Kinematics, workspace and singularity analysis of a multi-mode parallel robot

A family of reconfigurable parallel robots can change motion modes by passing through constraint singularities by locking and releasing some passive joints of the robot. This paper is about the kinematics, the workspace and singularity analysis of a 3-PRPiR parallel robot involving lockable Pi and R (revolute) joints. Here a Pi joint may act as a 1-DOF planar parallelogram if its lock-able P (prismatic) joint is locked or a 2-DOF RR serial chain if its lockable P joint is released. The operation modes of the robot include a 3T operation modes to three 2T1R operation modes with two different directions of the rotation axis of the moving platform. The inverse kinematics and forward kinematics of the robot in each operation modes are dealt with in detail. The workspace analysis of the robot allow us to know the regions of the workspace that the robot can reach in each operation mode. A prototype built at Heriot-Watt University is used to illustrate the results of this work.Comment: International Design Engineering Technical Conferences \& Computers and Information in Engineering Conference, Aug 2017, Cleveland, United States. 201

A method for extending planar axis-symmetric parallel manipulators to spatial mechanisms

This paper investigates axis-symmetric parallel manipulators, composed of a central base column and an arm system able to rotate around this column. The arm system includes several actuated upper arms, each connected to a manipulated platform by one or more lower arm linkages. Such manipulators feature an extensive positional workspace in relation to the manipulator footprint and equal manipulator properties in all radial half-planes defined by the common rotation-axis of the upper arms. The similarities between planar manipulators exclusively employing 2-degrees-of-freedom (2-DOF) lower arm linkages and lower mobility spatial manipulators only utilising 5-DOF lower arm linkages are analysed. The 2-DOF linkages are composed of a link with a 1-DOF hinge on both ends whilst the 5-DOF linkages utilise 3-DOF spherical joints and 2-DOF universal joints. By employing a proposed linkage substitution scheme, it is shown how a wide range of spatial axis-symmetric parallel manipulators can be derived from a limited range of planar manipulators of the same type

Singularity Analysis of the 4-RUU Parallel Manipulator using Grassmann-Cayley Algebra

International audienceThis paper deals with the singularity analysis of 4-DOF parallel manipulators with identical limb structures performing Schönflies motions, namely, three independent translations and one rotation about an axis of fixed direction. The 6x6 Jacobian matrix of such manipulators contains two lines at infinity among its six Plücker lines. Some points at infinity are thus introduced to formulate the superbracket of Grassmann-Cayley algebra, which corresponds to the determinant of the Jacobian matrix. By exploring this superbracket, all the singularity conditions of such manipulators can be enumerated. The study is illustrated through the singularity analysis of the 4-\underline RUU parallel manipulator

DETC2011-48510 TYPE SYNTHESIS OF 3-DOF PARALLEL MANIPULATORS WITH BOTH PLANAR AND TRANSLATIONAL OPERATION MODES

ABSTRACT Despite recent advances in the type synthesis of parallel manipulators with a mono-operation mode, such as translational parallel manipulators and spherical parallel manipulators, the type synthesis of parallel manipulators with multiple operation modes is still an open issue. This paper deals with the type synthesis of 3-DOF parallel manipulators with both planar and translational operation modes. The type synthesis of planar parallel manipulators, which refer to parallel manipulators in which the moving platform undergoes planar motion, is first dealt with using the virtual chain approach. Then, the types of 3-DOF parallel manipulators with both planar and translational operation modes are obtained. This work can be extended to the type synthesis of other classes of parallel manipulators with multiple operation modes

Translational parallel manipulator with Pa2 kinematic joints

The kinematic pair Pa2 is composed of two interlinked parallelograms. It has two degrees of freedom that generate a translational plane variable with position. It has a structure different from the PaPa pair, which is composed also by two parallelograms but generates a constant translational plane. Currently, the Pa2 pair is used at conceptual level but it is not used in al-most any practical application. There are advantages and drawbacks in using it. The main drawback is the high number of redundant constraints that this pair possesses. However, sub-stituting carefully the revolute joints by spherical joints can eliminate these redundant con-straints. Also, this pair constitutes a more rigid structure that replaces adequately the problem-atic passive prismatic joints. In this paper, will be presented a preliminary study of a translational parallel manipulator (PM) based on the use of the Pa2 pair: the 3-PPa2 that contains redundant constraints in its global structure. To study the potentiality of the PM presented in this paper, the following analyses will be done: position and velocity (direct and inverse kinematics), workspace and singularity analysis. Also the potentiality to be optimised will be studied.This work was supoorted by the Spanish Government through the Ministerio de Economía y Competitividad (Project DPI2015-67626-P (MINECO/FEDER, UE)), the financial support from the University of the Basque Country (UPV/EHU) under the program UFI 11/29 and the support to the research group, through the project with ref. IT949-16, given by the Departamento de Educación, Política Lingüística y Cultura of the Regional Government of the Basque Country

