scholarly journals Design of a Lockable Spherical Joint for a Reconfigurable 3-URU Parallel Platform

Robotics ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 42 ◽  
Author(s):  
Matteo Palpacelli ◽  
Luca Carbonari ◽  
Giacomo Palmieri ◽  
Massimo Callegari
Keyword(s):  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Preliminary Design ◽  
Kinematic Structure ◽  
Spherical Joint ◽  
Pure Rotation ◽  
Fixed Base ◽  
Lower Mobility ◽  
Parallel Platform ◽  
Robotic Applications

This article deals with the functional and preliminary design of a reconfigurable joint for robotic applications. Such mechanism is a key element for a class of lower mobility parallel manipulators, allowing a local reconfiguration of the kinematic chain that enables a change in platform’s mobility. The mechanism can be integrated in the kinematic structure of a 3-URU manipulator, which shall accordingly gain the ability to change mobility from pure translation to pure rotation. As a matter of fact, special kinematics conditions must be met for the accomplishment of this task. Such peculiar requirements are described and properly exploited for the design of an effective reconfigurable mechanism. A detailed description of the joint operational principle is provided, also showing how to design it when is physically located at the fixed base of the manipulator.

scholarly journals Structural Synthesis of Articulated Manipulators with Non-Fractionated or Fractionated Kinematic Chains without Isomorphism

2021 ◽  
Vol 11 (20) ◽  
pp. 9658
Author(s):  
Ho Sung Park ◽  
Jae Kyung Shim ◽  
Woon Ryong Kim ◽  
Tae Woong Yun
Keyword(s):  
Structural Characteristics ◽  
Kinematic Chain ◽  
Kinematic Structure ◽  
Free Graph ◽  
Kinematic Chains ◽  
Conceptual Design Phase ◽  
Fixed Base ◽  
Force Transmissibility ◽  
Isomorphic Graphs ◽  
Two Degree Of Freedom

As the kinematic structure of an articulated manipulator affects the characteristics of its motion, rigidity, vibration, and force transmissibility, finding the most suitable kinematic structure for the desired task is important in the conceptual design phase. This paper proposes a systematic method for generating non-isomorphic graphs of articulated manipulators that consist of a fixed base, an end-effector, and a two-degree-of-freedom (DOF) intermediate kinematic chain connecting the two. Based on the analysis of the structural characteristics of articulated manipulators, the conditions that must be satisfied for manipulators to have a desired DOF is identified. Then, isomorphism-free graph generation methods are proposed based on the concepts of the symmetry of a graph, and the number of graphs generated are determined. As a result, 969 graphs of articulated manipulators that have two-DOF non-fractionated intermediate kinematic chains and 33,438 graphs with two-DOF fractionated intermediate kinematic chains are generated, including practical articulated manipulators widely used in industry.

Non-overconstrained 3-dof spherical parallel manipulators of type: 3-RCC, 3-CCR, 3-CRC

Robotica ◽  
2005 ◽  
Vol 24 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Mourad Karouia ◽  
Jacques M. Hervé
Keyword(s):  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Structural Type ◽  
Parallel Mechanisms ◽  
Structural Types ◽  
Special Cases ◽  
Algebraic Properties ◽  
Analysis And Synthesis ◽  
Fixed Base ◽  
Type 3

Non-overconstrained 3-dof spherical parallel manipulators of a structural type 3-RCC, 3-CCR, 3-CRC are introduced. The mechanism has three limbs that connect in parallel the moving platform to the fixed base. Each limb is an opened kinematic chain made of a sequence of one revolute pair R and two cylindrical pairs C. The orientation of the end-effector is obtained by actuating simultaneously the three limbs. A structural type analysis and synthesis, which is based on the algebraic properties of a Lie group of the displacement set, is employed to find the geometrical conditions for the assembly of these spherical parallel mechanisms and also the structurally singular configurations. Then an enumeration of the structural types is given and remarkable special cases of orientational mechanisms are also described, namely 3-HGR, 3-RGH and 3-HGH.

Geometric Interpretation of Singular Configurations of a Class of Parallel Manipulators

2011 ◽  
Author(s):  
Xianwen Kong ◽  
Jingjun Yu ◽  
Cle´ment Gosselin
Keyword(s):  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Geometric Interpretation ◽  
Spherical Joint ◽  
Kinematic Singularity ◽  
Geometric Characteristics ◽  
Singular Configurations ◽  
Parallel Kinematic ◽  
Forward Kinematic

This paper proposes an equivalent serial kinematic chain approach to identify the geometric characteristics of singular configurations of a class of parallel manipulators, which can be reduced to a structure composed of three XS and/or SX legs. Here, S and X denote respectively a spherical joint and a one-degree-of-freedom joint or generalized joint. The equivalent serial kinematic chain associated with a parallel kinematic chain composed of two XS legs is first obtained using the concept of reciprocal screws. The forward kinematic singularity (also static singularity) analysis of the parallel manipulators is then reduced to the singularity (stability) analysis of a single-loop structure. Finally, the geometric characteristics of singular configurations of the class of parallel manipulators are obtained with almost no algebraic derivation.

