A Number Synthesis Survey of Three-Dimensional Mechanisms

1965 ◽  
Vol 87 (2) ◽  
pp. 213-218 ◽  
Author(s):  
L. Harrisberger
Keyword(s):  
Practical Importance ◽  
Three Dimensional ◽  
Intensive Study ◽  
Simple Loop ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Number Synthesis ◽  
Space Mechanisms ◽  
Existence Criteria ◽  
Special Space

The applicability and limitations of the present existence criteria for space mechanisms are discussed. The number synthesis technique is applied to the Kutzbach Criterion to identify all the possible simple loop, single degree of freedom space mechanisms which incorporate the known physically realizable pairs. An examination of the 138 kinds of space four-link mechanisms is made within the boundaries of practical realizability to identify the nine kinds of four-link mechanisms which are worthy of intensive study and application. In addition, the practical importance of the several known “special” space mechanisms which exist outside the Kutzbach Criterion is noted.

A Method for Type Synthesis of Mechanisms Using Phase Diagrams

1994 ◽  
Author(s):  
Sio-Hou Lei ◽  
Ying-Chien Tsai
Keyword(s):  
Phase Diagram ◽  
Degrees Of Freedom ◽  
Practical Application ◽  
Type Synthesis ◽  
Planar Mechanisms ◽  
Simple Loop ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Spatial Mechanisms ◽  
Synthesis Of Mechanisms

Abstract A method for synthesizing the types of spatial as well as planar mechanisms is expressed in this paper by using the concept of phase diagram in metallurgy. The concept represented as a type synthesis technique is applied to (a) planar mechanisms with n degrees of freedom and simple loop, (b) spatial mechanisms with single degree of freedom and simple loop, to enumerate all the possible mechanisms with physically realizable kinematic pairs. Based on the technique described, a set of new reciprocating mechanisms is generated as a practical application.

scholarly journals Development of n-DoF Preloaded Structures for Impact Mitigation in Cobots

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
S. Seriani ◽  
P. Gallina ◽  
L. Scalera ◽  
V. Lughi
Keyword(s):  
Three Dimensional ◽  
Impact Loads ◽  
Single Degree Of Freedom ◽  
Impact Mitigation ◽  
Single Degree ◽  
Future Developments ◽  
Core Issue ◽  
Comprehensive Framework ◽  
Peculiar Behavior ◽  
Good Agreement

A core issue in collaborative robotics is that of impact mitigation, especially when collisions happen with operators. Passively compliant structures can be used as the frame of the cobot, although, usually, they are implemented by means of a single-degree-of-freedom (DoF). However, n-DoF preloaded structures offer a number of advantages in terms of flexibility in designing their behavior. In this work, we propose a comprehensive framework for classifying n-DoF preloaded structures, including one-, two-, and three-dimensional arrays. Furthermore, we investigate the implications of the peculiar behavior of these structures—which present sharp stiff-to-compliant transitions at design-determined load thresholds—on impact mitigation. To this regard, an analytical n-DoF dynamic model was developed and numerically implemented. A prototype of a 10DoF structure was tested under static and impact loads, showing a very good agreement with the model. Future developments will see the application of n-DoF preloaded structures to impact-mitigation on cobots and in the field of mobile robots, as well as to the field of novel architected materials.

Phase Space Interpretation and Stability Analysis of a Self Excited, Friction Damped Turbine Airfoil

1997 ◽  
Author(s):  
E. Pesheck ◽  
C. Pierre
Keyword(s):  
Stability Analysis ◽  
Phase Space ◽  
Asymptotic Methods ◽  
Three Dimensional ◽  
Space Representation ◽  
Free Response ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Dimensional Phase Space ◽  
Phase Space Representation

Abstract The free response motion of a self excited, friction damped, single-degree of freedom, turbine airfoil model is determined utilizing both exact and asymptotic methods. A three-dimensional phase space representation is used to examine the system’s global stability, and to further intuitive understanding of the system dynamics. Conclusions are reached regarding the validity and application of stability predictions through comparison of approximate and exact solutions.

Design of Cylindrical and Axisymmetric Origami Structures Based on Generalized Miura-Ori Cell

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Yucai Hu ◽  
Haiyi Liang ◽  
Huiling Duan
Keyword(s):  
Three Dimensional ◽  
Design Methods ◽  
Geometric Design ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Flat Sheet ◽  
Folded Structure

Origami has shown its potential in designing a three-dimensional folded structure from a flat sheet of material. In this paper, we present geometric design methods to construct cylindrical and axisymmetric origami structures that can fit between two given surfaces. Due to the symmetry of the structures, a strip of folds based on the generalized Miura-ori cells is first constructed and then replicated longitudinally/circumferentially to form the cylindrical/axisymmetric origami structures. In both designs, algorithms are presented to ensure that all vertexes are either on or strictly within the region between the target surfaces. The conditions of flat-foldability and developability are fulfilled at the inner vertexes and the designs are rigid-foldable with a single degree-of-freedom. The methods for cylindrical and axisymmetric designs are similar in implementation and of potential in designing origami structures for engineering purposes, such as foldcores, foldable shelters, and metamaterials.

