Geometric Error Effects on Manipulators' Positioning Precision: A General Analysis and Evaluation Method

2016 ◽  
Vol 8 (6) ◽  
Author(s):  
Henrique Simas ◽  
Raffaele Di Gregorio
Keyword(s):  
Degrees Of Freedom ◽  
Evaluation Method ◽  
Geometric Error ◽  
Design Stage ◽  
Positioning Precision ◽  
Six Degrees Of Freedom ◽  
Analysis And Evaluation ◽  
Lower Mobility ◽  
General Method

Manufacturing and assembly (geometric) errors affect the positioning precision of manipulators. In six degrees-of-freedom (6DOF) manipulators, geometric error effects can be compensated through suitable calibration procedures. This, in general, is not possible in lower-mobility manipulators. Thus, methods that evaluate such effects must be implemented at the design stage to determine both which workspace region is less affected by these errors and which dimensional tolerances must be assigned to match given positioning-precision requirements. In the literature, such evaluations are mainly tailored on particular architectures, and the proposed techniques are difficult to extend. Here, a general discussion on how to take into account geometric error effects is presented together with a general method to solve this design problem. The proposed method can be applied to any nonoverconstrained architecture. Eventually, as a case study, the method is applied to the analysis of the geometric error effects of the translational parallel manipulator (TPM) Triflex-II.

A 2(3-RRPS) parallel manipulator inspired by Gough–Stewart platform

Robotica ◽  
2012 ◽  
Vol 31 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Jaime Gallardo-Alvarado ◽  
Mario A. García-Murillo ◽  
Eduardo Castillo-Castaneda
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Parallel Manipulators ◽  
Forward Kinematics ◽  
Triangular Prism ◽  
Input Output ◽  
Six Degrees Of Freedom ◽  
Moving Platform

SUMMARYThis study addresses the kinematics of a six-degrees-of-freedom parallel manipulator whose moving platform is a regular triangular prism. The moving and fixed platforms are connected to each other by means of two identical parallel manipulators. Simple forward kinematics and reduced singular regions are the main benefits offered by the proposed parallel manipulator. The Input–Output equations of velocity and acceleration are systematically obtained by resorting to reciprocal-screw theory. A case study, which is verified with the aid of commercially available software, is included with the purpose to exemplify the application of the method of kinematic analysis.

The User Pre-Occupancy Evaluation Method in designer–client communication in early design stage: A case study

2013 ◽  
Vol 32 ◽  
pp. 112-124 ◽  
Author(s):  
Weilin Shen ◽  
Xiaoling Zhang ◽  
Geoffrey Qiping Shen ◽  
Terrence Fernando
Keyword(s):  
Evaluation Method ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Client Communication

MAINTAINABILITY ANALYSIS AND EVALUATION OF FLEXIBLE CABLES BASED ON DELMIA

2016 ◽  
Vol 40 (5) ◽  
pp. 995-1005 ◽  
Author(s):  
Meixia Tu ◽  
Lv Chuan ◽  
Meihui Wang ◽  
Dong Zhou ◽  
Yiliu Xu ◽  
...  
Keyword(s):  
Evaluation System ◽  
Evaluation Method ◽  
Evaluation Criteria ◽  
Analysis And Evaluation ◽  
Complex Products ◽  
Integrated Platform ◽  
Maintainability Analysis ◽  
Flexible Cables ◽  
Virtual Maintenance

This paper presents a virtual maintenance application for the maintainability analysis and evaluation of flexible cables to provide recommendations on the maintainability of products containing cables during the early stages of product design. This paper provides a methodology for complex products containing cables detecting the potential defects via virtual maintenance technology. An integrated platform for analyzing and evaluating cable maintenance in a virtual environment is designed. Then, based on the maintenance simulation platform DELMIA, a cable maintainability evaluation system is proposed. The system consists of an evaluation element, a evaluation criteria, and an evaluation method. A case study on aviation aircraft subsystem disassembly was used to validate the feasibility of virtual maintenance in improving cable maintainability designs.

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.

