scholarly journals Branch Reconfiguration of Bricard Linkages Based on Toroids Intersections: Plane-Symmetric Case

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
P. C. López-Custodio ◽  
J. S. Dai ◽  
J. M. Rico
Keyword(s):  
Degrees Of Freedom ◽  
Symmetric Case ◽  
Complete Theory ◽  
Plane Symmetry ◽  
Special Configuration ◽  
Conical Singularities ◽  
Plane Symmetric ◽  
Isolated Points ◽  
First Time ◽  
Special Plane

This paper for the first time reveals a set of special plane-symmetric Bricard linkages with various branches of reconfiguration by means of intersection of two generating toroids, and presents a complete theory of the branch reconfiguration of the Bricard plane-symmetric linkages. An analysis of the intersection of these two toroids reveals the presence of coincident conical singularities, which lead to design of the plane-symmetric linkages that evolve to spherical 4R linkages. By examining the tangents to the curves of intersection at the conical singularities, it is found that the linkage can be reconfigured between the two possible branches of spherical 4R motion without disassembling it and without requiring the usual special configuration connecting the branches. The study of tangent intersections between concentric singular toroids also reveals the presence of isolated points in the intersection, which suggests that some linkages satisfying the Bricard plane-symmetry conditions are actually structures with zero finite degrees-of-freedom (DOF) but with higher instantaneous mobility. This paper is the second part of a paper published in parallel by the authors in which the method is applied to the line-symmetric case.

Branch Reconfiguration of Bricard Linkages Based on Toroids Intersections: Line-Symmetric Case

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
P. C. López-Custodio ◽  
J. S. Dai ◽  
J. M. Rico
Keyword(s):  
Symmetric Case ◽  
Plane Symmetric ◽  
Bifurcation Points ◽  
The Family ◽  
Different Types ◽  
The Common ◽  
First Time ◽  
Made In

This paper for the first time investigates a family of line-symmetric Bricard linkages by means of two generated toroids and reveals their intersection that leads to a set of special Bricard linkages with various branches of reconfiguration. The discovery is made in the concentric toroid–toroid intersection. By manipulating the construction parameters of the toroids, all possible bifurcation points are explored. This leads to the common bi-tangent planes that present singularities in the intersection set. The study reveals the presence of Villarceau and secondary circles in the toroid–toroid intersection. Therefore, a way to reconfigure the Bricard linkage to a pair of different types of Bennett linkage is uncovered. Further, a linkage with two Bricard and two Bennett motion branches is explored. In addition, the paper reveals the Altmann linkage as a member of the family of special line-symmetric Bricard linkage studied in this paper. The method is applied to the plane-symmetric case in the following paper published together with this paper.

A Spatial Eight-Bar Linkage and Its Association With the Deployable Platonic Mechanisms

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
Guowu Wei ◽  
Jian S. Dai
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Structure Parameters ◽  
Reciprocating Motion ◽  
Motion Feature ◽  
Plane Symmetric ◽  
Dual Plane ◽  
Straight Line ◽  
First Time ◽  
Geometry And Kinematics

This paper presents for the first time a novel two degrees of freedom (2-DOF) single-looped dual-plane-symmetric spatial eight-bar linkage with exact straight-line motion. Geometry and kinematics of the eight-bar linkage are investigated and closed-form equations are presented revealing the exact straight-line motion feature of the linkage on the condition that two symmetric inputs are given. In order to secure two symmetric inputs, a geared eight-bar linkage is then proposed converting the linkage into a 1-DOF linkage of exact straight-line motion. The direction of the straight-line motion produced by the proposed eight-bar linkage is changeable and is only dependent on the structure parameters of the two pairs of V-shaped R-R dyads of the linkage. Further, the proposed eight-bar linkage is applied to the synthesis and construction of a group of deployable Platonic mechanisms with radially reciprocating motion. The virtual-center-based (VCB) method is presented for the synthesis and prototypes of the deployable Platonic mechanisms are fabricated verifying the mobility and motion of the proposed mechanisms.

scholarly journals Additive Manufacturing for Effective Smart Structures: The Idea of 6D Printing

2021 ◽  
Vol 5 (5) ◽  
pp. 119
Author(s):  
Stelios K. Georgantzinos ◽  
Georgios I. Giannopoulos ◽  
Panteleimon A. Bakalis
Keyword(s):  
Additive Manufacturing ◽  
Degrees Of Freedom ◽  
Smart Structures ◽  
Interaction Mechanism ◽  
Modeling And Simulations ◽  
Environmental Stimulus ◽  
Material Component ◽  
Design And Manufacturing ◽  
First Time ◽  
Printing Techniques

This paper aims to establish six-dimensional (6D) printing as a new branch of additive manufacturing investigating its benefits, advantages as well as possible limitations concerning the design and manufacturing of effective smart structures. The concept of 6D printing, to the authors’ best knowledge, is introduced for the first time. The new method combines the four-dimensional (4D) and five-dimensional (5D) printing techniques. This means that the printing process is going to use five degrees of freedom for creating the final object while the final produced material component will be a smart/intelligent one (i.e., will be capable of changing its shape or properties due to its interaction with an environmental stimulus). A 6D printed structure can be stronger and more effective than a corresponding 4D printed structure, can be manufactured using less material, can perform movements by being exposed to an external stimulus through an interaction mechanism, and it may learn how to reconfigure itself suitably, based on predictions via mathematical modeling and simulations.

