und rechteckige Objekte das Lösungskonzept für die Entwicklung eines weiteren Algorithmus beschrieben. In Kapitel 1 wird eine Klassifizierung von Greifern basierend auf der Anpassungsfähigkeit vorgestellt. In Kapitel 2 werden Lösungskonzepte, Modelle und Theorien vorgestellt. In Kapitel 3 werden Ablaufdiagramme der Algorithmen dargestellt. In Kapitel 4 wird die Entwicklung des Algorithmus für elliptische Objekte und deren Betriebsmodi beschrieben. In Kapitel 5 werden Greifgeometrien für quadratische bzw. Rechteckige sowie für dreieckige Objekte analysiert und die Ideen eines Algorithmus für quadratisch bzw. rechteckige Objekte beschrieben. In Kapitel 6 wird ein kurzer Überblick über die zukünftige Arbeiten.Reliable and gentle gripping is a major concern in the development of new gripping devices. The larger contact surface between the gripper and the gripping object, the gentler and more reliable the gripping process. In order to achieve this goal, further investigations on adaptive passive grippers have been carried out in the recent decades. A new branch of research in the field of self-adaptive grippers are compliant leaf-spring-like gripping elements (gripper fingers). Its mode of operation is based on the elastic buckling of the gripping elements as a result of a translatory drive movement. The present work focuses on improving the gripping process by increasing significantly the contact length between the compliant leaf-spring-like gripper fingers and the object to be gripped. In order to solve this task, a suitable gripper geometry for a given gripping object should be calculated The specific calculation of the required gripper geometry for a known gripping object is not possible; therefore, this work aims in the opposite direction. For a defined gripping geometry, the shape of the matching “ideal” gripping object is determined and then compared with the desired object to be gripped. In case of a deviation in the size, the gripper geometry is iteratively changed until its suitable gripper geometry has been found. In the present work, the determination of the “ideal” gripping object is the first task to deal with. An algorithm has been developed to determine the shape of a round-elliptical object for a given gripper geometry. The algorithm uses as data input the bend lines of the compliant twogripper finger under different boundary conditions. As data output, the algorithm returns the shape of the matching gripping object. For square-rectangular and triangular objects, different gripping geometries have been investigated. Furthermore, for square-rectangular objects, solution concepts for the development of an algorithm is described. In chapter 1, a classification based on adaptability is presented. In chapter 2, solution concepts, models and theories involved are introduced. In chapter 3, process flow diagrams of the algorithms are presented. In chapter 4, the development of the algorithm for elliptical objects and its operation modes are described. In chapter 5, gripping geometries for square-rectangular and triangular objects are analysed and the ideas of an algorithm for square-rectangular objects are described. In chapter 6, a brief overview of the futur work is commented.Tesi

A New Approach to Dynamic Modeling of Continuum Robots

ABSTRACT In this thesis, a new approach for developing practically realizable dynamic models for continuum robots is proposed. Based on the new dynamic models developed, a novel technique for analyzing the capabilities of continuum manipulators to be employed in various real world applications has also been proposed and developed. A section of a continuum arm is modeled using lumped model elements (masses, springs and dampers). It is shown that this model, although an approximation to a continuum structure, can be used to conveniently analyze the dynamics of the arm with suitable tradeoff in accuracy of modeling. This relatively simple model is more plausible to implement in an actual real-time controller when compared to other techniques of modeling continuum arms. Principles of Lagrangian dynamics are used to derive the expressions for the generalized forces in the system. The force exerted by McKibben actuators at different pressure level - length pairs is characterized and is incorporated into this dynamic model. The constraints introduced in the analytical model conform to the physical and operational limitations of the Octarm VI continuum robot manipulator. The model is validated by comparing the results of numerical simulation with the physical measurements of a continuum arm prototype built using McKibben actuators. Based on the new lumped parameter dynamic model developed for continuum robots, a technique for deducing measures of manipulability, forces and impacts that can be sustained or imparted by the tip of a continuum robot has been developed. These measures are represented in the form of ellipsoids whose volume and orientation gives information about the various functional capabilities (end effector velocities, forces and impacts) of the arm at a particular configuration. The above mentioned ellipsoids are exemplified for different configurations of the continuum section arm and their physical significances are analyzed. The new techniques proposed and methodologies adopted in this thesis supported by experimental results represent a significant contribution to the field of continuum robots