General method for kinematic synthesis of manipulators with task specifications

Robotica ◽  
1997 ◽  
Vol 15 (6) ◽  
pp. 653-661 ◽  
Author(s):  
F.B. Ouezdou ◽  
S. Régnier
Keyword(s):  
Degrees Of Freedom ◽  
Inverse Kinematic ◽  
Synthesis Problem ◽  
Inverse Kinematic Problem ◽  
Kinematic Synthesis ◽  
Six Degrees Of Freedom ◽  
Cluttered Environment ◽  
Dimensional Parameters ◽  
Joint Limits ◽  
General Method

This paper deals with the kinematic synthesis of manipulators. A new method based on distributed solving is used to determine the dimensional parameters of a general manipulator which is able to reach a set of given tasks specified by orientation and position. First, a general Distributed Solving Method (DSM) is presented in three steps: the problem statement, the objective functions formulations and the minimum parameters values determination. Then, this method is applied to solve the synthesis of the Denavit and Hartenberg set of parameters of a manipulator with a given kinematic structure. In this case, the kind and the number of joints are specified and a set of constraints are included such as joint limits, range of dimensional parameters and geometrical obstacles avoidance. We show that if the Denavit and Hartenberg parameters (DH) are known, the synthesis problem is reduced to an inverse kinematic problem. We show also how the problem of robot base placement can be solved by the same method. A general algorithm is given for solving the synthesis problem for all kind of manipulators. The main contribution of this paper is a general method for kinematic synthesis of all kind of manipulators and some examples are presented for a six degrees of freedom manipulator in cluttered environment.

Conceptual Design of Lower-Mobility Parallel Manipulators Based on Wrench Graphs

2014 ◽  
Author(s):  
Gamal El-Ghazaly ◽  
Stéphane Caro
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Three Dimensional ◽  
Main Idea ◽  
Parallel Manipulators ◽  
Geometric Constraints ◽  
Design Stage ◽  
Case Scenario ◽  
Worst Case ◽  
Lower Mobility

This paper presents a design methodology for lower-mobility parallel manipulators based on classification of wrench systems into four main classes. Wrench systems are represented in a three-dimensional projective space ℙ3 using wrench graphs where it is easy to incorporate geometric constraints to have simple singularity conditions using Grassmann-Cayley algebra (GCA). The main idea of the approach is to design a PM with an overall (constraint and actuation) wrench system that complies with a given wrench graph for which singularity conditions have been predetermined. The main advantage of this methodology is that the singularity conditions are already known a priori and consequently, it gives an opportunity to avoid such conditions at the design stage and make them unreachable. In the worst case scenario, where none of singularity conditions cannot be avoided, one can have a PM with known singular configurations which are always difficult to determine for already designed manipulators. As illustrative examples, two different five degrees-of-freedom (dof) mechanisms have been designed based on some of the defined wrench graphs giving 3T2R motion pattern. The first mechanism has some avoided singularities and the second one is free of singularity.

scholarly journals A RESEARCH ON QUALITY EVALUATION METHOD FOR THEMATIC MONITORING RESULTS

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 1221-1224
Author(s):  
C. X. Chen ◽  
J. X. Zhang ◽  
H. T. Zhao ◽  
C. Li ◽  
Y. Zhao
Keyword(s):  
Quality Evaluation ◽  
Evaluation Method ◽  
Evaluation Model ◽  
Chinese Government ◽  
Quality Inspection ◽  
The Public ◽  
Analysis And Evaluation ◽  
Disaster Monitoring ◽  
The Government

Abstract. The geographical condition is a very important component of a country's national condition, and geographical conditions monitoring (GCM) has been a great concern to the Chinese government. In accordance with application areas, GCM can be divided into fundamental monitoring, thematic monitoring, and disaster monitoring. Thematic monitoring is a special type of designated subject monitoring that concerns the public or the government. This paper mainly discusses the quality evaluating method of thematic monitoring results (TMRs). Based on analysis, referring to GB/T 24356-2009 “Quality Inspection and Acceptance of Surveying and Mapping Achievements”, TMRs data Including monitoring data results, analysis and evaluation results, map results and monitoring report results. The operability of the quality evaluation model is illustrated by a case study of the quality inspection of urban geographic national condition monitoring.