Free Vibration Analysis of Two-Stage Planetary Gear With Friction

2018 ◽  
Author(s):  
Wei Liu ◽  
Yunbo Yuan ◽  
Tao He ◽  
Donghua Wang
Keyword(s):  
Free Vibration ◽  
Degrees Of Freedom ◽  
Sliding Friction ◽  
Free Vibration Analysis ◽  
Planetary Gear ◽  
Two Stage ◽  
Second Stage ◽  
Torsional Coupling ◽  
Coupling Dynamic ◽  
First Time

Considering the effect of teeth surface sliding friction, free vibration of two-stage planetary gears (TPG) is studied theoretically for the first time. The lateral-torsional coupling dynamic model and equation are established with three degrees of freedom: two translations and one rotation. The change rule of natural frequency is discussed with the case of first stage planetary gear’s number 4 and second stage planetary gear’s number 3, 4 and 5. Afterwards three vibration modes are summarized by calculating the free vibration. In order to understand the behavior of friction, the effect of friction on natural frequencies is analyzed for the case of considering friction and not considering friction. Furthermore, the ‘self-coupling’ phenomenon is obtained from the vibration of center component of TPG Meanwhile, the ‘mutual coupling’ is obtained between the first-stage planetary gear (FPG) and the second-stage planetary gear (SPG).

General Mathematical Model of Multi-Arm Cooperating Robots With Elastic Interconnection at the Contact

1997 ◽  
Vol 119 (4) ◽  
pp. 707-717 ◽  
Author(s):  
Milovan Z˘ivanovic´ ◽  
Miomir Vukobratovic´
Keyword(s):  
Mathematical Model ◽  
Degrees Of Freedom ◽  
Dynamic Environment ◽  
Six Degrees Of Freedom ◽  
General Mathematical Model ◽  
Cooperating Robots ◽  
Six Degree Of Freedom ◽  
Physical Phenomena ◽  
First Time ◽  
Object Dynamic

The procedure of modeling and the complete general form mathematical model of manipulators with six degrees of freedom in cooperative work are presented in the paper, together with the solution of undefiniteness problem with respect to force distribution. For the first time, a system of active spatial six-degree-of-freedom mechanisms elastically interconnected with the object (dynamic environment) is modeled. The reason for the emergence of the undefiniteness problem with respect to force is explained and the procedure for solving this problem given. Unlike the approaches given in the available literature, the undefiniteness problem with respect to force is solved in accordance with physical phenomena. The modeling procedure is illustrated by a simplified example.

scholarly journals Complex gaze stabilization in mantis shrimp

2018 ◽  
Vol 285 (1878) ◽  
pp. 20180594 ◽  
Author(s):  
Ilse M. Daly ◽  
Martin J. How ◽  
Julian C. Partridge ◽  
Nicholas W. Roberts
Keyword(s):  
Visual System ◽  
Degrees Of Freedom ◽  
Wide Field ◽  
Gaze Stabilization ◽  
Mantis Shrimp ◽  
Rotational Degrees Of Freedom ◽  
Almost All ◽  
First Time ◽  
Torsional Rotation ◽  
Rotational Freedom

Almost all animals, regardless of the anatomy of the eyes, require some level of gaze stabilization in order to see the world clearly and without blur. For the mantis shrimp, achieving gaze stabilization is unusually challenging as their eyes have an unprecedented scope for movement in all three rotational degrees of freedom: yaw, pitch and torsion. We demonstrate that the species Odontodactylus scyllarus performs stereotypical gaze stabilization in the yaw degree of rotational freedom, which is accompanied by simultaneous changes in the pitch and torsion rotation of the eye. Surprisingly, yaw gaze stabilization performance is unaffected by both the torsional pose and the rate of torsional rotation of the eye. Further to this, we show, for the first time, a lack of a torsional gaze stabilization response in the stomatopod visual system. In the light of these findings, we suggest that the neural wide-field motion detection network in the stomatopod visual system may follow a radially symmetric organization to compensate for the potentially disorientating effects of torsional eye movements, a system likely to be unique to stomatopods.

