A New Algorithm for Measuring and Optimizing the Manipulability Index

The estimation of the performance characteristics of robot manipulators is crucial in robot application and design. Furthermore, studying the manipulability index for every point within the workspace of any serial manipulator is considered an important problem. Such studies are required for designing trajectories to avoid singular configurations. In this article, a new method for measuring the manipulability index is proposed, and then some simulations are performed on different industrial manipulators such as the Puma 560 manipulator, a six DOF manipulator and the Mitsubishi Movemaster manipulator

Design, Dimensional Synthesis and Evaluation of a Novel 2-DOF Spherical RCM Mechanism for Minimally Invasive Surgery

With the development of minimally invasive surgery (MIS) technology, higher requirements are put forward for the performance of remote center of motion (RCM) manipulator. This paper presents the conceptual design of a novel two degrees of freedom (2-DOF) spherical RCM mechanism, whose axes of all revote joints share the same RCM. Compared with the existing design, the proposed mechanism indicates a compact design and high structure stability, and the same scissor-like linkage makes it easy to realize modular design. It also has the advantages of singularity free and motion decoupling in its workspace, which simplifies the implementation and control of the manipulator. In addition, compared with the traditional spherical scissor linkage mechanism, the proposed mechanism adds a rotation constraint on the output shaft to provide better operating performance. In this paper, the kinematics and singularities of different cases are deduced and compared, and the kinematic model of the best case is established. According to the workspace and constraints in MIS, the optimal structural parameters of the mechanism are determined by dimensional synthesis with the goal of optimal global operation performance. Furthermore, a prototype is assembled to verify the performance of the proposed mechanism. The experimental results show that the 2-DOF prototype can provide a reliable RCM point. The compact design makes the manipulator have potential application prospects in MIS

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

Metodologia de desenvolvimento de um manipulador hidráulico para atuação na indústria

Este trabalho aborda o desenvolvimento de uma metodologia para a da determinação de parâmetros de projeto de uma classe de robôs industriais hidráulicos com atuadores lineares diretamente acoplados aos elos. Um robô típico desta classe pode ser dividido em três partes: a base, o braço e o punho, sendo que, no presente trabalho, é abordado o desenvolvimento do braço. São propostos métodos sistemáticos para a determinação das dimensões dos elos, dos cursos angulares das juntas, dos pontos de acoplamento dos atuadores, da estrutura principal dos elos, e para a sistematização do procedimento de especificação dos atuadores e unidades de potência hidráulica. Estes métodos dependem da predefinição por um projetista das necessidades técnicas das tarefas que o robô deve realizar, a partir dos quais os métodos então buscam a determinação dos parâmetros ótimos do braço para estas tarefas. Também é apresentada a cinemática direta, inversa, e a matriz Jacobiana, e é feito o equacionamento da dinâmica do braço em forma matricial, considerando a influência da inércia e peso dos atuadores, de modo a permitir a análise dos carregamentos e facilitar o controle. As equações propostas são verificadas com comparações com softwares comerciais e resultados disponíveis na literatura. Um programa computacional que implementa a metodologia deste trabalho foi desenvolvido e aplicado para determinar os parâmetros de dois braços propostos como estudo de casos. A metodologia se mostrou capaz de rapidamente especificar o braço adequado para cada caso, calculando as características de desempenho que deverão possuir se construídos. Estes dados podem ser aplicados para a construção de um robô hidráulico, ou para assistir o projetista a determinar se um robô hidráulico é adequado ou não para realizar as tarefas predefinidas.This work presents the development of a methodology for the determination of the design variables of a class of hydraulic industrial robots with linear actuators directly coupled to the links. A typical robot of this class can be divided in three parts: the base, the arm and the wrist, of which the development of the arm is tackled in this work. Systematic methods are proposed for the determination of the links’ dimensions, the joints’ angular strokes, the coupling points for the actuators, the main structure of the links, and for the systematization of the procedure used to specify the actuators and pumps. These methods depend on the technical specifications, predefined by the designer, that are required for the arm to be able to perform a given set of tasks, and then seek the optimum parameters for the arm. The direct and inverse kinematics are also presented, as well as the Jacobian matrix, and the dynamics of the arm are calculated in matrix form, taking into consideration the inertia and weight of the actuators, so as to allow the analysis of the structural loads and facilitate the control. The proposed equations are verified via comparisons with commercial software and results found in the literature. A computer program that implements the methodology of this work was developed and used to determine the parameters of two proposed arms as a case study. The program was able to quickly specify the configurations for the arm of each case, and also calculate the performance characteristics the arms should possess if built. This data can be used to build a hydraulic arm, or even to help the designer to determine if a hydraulic robot is ideal or not for the given set of tasks