A methodology for static stiffness mapping in lower mobility parallel manipulators with decoupled motions

Robotica ◽  
2009 ◽  
Vol 28 (5) ◽  
pp. 719-735 ◽  
Author(s):  
Charles Pinto ◽  
Javier Corral ◽  
Oscar Altuzarra ◽  
Alfonso Hernández
Keyword(s):  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Added Value ◽  
Computational Time ◽  
Static Stiffness ◽  
Experimental Prototype ◽  
Experimental Tool ◽  
Lower Mobility ◽  
Set Up ◽  
Two Degree Of Freedom

SUMMARYIn this paper a general methodology for obtaining static stiffness maps in lower mobility parallel manipulators is proposed. The main objective is to define a set of guidelines, which allow the experimental work to be optimized and computational time to be reduced. First, a two-degree-of-freedom (DOF) mechanism will be used for methodology validation, since it is the stiffness of the basic kinematic chain of the manipulator that is to be analysed. Two mathematical models of this mechanism and an experimental prototype will be considered for the validation. After that, the methodology will be applied to a lower mobility (4-DOF) parallel manipulator. In this paper, the experimental prototype and its set-up is highly important because some particular features of the experimental analysis will be defined. This paper introduces a key experimental tool: the preload, which allows the clearances and possible assembling errors to be considered. The added value from the application of this procedure is the obtaining of graphs that describe, in an intuitive and useful way, the behaviour of the manipulator's stiffness inside its workspace as a function of the mobile platform position and orientation.

Design of a Human Knee Reeducation Mechanism

2019 ◽  
Vol 11 (1) ◽  
pp. 42-53
Author(s):  
Allaoua Brahmia ◽  
Ridha Kelaiaia
Keyword(s):  
Lower Limb ◽  
Mechanical Design ◽  
Kinematic Chain ◽  
Lower Limbs ◽  
Kinematic Structure ◽  
Robotic Device ◽  
Human Knee ◽  
Kinematic Study ◽  
Rehabilitation Exercise ◽  
New Machine

Abstract To establish an exercise in open muscular chain rehabilitation (OMC), it is necessary to choose the type of kinematic chain of the mechanical / biomechanical system that constitutes the lower limbs in interaction with the robotic device. Indeed, it’s accepted in biomechanics that a rehabilitation exercise in OMC of the lower limb is performed with a fixed hip and a free foot. Based on these findings, a kinematic structure of a new machine, named Reeduc-Knee, is proposed, and a mechanical design is carried out. The contribution of this work is not limited to the mechanical design of the Reeduc-Knee system. Indeed, to define the minimum parameterizing defining the configuration of the device relative to an absolute reference, a geometric and kinematic study is presented.

Selecting Kinematic Structures of Parallel Manipulators Using Symmetry and Connectivity

2015 ◽  
Author(s):  
Roberto Simoni ◽  
Henrique Simas ◽  
Daniel Martins
Keyword(s):  
Conceptual Design ◽  
Kinematic Chain ◽  
Parallel Manipulators ◽  
Connectivity Matrix ◽  
Early Stages

This paper presents an application of symmetry and connectivity to select kinematic structures of parallel manipulators. One kinematic chain can originate several mechanisms and each mechanism can originate several parallel manipulators and, in early stages of conceptual design, it is difficult to decide what is the most promising one. Hunt [1] introduced the concept of connectivity and, since then, the connectivity has been used as an important parameter to select the most appropriated parallel manipulators to develop determined task. However, it is difficult to analyze non isomorphic parallel manipulators from the connectivity matrix. In this sense, in this paper, we apply symmetry to reduce the set of parallel manipulators to a manageable few with the desired connectivity. As a result, all promising parallel manipulators originating from a kinematic chain can be analyzed without isomorphisms.