On the Flexibility of Spatial Kinematic Chains

1986 ◽  
Vol 10 (4) ◽  
pp. 213-218
Author(s):  
A.C. Rao
Keyword(s):  
Graph Theory ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Structural Arrangement ◽  
Kinematic Chains ◽  
Single Degree ◽  
A Chain ◽  
Space Mechanisms

A number of distinct or non-isomorphic kinematic chains exist for a specified number of links and joints. For example, sixteen distinct chains can be obtained with eight links and two hundred and thirty chains with ten links having a single degree of freedom. Similarly, many space mechanisms can be formed with four links and joints having different degrees of freedom. So far no measure is available to know which of these possesses greater mobility or flexibility. Flexibility is not to be confused with the degree of freedom. Intuitively one feels that a six-link chain has greater flexibility than a four-bar chain both having the same degrees of freedom. Though the mobility of a chain increases with the number of links one is not sure how the structural arrangement, type of links and joints, their numbers and sequence etc. influence the same. Combining graph theory with the concepts of probability, simple formulae are developed to investigate the relative merits of spatial and planar kinematic chains. The greater the flexibility or mobility of the chain, the higher is the ability to meet the motion requirements, i.e., a chain having greater entropy can be expected, say, to reproduce a given function more accurately.

Kinematic Design of Deployable Structures With Low Actuation Requirements Based on Pop-Up Folding

2021 ◽  
Author(s):  
Eduardo E. Montano ◽  
Edwin A. Peraza Hernandez
Keyword(s):  
Strain Energy ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Kinematic Modeling ◽  
Deployable Structures ◽  
Design Algorithm ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Area And Volume

Abstract This paper presents the kinematic modeling and design of deployable structures inspired by pop-up books. These pop-up structures can exhibit large changes in area and volume through deployment motion that resembles opening the pages of a book. The pop-up structures have a modular topology and are formed by multiple parallelepiped units, here termed as pop-up units. The analysis of the kinematics of single pop-up units and assemblies of these that form larger structures is presented. An algorithm that integrates multiple pop-up units to form structures that approximate two-dimensional and three-dimensional target shapes when deployed is subsequently devised. The algorithm ensures that the structures formed by the assemblies of multiple pop-up units retain the single degree of freedom of a pop-up unit. The stored strain energy of these structures, which can provide the means to deploy them in practice, is also analyzed. Finally, various examples showing the applicability of the design algorithm in the synthesis of pop-up structures that approximate a diverse set of two-dimensional and three-dimensional target shapes are provided. The pop-up structures can be applied to a large spectrum of applications that need extensive deployment from small volumes while requiring a low number of degrees of freedom. These applications may include aerospace structures and MEMS.

Synthesis of Spatial Mechanism UR-2SS for Path Generation

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Wen-Yeuan Chung
Keyword(s):  
Three Dimensional ◽  
Kinematic Chain ◽  
Degree Of Freedom ◽  
Path Generation ◽  
Single Degree Of Freedom ◽  
Numerical Examples ◽  
Spatial Mechanism ◽  
Single Degree ◽  
Three Stages ◽  
Moving Platform

This article presents a new spatial mechanism with single degree of freedom (DOF) for three-dimensional path generation. The path can be defined by prescribing at most seven precision points. The moving platform of the mechanism is supported by a U-R (universal-revolute) leg and two S–S (spherical–spherical) legs. The driving unit is the first axis of the universal pair. The U-R leg is synthesized first with the problem of order defects being considered. Precision points then lead to prescribed poses of the moving platform. Two S–S legs are then synthesized to meet these poses. This spatial mechanism with a given input is analogous to a planar kinematic chain so that all possible configurations of the spatial mechanism can be constructed. A strategy consisting of three stages for evaluating branch defects is developed with the aid of the characteristic of double configurations and the technique of coding three constituent four-bar linkages. Two numerical examples are presented to illustrate the design, the evaluation of defects, and the performance of the mechanism.

Chaos and Three-Dimensional Horseshoes in Slowly Varying Oscillators

1988 ◽  
Vol 55 (4) ◽  
pp. 959-968 ◽  
Author(s):  
Stephen Wiggins ◽  
Steven W. Shaw
Keyword(s):  
Chaotic Dynamics ◽  
Three Dimensional ◽  
Equation Of Motion ◽  
Necessary Condition ◽  
Stable And Unstable Manifolds ◽  
Chaotic Motions ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Unstable Manifolds ◽  
Additional Equation

We present general results pertaining to chaotic motions in a class of systems termed slowly varying oscillators which consist of weakly perturbed single-degree-of-freedom systems in which parameters vary slowly in time according to an additional equation of motion. Our results include an analytical method for detecting transversal intersections of stable and unstable manifolds (typically a necessary condition for chaotic motions to exist) and a detailed description of the chaotic dynamics that occur when this situation exists.

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