Motion/Force Transmission Analysis of Parallel Mechanisms With Planar Closed-Loop Subchains

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Kristan Marlow ◽  
Mats Isaksson ◽  
Jian S. Dai ◽  
Saeid Nahavandi
Keyword(s):  
Performance Measures ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Six Degrees Of Freedom ◽  
Lower Mobility ◽  
Transmission Ability

Singularities are one of the most important issues affecting the performance of parallel mechanisms. A parallel mechanism with less than six degrees of freedom (6DOF) is classed as having lower mobility. In addition to input–output singularities, such mechanisms potentially suffer from singularities among their constraints. Furthermore, the utilization of closed-loop subchains (CLSCs) may introduce additional singularities, which can strongly affect the motion/force transmission ability of the entire mechanism. In this paper, we propose a technique for the analysis of singularities occurring within planar CLSCs, along with a finite, dimensionless, frame invariant index, based on screw theory, for examining the closeness to these singularities. The integration of the proposed index with existing performance measures is discussed in detail and exemplified on a prototype industrial parallel mechanism.

Singularity Analysis of Large Workspace 3RRRS Parallel Mechanism Using Line Geometry and Linear Complex Approximation

2010 ◽  
Vol 3 (1) ◽  
Author(s):  
Alon Wolf ◽  
Daniel Glozman
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Singularity Analysis ◽  
Community Research ◽  
Parallel Mechanisms ◽  
Line Geometry ◽  
Equilibrium Equations ◽  
Six Degrees Of Freedom ◽  
Singular Configurations

During the last 15 years, parallel mechanisms (robots) have become more and more popular among the robotics and mechanism community. Research done in this field revealed the significant advantage of these mechanisms for several specific tasks, such as those that require high rigidity, low inertia of the mechanism, and/or high accuracy. Consequently, parallel mechanisms have been widely investigated in the last few years. There are tens of proposed structures for parallel mechanisms, with some capable of six degrees of freedom and some less (normally three degrees of freedom). One of the major drawbacks of parallel mechanisms is their relatively limited workspace and their behavior near or at singular configurations. In this paper, we analyze the kinematics of a new architecture for a six degrees of freedom parallel mechanism composed of three identical kinematic limbs: revolute-revolute-revolute-spherical. We solve the inverse and show the forward kinematics of the mechanism and then use the screw theory to develop the Jacobian matrix of the manipulator. We demonstrate how to use screw and line geometry tools for the singularity analysis of the mechanism. Both Jacobian matrices developed by using screw theory and static equilibrium equations are similar. Forward and inverse kinematic solutions are given and solved, and the singularity map of the mechanism was generated. We then demonstrate and analyze three representative singular configurations of the mechanism. Finally, we generate the singularity-free workspace of the mechanism.

Motion/Force Transmission Analysis of Planar Parallel Mechanisms With Closed-Loop Subchains

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Kristan Marlow ◽  
Mats Isaksson ◽  
Saeid Nahavandi
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Transmission Performance ◽  
Specific Mechanism ◽  
Serial Chain ◽  
Four Bar Linkage

Singularities are one of the most important issues affecting the performance of parallel mechanisms. Therefore, analysis of their locations and closeness is essential for the development of a high-performance mechanism. The screw theory based motion/force transmission analysis provides such a closeness measure in terms of the work performed between specific mechanism twists and wrenches. As such, this technique has been applied to many serial chain parallel mechanisms. However, the motion/force transmission performance of parallel mechanisms with mixed topology chains is yet to be examined. These chains include linkages in both series and parallel, where the parallel portion is termed a closed-loop subchain (CLSC). This paper provides an analysis of such chains, where the CLSC is a planar four-bar linkage. In order to completely define the motion/force transmission abilities of these mechanisms, adapted wrench definitions are introduced. The proposed methodology is applied to a family of two degrees-of-freedom planar axis-symmetric parallel mechanisms, each with a different CLSC configuration. The presented analysis provides the first complete motion/force transmission analysis of such mechanisms.

Analysis and Design of Lower-Mobility Parallel Mechanism of Non-Symmetrical Based on Variable Topology Theory

2011 ◽  
Vol 201-203 ◽  
pp. 1907-1912
Author(s):  
Rong Jiang Cui ◽  
Zong He Guo ◽  
Zi Xun Yin ◽  
Song Song Zhu
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Basic Variable ◽  
Analysis And Design ◽  
And Topology ◽  
Variable Topology ◽  
Lower Mobility ◽  
Branched Chain ◽  
Mechanism Theory

