Type Synthesis of Two Degrees-of-Freedom Rotational Parallel Mechanisms With a Fixed Center-of-Rotation Based on a Graphic Approach

2012 ◽  
Author(s):  
K. Wu ◽  
J. J. Yu ◽  
S. Z. Li ◽  
G. H. Zong ◽  
Xianwen Kong
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Two Degrees Of Freedom ◽  
Center Of Rotation ◽  
Parasitic Motion ◽  
Performance Requirements ◽  
Rotary Stage ◽  
Fixed Center

Mechanisms usually have to be particularly designed to meet the high-performance requirements in terms of different applications. For instance, Two degrees of freedom (DOF) rotational parallel mechanisms (RPMs) with a fixed center-of-rotation can eliminate parasitic motion and could provide the rotary stage with excellent dynamic stability, good controllability and easy operation. Therefore, this paper mainly aims at synthesizing 2-DOF RPMs with fixed center-of-rotation, a class of special RPMs with potential excellent performances. A graphic approach based on freedom and constraint spaces is introduced firstly. The constraint spaces of a class of the existing 2-DOF RPMs are illustrated, and the corresponding type synthesis patterns are summarized by comparing the geometric properties of those spaces with the mechanism characteristic. After fully decomposing the four-dimensional constraint space into sub-constraint spaces, a general type synthesis procedure is proposed based on the freedom and constraint topology. Two novel 2-DOF RPMs with fixed center-of-rotation are constructed based on the proposed method and procedure. The proposed graphic approach proves to be effective and simple to synthesizing those parallel mechanisms with some special performance.

Implementation of Particular Models of Innovative Servomechanisms

2013 ◽  
Vol 389 ◽  
pp. 415-420
Author(s):  
Davide Moscatelli
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Positioning Precision ◽  
Two Degrees Of Freedom ◽  
Model Based ◽  
High Dynamic ◽  
Model Based Analysis

This paper describes a model based analysis of a differential planar servomechanism (two degrees of freedom); this system is meant to achieve high performance as regards the positioning precision (meant as both repeatability and accuracy) keeping a relative high dynamic.

Experimental Verification of Linear and Adaptive Control Techniques for a Two Degrees-of-Freedom Helicopter

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Pavan Nuthi ◽  
Kamesh Subbarao
Keyword(s):  
Flight Control ◽  
High Performance ◽  
Degrees Of Freedom ◽  
Reference Model ◽  
Design Procedure ◽  
Linear Quadratic ◽  
Two Degrees Of Freedom ◽  
Test And Evaluation ◽  
Modeling Uncertainties ◽  
Model Tuning

This paper presents the design procedure and experimental results of a high performance adaptive augmentation technique applied to a controller derived based on linear quadratic methods. The Quanser two degrees-of-freedom (2DOF) helicopter was chosen as the experimental platform on which these controllers were implemented. The paper studies the implementation of each of these controllers standalone as well as in the augmented scheme, and discusses its performance and robustness for cases with parametric uncertainties, and unmodeled dynamics. An attempt is made to combine linear quadratic tracker's reliability with the adaptive augmentation's robustness toward modeling uncertainties. It is found that appropriate tuning of parameters in the adaptive framework is key to its performance and thus the process of choosing the parameters is elaborated along with guidelines for choosing a reference model. Tuning considerations for controller implementation on the experimental setup as compared to the same on the numerical model are also addressed. The experiments performed on this system serve as a suitable research test and evaluation basis for robotics and flight control applications.

Investigations on the principle of full decoupling and type synthesis of 2R1T and 2R parallel mechanisms

2019 ◽  
Vol 43 (2) ◽  
pp. 263-271 ◽  
Author(s):  
Yundou Xu ◽  
Bei Wang ◽  
Zhifeng Wang ◽  
Yun Zhao ◽  
Wenlan Liu ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Rotational Degrees Of Freedom ◽  
The Relationship

Based on the relationship between constraint wrenches and rotational axes, the principle of full decoupling of two rotational degrees of freedom (DOFs) for a two-rotation and one-translation (2R1T) parallel mechanism and two-rotation (2R) parallel mechanism with three supporting branches is systematically analyzed. Two conditions for full decoupling of two rotational DOFs of such mechanisms are obtained. The relationship between the two rotational axes of the parallel mechanisms is classified into two cases: intersecting and different. Next, based on the two conditions, type synthesis of the 2R1T and 2R parallel mechanisms with fully decoupled two rotational DOFs is carried out. A series of novel 2R1T and 2R parallel mechanisms with fully decoupled two rotational DOFs are obtained, such as RPU–UPR–RPR. Several of these mechanisms contain only eight single-DOF passive joints, one fewer than in existing mechanisms of this type, and thus have broad applications.