Design and locomotion analysis of a novel deformable mobile robot with two spatial reconfigurable platforms and three kinematic chains

2016 ◽  
Vol 231 (8) ◽  
pp. 1481-1499 ◽  
Author(s):  
Wan Ding ◽  
Qiang Ruan ◽  
Yan-an Yao
Keyword(s):  
Mobile Robot ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Dynamic Simulations ◽  
Gait Planning ◽  
Plane Symmetric ◽  
Kinematic Chains ◽  
Reconfigurable Platforms ◽  
Actuation Systems

A novel five degrees of freedom deformable mobile robot composed of two spatial reconfigurable platforms and three revolute–prismatic–spherical kinematic chains acting in parallel to link the two platforms is proposed to realize large deformation capabilities and multiple locomotion modes. Each platform is an improved deployable single degrees of freedom three-plane-symmetric Bricard linkage. By taking advantage of locomotion collaborating among platforms and kinematic chains, the mobile robot can fold into stick-like shape and possess omnidirectional rolling and worm-like motions. The mechanism design, kinematics, and locomotion feasibility are the main focus. Through kinematics and gait planning, the robot is analyzed to have the capabilities of rolling and turning. Based on its deformation, the worm-like motion performs the ability to overcome narrow passages (such as pipes, holes, gaps, etc.) with large range of variable size. Dynamic simulations with detailed three-dimensional model are carried out to verify the gait planning and provide the variations of essential motion and dynamic parameters in each mode. An experimental robotic system with servo and pneumatic actuation systems is built, experiments are carried out to verify the validity of the theoretical analysis and the feasibility of the different locomotion functions, and its motion performances are compared and analyzed with collected data.

Inertially Coupled Galloping of Iced Conductors

1992 ◽  
Vol 59 (1) ◽  
pp. 140-145 ◽  
Author(s):  
P. Yu ◽  
A. H. Shah ◽  
N. Popplewell
Keyword(s):  
Periodic Solutions ◽  
Cross Section ◽  
Mixed Mode ◽  
Bifurcation Theory ◽  
Degrees Of Freedom ◽  
Center Of Mass ◽  
Asymptotic Solutions ◽  
Periodic Motions ◽  
Two Degrees Of Freedom ◽  
First Time

This paper is concerned with the galloping of iced conductors modeled as a two-degrees-of-freedom system. It is assumed that a realistic cross-section of a conductor has eccentricity; that is, its center of mass and elastic axis do not coincide. Bifurcation theory leads to explicit asymptotic solutions not only for the periodic solutions but also for the nonresonant, quasi-periodic motions. Critical boundaries, where bifurcations occur, are described explicitly for the first time. It is shown that an interesting mixed-mode phenomenon, which cannot happen in cocentric cases, may exist even for nonresonance.

Growth of Cubic Silicon Carbide on Silicon Using Hot Filament CVD

2017 ◽  
Vol 897 ◽  
pp. 91-94
Author(s):  
Philip Hens ◽  
Ryan Brow ◽  
Hannah Robinson ◽  
Michael Cromar ◽  
Bart van Zeghbroeck
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Degrees Of Freedom ◽  
Thick Layer ◽  
Chemical Vapor ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Hot Filament ◽  
Cubic Silicon Carbide ◽  
First Time

In this paper, we report, for the first time, growth of high-quality single-crystalline 3C-SiC on silicon substrates using Hot Filament Chemical Vapor Deposition (HF-CVD). Rocking curve X-Ray diffraction (XRD) measurements revealed a full-width at half maximum (FWHM) as low as 333 arcsec for a 15 μm thick layer. Low tensile strain, below 0.1%, was measured using Raman spectroscopy. This quality was achieved with a carefully optimized process making use of the additional degrees of freedom the hot filaments create. For example, the hot filaments allow for precursor pre-cracking. Additionally, they allow a tuning of the vertical thermal gradient which creates an improved thermal field compared to classic Chemical Vapor Deposition techniques used for the deposition of this material today.

scholarly journals General relativity and cosmology

2015 ◽  
Vol 24 (14) ◽  
pp. 1530030
Author(s):  
Martin Bucher ◽  
Wei-Tou Ni
Keyword(s):  
General Relativity ◽  
Quantum Gravity ◽  
Gravitational Waves ◽  
100Th Anniversary ◽  
Complete Theory ◽  
Historical Overview ◽  
Field Equations ◽  
First Time

This year marks the 100th anniversary of Einstein’s 1915 landmark paper “Die Feldgleichungen der Gravitation” in which the field equations of general relativity were correctly formulated for the first time, thus rendering general relativity a complete theory. Over the subsequent hundred years, physicists and astronomers have struggled with uncovering the consequences and applications of these equations. This paper, which was written as an introduction to six chapters dealing with the connection between general relativity and cosmology that will appear in the two-volume book One Hundred Years of General Relativity: From Genesis and Empirical Foundations to Gravitational Waves, Cosmology and Quantum Gravity, endeavors to provide a historical overview of the connection between general relativity and cosmology, two areas whose development has been closely intertwined.

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