Stiffness Analysis of Overconstrained Parallel Manipulators

The paper presents a new stiffness modeling method for overconstrained parallel manipulators with flexible links and compliant actuating joints. It is based on a multidimensional lumped-parameter model that replaces the link flexibility by localized 6-dof virtual springs that describe both translational/rotational compliance and the coupling between them. In contrast to other works, the method involves a FEA-based link stiffness evaluation and employs a new solution strategy of the kinetostatic equations for the unloaded manipulator configuration, which allows computing the stiffness matrix for the overconstrained architectures, including singular manipulator postures. The advantages of the developed technique are confirmed by application examples, which deal with comparative stiffness analysis of two translational parallel manipulators of 3-PUU and 3-PRPaR architectures. Accuracy of the proposed approach was evaluated for a case study, which focuses on stiffness analysis of Orthoglide parallel manipulator

Biokinematic analysis of human body

Thesis (Doctoral)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2011Includes bibliographical references (leaves: 118-123)Text in English; Abstract: Turkish and Englishxiii, 123 leavesThis thesis concentrates on the development of rigid body geometries by using method of intersections, where simple geometric shapes representing revolute (R) and prismatic (P) joint motions are intersected by means of desired space or subspace requirements to create specific rigid body geometries in predefined octahedral fixed frame. Using the methodical approach, space and subspace motions are clearly visualized by the help of resulting geometrical entities that have physical constraints with respect to the fixed working volume. Also, this work focuses on one of the main areas of the fundamental mechanism and machine science, which is the structural synthesis of robot manipulators by inserting recurrent screws into the theory. After the transformation unit screw equations are presented, physical representations and kinematic representations of kinematic pairs with recurrent screws are given and the new universal mobility formulations for mechanisms and manipulators are introduced. Moreover the study deals with the synthesis of mechanisms by using quaternion and dual quaternion algebra to derive the objective function. Three different methods as interpolation approximation, least squares approximation and Chebyshev approximation is introduced in the function generation synthesis procedures of spherical four bar mechanism in six precision points. Separate examples are given for each section and the results are tabulated. Comparisons between the methods are also given. As an application part of the thesis, the most important elements of the human body and skeletal system is investigated by means of their kinematic structures and degrees of freedom. At the end of each section, an example is given as a mechanism or manipulator that can represent the behavior of the related element in the human body

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Origami-inspired structures and materials: analysis and metamaterial properties and seismic design of hybrid masonry structural systems

