General inverse solution of six-degrees-of-freedom serial robots based on the product of exponentials model

2018 ◽  
Vol 38 (3) ◽  
pp. 361-367 ◽  
Author(s):  
Haixia Wang ◽  
Xiao Lu ◽  
Wei Cui ◽  
Zhiguo Zhang ◽  
Yuxia Li ◽  
...  
Keyword(s):  
Design Methodology ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Complex Problem ◽  
Content Type ◽  
Geometrical Properties ◽  
Closed Form Solutions ◽  
Six Degrees Of Freedom ◽  
Serial Robots ◽  
Six Dof

Purpose Developing general closed-form solutions for six-degrees-of-freedom (DOF) serial robots is a significant challenge. This paper thus aims to present a general solution for six-DOF robots based on the product of exponentials model, which adapts to a class of robots satisfying the Pieper criterion with two parallel or intersecting axes among its first three axes. Design/methodology/approach The proposed solution can be represented as uniform expressions by using geometrical properties and a modified Paden–Kahan sub-problem, which mainly adopts the screw theory. Findings A simulation and experiments validated the correctness and effectiveness of the proposed method (general resolution for six-DOF robots based on the product of exponentials model). Originality/value The Rodrigues rotation formula is additionally used to turn the complex problem into a solvable trigonometric function and uniformly express six solutions using two formulas.

Workspace, dexterity and dimensional optimization of microhexapod

2015 ◽  
Vol 35 (4) ◽  
pp. 341-347 ◽  
Author(s):  
E. Rouhani ◽  
M. J. Nategh
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Screw Theory ◽  
Design Parameters ◽  
Dimensional Synthesis ◽  
Content Type ◽  
Workspace Analysis ◽  
The Difference ◽  
Flexure Joints ◽  
6 Degrees Of Freedom

Purpose – The purpose of this paper is to study the workspace and dexterity of a microhexapod which is a 6-degrees of freedom (DOF) parallel compliant manipulator, and also to investigate its dimensional synthesis to maximize the workspace and the global dexterity index at the same time. Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Design/methodology/approach – Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Findings – It has been shown that the proposed procedure for the workspace calculation can considerably speed the required calculations. The optimization results show that a converged-diverged configuration of pods and an increase in the difference between the moving and the stationary platforms’ radii cause the global dexterity index to increase and the workspace to decrease. Originality/value – The proposed algorithm for the workspace analysis is very important, especially when it is an objective function of an optimization problem based on the search method. In addition, using screw theory can simply construct the homogeneous Jacobian matrix. The proposed methodology can be used for any other micromanipulator.

Unified Rotational and Translational Stiffness Characterization of Compliant Shell Mechanisms

2018 ◽  
Author(s):  
Joost R. Leemans ◽  
Charles J. Kim ◽  
Werner W. P. J. van de Sande ◽  
Just L. Herder
Keyword(s):  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Screw Theory ◽  
Characterization Methods ◽  
Six Degrees Of Freedom ◽  
Thin Walled Structures ◽  
Spatial Mechanisms ◽  
Eigen Decomposition ◽  
Comprehensive Characterization

Compliant shell mechanisms utilize spatially curved thin-walled structures to transfer or transmit force, motion or energy through elastic deformation. To design with spatial mechanisms designers need comprehensive characterization methods, while existing methods fall short of meaningful comparisons between rotational and translational degrees of freedom. This paper presents two approaches, both of which are based on the principle of virtual loads and potential energy, utilizing properties of screw theory, Plücker coordinates and an eigen-decomposition, leading to two unification lengths that can be used to compare and visualize all six degrees of freedom directions and magnitudes of compliant mechanisms in a non-arbitrary physically meaningful manner.

scholarly journals On the predictability of economic structural change by the Poincaré–Bendixson theory

foresight ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 250-265 ◽  
Author(s):  
Denis Stijepic
Keyword(s):  
Structural Change ◽  
Design Methodology ◽  
Economic Structure ◽  
Content Type ◽  
Geometrical Properties ◽  
Modeling Methods ◽  
Modeling And Prediction ◽  
Long Run ◽  
Topological Modeling

Purpose The three-sector framework (relating to agriculture, manufacturing and services) is one of the major concepts for studying the long-run change of the economic structure. This paper aims to discuss the system-theoretical classification of the structural change in the three-sector framework and, in particular, its predictability by the Poincaré–Bendixson theory. Design/methodology/approach This study compares the assumptions of the Poincaré–Bendixson theory to the typical axioms of structural change modeling, the empirical evidence on the geometrical properties of structural change trajectories and the methodological arguments referring to the laws of structural change. Findings The findings support the assumption that the structural change phenomenon is representable by a dynamical system that is predictable by the Poincaré–Bendixson theory. This result implies, among others, that in the long run, structural change is either transitory or cyclical and can be used in further geometrical/topological long-run structural change modeling and prediction. Originality/value Although widespread in mathematics, geometrical/topological modeling methods have not been used in modeling and prediction of long-run structural change, despite the fact that they seem to be predestined for this purpose owing to their global, system-theoretical nature, allowing for a reduction of ideology content of predictions and greater robustness of results.

