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.

Kinematic Modelling and VR Simulation of a 3DOF Medical Parallel Robot with One Decoupled Motion

2013 ◽  
Vol 837 ◽  
pp. 567-572
Author(s):  
Nadia Cretescu ◽  
Mircea Neagoe ◽  
Radu Saulescu
Keyword(s):  
Kinematic Model ◽  
Kinematic Chain ◽  
Parallel Robot ◽  
Parallel Structure ◽  
Level Control ◽  
Kinematic Chains ◽  
Fixed Base ◽  
Decoupled Motion ◽  
Kinematic Modelling ◽  
High Level

The robot studied in the paper has a 3DOF parallel structure of type 1PRRR+2PRPaR, with two coupled motions and one decoupled motion, composed by a mobile platform connected to the fixed base by three kinematic chains (one open kinematic chain of Prismatic Revolute Revolute Revolute type and two kinematic chains of Prismatic Revolute Parallelogram Revolute type). An analytical kinematic modelling of the parallel robot of type 1PRRR+2PRPaR is firstly presented in this paper, followed by a numerical simulation of the closed-form kinematic model and by a Virtual Reality (VR) application with control aspects. An innovative user interface for high-level control of the parallel 1PRRR+2PRPaR type robot is developed in MATLAB - Simulink and SimMechanics environment.

Identification of Isomorphism of Kinematic Chains Through Link’s Adjacent-Chain Table

1992 ◽  
Author(s):  
Jin-Kui Chu ◽  
Wei-qing Cao
Keyword(s):  
Kinematic Chain ◽  
Kinematic Chains ◽  
Adjacent Chain ◽  
Topological Relationships ◽  
Isomorphic Graphs ◽  
Traditional Representation

Abstract A completely new concept about the kinematic chain, called the link’s adjacent-chain table (shortened as ACT), is originated in this paper. It is an invariant which can be used to describe the topological relationships between links in the kinematic chain (shortened as KC). In comparison with the traditional representation of the KC, i.e. with the adjacent matrix, link’s ACT is much more audio-visual and simpler. Using the link’s ACT, the isomorphism of the KC can be easily determined. Among the existing methods for the identification of the isomorphic graphs, link’s ACT takes the least time in calculation. So it’s introduction of the link’s ACT leads to a effectual solution to identify the isomorphism of the KC.

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.

The Stratified Representation of Mechanisms

1990 ◽  
Vol 112 (4) ◽  
pp. 514-519 ◽  
Author(s):  
W. E. Fang ◽  
F. Freudenstein
Keyword(s):  
Characteristic Polynomial ◽  
Structural Information ◽  
Traditional Approach ◽  
Structural Characteristics ◽  
New Method ◽  
Kinematic Structure ◽  
Kinematic Chains ◽  
Order Of Magnitude

A new method for the representation of the kinematic structure of mechanisms has been proposed. This scheme is an order-of-magnitude faster in enumerating mechanisms than the conventional characteristic-polynomial approach. Moreover, unlike the traditional approach, it never fails to identify a mechanism and all structural information relating to the mechanism can be retrieved from this representation. Classification of mechanisms based on structural characteristics is built-in as well. Using this method, the graphs of approximately one million kinematic chains have been generated and stored in a computer.

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.

Structure Based Grading of Kinematic Chains

2014 ◽  
Vol 575 ◽  
pp. 501-506 ◽  
Author(s):  
Shubhashis Sanyal ◽  
G.S. Bedi
Keyword(s):  
Structural Properties ◽  
Structural Property ◽  
Kinematic Chain ◽  
Degree Of Freedom ◽  
Kinematic Chains ◽  
Structural Differences ◽  
The Individual ◽  
Independent Loops

Kinematic chains differ due to the structural differences between them. The location of links, joints and loops differ in each kinematic chain to make it unique. Two similar kinematic chains will produce similar motion properties and hence are avoided. The performance of these kinematic chains also depends on the individual topology, i.e. the placement of its entities. In the present work an attempt has been made to compare a family of kinematic chains based on its structural properties. The method is based on identifying the chains structural property by using its JOINT LOOP connectivity table. Nomenclature J - Number of joints, F - Degree of freedom of the chain, N - Number of links, L - Number of basic loops (independent loops plus one peripheral loop).

