Degree of Freedom and Dynamic Analysis of the Multi-Loop Coupled Passive-Input Overconstrained Deployable Tetrahedral Mechanisms for Truss Antennas

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Yundou Xu ◽  
Yang Chen ◽  
Wenlan Liu ◽  
Xiaofei Ma ◽  
Jiantao Yao ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Equation ◽  
Degrees Of Freedom ◽  
High Accuracy ◽  
Degree Of Freedom ◽  
Lagrange Method ◽  
Overconstrained Mechanisms ◽  
Serial Chains ◽  
Torsion Springs

Abstract Recently, the truss antennas with deployable tetrahedron unit mechanisms have been successfully applied in orbit, owing to the advantages of large calibers, high accuracy, and large folding ratios. As multiloop coupled mechanisms, deployable tetrahedral mechanisms have multiple different output links, whose supporting limbs connecting output links and the base are mutually coupled. These mechanisms are also called the passive-input overconstrained mechanisms because their passive torsion springs are used as drivers and because the number of the drivers contained is more than the degrees of freedom (DOFs). In this work, a method based on the equivalent concept of first link-removing and then restoring is proposed for the DOF analysis of the multiloop coupled deployable tetrahedral mechanisms. With one coupled chain removed, the equivalent serial chains between the coupled components and the base are established in the remainder of the mechanisms. Then, the coupled chain removed is restored and the equivalent of the multiloop coupled mechanisms is obtained. The Lagrange method is used to establish the dynamic equation of the passive-input overconstrained mechanisms; the influence of the stiffness and number of torsion springs on the unfolding motion is examined.

Accelerometer correction for the dynamic analysis of damped multi-degree of freedom systems

1969 ◽  
Vol 59 (4) ◽  
pp. 1591-1598
Author(s):  
G. A. McLennan
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Exact Method ◽  
Three Degrees Of Freedom

Abstract An exact method is developed to eliminate the accelerometer error in dynamic response calculations for damped multi-degree of freedom systems. It is shown that the exact responses of a system can be obtained from the approximate responses which are conventionally calculated from an accelerogram. Response calculations were performed for two typical systems with three degrees of freedom for an assumed pseudo-earthquake. The results showed that the approximate responses may contain large errors, and that the correction developed effectively eliminates these errors.

The Dynamic Analysis and Design of Relatively Flexible Cam Mechanisms Having More Than One Degree of Freedom

1959 ◽  
Vol 81 (4) ◽  
pp. 323-331 ◽  
Author(s):  
R. C. Johnson
Keyword(s):  
Dynamic Analysis ◽  
Numerical Method ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
General Analysis ◽  
Two Degrees Of Freedom ◽  
Analysis And Design ◽  
Significant Figures ◽  
Cam Systems ◽  
General Method

The author presents a simple numerical method for analyzing and designing cam systems which have more than one degree of freedom. Illustrative examples are given for follower systems having two degrees of freedom. In addition to the general analysis and design methods which are derived, the examples also illustrate the importance of significant figures in the calculating procedure and the importance of the consideration of the distribution of mass throughout elastic regions. The general method of analysis and design can be extended to follower systems having more degrees of freedom than two.

Dynamic Analysis of 6-DOF Large Displacement Composite Simulation Platform

2012 ◽  
Vol 233 ◽  
pp. 181-185 ◽  
Author(s):  
Xiang Ming Liu ◽  
Hong Yi Yan
Keyword(s):  
Optimal Design ◽  
Dynamic Analysis ◽  
Dynamic Equation ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Lagrange Equation ◽  
Stewart Platform ◽  
Simulation Platform ◽  
Structural Dynamic ◽  
Depth Analysis

For the problem of Typical Stewart Platform with small workspace and poor flexibility, the paper proposed a new 6-DOF simulator platform. The simulator platform compounds the three-bar parallel mechanism with moving degrees of freedom and the three-axis turntable with rotating degrees of freedom, it can repeat any attitude of 6-DOF in space. Effectively solve the problem of Typical Stewart Platform with small workspace and poor flexibility. Using Lagrange equation establish dynamic equation of the simulator platform, and using MATLAB in-depth analysis its dynamics. It can provide a reference for the optimal design of structural dynamic of the simulation platform.

scholarly journals Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3740
Author(s):  
Olafur Oddbjornsson ◽  
Panos Kloukinas ◽  
Tansu Gokce ◽  
Kate Bourne ◽  
Tony Horseman ◽  
...  
Keyword(s):  
Hall Effect ◽  
Degrees Of Freedom ◽  
Reactor Core ◽  
Degree Of Freedom ◽  
Life Extension ◽  
Scale Model ◽  
Design Development ◽  
Seismic Safety ◽  
Six Degrees Of Freedom ◽  
Six Degree Of Freedom

This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

Dynamic modeling and power optimization of a 4RPSP+PS parallel flight simulator machine

Robotica ◽  
2021 ◽  
pp. 1-26
Author(s):  
Soheil Zarkandi
Keyword(s):  
Power Consumption ◽  
Dynamic Modeling ◽  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Pareto Front ◽  
Essential Role ◽  
Power Optimization ◽  
Optimal Designs ◽  
Flight Simulator ◽  
Lagrange Method