Investigation of the flight behavior of a flare-stabilized projectile using 6DoF simulations coupled with CFD

2019 ◽  
Vol 30 (9) ◽  
pp. 4185-4201
Author(s):  
Daniel Klatt ◽  
Michael Proff ◽  
Robert Hruschka
Keyword(s):  
Degrees Of Freedom ◽  
Rigid Body Dynamics ◽  
Flight Behavior ◽  
Free Flight ◽  
Aerodynamic Coefficients ◽  
Cfd Simulations ◽  
Time Resolved ◽  
Content Type ◽  
Six Degrees Of Freedom ◽  
Computational Fluid Dynamics Cfd

Purpose The present work aims to investigate the capabilities of accurately predicting the six-degrees-of-freedom (6DoF) trajectory and the flight behavior of a flare-stabilized projectile using computational fluid dynamics (CFD) and rigid body dynamics (RBD) methods. Design/methodology/approach Two different approaches are compared for calculating the trajectory. First, the complete matrix of static and dynamic aerodynamic coefficients for the projectile is determined using static and dynamic CFD methods. This discrete database and the data extracted from free-flight experiments are used to simulate flight trajectories with an in-house developed 6DoF solver. Second, the trajectories are simulated solving the 6DoF motion equations directly coupled with time resolved CFD methods. Findings Virtual fly-out simulations using RBD/CFD coupled simulation methods well reproduce the motion behavior shown by the experimental free-flight data. However, using the discrete database of aerodynamic coefficients derived from CFD simulations shows a slightly different flight behavior. Originality/value A discrepancy between CFD 6DoF/RBD simulations and results obtained by the MATLAB 6DoF-solver based on discrete CFD data matrices is shown. It is assumed that not all dynamic effects on the aerodynamics of the projectile are captured by the determination of the force and moment coefficients with CFD simulations based on the classical aerodynamic coefficient decomposition.

scholarly journals Kinematics analysis of a new parallel robotics

2020 ◽  
Vol 17 (2) ◽  
pp. 172988142091995
Author(s):  
Shi Baoyu ◽  
Wu Hongtao
Keyword(s):  
Degrees Of Freedom ◽  
Screw Theory ◽  
Parallel Robot ◽  
Virtual Prototype ◽  
Motion Platform ◽  
Closed Form Solutions ◽  
New Type ◽  
Virtual Prototype Technology ◽  
Parallel Robotics ◽  
D Model

A new type of parallel robot ROBO_003 is presented. Its mechanisms, kinematics, and virtual prototype technology are introduced. The research of degrees of freedom (DOF) is based on screw theory, a set of screw is separated as a branch, which named as constrain screw. The type of three DOF gained by counting constrain screw, the moving platform’s frame, and base platform’s frame is set, respectively, a complete kinematic research including closed-form solutions for direct kinematic problem. The 3-D model of ROBO_003 is established using SOLIDWORKS; position and orientation of motion platform can be gained using ADMAS, which is a type of virtual prototype technology. The resultant shows that the structure of ROBO_003 is reasonable, three DOF of motion platform can be operated in a reasonable range, the solutions to the direct kinematics are right, and robot ROBO_003 can be used in many industrial fields. The research of this article provides a basis for the practical application of parallel robotics ROBO_003.

