A Novel Approach to Kinematic Characteristics Analysis of Parallel Manipulators with Fewer Than Six DOF

2006 ◽  
Author(s):  
Tieshi Zhao ◽  
Yanzhi Zhao ◽  
Zhen Huang ◽  
Xiao Qi
Keyword(s):  
Parallel Manipulators ◽  
Kinematic Characteristics ◽  
Novel Approach ◽  
Characteristics Analysis ◽  
Six Dof

A Novel Method on Singularity Analysis in Parallel Manipulators

2006 ◽  
Author(s):  
Hodjat Pendar ◽  
Maryam Mahnama ◽  
Hassan Zohoor
Keyword(s):  
Closed Loop ◽  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Parallel Mechanisms ◽  
Kinematic Chains ◽  
Working Space ◽  
Novel Approach ◽  
Main Technique ◽  
Novel Method ◽  
Constraint Plane

A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a better understanding of geometrical interpretation of singularities in parallel mechanisms. Here we have introduced the Constraint Plane Method (CPM) and some of its applications in parallel mechanisms. The main technique used here, is based on Ceva Theorem.

Synthesis of scaling mechanisms for geometric figures with angulated-straight elements

2013 ◽  
Vol 227 (12) ◽  
pp. 2795-2809 ◽  
Author(s):  
Guochao Bai ◽  
Qizheng Liao ◽  
Duanling Li ◽  
Shimin Wei
Keyword(s):  
Radial Direction ◽  
Regular Polygon ◽  
Design Parameters ◽  
Synthesis Methods ◽  
Fixed Angle ◽  
Geometric Characteristics ◽  
Geometric Figures ◽  
Kinematic Characteristics ◽  
Rotation Method ◽  
Characteristics Analysis

Angulated-straight element is proposed by combining pantograph element and Hoberman element. It is prepared to construct scaling mechanisms for geometric figures. Angulated-straight element is a kind of scissor-like element that moves along a fixed angle in radial direction, coined radial-scaling element. To explore the advantages of this new element, scaling characteristics of the radial-scaling element are proposed, such as configurations, kinematic characteristics and scaling ratio. Scaling characteristics of hybrid-radial-scaling element are also investigated to enlarge the scaling ratio of radial-scaling element. All configurations of angulated-straight element are synthesized by a rotation method presented in this article. The kinematic characteristics and scaling ratios are analyzed and compared between angulated-straight element and Hoberman element. Synthesis methods of scaling mechanisms for geometric figures are presented by combining the geometric characteristics and design parameters of regular polygon and regular polyhedron. The result shows that shapes and combinations of linkages determine the scaling characteristics of the radial-scaling element. Scaling characteristics analysis of scaling elements is a useful basic theory for choosing and constructing scaling mechanisms. Types of scaling mechanism are enriched. These scaling mechanisms have a certain value of application.

A Class of Parallel Manipulators Based on Kinematically Simple Branches

1994 ◽  
Vol 116 (3) ◽  
pp. 908-914 ◽  
Author(s):  
R. P. Podhorodeski ◽  
K. H. Pittens
Keyword(s):  
Parallel Manipulators ◽  
Parallel Structure ◽  
End Effector ◽  
Forward Displacement ◽  
Parallel Class ◽  
Serial Chain ◽  
Order Polynomial ◽  
Six Dof ◽  
Actuated Joints ◽  
Chain Branch

Parallel manipulators consisting of serial branches acting in parallel on a common end effector are examined. All nonredundant, six DOF manipulators corresponding to this in-parallel class of structures are enumerated. A specific in-parallel structure, three branches with two actuated joints per branch (3–2,2,2), is chosen as most promising based upon performance considerations. A class of kimematically simple (KS) serial-chain branch joint layouts suitable for the chosen in-parallel structure is defined. Arguments based upon kinematic equivalency of the branches and mobility of the assembled in-parallel manipulator chain are used to show that there exist only five unique branch joint-layouts belonging to the KS class. It is demonstrated that the solution to the inverse displacement problem for in-parallel manipulators based on the KS branches can be expressed in a closed form. Furthermore, the 3–2,2,2 in-parallel manipulators are shown to belong to a family of manipulators whose forward displacement solutions can be resolved through roots of a 16th order polynomial.

