Modelling and analysis for a cylindrical net-shell deployable mechanism

2019 ◽  
Vol 22 (15) ◽  
pp. 3149-3160
Author(s):  
Fei Lin ◽  
Chuanzhi Chen ◽  
Jinbao Chen ◽  
Meng Chen
Keyword(s):  
Cylindrical Surface ◽  
Screw Theory ◽  
Equivalent Model ◽  
Analysis Method ◽  
Deployable Structures ◽  
Single Degree Of Freedom ◽  
Space Industry ◽  
Smooth Motion ◽  
Motion Performance ◽  
Deployable Mechanism

Existing cylindrical deployable structures have poor controllability of deployment or weak bearing capacity. In order to satisfy the application needs of cylindrical deployable structures in the space industry, a cylindrical net-shell deployable mechanism is established in this article. The proposed cylindrical net-shell deployable mechanism has a regular cuboid shape in the folded state and a truss structure in the deployed state, and it can fit cylindrical surface, parabolic cylindrical surface, sine cylindrical surface and so on. Furthermore, based on reciprocal screw theory and screw synthesis theory, the mobility of cylindrical net-shell deployable mechanism in the whole motion cycle is analysed by the proposed equivalent model method. Results show that the cylindrical net-shell deployable mechanism is a single-degree-of-freedom mechanism. Moreover, a prototype is manufactured, and its motion performance is tested. The experiment shows that the cylindrical net-shell deployable mechanism has a smooth motion performance, and the mobility analysis method for complex coupled mechanism in this study is valid. This study has a certain significance in expanding the application field of cylindrical shell structure.

scholarly journals An Efficient Time-Variant Reliability Analysis Method with Mixed Uncertainties

Algorithms ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 229
Author(s):  
Fangyi Li ◽  
Yufei Yan ◽  
Jianhua Rong ◽  
Houyao Zhu
Keyword(s):  
Reliability Analysis ◽  
Limit State ◽  
Random Variables ◽  
Equivalent Model ◽  
Independent Random Variables ◽  
Problem Analysis ◽  
Analysis Method ◽  
Calculation Algorithm ◽  
Reliability Problem ◽  
Interval Variables

In practical engineering, due to the lack of information, it is impossible to accurately determine the distribution of all variables. Therefore, time-variant reliability problems with both random and interval variables may be encountered. However, this kind of problem usually involves a complex multilevel nested optimization problem, which leads to a substantial computational burden, and it is difficult to meet the requirements of complex engineering problem analysis. This study proposes a decoupling strategy to efficiently analyze the time-variant reliability based on the mixed uncertainty model. The interval variables are treated with independent random variables that are uniformly distributed in their respective intervals. Then the time-variant reliability-equivalent model, containing only random variables, is established, to avoid multi-layer nesting optimization. The stochastic process is first discretized to obtain several static limit state functions at different times. The time-variant reliability problem is changed into the conventional time-invariant system reliability problem. First order reliability analysis method (FORM) is used to analyze the reliability of each time. Thus, an efficient and robust convergence hybrid time-variant reliability calculation algorithm is proposed based on the equivalent model. Finally, numerical examples shows the effectiveness of the proposed method.

scholarly journals Predicting Maximum and Cumulative Response of A Base-isolated Building Using Pushover Analysis

Buildings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 91
Author(s):  
Kenji Fujii ◽  
Yoshiyuki Mogi ◽  
Takumi Noguchi
Keyword(s):  
Seismic Design ◽  
Pushover Analysis ◽  
Analysis Method ◽  
Single Degree Of Freedom ◽  
Local Responses ◽  
Single Degree ◽  
Cumulative Response ◽  
Cumulative Strain ◽  
Lead Rubber Bearings ◽  
Rubber Bearings