Abstract Reducing consumed power of a robotic machine has an essential role in enhancing its energy efficiency and must be considered during its design process. This paper deals with dynamic modeling and power optimization of a four-degrees-of-freedom flight simulator machine. Simulator cabin of the machine has yaw, pitch, roll and heave motions produced by a 4RPSP+PS parallel manipulator (PM). Using the Euler–Lagrange method, a closed-form dynamic equation is derived for the 4RPSP+PS PM, and its power consumption is computed on the entire workspace. Then, a newly introduced optimization algorithm called multiobjective golden eagle optimizer is utilized to establish a Pareto front of optimal designs of the manipulator having a relatively larger workspace and lower power consumption. The results are verified through numerical examples.

The thermodynamics of intracrystalline sorption I. Models of the sorbed state

1956 ◽  
Vol 234 (1196) ◽  
pp. 24-34 ◽  
Keyword(s):  
Mobile Phase ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Translational Degree ◽  
Sorbate Concentration ◽  
The Ideal

Three basic models of the intracrystalline sorbed state are discussed: a localized phase, a mobile phase possessing two translational degrees of freedom, and a mobile phase with one translational degree of freedom. The isotherm and entropy of each of these models have been investigated for the ideal phase, and where possible the influence of sorbate-sorbate interactions has been considered. Expressions for the molal and differential entropies of each model are given as a function of sorbate concentration. The method of comparing theoretical isotherms and entropies with experimental observations is outlined.

Selection of Degrees of Freedom for Dynamic Analysis

1987 ◽  
Vol 109 (1) ◽  
pp. 65-69 ◽  
Author(s):  
K. W. Matta
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
General Purpose ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Large Complex ◽  
Static Condensation ◽  
Basis Vectors ◽  
Selection Of

A technique for the selection of dynamic degrees of freedom (DDOF) of large, complex structures for dynamic analysis is described and the formulation of Ritz basis vectors for static condensation and component mode synthesis is presented. Generally, the selection of DDOF is left to the judgment of engineers. For large, complex structures, however, a danger of poor or improper selection of DDOF exists. An improper selection may result in singularity of the eigenvalue problem, or in missing some of the lower frequencies. This technique can be used to select the DDOF to reduce the size of large eigenproblems and to select the DDOF to eliminate the singularities of the assembled eigenproblem of component mode synthesis. The execution of this technique is discussed in this paper. Examples are given for using this technique in conjunction with a general purpose finite element computer program GENSAM[1].

scholarly journals An approach to quantify the influence of ground motion uncertainty on elastoplastic system acceleration in incremental dynamic analysis

2017 ◽  
Vol 20 (11) ◽  
pp. 1744-1756 ◽  
Author(s):  
Peng Deng ◽  
Shiling Pei ◽  
John W. van de Lindt ◽  
Hongyan Liu ◽  
Chao Zhang
Keyword(s):  
Dynamic Analysis ◽  
Ground Motion ◽  
Earthquake Engineering ◽  
Structural Response ◽  
Incremental Dynamic Analysis ◽  
Degree Of Freedom ◽  
Maximum Acceleration ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Performance Based Earthquake Engineering

Inclusion of ground motion–induced uncertainty in structural response evaluation is an essential component for performance-based earthquake engineering. In current practice, ground motion uncertainty is often represented in performance-based earthquake engineering analysis empirically through the use of one or more ground motion suites. How to quantitatively characterize ground motion–induced structural response uncertainty propagation at different seismic hazard levels has not been thoroughly studied to date. In this study, a procedure to quantify the influence of ground motion uncertainty on elastoplastic single-degree-of-freedom acceleration responses in an incremental dynamic analysis is proposed. By modeling the shape of the incremental dynamic analysis curves, the formula to calculate uncertainty in maximum acceleration responses of linear systems and elastoplastic single-degree-of-freedom systems is constructed. This closed-form calculation provided a quantitative way to establish statistical equivalency for different ground motion suites with regard to acceleration response in these simple systems. This equivalence was validated through a numerical experiment, in which an equivalent ground motion suite for an existing ground motion suite was constructed and shown to yield statistically similar acceleration responses to that of the existing ground motion suite at all intensity levels.

Research on Simulation Customers Participate Type in Open Innovation

2014 ◽  
Vol 926-930 ◽  
pp. 2054-2057
Author(s):  
Jun Hui He
Keyword(s):  
Open Innovation ◽  
Degrees Of Freedom ◽  
New Products ◽  
Innovation Process ◽  
Degree Of Freedom ◽  
Three Dimensions ◽  
Dynamic Evolution ◽  
Evolution Simulation ◽  
High Degree

This paper proposed customers to participate typology based on three dimensions, which are the customers’ autonomy in the process, the nature of the firm‐customer collaboration, and the stage of the innovation process. Then proposed customers to participate in the type of open innovation framework. Through the static comparative and dynamic evolution simulation found: customers tend to be open to participate in the development of new products pre innovation, the tendency to begin to choose the low participation of degrees of freedom, and ultimately tend to opt for a high degree of freedom to participate.

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