Kinematic analysis and dimensional optimization of a 2R2T parallel manipulator

International audienceThe need of a device providing two translational (2T) and two rotational (2R) movements led us to the design a 3UPS-1RPU parallel manipulator. The manipulator consisted on a mobile platform connected to a base through four legs. That is, the manipulator layout has one central leg and three external legs at the same radial distance. By studying different locations of the legs anchoring point, we improved the first layout design, yet not the optimal one. On this basis, this paper focus on the optimal dimensional design of the manipulator. To this end, we put forward the kinematics equations of the manipulator in accordance to the anchoring points coordinates. Through a numerical approach, the equations enable to find the manipulator workspace. Also, we find a global manipulability index using a local dexterity measure. The latter index serves as optimal function. The optimization process considers joint constraints. Thus, we built a nonlinear optimization problem solved through sequential quadratic programming algorithms. We start by optimizing only a small set of parameters rather than the entire set, which gives us insights on the initial guess to optimize using the entire set. The optimal design layout varies from the original layout. Findings suggest that a task-oriented reconfiguration strategy can improve manipulator performance

Pick-and-place Machine Design with Vision Module

Abstract: This paper presents the design and development of a pick-and-place machine for integrated circuit (IC) packages. This paper begins with the conceptual design and its design considerations. A stress simulation has been carried out on the pickup arm. In the hardware part, several components are carefully selected or custom designed, fabricated and assembled for the electronics system, pneumatic system and mechanical system. In the software part, a graphical user interface (GUI) has been developed using MFC in C++ programming language. The performance of the machine has been tested in terms of pick-and-place speed and placement repeatability. The outcome was a pick-and-place machine that is capable to achieve speeds of up to 1500UPH using a simple design and readily available industrial components

Análisis y síntesis estructural de manipuladores paralelos de baja movilidad con múltiples modos de operación

212 p.Los manipuladores paralelos de baja movilidad son, sin duda, un tipo de robots quepresentan importantes ventajas, en ciertos aspectos, sobre los denominadosmanipuladores serie, especialmente cuando se requiere mayor rigidez, aún a costa deuna reducción del espacio de trabajo del manipulador paralelo.El desarrollo de nuevas arquitecturas de este tipo de manipuladores ha recibido notableimpulso desde la segunda mitad del siglo XX, si bien su implantación industrial tienenotables resistencias debido a la complejidad de la cinemática y a la dificultad decontrol en tiempo real y limitaciones de espacio de trabajo.Esta Tesis Doctoral se centra en el desarrollo de una sistemática de generación dediferentes arquitecturas de manipuladores paralelos de baja movilidad, es decir, demenos de seis grados de libertad. A partir de ella, se estudiarán diferentesconfiguraciones de manipuladores reconfigurables, capaces de adaptarse a diferentestareas, es decir, manipuladores con capacidad de multioperacionalidad.Este trabajo comenzará con una breve descripción de los principales métodos desíntesis estructural o morfológica de manipuladores paralelos.A continuación se realizará el estudio de todas las posibles arquitecturas demanipuladores paralelos de 3 grados de libertad con tres cadenas cinemáticas idénticasy preferentemente dispuestas de forma simétrica. Se recogerán posiblesmaterializaciones de cada tipología, referenciándose aquellos autores que ya handescrito el manipulador concreto correspondiente. También se recogerán algunasarquitecturas que no se han encontrado en las referencias estudiadas. Asimismo seresumirá el procedimiento utilizado, y el conjunto de premisas, para el desarrollo delestudio de las familias de manipuladores paralelos de 3 grados de libertad.Posteriormente se desarrollará un procedimiento general para el estudio y generaciónestructural de manipuladores paralelos de baja movilidad con múltiples modos deoperación a partir de combinaciones de cadenas cinemáticas de seis grados de libertad.Una vez definida esta metodología, se aplicará al análisis cinemático de la plataformade Gough-Stewart y al manipulador paralelo 3-CPCR, de seis grados de libertad.Restringiendo algunos grados de libertad y actuando sobre el resto de las variables deentrada de este manipulador, se obtienen manipuladores paralelos de baja movilidadcon un determinado modo de operación o movimiento.Adicionalmente, a partir del procedimiento desarrollado para los manipuladoresparalelos de 6 grados de libertad, se definirá una metodología específica para elplanteamiento de las ecuaciones del problema de velocidad de manipuladores paralelosde baja movilidad, de aplicación general a cualquier configuración.Por último se expondrán las posibles líneas futuras de estudio a partir de los análisis ymetodologías desarrollados en la presente Tesis Doctoral. Es de destacar la posibilidadde obtener un vademécum de manipuladores paralelos de baja movilidad a partir decombinaciones de las cadenas de 6 grados de libertad recogidas en este trabajo