Geometric synthesis of spatial parallel manipulators with fewer than six degrees of freedom

2002 ◽  
Vol 216 (12) ◽  
pp. 1175-1185 ◽  
Author(s):  
T S Zhao ◽  
J S Dai ◽  
Z Huang
Keyword(s):  
Mechanism Design ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Algebraic Approach ◽  
Structural Complexity ◽  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Kinematic Pair ◽  
Type Synthesis ◽  
Six Degrees Of Freedom

Manipulators with fewer than six degrees of freedom meet specific tasks and have the advantage of reducing structural complexity, design redundancy and cost. In order to construct parallel manipulators for given tasks, this paper develops an algebraic approach to type synthesis of spatial parallel mechanisms with fewer than six degrees of freedom based on the screw theory. With the proposed steps (i.e. describing restraining screws, identifying basic kinematic pair (KP) screws reciprocal to the restraining screws, linearly transforming the basic KP screws to obtain equivalent serial limbs and allocating the serial limbs) new parallel mechanisms can be constructed. The approach converts a mechanism design into a screw algebra operation, in which screws describe kinematic pairs and constraints between links. As examples, synthesis procedures of parallel mechanisms with four degrees of freedom are given, from which five novel parallel mechanisms result.

Mobility and Singularity Analysis of a Class of 2-DOF Rotational Parallel Mechanisms Using a Visual Graphic Approach

2011 ◽  
Author(s):  
J. J. Yu ◽  
X. Dong ◽  
X. Pei ◽  
G. H. Zong ◽  
Xianwen Kong ◽  
...  
Keyword(s):  
System Theory ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Parallel Mechanisms ◽  
Two Degrees Of Freedom ◽  
Simple Rules ◽  
Study Case ◽  
Formula Derivation ◽  
Visual Graphic

In this paper, a simple and straightforward visual graphic approach for mobility and singularity analysis of mechanisms is introduced. Although the proposed method is established upon the reciprocal screw system theory, it needs no formula derivation instead knowing about a few simple rules. As a study case, mobility and singularity analysis for a class of two degrees-of-freedom (DOF) rotational parallel mechanisms i.e. well-know Omni-Wrist III with four limbs, and its two derived architectures with three limbs (named T-type and δ-type) is analyzed by the proposed method. As a result, a novel PKM derived from Omni-Wrist III is presented, which has the DOF and kinematics property close to Omni Wrist III.

Type synthesis of parallel mechanisms with three translational degrees of freedom*

2003 ◽  
Vol 13 (7) ◽  
pp. 536-545
Author(s):  
Jingjun Yu ◽  
Tieshi Zhao ◽  
Shusheng Bi ◽  
Guanghua Zong ◽  
Zhen Huang
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis

scholarly journals A simple and visually orientated approach for type synthesis of overconstrained 1T2R parallel mechanisms

Robotica ◽  
2018 ◽  
Vol 37 (7) ◽  
pp. 1161-1173 ◽  
Author(s):  
Tian Huang ◽  
Chenglin Dong ◽  
Haitao Liu ◽  
Tao Sun ◽  
Derek G. Chetwynd
Keyword(s):  
Degrees Of Freedom ◽  
Evaluation Criteria ◽  
Cost Effective ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Output Link ◽  
Component Design ◽  
Hybrid Module ◽  
Visual Approach ◽  
Rational Component

SUMMARYThis paper presents a simple and highly visual approach for the type synthesis of a family of overconstrained parallel mechanisms that have one translational and two rotational movement capabilities. It considers, especially, mechanisms offering the accuracy and dynamic response needed for machining applications. This family features a spatial limb plus a member of a class of planar symmetrical linkages, the latter connected by a revolute joint either to the machine frame at its base link or to the platform at its output link. Criteria for selecting suitable structures from among numerous candidates are proposed by considering the realistic practical requirements for reconfigurability, movement capability, rational component design and so on. It concludes that a few can simultaneously fulfil the proposed criteria, even though a variety of structures have been presented in the literature. Exploitation of the proposed structures and evaluation criteria then leads to a novel five degrees of freedom hybrid module named TriMule. A significant potential advantage of the TriMule over the Tricept arises because all the joints connecting the base link and the machine frame can be integrated into one single, compact part, leading to a lightweight, cost effective and flexible design particularly suitable for configuring various robotized manufacturing cells.

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