First, the branched-chain of parallel mechanism was Classified according to reciprocal screw theory. Then, the introduction of variable topology mechanism theory, with the characteristics of parallel mechanisms themselves, the definition and basic variable topology means of variable topology parallel mechanism were given. With evolutionary theory, the method to design lower-mobility parallel mechanisms of non-asymmetric was proposed based on variable topology mechanism theory .Taking 3-RPS as ideal mechanism and topology synthesis was carried out, besides 2-RPS mechanism were analyzed. The introduction of variable topology mechanism theory provided a theoretical basis and innovative approaches for the synthesis configuration of Lower-mobility parallel mechanisms of non-asymmetric.

scholarly journals Type Synthesis of 3-Translational Redundant Actuated Parallel Mechanisms With Closed-Loop Branch Chains Based On Graphical Approach

2021 ◽  
Author(s):  
Yongquan Li ◽  
Hong-Sheng Jiang ◽  
Tian-Yu Zheng ◽  
Ke-Long Xi ◽  
Han Jing ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Parallel Mechanism ◽  
Large Scale ◽  
Vibration Isolation ◽  
Closed Loop ◽  
Screw Theory ◽  
Simple Calculation ◽  
Parallel Mechanisms ◽  
Logistics Industry ◽  
Graphical Approach

Abstract The 3-translational parallel mechanism is widely used in industrial, medical, and military fields, among others. With the development of the national logistics industry, a pressing need for a kind of 3-translational parallel mechanism emerged. Such mechanisms have high stiffness and high bearing capacity and are used for cargo handling and sorting. A novel method based on the graphical approach was proposed for the synthesis of 3-translational redundancy actuated parallel mechanism with closed-loop branch chains. The new mechanism has four symmetrically arranged branch chains, which eases subsequent kinematics and dynamics analyses while providing good mechanical properties. Based on the graphical approach theory, according to the constraint number contained in the branch chain, two types of redundant driven branch chains with closed-loop structures were constructed. The first type includes rotation constraint in one direction, while the second type includes the rotation constraint in two directions. Based on various combinations of two branch chain types, their allocation schemes can be divided into two types. Moreover, said these two allocation schemes can be integrated into at least 500 and 400 types of 3-translational redundant actuated parallel mechanisms with closed-loop branch chains. Then, the degree of freedom properties of representative mechanisms were tested using the screw theory. A large number of novel mechanisms were integrated assessed using this method, and branch chains such mechanisms were symmetrically distributed. They have a strong bearing capacity, simple calculation, and control, and can be applied to the handling and sorting of goods, large-scale precision machine tools, and large construction machinery vibration isolation systems, among others.

Mobility Analysis of a Novel 3-5R Parallel Mechanism Family

2004 ◽  
Vol 126 (1) ◽  
pp. 79-82 ◽  
Author(s):  
Q. C. Li ◽  
Z. Huang
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Kinematic Chain ◽  
Parallel Mechanisms ◽  
Mobility Analysis

Mobility analysis of a novel 3-5R parallel mechanism family whose limb consists of a 2R and a 3R parallel subchain is performed by the aid of screw theory. A mobility criterion applicable to such 3-leg parallel mechanisms in which each kinematic chain contains five kinematic pairs is proposed. It is shown that under different structural conditions, the 3-5R parallel mechanism can have 3, 4, or 5 DOF (degrees of freedom). The structural conditions that guarantee the full-cycle mobility are analyzed. The analysis and the method presented in this paper will be helpful in using such a 3-5R parallel mechanism family and introduce new insights into the mobility analysis of parallel mechanisms.

scholarly journals A New Metamorphic Parallel Leg Mechanism with Reconfigurable Moving Platform

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yong Xu ◽  
Zheng Liang ◽  
Jiali Liu
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Screw Theory ◽  
Degree Of Freedom ◽  
Walking Robots ◽  
Metamorphic Mechanism ◽  
Parallel Leg Mechanism ◽  
Moving Platform ◽  
Configuration Synthesis

This paper proposes the concept of full configuration state of metamorphic mechanism. Based on the concept, the configuration synthesis principle of metamorphic parallel mechanism is put forward. Firstly, a metamorphic parallel mechanism in full configuration state is synthesized, and then full configuration state evolves into a specific configuration state by increasing constraints or decreasing degrees of freedom. A reconfigurable moving platform based on the triple symmetric Bricard spatial closed-loop mechanism with a single degree of freedom is proposed. Based on this, a new method for switching motion configuration states of the metamorphic parallel mechanism is constructed. According to the configuration synthesis principle presented above, a novel metamorphic parallel mechanism that can switch between three- and four-degree-of-freedom is synthesized, and then the triple symmetric Bricard spatial closed-loop mechanism is used as the reconfigurable moving platform (that is, the reconfigurable foot of a walking robot) of the metamorphic mechanism, and thus, a novel metamorphic parallel leg mechanism is created. The screw theory is used to verify the degrees of freedom of the new type of metamorphic parallel leg. The proposed metamorphic parallel leg mechanism is expected to improve flexibility and adaptability of walking robots in unstructured environment.