New Indices for Optimal Design of Redundantly Actuated Parallel Manipulators

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Qinchuan Li ◽  
Ningbin Zhang ◽  
Feibo Wang
Keyword(s):  
Optimal Design ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Mean Value ◽  
Transmission Performance ◽  
Transmission Index ◽  
Redundantly Actuated ◽  
Lower Mobility ◽  
Six Dof ◽  
Force Transmissibility

Redundantly actuated parallel manipulators (PMs) receive growing interest due to their reduced singularity and enlarged workspace. This paper proposes new indices for optimal design and analysis of redundantly actuated PMs by evaluating their motion/force transmissibility. First, we proposed a method to extract a multi-DOF (degrees-of-freedom) redundantly actuated PM into several subsidiary one-DOF PMs with two or more actuators by locking some actuators in an ergodic manner. Then, a new index of output transmission performance is proposed by investigating the mean value of the instantaneous power produced by the multiple actuation wrenches and one twist of the moving platform of one-DOF PMs. A local transmission index (LTI) is defined as the minimum value of the index of output and input transmission performance. A global transmission index (GTI) is then established based on the LTI. The proposed LTI and GTI are coordinate-free and have clear physical interpretation. Finally, the validity and universality of the new indices are demonstrated by optimization and analysis of redundantly actuated lower-mobility PMs with extra articulated six-DOF or limited-DOF limbs.

Synthesis and Analysis of 4-DOF Parallel Manipulators of Computer Aided Geometry Approach

2014 ◽  
Vol 912-914 ◽  
pp. 1010-1016
Author(s):  
Yan Hua Zhang ◽  
Xiu Ju Du ◽  
Bai Yong Zhang
Keyword(s):  
Computer Simulation ◽  
Kinematic Analysis ◽  
Geometric Approach ◽  
Parallel Manipulators ◽  
Geometric Constraints ◽  
Type Synthesis ◽  
Moving Platforms ◽  
Kinematic Characteristics ◽  
Computer Aided

A novel computer aided geometry approach for type synthesis and analysis of new spatial 4-DOF parallel manipulators is put forward, and create the computer simulation mechanisms of parallel manipulators using the geometric constraints and dimension driving techniques in CAD software, Based on the computer simulation mechanisms of parallel manipulators, several new spatial 4-DOF parallel manipulators are synthesized, the kinematic characteristics of the moving platforms are analyzed by computer simulation. The results of computer simulation prove that the computer aided geometric approach for solving type synthesis and kinematic analysis is not only fairly quick and straightforward, but also has the advantages of accuracy.

A Novel Approach to Kinematic Reliability Analysis for Planar Parallel Manipulators

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Qiangqiang Zhao ◽  
Junkang Guo ◽  
Dingtang Zhao ◽  
Dewen Yu ◽  
Jun Hong
Keyword(s):  
Reliability Analysis ◽  
Error Propagation ◽  
Simulation Method ◽  
Parallel Manipulators ◽  
Plane Motion ◽  
Error Sources ◽  
Novel Approach ◽  
Safe Region ◽  
Motion Groups ◽  
Planar Parallel Manipulators

Abstract Kinematic reliability is an essential index that assesses the performance of the mechanism associating with uncertainties. This study proposes a novel approach to kinematic reliability analysis for planar parallel manipulators based on error propagation on plane motion groups and clipped Gaussian in terms of joint clearance, input uncertainty, and manufacturing imperfection. First, the linear relationship between the local pose distortion coming from the passive joint and that caused by other error sources, which are all represented by the exponential coordinate, are established by means of the Baker–Campbell–Hausdorff formula. Then, the second-order nonparametric formulas of error propagation on independent and dependent plane motion groups are derived in closed form for analytically determining the mean and covariance of the pose error distribution of the end-effector. On this basis, the kinematic reliability, i.e., the probability of the pose error within the specified safe region, is evaluated by a fast algorithm. Compared to the previous methods, the proposed approach has a significantly high precision for both cases with small and large errors under small and large safe bounds, which is also very efficient. Additionally, it is available for arbitrarily distributed errors and can analyze the kinematic reliability only regarding either position or orientation as well. Finally, the effectiveness and advantages of the proposed approach are verified by comparing with the Monte Carlo simulation method.