Cinemàtica i Control en entorns multi-robot

Un dels camps de la robòtica que estan despertant gran interès per part de la comunitat científica és el dels entorns multirobot. Aquest nom genèric inclou diferents tipus de sistemes amb característiques i problemàtiques força diferenciades. En aquest treball s'utilitza aquest terme per fer referència a cel·les robotitzades composades per més d'un robot treballant coordinadament, entès robot com braç manipulador. En aquesta tesis s'han abordat diferents aspectes relacionats amb la cinemàtica i el control de sistemes multirobot. Dins de la cinemàtica s'han estudiat en detall les característiques de l'espai del treball i les mesures de manipulabilitat dels sistemes multirobot. En aquesta línia s'ha proposat una nova metodologia per estudiar l'espai de treball del sistemes multirobot basada en els conceptes de figura destra i figura realitzable. Aquestes dues figures geomètriques generades a partir dels espais de treball individuals, permeten descriure l'espai de treball com la intersecció de figures geomètriques. Aquest interpretació permet dissenyar de forma intuïtiva cel·les multirobot en les que hi ha manipulació conjunta. La metodologia s'ha implementat en el cas de dos tipus de robots, SCARA, i PUMA.Dins els aspectes de dinàmica i control tractats en la tesi, cal diferenciar els referents a la dinàmica dels sistemes multirobot i els referents als sistemes en els que cadascun dels robots té un control de posició.En l'àmbit de la dinàmica pròpiament dita s'ha analitzat en detall la formulació en equacions algebraic diferencials (DAE) dels sistemes mecànics amb restriccions holònomes, cas genèric dins el que s'engloben els sistemes multirobot amb manipulació rígida d'objectes rígids. Aquesta formulació permet obtenir el comportament del sistema a partir de les equacions que descriuen el comportament individual de cadascun dels robots i dels conjunt de restriccions cinemàtiques que actuen sobre el sistema.En el cas dels robots amb control de posició, el comportament i el control presenten unes característiques totalment diferents. Per aquest tipus d'entorns s'han proposat, dos enfocs de control diferents: un basat en el control híbrid, i un altre basat en control d'impedància. En l'enfoc de control híbrid es descompossa el sistema en eixos sobre els que s'aplica control de posició i eixos en els que s'aplica control de força, aquests darrers corresponen a les forces internes. Aquest plantejament és totalment centralitzat, es a dir, hi ha un element central encarregat de controlar el comportament del sistema. Com a principal aportació dins aquesta línia, s'ha proposat una metodologia per identificar el comportament de les forces internes que actuen sobre el sistema.Com alternativa, al control híbrid s'ha desenvolupat un esquema de control basat en la imposició d'un comportament d'impedància en cadascun dels robots. Aquest plantejament és totalment desacoblat, és a dir cadascun dels controladors realitza la seva funció sense necessitat d'un intercanvi d'informació amb la resta de controladors. La principal aportació dins aquesta línia és que el comportament d'impedància s'ha plantejat sobre SE(3), el que fa que els comportaments obtinguts estiguin d'acord amb la topologia de l'espai de treball.La tesi finalitza amb una presentació de les principals conclusions i línies de treball obertes per treballs futurs.One field in today robotics in which a lot of people are working is the one concerning multirobot systems. This generic name includes different kinds of systems, each one with its own characteristics and problems. In this work "multirobot system" refers to work cells composed by several robots working in a coordinated way. In this thesis several aspects related with kinematics and control of multirobot systems has been studied. Inside cinematic the workspace and manipulability measures for multirobots systems have been studied in detail. A new methodology to study multirobot systems workspace has been proposed, this approach is based on the dexterous figure and the reachable figure concepts. These two geometric figures are obtained from the individual workspace. A key issue in this new approach is the fact the multirobot workspace can be described as the intersection of several geometric figures, this introduces a new understanding which can be of great interest in the geometric design of multirobot workcell. This methodology has been used in the analysis and design of workcells composed by SCARA and PUMA robots.Inside dynamics and control aspects, the dissertation includes two different problems, one related with multirobot dynamics modeling and control and another related with control of multirobot systems where the different robots are position controlled.In the dynamic related aspects, a new formulation based on the formulation of robotic system with holonomic constraints as Diferential Algebraic Equation Systems (DAE). One particular case of this generic kind of systems is multirobot systems which rigidly manipulate a rigid object. This approach allows obtaining the system behavior from the dynamic equations describing the individual behavior and the set of equations describing the holonomic constrains over the systems.For the multirobot systems formed by position controlled robots, two different strategies have been proposed and tested in a real workcell. The first one is based on the hybrid control approach and the second one is based on the impedance control approach.The hybrid control approach decomposes the space in several axes, some of them are controlled in position and the others are force controlled. These force controlled axes are the ones related with internal force control. Hybrid control follows a centralized approach, so a central coordination element is needed. Inside this area a new methodology to identify and control the internal forces dynamics has been proposed.A different approach has been proposed, impedance control is based on defining an individual behaviour for each robot. This approach is decoupled by definition, in other works each robot do not need information from the other robots. Most important contributions inside this area, is the fact that the individual behaviour is defined over SE(3), this means that obtained movements are topologicaly coherent.The dissertation concludes with some conclusions and future works

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