The evaluation of the maximum and cumulative response is an important issue for the seismic design of new base-isolated buildings. This study predicts the maximum and cumulative response of a 14-story reinforced concrete base-isolated building using a set of pushover analyses. In the proposed pushover analysis method, the maximum and cumulative responses of the first and higher modes are evaluated from the nonlinear analysis of equivalent single-degree-of-freedom (SDOF) models. Then, the maximum local responses are predicted by enveloping the two pushover analysis results by referring to the contribution of the first and higher modal responses, while the cumulative strain energies of the lead-rubber bearings and steel dampers are predicted from the cumulative response of the first mode. The results reveal that the responses predicted by the proposed set of pushover analyses have satisfactory accuracy.

scholarly journals Symmetric waterbomb origami

2016 ◽  
Vol 472 (2190) ◽  
pp. 20150846 ◽  
Author(s):  
Yan Chen ◽  
Huijuan Feng ◽  
Jiayao Ma ◽  
Rui Peng ◽  
Zhong You
Keyword(s):  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Solar Panels ◽  
Deployable Structures ◽  
Single Degree Of Freedom ◽  
Folding Process ◽  
Multiple Degrees Of Freedom ◽  
Single Degree ◽  
Flat Roofs ◽  
Additional Constraints

The traditional waterbomb origami, produced from a pattern consisting of a series of vertices where six creases meet, is one of the most widely used origami patterns. From a rigid origami viewpoint, it generally has multiple degrees of freedom, but when the pattern is folded symmetrically, the mobility reduces to one. This paper presents a thorough kinematic investigation on symmetric folding of the waterbomb pattern. It has been found that the pattern can have two folding paths under certain circumstance. Moreover, the pattern can be used to fold thick panels. Not only do the additional constraints imposed to fold the thick panels lead to single degree of freedom folding, but the folding process is also kinematically equivalent to the origami of zero-thickness sheets. The findings pave the way for the pattern being readily used to fold deployable structures ranging from flat roofs to large solar panels.

A Shortcut Fatigue Analysis Method

1990 ◽  
Vol 112 (1) ◽  
pp. 1-5 ◽  
Author(s):  
H. M. Thompson
Keyword(s):  
Fatigue Life ◽  
Transfer Function ◽  
Fatigue Analysis ◽  
Analysis Method ◽  
Dynamic Amplification Factor ◽  
Single Degree Of Freedom ◽  
At Resonance ◽  
Order Of Magnitude ◽  
Dynamic Amplification ◽  
Good Agreement

A shortcut fatigue analysis method is presented which can be used to provide fatigue life estimates during the preliminary design phase of deepwater fixed platforms. For this type of structure, the method is intended to provide order of magnitude fatigue life estimates only. For simpler structures, such as deepwater offshore caissons, the shortcut analysis can provide good agreement with a detailed spectral fatigue analysis. The fundamental assumption of the method is that the dynamic transfer function can be closely approximated by the product of the static transfer function and a single degree of freedom dynamic amplification factor, which has been adjusted to produce a “fit” to the true DAF at resonance. Only one dynamic analysis of the structure needs to be performed, i.e., to determine the true DAF at resonance.

A New Index of Static Actuation Force Sensitivity of Mechanisms Based on Unified Forward Jacobian Matrix

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Xu Wang ◽  
Weizhong Guo ◽  
Youcheng Han
Keyword(s):  
Jacobian Matrix ◽  
Screw Theory ◽  
Structural Constraints ◽  
Parallel Mechanisms ◽  
Analysis Method ◽  
Actuation Force ◽  
Force Sensitivity ◽  
Differential Operation ◽  
Static Equation ◽  
Pose Optimization

Abstract This paper proposes a novel performance index, which is called static actuation force sensitivity (SAFS), to investigate the response of the actuation forces when the amplitude of the suffered load of the end-effector has a change. Smaller SAFS can protect the actuations, and the load is mainly suffered by the structural constraints. This work starts with the construction of the unified forward Jacobian matrix of both serial and parallel mechanisms by screw theory. Then, with the forward Jacobian matrix, the inverse static equation is established. SAFS is thus introduced by the “partial differential” operation on the inverse static equation. SAFS is only related to the position of the whole mechanism and the direction of the suffered load, but not related to the detailed value of the amplitude of the load and the detailed value of the actuation forces; thus, SAFS can reveal the essence of static force capacities of the mechanisms. The example mechanism (namely, the 3revolute-prismatic-spherical (RPS) parallel mechanism) is used to illustrate the distribution of SAFS both over the workspace and at a certain pose. The analysis method of SAFS and the proposed index are expected to be applied to the pose optimization in the motion planning of the mechanisms to protect the actuations.