Design of Large-Range XY Compliant Parallel Manipulators Based on Parasitic Motion Compensation

2013 ◽  
Author(s):  
Guangbo Hao ◽  
Qiaoling Meng ◽  
Yangmin Li
Keyword(s):  
Large Range ◽  
Coupling Effect ◽  
Parallel Manipulators ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Parasitic Motion ◽  
Prior Art ◽  
Characteristics Analysis ◽  
Optimization Function ◽  
Cross Axis

This paper presents a large-range decoupled XY compliant parallel manipulator (CPM) with good dynamics (no under-constrained/non-controllable mass). The present XY CPM is composed of novel parallelogram flexure modules (NPFMs) that are parallel four-bar mechanisms as prismatic (P) joints with four identical monolithic cross-spring flexural pivots, flexure revolute (R) joints. The parasitic translation of the NPFM is compensated via the rotational centre shift of the flexure R joint thereof based on the prior art. The optimization function and optimised geometrical parameters are investigated for the NPFM at first to achieve the largest translation. The design of a large-range XY CPM is then implemented according to the fully symmetrical 4-PP parallel kinematic mechanism (PKM) and through using the optimised NPFMs. Finally, the simplified analytical stiffness modelling and finite element analysis (FEA) are undertaken for the static and/or dynamic characteristics analysis of the 4-PP XY CPM. It is shown from FEA in the example case that the present 4-PP XY CPM has good performance characteristics such as large-range motion space (10 mm × 10 mm with the total dimension of 465 mm× 465 mm), no non-controllable mass, monolithic configuration, maximal kinematostatic decoupling (cross-axis coupling effect less than 1.2%), maximal actuator isolation (input coupling effect less than 0.13%) and well-constrained parasitic rotation (less than 0.4 urad). In addition, the stiffness-enhanced NPFM using over-constraint is proposed to produce a first/second modal frequency of about 100 Hz for the resulting XY CPM.

scholarly journals A Novel Approach for Detecting Rotational Angles of a Precision Spherical Joint Based on a Capacitive Sensor

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 280 ◽  
Author(s):  
Wen Wang ◽  
He Yang ◽  
Min Zhang ◽  
Zhanfeng Chen ◽  
Guang Shi ◽  
...  
Keyword(s):  
Real Time ◽  
Capacitive Sensor ◽  
Parallel Manipulators ◽  
Angle Measurement ◽  
Mechanical Transmission ◽  
Spherical Joint ◽  
Rotational Angle ◽  
Loop Control ◽  
Novel Approach ◽  
The Mathematical Model

Precision spherical joints are commonly employed as multiple degree-of-freedom (DOF) mechanical hinges in many engineering applications, e.g., robots and parallel manipulators. Real-time and precise measurement of the rotational angles of spherical joints is not only beneficial to the real-time and closed-loop control of mechanical transmission systems, but also is of great significance in the prediction and compensation of their motion errors. This work presents a novel approach for rotational angle measurement of spherical joints with a capacitive sensor. First, the 3-DOF angular motions of a spherical joint were analyzed. Then, the structure of the proposed capacitive sensor was presented, and the mathematical model for the rotational angles of a spherical joint and the capacitance of the capacitors was deduced. Finally, the capacitance values of the capacitors at different rotations were simulated using Ansoft Maxwell software. The simulation results show that the variation in the simulated capacitance values of the capacitors is similar to that of the theoretical values, suggesting the feasibility and effectiveness of the proposed capacitive detection method for rotational angles of spherical joints.

Disturbed Configuration Bifurcation Characteristics of Gough–Stewart Parallel Manipulators at Singular Points

2007 ◽  
Vol 130 (2) ◽  
Author(s):  
Yu-Xin Wang ◽  
Yu-Tong Li
Keyword(s):  
Parallel Manipulators ◽  
Singular Points ◽  
Unperturbed System ◽  
Rank Reduction ◽  
Universal Unfolding ◽  
Novel Approach ◽  
Parallel Machine Tools ◽  
Perturbation Parameters ◽  
Pass Through ◽  
Point Type

In this paper, the disturbed configuration bifurcation characteristics of Gough–Stewart parallel manipulators at singular points are investigated. At first, the expended equation corresponding with the kinematics equation of the manipulator is introduced for eliminating the rank reduction and obtaining all of the theoretical singular points. Then, the assembly configurations at the singular points and the configuration bifurcation characteristics near them have been studied. It is found that the configuration bifurcation characteristics at the singular points belong to the turning point type through the Golubitsky–Schaeffer normal form identification. Next, utilizing the universal unfolding approach, the configuration bifurcation characteristics under the perturbation parameters applied to the extendable legs are analyzed. The investigation reveals that all configuration branches converged in the same singular point in the unperturbed system will be separated in the disturbed system. Based on this discovery, a novel approach for the parallel manipulator to pass through the singular points with a desired configuration is presented. The method presented in this paper can be utilized as the singularity avoidance approach for the parallel manipulators with strict trace and exact orientation control requirements, such as virtual parallel machine tools.

Sign in / Sign up

Export Citation Format

Share Document