Motion and force control method of 7-DOF cable-driven rehabilitation exoskeleton robot

2018 ◽  
Vol 38 (5) ◽  
pp. 595-605 ◽  
Author(s):  
Wencheng Ni ◽  
Hui Li ◽  
Zhihong Jiang ◽  
Bainan Zhang ◽  
Qiang Huang
Keyword(s):  
Design Methodology ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Body Measurements ◽  
Joint Movement ◽  
Content Type ◽  
Rehabilitation Training ◽  
Exoskeleton Robot ◽  
Training Mode ◽  
Active Rehabilitation

Purpose The purpose of this paper is to design an exoskeleton robot and present a corresponding rehabilitation training method for patients in different rehabilitation stages. Design/methodology/approach This paper presents a lightweight seven-degrees-of-freedom (DOF) cable-driven exoskeleton robot that is wearable and adjustable. After decoupling joint movement caused by a cable-driven mechanism, active rehabilitation training mode and passive rehabilitation training mode are proposed to improve the effect of rehabilitation training. Findings Simulations and experiments have been carried out, and the results validated the feasibility of the proposed mechanism and methods by a fine rehabilitative effect with different persons. Originality/value This paper designed a 7-DOF cable-driven exoskeleton robot that is suitable for patients of different body measurements and proposed the active rehabilitation training mode and passive rehabilitation training mode based on the cable-driven exoskeleton robot.

Dynamics Simulation of a Six-DOF Tunnel Segment Erector for Tunnel Boring Machine Based on Virtual Prototype

2012 ◽  
Vol 251 ◽  
pp. 231-234
Author(s):  
Gang Li ◽  
Ya Dong Chen ◽  
Bo Wang ◽  
Wan Shan Wang
Keyword(s):  
Degrees Of Freedom ◽  
Tunnel Boring Machine ◽  
Virtual Prototype ◽  
Dynamics Simulation ◽  
Design Parameters ◽  
Six Degrees Of Freedom ◽  
Tunnel Boring ◽  
Six Dof ◽  
Freedom Movement ◽  
Segment Erector

In this paper, we present the modeling and dynamics simulation of a six-DOF tunnel segment erector for tunnel boring machine (TBM), which is performed in the virtual prototype platform. The 3D virtual assembling model of a tunnel segment erector is built based on Pro/E software according to its design parameters such as structure and size. After the interference inspection, the model is imported into ADAMS through the interface module of Mech/Pro. The model is simplified and optimized reasonably and various constraints are applied under variety working conditions. The results of simulation show that the design has six degrees of freedom movement capacity which meets the design requirements. At the same time the dynamics characteristics of drives and the forces of each part are obtained and they will provide a boundary condition for strength check and basis for the power system design which is important for the further optimal design.

An efficient reformulation of a multiscale method for the eddy current problem

2017 ◽  
Vol 36 (5) ◽  
pp. 1421-1429
Author(s):  
Markus Schöbinger ◽  
Karl Hollaus ◽  
Joachim Schöberl
Keyword(s):  
Eddy Current ◽  
Design Methodology ◽  
Degrees Of Freedom ◽  
Current Problem ◽  
Multiscale Method ◽  
Content Type ◽  
Eddy Current Problem ◽  
Laminate Thickness ◽  
The Cost ◽  
Laminated Material

Purpose This paper aims to improve the efficiency of a numerical method to treat the eddy current problem on a laminated material, where using a mesh that resolves each individual laminate would be too computationally expensive. Design/methodology/approach The domain is modeled using a coarse mesh that treats the laminated material as a bulk with averaged properties. The fine-structured behavior is recovered by introducing micro-shape functions in the ansatz space. One such method is analyzed to find further model restrictions. Findings By using a special reformulation, it is possible to eliminate the additional degrees of freedom introduced by the multiscale ansatz at the cost of an additional modeling error that decreases with the laminate thickness. Originality/value The paper gives a computationally more efficient approximate variant to a known multiscale method.

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.

Executive options with inflated equity prices

2014 ◽  
Vol 10 (3) ◽  
pp. 266-292 ◽  
Author(s):  
Linus Wilson ◽  
Yan Wendy Wu
Keyword(s):  
Boards Of Directors ◽  
Stock Price ◽  
Design Methodology ◽  
Ceo Compensation ◽  
Managerial Compensation ◽  
Equity Prices ◽  
Content Type ◽  
Closed Form Solutions ◽  
Compensation Package ◽  
Applied Game Theory

Purpose – The purpose of this paper is to solve the optimal managerial compensation problem when shareholders are either naïvely optimistic or rational. Design/methodology/approach – The paper uses applied game theory to derive the optimal CEO compensation package with over optimistic shareholders. Findings – The results suggest that boards of directors should decrease option grants to CEOs when equity is likely to be irrationally overvalued at the date when the CEO's options vest. Research limitations/implications – The implications of the model are consistent with the available empirical evidence. In addition, the model generates new testable predictions about managerial stock price manipulation, the number of options granted, and the magnitude of the options’ strike prices that have not yet been formally tested. Originality/value – This is the only paper to derive closed-form solutions to optimal CEO compensation when shareholders are naïvely optimistic.

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