This dissertation includes two major sections. The first section presents the research on creating and studying novel classes of origami-inspired metamaterials and structures. The second section deals with seismic design of hybrid masonry structural systems. 1) Origami-Inspired Structures and Materials Origami, the traditional Japanese art of paper folding, has been recognized to be a significant source of inspiration in science and engineering. Specifically, its principles have been used for innovative design of mechanical metamaterials for which material properties arise from their geometry and structural layout. Most research on origami-inspired materials relies on known patterns, especially on the Miura-ori, i.e., a classic origami pattern with outstanding properties and a wide range of applications. Motivated by outstanding properties and a broad range of applications of the Miura-ori, in this dissertation, inspired by the kinematics of a one-degree of freedom zigzag strip, we create a novel class of cellular folded sheet mechanical metamaterials. The class of the patterns combines origami folding techniques with kirigami cutting. Using both analytical and numerical models, we study the key mechanical properties of the folded materials. We show that they possess properties as remarkable as those of the Miura-ori on which there has been a surge of research interest. Consequently, the introduced patterns are single degree of freedom (DOF), developable, rigid-foldable and flat-foldable. Furthermore, we show that depending on the geometry, these materials exhibit both negative and positive in-plane Poisson’s ratio. By introducing a novel class of zigzag-base materials, the current study extends the properties of the Miura-ori to those of the class of one-DOF zigzag-base patterns, and our work shows that Miura-ori is only one pattern in this class with such properties. Hence, by expanding upon the design space of the Miura-ori, our patterns are appropriate for a wide range of applications, from mechanical metamaterials to light cellular foldcore sandwich panels and deployable structures at both small and large scales. Furthermore, this study unifies the concept of the in-plane Poisson’s ratio from the literature for similar materials and extends it to this novel class of zigzag-base folded sheet metamaterials. Moreover, in this dissertation, by dislocating the zigzag strips of a Miura-ori pattern along the joining ridges, we create a class of one-degree of freedom (DOF) cellular mechanical metamaterials. We further show that dislocating zigzag strips of the Miura-ori along the joining ridges, preserves and/or tunes the outstanding properties of the Miura-ori. The introduced materials are lighter than their corresponding Miura-ori patterns due to the presence of holes in the patterns. They are also amenable to similar modifications available for Miura-ori which make them appropriate for a wide range of applications across the length scales. Additionally, we study the Eggbox pattern. Similarly to Miura-ori, a regular Eggbox folded sheet includes parallelogram facets which are connected along fold lines. However, Eggbox sheets cannot be folded from a flat sheet of material, and contrary to Miura-ori which has received considerable interest in the literature, there are fewer studies available on Eggbox folded sheet material. By employing both analytical and numerical models, we review and study the key in-plane mechanical properties of the Eggbox folded sheet, and we present cellular folded metamaterials containing Miura-ori and Eggbox cells. The entire structure of the folded materials is a one-DOF mechanism system and, similarly to Eggbox sheets, the materials composed of layers of Eggbox folded sheets are bi-directionally flat-foldable, resulting in a material flexible in those directions, but stiff in the third direction. 2) Seismic Design of Hybrid Masonry Structural Systems Hybrid masonry is an innovative seismic lateral-load resisting system. The system comprises reinforced masonry panels within a steel-framed structure as well as steel connector plates which attach the surrounding steel frame to the masonry panel. Depending on the interfacial conditions between a masonry panel and the steel frame, the system is categorized into three major groups: Types I, II and III. The first part of the research on hybrid masonry systems, in this dissertation, includes a series of exploratory studies aimed at understanding the global behavior of various types of hybrid masonry panels and setting the stage for the study on seismic design of the systems. In this regard, computational analyses were carried out to study the distribution of lateral forces between a masonry panel and a frame in various types of hybrid masonry structural systems. The results are used to demonstrate differences in lateral-force distributions in hybrid masonry systems with different boundary conditions and with various panel aspect ratios as well as with different stiffness of the wall to that of the frame. Furthermore, this study presents the general methodology for seismic design of Type I hybrid masonry systems as well as the steps of a capacity design process in which two favorable ductile modes of behavior are considered: steel connector plates behaving as fuses or flexural yielding of the masonry panels. Moreover, using the proposed approaches we design several prototype buildings located in a high seismic region and investigate viability of hybrid masonry as a new seismic lateral-load resisting system. According to this design framework and the exploratory studies, both approaches are shown to be feasible for developing realistic system configurations. Finally, in this study, an integrated approach for performance-based seismic analysis and design of hybrid masonry Type I systems with fuse connector plates is presented. The procedure used in this study is based on the Capacity Spectrum Method. The proposed method includes an iterative process through which a hybrid masonry structural system with fuse connector plates is designed depending on its energy dissipation capacity. In this regard, the value of the system R factor is regulated in the process. In this study, application of the method for design of a sample hybrid masonry building system is presented

Structural and kinematic synthesis of overconstrained mechanisms

Thesis (Doctoral)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2012Includes bibliographical references (leaves: 133-140)Text in English; Abstract: Turkish and Englishxiii, 140 leavesInvestigation on overconstrained mechanisms needs attention especially in the structural synthesis. Knowing overconstrained conditions and including them in the design process will help creating manipulators with less degree of freedom (DoF) and more rigidity. Also this knowledge of overconstrained conditions will clarify concept of mobility of the parallel manipulators. Another subject, kinematic synthesis of overconstrained mechanisms, is important because it will allow describing a function, path, or motion with less DoF less number of joints. The aim of this thesis is to describe a generalized approach for structural synthesis and creation of new overconstrained manipulators and to describe a potentially generalizable approach for function and motion generation synthesis of overconstrained mechanism. Moreover, screw theory is investigated as a mathematical base for defining kinematics of overconstrained mechanisms. Also, overconstrained mechanisms are investigated and generation of new mechanisms is introduced with examples. Some mathematical models for the subspace geometries are given. A method for defining overconstrained simple structural groups is introduced and extended to design of manipulators with examples and solid drawings. Linear approximation and least squares approximation methods are used for the function generation and motion generation of overconstrained 6R mechanisms. A gap of describing overconstrained manipulators is filled in the area of structural synthesis. A general methodology is described for structural synthesis, mobility and motion calculations of overconstrained manipulators using simple structural groups. A potentially generalizable method for the kinematic synthesis of overconstrained manipulators is described both for function and motion generation