Automation and Robotics: Latest Achievements, Challenges and Prospects

This SI presents the latest achievements, challenges and prospects for drives, actuators, sensors, controls and robot navigation with reverse validation and applications in the field of industrial automation and robotics. Automation, supported by robotics, can effectively speed up and improve production. The industrialization of complex mechatronic components, especially robots, requires a large number of special processes already in the pre-production stage provided by modelling and simulation. This area of research from the very beginning includes drives, process technology, actuators, sensors, control systems and all connections in mechatronic systems. Automation and robotics form broad-spectrum areas of research, which are tightly interconnected. To reduce costs in the pre-production stage and to reduce production preparation time, it is necessary to solve complex tasks in the form of simulation with the use of standard software products and new technologies that allow, for example, machine vision and other imaging tools to examine new physical contexts, dependencies and connections

Progettazione e Controllo di Mani Robotiche

The application of dexterous robotic hands out of research laboratories has been limited by the intrinsic complexity that these devices present. This is directly reflected as an economically unreasonable cost and a low overall reliability. Within the research reported in this thesis it is shown how the problem of complexity in the design of robotic hands can be tackled, taking advantage of modern technologies (i.e. rapid prototyping), leading to innovative concepts for the design of the mechanical structure, the actuation and sensory systems. The solutions adopted drastically reduce the prototyping and production costs and increase the reliability, reducing the number of parts required and averaging their single reliability factors. In order to get guidelines for the design process, the problem of robotic grasp and manipulation by a dual arm/hand system has been reviewed. In this way, the requirements that should be fulfilled at hardware level to guarantee successful execution of the task has been highlighted. The contribution of this research from the manipulation planning side focuses on the redundancy resolution that arise in the execution of the task in a dexterous arm/hand system. In literature the problem of coordination of arm and hand during manipulation of an object has been widely analyzed in theory but often experimentally demonstrated in simplified robotic setup. Our aim is to cover the lack in the study of this topic and experimentally evaluate it in a complex system as a anthropomorphic arm hand system

Soft Robotics: Design for Simplicity, Performance, and Robustness of Robots for Interaction with Humans.

This thesis deals with the design possibilities concerning the next generation of advanced Robots. Aim of the work is to study, analyse and realise artificial systems that are essentially simple, performing and robust and can live and coexist with humans. The main design guideline followed in doing so is the Soft Robotics Approach, that implies the design of systems with intrinsic mechanical compliance in their architecture. The first part of the thesis addresses design of new soft robotics actuators, or robotic muscles. At the beginning are provided information about what a robotic muscle is and what is needed to realise it. A possible classification of these systems is analysed and some criteria useful for their comparison are explained. After, a set of functional specifications and parameters is identified and defined, to characterise a specific subset of this kind of actuators, called Variable Stiffness Actuators. The selected parameters converge in a data-sheet that easily defines performance and abilities of the robotic system. A complete strategy for the design and realisation of this kind of system is provided, which takes into account their me- chanical morphology and architecture. As consequence of this, some new actuators are developed, validated and employed in the execution of complex experimental tasks. In particular the actuator VSA-Cube and its add-on, a Variable Damper, are developed as the main com- ponents of a robotics low-cost platform, called VSA-CubeBot, that v can be used as an exploratory platform for multi degrees of freedom experiments. Experimental validations and mathematical models of the system employed in multi degrees of freedom tasks (bimanual as- sembly and drawing on an uneven surface), are reported. The second part of the thesis is about the design of multi fingered hands for robots. In this part of the work the Pisa-IIT SoftHand is introduced. It is a novel robot hand prototype designed with the purpose of being as easily usable, robust and simple as an industrial gripper, while exhibiting a level of grasping versatility and an aspect comparable to that of the human hand. In the thesis the main theo- retical tool used to enable such simplification, i.e. the neuroscience– based notion of soft synergies, are briefly reviewed. The approach proposed rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive underactuated mechanisms, which is called the method of adaptive synergies, is discussed. This ap- proach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the method of adaptive syner- gies, the Pisa–IIT SoftHand is then described in detail. The design and implementation of the prototype hand are shown and its effec- tiveness demonstrated through grasping experiments. Finally, control of the Pisa/IIT Hand is considered. Few different control strategies are adopted, including an experimental setup with the use of surface Electromyographic signals

Advances of Italian Machine Design

This 2028 Special Issue presents recent developments and achievements in the field of Mechanism and Machine Science coming from the Italian community with international collaborations and ranging from theoretical contributions to experimental and practical applications. It contains selected contributions that were accepted for presentation at the Second International Conference of IFToMM Italy, IFIT2018, that has been held in Cassino on 29 and 30 November 2018. This IFIT conference is the second event of a series that was established in 2016 by IFToMM Italy in Vicenza. IFIT was established to bring together researchers, industry professionals and students, from the Italian and the international community in an intimate, collegial and stimulating environment