Pantopteron-4: a New 3T1R Decoupled Parallel Manipulator for Pick-and-Place Applications

International audienceIn this paper, a novel 4-DOF decoupled parallel manipulator with Schoenflies motions, called the Pantopteron-4, is presented. This manipulator is able to perform the same movements as the Isoglide4 or the Quadrupteron, but, due to its architecture which is made of three pantograph linkages, an amplification of the movements between the actuators and the platform displacements is achieved. Therefore, having the same actuators for both robots, the Pantopteron-4 displaces (theoretically) many-times faster than the Isoglide4 or the Quadrupteron, depending on the magnification factor of the pantograph linkages. Thus, this mechanism is foreseen to be used in applications where the velocities and accelerations have to be high, as in pick-and-place. First, the kinematics of the Pantopteron-4 is presented. Then, its workspace is analyzed. Finally, a prototype of the mechanism is shown and conclusions are given

Performance-Based Design of the CRS-RRC Schoenflies-Motion Generator

Rigid-body displacements obtained by combining spatial translations and rotations around axes whose direction is fixed in the space are named Shoenflies' motions. They constitute a 4-dimensional (4-D) subgroup, named Shoenflies' subgroup, of the 6-D displacement group. Since the set of rotation-axis' directions is a bi-dimensional space, the set of Shoenflies' subgroups is a bi-dimensional space, too. Many industrial manipulations (e.g., pick-and-place on a conveyor belt) require displacements that belong to only one Schoenflies' subgroup and can be accomplished by particular 4-degrees-of-freedom (4-DOF) manipulators (Shoenflies-motion generators (SMGs)). The first author has recently proposed a novel parallel SMG of type CRS-RRC (1). Such SMG features a single-loop architecture with actuators on the base and a simple decoupled kinematics. Here, firstly, an organic review of the previous results on this SMG is presented; then, its design is addressed by considering its kinetostatic performances. The adopted design procedure optimizes two objective functions, one (global conditioning index (GCI)) that measures the global performance and the other (CImin) that evaluates the worst local performance in the useful workspace. The results of this optimization procedure are the geometric parameters' values that make the studied SMG have performances comparable with those of commercial SMGs. In addition, a realistic 3D model that solves all the manufacturing doubts with simple and cheap solutions is presented

A New 3-DoF Planar Parallel Manipulator with Unlimited Rotation Capability

International audienceMost of three-degree-of-freedom (3-DoF) planar parallel manipulators encountered today have a common disadvantage that is their low rotational capability. However, for many industrial applications, by example in automated assembly systems, cutting machines, simulators, or micro-motion manipulators, a high rotation capability is needed. To overcome such a difficulty, this paper focuses its attention on the proposal of a new 3-DoF planar parallel manipulator capable of high rotational capability. Firstly, structure and mobility of the suggested manipulator are discussed. Then the forward and inverse kinematic problems are analyzed, as well as it is disclosed its singular configurations. The shaking force and shaking moment balancing are also considered. The proposed design concept is illustrated by a driven demonstrator which is a first model of the suggested manipulator

Static force capabilities and dynamic capabilities of parallel mechanisms equipped with safety clutches

Cette thèse étudie les forces potentielles des mécanismes parallèles plans à deux degrés de liberté équipés d'embrayages de sécurité (limiteur de couple). Les forces potentielles sont étudiées sur la base des matrices jacobienne. La force maximale qui peut être appliquée à l'effecteur en fonction des limiteurs de couple ainsi que la force maximale isotrope sont déterminées. Le rapport entre ces deux forces est appelé l'efficacité de la force et peut être considéré ; comme un indice de performance. Enfin, les résultats numériques proposés donnent un aperçu sur la conception de robots coopératifs reposant sur des architectures parallèles. En isolant chaque lien, les modèles dynamiques approximatifs sont obtenus à partir de l'approche Newton-Euler et des équations de Lagrange pour du tripteron et du quadrupteron. La plage de l'accélération de l'effecteur et de la force externe autorisée peut être trouvée pour une plage donnée de forces d'actionnement.This thesis investigates the force capabilities of two-degree-of-freedom planar parallel mechanisms that are equipped with safety clutches (torque limiters). The force capabilities are studied based on the Jacobian matrices. The maximum force that can be applied at the end-effector for given torque limits (safety index) is determined together with the maximum isotropic force that can be produced. The ratio between these two forces, referred to as the force effectiveness, can be considered as a performance index. Finally, some numerical results are proposed which can provide insight into the design of cooperation robots based on parallel architectures. Considering each link and slider system as a single body, approximate dynamic models are derived based on the Newton-Euler approach and Lagrange equations for the tripteron and the quadrupteron. The acceleration range or the external force range of the end-effector are determined and given as a safety consideration with the dynamic models

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

Kinematics and Performance Analysis of 2R2T Parallel Manipulator with Partially Decoupled Motion