Kinematics and Robot Design II (KaRD2019) and III (KaRD2020)

This volume collects papers published in two Special Issues “Kinematics and Robot Design II, KaRD2019” (https://www.mdpi.com/journal/robotics/special_issues/KRD2019) and “Kinematics and Robot Design III, KaRD2020” (https://www.mdpi.com/journal/robotics/special_issues/KaRD2020), which are the second and third issues of the KaRD Special Issue series hosted by the open access journal robotics.The KaRD series is an open environment where researchers present their works and discuss all topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. It aims at being an established reference for researchers in the field as other serial international conferences/publications are. Even though the KaRD series publishes one Special Issue per year, all the received papers are peer-reviewed as soon as they are submitted and, if accepted, they are immediately published in MDPI Robotics. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”.KaRD2019 together with KaRD2020 received 22 papers and, after the peer-review process, accepted only 17 papers. The accepted papers cover problems related to theoretical/computational kinematics, to biomedical engineering and to other design/applicative aspects

Real-time fluid simulations under smoothed particle hydrodynamics for coupled kinematic modelling in robotic applications

Although solids and fluids can be conceived as continuum media, applications of solid and fluid dynamics differ greatly from each other in their theoretical models and their physical behavior. That is why the computer simulators of each turn to be very disparate and case-oriented. The aim of this research work, captured in this thesis book, is to find a fluid dynamics model that can be implemented in near real-time with GPU processing and that can be adapted to typically large scales found in robotic devices in action with fluid media. More specifically, the objective is to develop these fast fluid simulations, comprising different solid body dynamics, to find a viable time kinematic solution for robotics. The tested cases are: i) the case of a fluid in a closed channel flowing across a cylinder, ii) the case of a fluid flowing across a controlled profile, and iii), the case of a free surface fluid control during pouring. The implementation of the former cases settles the formulations and constraints to the latter applications. The results will allow the reader not only to sustain the implemented models but also to break down the software implementation concepts for better comprehension. A fast GPU-based fluid dynamics simulation is detailed in the main implementation. The results show that it can be used in real-time to allow robotics to perform a blind pouring task with a conventional controller and no special sensing systems nor knowledge-driven prediction models would be necessary.Aunque los sólidos y los fluidos pueden concebirse como medios continuos, las aplicaciones de la dinámica de sólidos y fluidos difieren mucho entre sí en sus modelos teóricos y su comportamiento físico. Es por eso que los simuladores por computadora de cada uno son muy dispares y están orientados al caso de su aplicación. El objetivo de este trabajo de investigación, capturado en este libro de tesis, es encontrar un modelo de dinámica de fluidos que se pueda implementar cercano al tiempo real con procesamiento GPU y que se pueda adaptar a escalas típicamente grandes que se encuentran en dispositivos robóticos en acción con medios fluidos. Específicamente, el propósito es desarrollar estas simulaciones de fluidos rápidos, que comprenden diferentes dinámicas de cuerpos sólidos, para encontrar una solución cinemática viable para robótica. Los casos probados son: i) el caso de un fluido en canal cerrado que fluye a través de un cilindro, ii) el caso de un fluido que fluye a través de un alabe controlado, y iii), el caso del control de un fluido de superficie libre durante el vertido. La implementación de estos primeros casos establece las formulaciones y limitaciones de aplicaciones futuras. Los resultados permitirán al lector no solo sostener los modelos implementados sino también desglosar los conceptos de la implementación en software para una mejor comprensión. En la implementación principal se consigue una simulación rápida de dinámica de fluidos basada en GPU. Los resultados muestran que esta implementación se puede utilizar en tiempo real para permitir que la robótica realice una tarea de vertido ciego con un controlador convencional sin que sea necesario algún sistema de sensado especial ni algún modelo predictivo basados en el conocimiento.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Carmen Martínez Arévalo.- Secretario: Luis Santiago Garrido Bullón.- Vocal: Benjamín Hernández Arreguí