A Novel 1-DOF Deployable Mechanism for Parabolic Cylindrical Surface Approximation

2019 ◽  
Author(s):  
Hang Xiao ◽  
Shengnan Lu ◽  
Xilun Ding
Keyword(s):  
Cylindrical Surface ◽  
Static Load ◽  
Geometric Parameters ◽  
Surface Approximation ◽  
Magnification Ratio ◽  
Load Analysis ◽  
Deployable Mechanism

Abstract This paper presents a novel deployable mechanism for approximating the parabolic cylindrical surface. The proposed mechanism, which can deploy and fold synchronously in the radial and axial directions, is constructed by double four-bar linkages and scissor linkages. In the fully deployed configuration, the mechanism can approximate a cylindrical surface. It can also be folded compactly into a bundle. The radial and axial deployable mechanisms are described and their position kinematics are solved. A synchronous mechanism is designed to ensure the synchronous movement of the radial and axial mechanisms. Geometric parameters of the mechanism for approximating a given parabolic cylindrical surface are obtained. The magnification ratio of the designed mechanism is calculated. The best choice of actuator is determined through static-load analysis.

Geometric Design of a Bio-Inspired Flapping Wing Mechanism Based on Bennett-Derived 6R Deployable Mechanisms

2014 ◽  
Author(s):  
Huang Hailin ◽  
Li Bing
Keyword(s):  
Flapping Wing ◽  
Geometric Design ◽  
Geometric Parameters ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Flapping Motion ◽  
Single Degree ◽  
Revolute Joints ◽  
Air Vehicle ◽  
Deployable Mechanism

In this paper, we present the concept of designing flapping wing air vehicle by using the deployable mechanisms. A novel deployable 6R mechanism, with the deploying/folding motion of which similar to the flapping motion of the vehicle, is first designed by adding two revolute joints in the adjacent two links of the deployable Bennett linkage. The mobility of this mechanism is analyzed based on a coplanar 2-twist screw system. An intuitive projective approach for the geometric design of the 6R deployable mechanism is proposed by projecting the joint axes on the deployed plane. Then the geometric parameters of the deployable mechanism can be determined. By using another 4R deployable Bennett connector, the two 6R deployable wing mechanisms can be connected together such that the whole flapping wing mechanism has a single degree of freedom (DOF).

Origami Kaleidocycle-Inspired Symmetric Multistable Compliant Mechanisms

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Hongchuan Zhang ◽  
Benliang Zhu ◽  
Xianmin Zhang
Keyword(s):  
Arbitrary Number ◽  
Compliant Mechanisms ◽  
Rotation Angle ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Mobility Analysis ◽  
Stable States ◽  
Deployable Structures ◽  
Basic Dimension ◽  
Metamorphic Robots

Compliant kaleidocycles can be widely used in a variety of applications, including deployable structures, origami structures, and metamorphic robots, due to their unique features of continuous rotatability and multistability. Inspired by origami kaleidocycles, a type of symmetric multistable compliant mechanism with an arbitrary number of units is presented and analyzed in this paper. First, the basic dimension constraints are developed based on mobility analysis using screw theory. Second, the kinematic relationships of the actual rotation angle are obtained. Third, a method to determine the number of stabilities and the position of stable states, including the solution for the parameterized boundaries of stable regions, is developed. Finally, experimental platforms are established, and the validity of the proposed multistable mechanisms is verified.

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