Synthesis and Balancing of Cam-Modulated Linkages

1987 ◽  
Author(s):  
P. Pracht ◽  
P. Minotti ◽  
M. Dahan
Keyword(s):  
Systematic Approach ◽  
Kinematic Chain ◽  
Path Generation ◽  
Industrial Manipulator ◽  
High Speeds ◽  
Structural Error ◽  
Mass Balancing ◽  
Four Bar Linkage ◽  
Robotic Applications ◽  
Class Of Functions

Abstract Linkages are inherently light, inexpensive, strong, adaptable to high speeds and have little friction. Moreover the class of functions suitable for linkage representation is large. For all these reasons numerous recent works deal with the problem of design mechanisms for robotic applications, but very often in terms of components such as gripper, transmission, balancing. We investigate a new application for linkages, using them to design industrial manipulator. The selected mechanism for this application is a four bar linkage with an adjustable lengh for exact path generation. This adjustment is performed by a track or cam which is substituted to a bar. By this mean, we define a cam-modulated linkage which possess superior accuracy potential and is capable of accomodating of industrial design restrictions. Such a kinematic chain is free from structural error for path generation and the presence of the track introduces the flexibility and versality in the usefull four bar chain. The synthesis technique of cam modulated linkage utilizes loop closure equations, envelop theory to find the centerline and the profile of the track. These techniques provide a systematic approach to the design of mechanism for path generation when extreme accuracy is required. In order to complete an contribution, we take in consideration the static balancing of the synthesized manipulator. To achieve static mass balancing we use the potential energy storage capabilities of linear springs, and integrated it with the non-linear motion of mechanism to provide an exact value of the desired counter loading functions. Examples are worked to demonstrate applications of these procedures and to illustrate the industrial potential of spring balancing and cam-modulated linkage.

scholarly journals Dimensional Synthesis of a Novel 3-URU Translational Manipulator Implemented through a Novel Method

Robotics ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Raffaele Di Gregorio
Keyword(s):  
Parallel Manipulators ◽  
Geometric Parameters ◽  
Dimensional Synthesis ◽  
Positioning Precision ◽  
Platform Motion ◽  
Operational Space ◽  
Lower Mobility ◽  
Novel Method ◽  
Block Diagonal

A dimensional synthesis of parallel manipulators (PMs) consists of determining the values of the geometric parameters that affect the platform motion so that a useful workspace with assigned sizes can be suitably located in a free-from-singularity region of its operational space. The main goal of this preliminary dimensioning is to keep the PM far enough from singularities to avoid high internal loads in the links and guarantee a good positioning precision (i.e., for getting good kinematic performances). This paper presents a novel method for the dimensional synthesis of translational PMs (TPMs) and applies it to a TPM previously proposed by the author. The proposed method, which is based on Jacobians’ properties, exploits the fact that TPM parallel Jacobians are block diagonal matrices to overcome typical drawbacks of indices based on Jacobian properties. The proposed method can be also applied to all the lower-mobility PMs with block diagonal Jacobians that separate platform rotations from platform translations (e.g., parallel wrists).

scholarly journals Denavit-Hartenberg Coordinate System for Robots with Tree-like Kinematic Structure

2016 ◽  
Vol 5 (4) ◽  
pp. 244
Author(s):  
Alexander Kovalchuk ◽  
F. Akhmetova
Keyword(s):  
Graph Theory ◽  
Coordinate System ◽  
Kinematic Chain ◽  
Kinematics And Dynamics ◽  
Kinematic Structure ◽  
Coordinate Systems ◽  
Reachability Graph ◽  
Joint Application ◽  
Linear Chains ◽  
Use Efficiency

<p class="MDPI17abstract"><span lang="EN-US">The paper presents a modified Denavit-Hartenberg coordinate system resulted from joint application of graph theory and the Denavit-Hartenberg coordinate system, which was developed to describe the kinematics of robot actuators with a linear open kinematic chain. It allows forming mathematical models of actuating mechanisms for the robots with tree-like kinematic structures. The work introduces the concept of primary and auxiliary coordinate systems. It considers an example of making the links’ reachability matrix and reachability graph for the tree-like actuating mechanism of a robotic mannequin. The use efficiency of the proposed modified Denavit-Hartenberg coordinate system is illustrated by the examples giving the mathematical description of the kinematics and dynamics of specific robots’ tree-like actuating mechanisms discussed in the previously published papers. It is shown that the proposed coordinate system can also be successfully applied to describe the actuating mechanisms of robots with a linear open kinematic chain, which is a particular case of the tree-like kinematic structure. The absence of branching joints in it does not require introducing auxiliary coordinate systems and the parameters f(i) and ns(i) are necessary only for the formal notation of equations, which have similar forms for the tree-like and linear chains. In this case, the modified and traditional coordinate systems coincide.</span></p>

Sign in / Sign up

Export Citation Format

Share Document