Dynamically Feasible Trajectories of Fully-Constrained Cable-Suspended Parallel Robots

Cable-Driven Parallel Robots employ multiple cables, whose lengths are controlled by winches, to move an end-effector (EE). In addition to the advantages of other parallel robots, such as low moving inertias and the potential for high dynamics, they also provide specific advantages, such as large workspaces and lower costs. Thus, over the last 30 years, they have been the object of academic research; also, they are being employed in industrial applications. The main issue with cable actuation is its unilaterality, as cables must remain in tension: if they become slack, there is a risk of losing control of the EE's pose. This complicates the control of cable-driven robots and is among the most studied topics in this field. Most previous works resort to extra cables or rigid elements pushing on the EE to guarantee that cables remain taut, but this complicates robot design. An alternative is to use the gravitational and inertial forces acting on the EE to keep cables in tension. This thesis shows that the robot's workspace can be greatly increased, by considering two model architectures. Moreover, practical limits to the feasibility of a motion, such as singularities of the kinematic chain and interference between cables, are considered. Even if a motion is feasible, there is no guarantee that it can be performed with an acceptable precision in the end-effector's pose, due to the inevitable errors in the positioning of the actuators and the elastic deflections of the structure. Therefore, a set of indexes are evaluated to measure the sensitivity of the end-effector's pose to actuation errors. Finally, the stiffness of one of the two architectures is modeled and indexes to measure the global compliance of the robot due to the elasticity of the cables are presented.I robot paralleli a cavi impiegano cavi, la cui lunghezza è controllata da argani, per muovere un elemento terminale o end-effector (EE). Oltre ai vantaggi degli altri robot paralleli, come basse inerzie in movimento e la possibilità di raggiungere velocità e accelerazioni elevate, possono anche fornire vantaggi specifici, come ampi spazi di lavoro e costi inferiori. Pertanto, negli ultimi 30 anni, questi robot sono stati oggetto di ricerche accademiche e stanno trovando applicazione anche in campo industriale. Il problema principale dell'azionamento mediante cavi è che è unilaterale, poiché i cavi possono essere tesi ma non compressi: quando diventano laschi, si rischia di perdere il controllo della posa dell'EE. Questo complica il controllo dei robot ed è uno dei temi più studiati nel settore. Gli studi compiuti sinora ricorrono prevalentemente a cavi addizionali o a elementi rigidi che spingono sull'EE per garantire che i cavi rimangano tesi, ma questo complica la progettazione dei robot. Un'alternativa è sfruttare le forze gravitazionali e inerziali che agiscono sull'EE per mantenere i cavi in tensione. Questa tesi dimostra che, in questo caso, lo spazio di lavoro del robot può essere notevolmente aumentato, applicando questo concetto a due architetture modello. Inoltre, vengono considerati i limiti imposti all'effettiva realizzabilità di un movimento, come le singolarità della catena cinematica e l'interferenza tra i cavi. Anche se un movimento è fattibile, non è garantito che si possa eseguire con precisione accettabile, a causa degli inevitabili errori di posizionamento degli attuatori e delle deformazioni elastiche della struttura. Si valutano quindi alcuni indici per misurare la sensibilità della posizione dell'elemento terminale agli errori di azionamento. Infine, è modellata la rigidezza di una delle due architetture proposte e sono presentati indici per misurare la cedevolezza globale del robot dovuta all'elasticità dei cavi

Kinematics and Robot Design IV, KaRD2021

This volume collects the papers published on the special issue “Kinematics and Robot Design IV, KaRD2021” (https://www.mdpi.com/journal/robotics/special_issues/KaRD2021), which is the forth edition of the KaRD special-issue series, hosted by the open-access journal “MDPI Robotics”. KaRD series is an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”. KaRD2021, after the peer-review process, accepted 12 papers. The accepted papers cover some theoretical and many design/applicative aspects