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.

scholarly journals Kinematic analysis of a novel 3-CRU translational parallel mechanism

2015 ◽  
Vol 6 (1) ◽  
pp. 57-64 ◽  
Author(s):  
B. Li ◽  
Y. M. Li ◽  
X. H. Zhao ◽  
W. M. Ge
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Screw Theory ◽  
Structural Characteristics ◽  
Parallel Mechanisms ◽  
Reachable Workspace ◽  
Potential Applications ◽  
Moving Platform ◽  
And Performance

Abstract. In this paper, a modified 3-DOF (degrees of freedom) translational parallel mechanism (TPM) three-CRU (C, R, and U represent the cylindrical, revolute, and universal joints, respectively) structure is proposed. The architecture of the TPM is comprised of a moving platform attached to a base through three CRU jointed serial linkages. The prismatic motions of the cylindrical joints are considered to be actively actuated. Kinematics and performance of the TPM are studied systematically. Firstly, the structural characteristics of the mechanism are described, and then some comparisons are made with the existing 3-CRU parallel mechanisms. Although these two 3-CRU parallel mechanisms are both composed of the same CRU limbs, the types of freedoms are completely different due to the different arrangements of limbs. The DOFs of this TPM are analyzed by means of screw theory. Secondly, both the inverse and forward displacements are derived in closed form, and then these two problems are calculated directly in explicit form. Thereafter, the Jacobian matrix of the mechanism is derived, the performances of the mechanism are evaluated based on the conditioning index, and the performance of a 3-CRU TPM changing with the actuator layout angle is investigated. Thirdly, the workspace of the mechanism is obtained based on the forward position analysis, and the reachable workspace volume is derived when the actuator layout angle is changed. Finally, some conclusions are given and the potential applications of the mechanism are pointed out.

scholarly journals Design and analysis of a six degrees of freedom serial–parallel robotic mechanism with multi-degree of freedom legs

2018 ◽  
Vol 15 (6) ◽  
pp. 172988141881264
Author(s):  
Ziwei Zhang ◽  
Guoying Meng
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Simple Structure ◽  
Parallel Mechanisms ◽  
Universal Joint ◽  
Six Degrees Of Freedom ◽  
In Series ◽  
Peristaltic Movement ◽  
High Flexibility ◽  
Analytic Models

A novel mobile serial–parallel mechanism with legs for in-pipe use is proposed. The mobile robotic mechanism is composed of two identical three-universal joint–prismatic joint–universal joint parallel mechanisms connected in series and two gripping modules. The proposed parallel mechanism has two rotational freedoms and one translational freedom. In addition, the parallel mechanism can achieve continuous and equivalent rotation. The singularities of the parallel mechanism are analyzed. The overall serial–parallel mechanism has six degrees of freedom, and each gripping module has four degrees of freedom. Each parallel mechanism in the waist module is driven by three servo-electric cylinders and each leg mechanism in the gripping modules is controlled by a linear actuator. The robotic mechanism can perform peristaltic movement and turning in space. The robotic mechanism possesses a simple structure and high flexibility, along with the merits of serial–parallel mechanism. In this article, analytic models for the kinematics and dynamics of the robotic mechanism are derived. Additionally, numerical examples are given, and their solutions are validated based on results obtained by SimMechanics and Adams.

A Screw Theory-Based Semi-Analytical Approach for Elastodynamics of the Tricept Robot

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Chenglin Dong ◽  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Lower Order ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Analytical Approach ◽  
Screw Theory ◽  
Mode Shapes ◽  
Fe Model ◽  
Six Degrees Of Freedom ◽  
Static Condensation ◽  
Elastodynamic Modeling

Taking the well-known Tricept robot as an example, this paper presents a semi-analytical approach for elastodynamic modeling of five or six degrees of freedom (DOF) hybrid robots composed of a 3-DOF parallel mechanism plus a 2- or 3-DOF wrist. Drawing heavily on screw theory combined with structural dynamics, the kinetic and elastic potential energies of the parallel mechanism and of the wrist are formulated using the dual properties of twist/wrench systems and a static condensation technique. This results in a 9-DOF dynamic model that enables the lower-order dynamic behavior over the entire workspace to be estimated in a very efficient and accurate manner. The lower-order natural frequencies and mode shapes estimated by the proposed approach are shown to have very good agreement with those obtained by a full-order finite element (FE) model. It thus provides a very time-effective tool for optimal design within a virtual prototyping framework for hybrid robot-based machine tools.

Sign in / Sign up

Export Citation Format

Share Document