An approach to analyze the position and orientation between two parts assembled by non-ideal planes

2020 ◽  
Vol 235 (1-2) ◽  
pp. 41-53
Author(s):  
Jian Zhang ◽  
Lihong Qiao ◽  
Zhicheng Huang ◽  
Nabil Anwer
Keyword(s):  
Performance Analysis ◽  
Degrees Of Freedom ◽  
Product Performance ◽  
Design Stage ◽  
Manufacturing Errors ◽  
Surface Deviations ◽  
Design Requirements ◽  
Position And Orientation ◽  
General Product

Performance analysis, which plays a key role in the design stage, is employed to estimate whether product performance can satisfy design requirements. In general, product performance is gained after parts are assembled; product performance is influenced by the position and orientation deviations (PODs) that occur in directions of the constrained degrees of freedom (DOFs) due to the surface deviations of mating-surfaces. Furthermore, PODs are uncertain because the surface deviations as well as positions in the unconstrained DOF directions can vary randomly. Thus, predicting the consequences of uncertain PODs on product performance is key for performance analysis. Considering that planes are extensively used in assemblies, this study aims to propose a statistical approach to analyze the uncertain PODs of non-ideal planes. A modeling method from the perspective of manufacturing errors is employed to describe the uncertain surface deviations. A method for computing the uncertain PODs based on the progressive adjustment of coordinate systems is proposed. The maximum PODs that characterize the most unfavorable assembly situation are determined as evaluation indicators. Finally, the effectiveness of the presented approach is verified by a case study. Because both the effects of uncertain surface deviations and uncertain positions on PODs can be considered, the approach is expected to help predict the practical effects of uncertain PODs on product performance accurately during the design stage.

A Systematic Approach for Accuracy Design of Lower-Mobility Parallel Mechanism

Robotica ◽  
2020 ◽  
Vol 38 (12) ◽  
pp. 2173-2188
Author(s):  
Wenjie Tian ◽  
Ziqian Shen ◽  
Dongpo Lv ◽  
Fuwen Yin
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Geometric Error ◽  
Error Modeling ◽  
Tolerance Allocation ◽  
Design Stage ◽  
Geometric Errors ◽  
End Effector ◽  
Allocation Method ◽  
Lower Mobility

SUMMARYGeometric accuracy is a critical performance factor for parallel robots, and regardless of error compensation, accuracy design or tolerance allocation is another way to ensure the pose accuracy of a robot at design stage. A general method of both geometric error modeling and accuracy design of lower-mobility parallel mechanisms is presented. First, a general approach for error modeling of lower-mobility parallel mechanism is proposed based on screw theory, and then the geometric errors affecting the compensatable and uncompensatable accuracy of the end-effector are separated using the properties of dual vector space. The pose error aroused by compensatable geometric errors can be compensated via kinematic calibration, while the uncompensatable geometric errors should be minimized during the manufacturing and assembly processes. Based on that, the tolerance allocation method is presented, giving each uncompensatable geometric error a proper tolerance by the use of reliability theory. Compared with the traditional tolerance allocation method, the advantages of the proposed method are as follows: the number of geometric errors to be allocated is greatly reduced; the results of serialized tolerance allocation can be obtained according to different reliability indices of pose accuracy of end-effector for designers to choose; on the premise of guaranteeing the same pose accuracy of end-effector, the allocated tolerances are loose and easy to realize. Finally, the proposed methods are successfully applied to an R(2-RPS&RP)&UPS lower-mobility parallel robot, and the effectiveness and practicability of the proposed method are verified.

Motion/Force Transmissibility Based Performance Evaluation of a 6-DOF Parallel Robot With 2-DOF Active Joints

2018 ◽  
Author(s):  
Bin Mei ◽  
Fugui Xie ◽  
Xin-Jun Liu ◽  
Xuan Luo
Keyword(s):  
Performance Evaluation ◽  
Degrees Of Freedom ◽  
Evaluation Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Six Degrees Of Freedom ◽  
Transmission Index ◽  
Force Transmissibility ◽  
Local Transmission ◽  
Active Joints

3-PP(Pa)S robot is a six degrees of freedom (DOFs) parallel mechanism with 2-DOF active planar joint. For the design and application of the 3-PP(Pa)S robot, it is essential to investigate the motion/force transmissibility of the robot. But previous studies of the motion/force transmissibility have mainly focused on the parallel robots with 1-DOF active joints and thus cannot be directly applied to the 3-PP(Pa)S robot. In this paper, input twist subspace, transmission wrench subspace and output twist subspace are investigated to build mathematical models of the twists and wrenches corresponding to the 2-DOF active planar joint. Afterwards, based on the previous established frame of the local transmission index, some extended performance evaluation indices are defined to describe the motion/force transmissibility of the 3-PP(Pa)S robot. On this basis, the singularity and motion/force transmissibility of this mechanism are investigated. The motion/force transmissibility evaluation method is meaningful and applicable for the 3-PP(Pa)S parallel robot with 2-DOF active joints and can be further applied to other mechanisms with multi-DOF active joints.

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