Type Synthesis and Performance Optimization of Parallel Manipulators

Parallel robots have been widely employed in industrial applications. There are still some challenging topics in the fundamental research, e.g., the primary problem mobility analysis has not been solved for about 150 years. A universal mobility equation for all kinds of parallel architectures has not been found. Another issue lies on the performance measurements for parallel manipulators. There are plenty of kinematic and dynamic performance indices. However, the various ranges and scales of these indicators make the optimal design considering multiple indices complicated. It is essential to search for a unified approach to normalize performance indicators. More dynamic performance measurement indicators should be raised to explore the dynamic features and complete the theory for parallel mechanisms. In this research, an improved mobility equation is designed to reveal the degrees of freedom for a special class of parallel robots. A novel methodology called the kinematic joint matrix is proposed. It possesses the mapping relations with parallel manipulators. A series of 2-6 degrees of freedom parallel architectures is denoted by the kinematic joint matrix. The theory of screw is employed to check the feasibility from several kinds of parallel structures. A special block diagram is introduced to distinguish various kinematic joint matrices. Since this family of parallel robots contains various motion characteristics, four parallel robots with distinct features are selected. Based on the kinematic models, three categories of singularities are explored. The operational and reachable workspaces of the pure-translational parallel robots are searched and the parametric analyses are reported. The linkage’s impacts for the reachable workspace of the mixed-motion parallel architectures are investigated. The novel performance level index is designed to unify the positive performance index and demonstrated the performance rank for any pose (position and orientation). The dexterity index is utilized as an example to verify the characteristics of the level index. The distributions and parametric analyses of two novel mass-related performances are studied. The dimension synthesis of a selected planar parallel robot is presented based on the non-dominated genetic algorithm II. The experiment results testify the correctness of the mobility and kinematic mathematical models of this mechanism

Parallel manipulators: practical applications and kinematic design criteria. Towards the modular reconfigurable robots

Post-PrintModern robotic manipulators play an essential role in industry, developing several tasks in an easy way, enhancing the accuracy of the final product and reducing the executing time. Also they can be found in other fields as aerospace industry, several medical applications, gaming industry, and so on. In particular, the parallel manipulators have acquired a great relevance in the last years. Indeed, many research activities and projects deal with the study and develop-ment of this type of robots. Nevertheless, usually, a bilateral communication between industry and research does not exist, even among the different existing research areas. This causes a lack of knowledge regarding works that have been carried out, the ones that are under devel-opment and the possible future investigations. Hence, once a specific field of knowledge has acquired a certain level of maturity, it is convenient to reflect its current state of the art. In this sense, the authors of this paper present a review of the different fields in which parallel ma-nipulators have a significant participation, and also the most active research topics in the anal-ysis and design of these robots. Besides, several contributions of the authors to this field are cited.The authors wish to acknowledge the financial support received from the Spanish Government through the "Ministerio de Economía y Competitividad" (Project DPI2015-67626-P (MINECO/FEDER, UE)), the financial support from the Uni-versity of the Basque Country (UPV/EHU) under the program UFI 11/29 and the support to the research group, through the project with ref. IT949-16, given by the "Departamento de Educación, Política Lingüística y Cultura" of the Regional Government of the Basque Country