Drive System Sizing of a 6-DOF Parallel Robotic Platform

2014 ◽  
Author(s):  
Hermes Giberti ◽  
Davide Ferrari
Keyword(s):  
Optimal Solution ◽  
Parallel Robot ◽  
Drive System ◽  
Pareto Optimal ◽  
Hardware In The Loop ◽  
Motion Simulation ◽  
Inverse Dynamic ◽  
Kinematic Chains ◽  
Fixed Base ◽  
Parallel Kinematic

In this work, it is considered a 6-DoF robotic device intended to be applied for hardware-in-the-loop (HIL) motion simulation with wind tunnel models. The requirements have led to a 6-PUS parallel robot whose linkages consist of six closed-loop kinematic chains, connecting the fixed base to the mobile platform with the same sequence of joints: actuated Prism (P), Universal (U), and Spherical (S). As is common for parallel kinematic manipulators (PKMs), the actual performances of the robot depend greatly on its dimensions. Therefore, a kinematic synthesis has been performed and several Pareto-optimal solutions have been obtained through a multi-objective optimization of the machine geometric parameters, using a genetic algorithm. In this paper, the inverse dynamic analysis of the robot is presented. Then, the results are used for the mechanical sizing of the drive system, comparing belt- to screw-driven units and selecting the motor-reducer groups. Finally, the best compromise Pareto-optimal solution is definitely chosen.

Combined Graph Layout Algorithms for Automated Sketching of Kinematic Chains

2012 ◽  
Author(s):  
Martín A. Pucheta ◽  
Nicolás E. Ulrich ◽  
Alberto Cardona
Keyword(s):  
Computational Cost ◽  
Kinematic Chain ◽  
Initial Position ◽  
Graph Representation ◽  
Combinatorial Algorithms ◽  
Graph Layout ◽  
Kinematic Chains ◽  
Aesthetic Characteristics ◽  
Edge Crossings ◽  
Independent Loops

The graph layout problem arises frequently in the conceptual stage of mechanism design, specially in the enumeration process where a large number of topological solutions must be analyzed. Two main objectives of graph layout are the avoidance or minimization of edge crossings and the aesthetics. Edge crossings cannot be always avoided by force-directed algorithms since they reach a minimum of the energy in dependence with the initial position of the vertices, often randomly generated. Combinatorial algorithms based on the properties of the graph representation of the kinematic chain can be used to find an adequate initial position of the vertices with minimal edge crossings. To select an initial layout, the minimal independent loops of the graph can be drawn as circles followed by arcs, in all forms. The computational cost of this algorithm grows as factorial with the number of independent loops. This paper presents a combination of two algorithms: a combinatorial algorithm followed by a force-directed algorithm based on spring repulsion and electrical attraction, including a new concept of vertex-to-edge repulsion to improve aesthetics and minimize crossings. Atlases of graphs of complex kinematic chains are used to validate the results. The layouts obtained have good quality in terms of minimization of edge crossings and maximization of aesthetic characteristics.

A Novel Method for Constructing Multi-Mode Deployable Polyhedron Mechanisms Using Symmetric Spatial RRR Compositional Units

2018 ◽  
Author(s):  
Jieyu Wang ◽  
Xianwen Kong
Keyword(s):  
Kinematic Chain ◽  
Degree Of Freedom ◽  
Single Loop ◽  
Kinematic Chains ◽  
The Third ◽  
Motion Modes ◽  
3D Printed ◽  
Novel Method ◽  
Multi Mode ◽  
Motion Mode

A novel construction method is proposed to construct multimode deployable polyhedron mechanisms (DPMs) using symmetric spatial RRR compositional units, a serial kinematic chain in which the axes of the first and the third revolute (R) joints are perpendicular to the axis of the second R joint. Single-loop deployable linkages are first constructed using RRR units and are further assembled into polyhedron mechanisms by connecting single-loop kinematic chains using RRR units. The proposed mechanisms are over-constrained and can be deployed through two approaches. The prism mechanism constructed using two Bricard linkages and six RRR limbs has one degree-of-freedom (DOF). When removing three of the RRR limbs, the mechanism obtains one additional 1-DOF motion mode. The DPMs based on 8R and 10R linkages also have multiple modes, and several mechanisms are variable-DOF mechanisms. The DPMs can switch among different motion modes through transition positions. Prototypes are 3D-printed to verify the feasibility of the mechanisms.

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>

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