© 2019, Chinese Society of Agricultural Machinery. All right reserved. A novel parallel manipulator with two rotations and two translations was proposed. The moving platform of the parallel manipulator was connected to the fixed base through four kinematic limbs. Four prismatic joints can be used as actuations to fully control the motion of manipulator. The mobility and motion characteristic of the manipulator were analyzed by using Lie Group theory. Position model of the parallel manipulator was established. Inverse and forward position solutions were analyzed. It was demonstrated that the analytical expressions can be obtained for the inverse and forward position solutions. Partially decoupled motion characteristic of the manipulator was analyzed. Position of the moving platform can be determined by two limbs. Singularity analysis was conducted based on Jacobian matrix. Singular configurations, including inverse kinematic singularity, forward kinematic singularity and combined singularity were analyzed. Workspace and singularity curves were determined. It was found that the singularities located near the boundary of the workspace and the parallel manipulator had relatively high rotational capability. The rotational ranges in two directions were -44°~60° and -35°~52°, respectively. Performance analysis was carried out by using the method of motion/force transmission. Performance distribution over the orientation workspace was sketched. Global performance index was used in optimal design of the manipulator. The proposed parallel manipulator can be used in many fields such as five axis machine and motion simulator

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

Investigation on the Effort Transmission in Planar Parallel Manipulators

International audienceIn the design of a mechanism, the quality of effort transmission is a key issue. Traditionally, the effort transmissivity of a mechanism is defined as the quantitative measure of the power flowing effectiveness from the input link(s) to the output link(s). Many researchers have focused their work on the study of the effort transmission in mechanisms and diverse indices have been defined. However, the developed indices have exclusively dealt with the studies of the ratio between the input and output powers and they do not seem to have been devoted to the studies of the admissible reactions in passive joints. However, the observations show that is possible for a mechanism to reach positions in which the transmission indices will have admissible values but the reaction(s) in passive joint(s) can reach excessively high values leading to the breakdown of the mechanism. In the present paper, a method is developed to ensure the admissible values of reactions in passive joints of planar parallel manipulators. It is shown that the increase of reactions in passive joints of a planar parallel manipulator depends not only on the transmission angle but also the position of the instantaneous centre of rotation of the platform. It allows the determination of the maximal reachable workspace of planar parallel manipulators taking into account the admissible reactions in its passive joints. The suggested method is illustrated vie a 5R planar parallel mechanism and a planar 3-RPR parallel manipulator. I Introduction Parallel manipulators have many advantages in terms of acceleration capacities and payload-to-weight ratio [1], but one of their main drawbacks concerns the presence of singularities [2]-[5]. It is known that in the neighbourhood of the singular positions the reactions in joints of a manipulator considerably grow up. In order to have a better understanding of this phenomenon, many researchers have focused their works on the analysis of the effort transmission in parallel manipulators. One of the evident criterions for evaluation of effort transmission is the transmission angle (or pressure angle which is equal to 90 degrees minus the transmission angle) [7]-[9]. The pressure angle is well known for characterizing the transmission quality in lower kinematic pairs, such as cams [10], but this idea was also used for effort transmission analysis in the parallel manipulators [7], [9]. To evaluate the effort transmission quality, several indexes have been introduced. One of the first attempts was proposed in [6]. This paper presents a criterion named the Transmission Index (TI) that is based on transmission wrench screw. The TI varies between 0 and 1. If it is equal to 0, the considered link is in a dead position, i.e. it cannot move anymore. If it is equal to 1, this link has the best static properties. In the same vein as [6], the study [11] generalizes the TI for spatial linkages and defines the Global TI (GTI). The authors also prove that the GTI is equal, for prismatic and revolute joints, to the cosine of the pressure angle. The conditioning index was also proposed [12] for characterizing the quality of transmission between the actuators and the end-effector. This index is based on the Jacobian matrix or its "norm", which relate the actuator velocities (efforts, resp.) to the platform twist (wrench, resp.) by the following relations:  t Jq  and T   w J τ , where J is the Jacobian matrix, t the platform twist, q  the input velocities,  the actuator efforts, and w the wrench applied on the platform. All these indices have been used in many works for design and analysis of parallel mechanisms [14]-[21]. However, it is also known that because of the non homogeneity of the terms of the Jacobian matrix, the conditioning index is not well appropriated for mechanisms having both translational and rotational degrees of freedom (DOF) [13]. Moreover, all the previously mentioned indices do not take into account the real characteristics of the actuators, i.e. the fact that their input efforts are bounded between [-max i  , max i  ] [13]. In order to solve this problem, in study [22] a numerical analysis method has been developed. It has been proposed to characterize the force workspace of robots taking into account a given fixed wrench applied on the platform and actuator efforts comprised in the boundary interval [-max i  , max i  ]. However, this workspace depends on the given direction and norm of the external force/moment and will change with the variation of the applied wrench. Moreover, for many robot applications, the external wrench direction is not known, contrary to its norm. Therefore, in [23], a way to compute the maximal workspac

Optimization of 3-DOF Parallel Motion Devices for Low-Cost Vehicle Simulators

Motion generation systems are becoming increasingly important in certain Virtual Reality (VR) applications, such as vehicle simulators. This paper deals with the analysis of the Inverse Kinematics (IK) and the reachable workspace of a three-degrees-of-freedom (3-DOF) parallel manipulator, proposing different transformations and optimizations in order to simplify its use with Motion Cueing Algorithms (MCA) for self-motion generation in VR simulators. The proposed analysis and improvements are performed on a 3-DOF heave-pitch-roll manipulator with rotational motors, commonly used for low-cost motion-based commercial simulators. The analysis has been empirically validated against a real 3-DOF parallel manipulator in our labs using an optical tracking system. The described approach can be applied to any kind of 3-DOF parallel manipulator, or even to 6-DOF parallel manipulators. Moreover, the analysis includes objective measures (safe zones) on the workspace volume that can provide a simple but efficient way of comparing the kinematic capabilities of different kinds of motion platforms for this particular application