scholarly journals Foldable Hexagonal Structures Based on the Threefold-Symmetric Bricard Linkage

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Fufu Yang ◽  
Zhong You ◽  
Yan Chen
Keyword(s):  
Degrees Of Freedom ◽  
Design Method ◽  
Hexagonal Structure ◽  
Alternative Form ◽  
Practical Applications ◽  
3D Space ◽  
Geometric Conditions ◽  
Foldable Structures ◽  
Motion Paths ◽  
Set Up

Abstract The threefold-symmetric Bricard linkage, a special type of Bricard linkage, is able to generate spatial motion in 3D space with well-defined threefold rotational symmetries and three symmetric planes, which makes it a robust base linkage in designing many one-degrees-of-freedom (DOF) foldable structures. However, its practical applications are limited, as the design method with the consideration of the actual assembly is still an ambiguous area. In this paper, a foldable hexagonal structure based on the alternative form of the threefold-symmetric Bricard linkage is designed and manufactured. Geometric conditions for achieving the desired deployment are analyzed at first. Then the relationship among kinematic variables of the linkage and the geometric parameters of physical bars with a regular triangular cross-section are set up. Finally, an intuitive approach is presented to detect two types of physical blockages in the motion paths of deployment. The proposed method supplies a convenient way to design foldable hexagonal structures for potential practical applications.

scholarly journals Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 444
Author(s):  
Guoning Si ◽  
Liangying Sun ◽  
Zhuo Zhang ◽  
Xuping Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Polyimide Film ◽  
Zebrafish Embryos ◽  
Multiple Degrees Of Freedom ◽  
Electrothermal Actuator ◽  
3D Space ◽  
Pick And Place

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

scholarly journals Research on Improving the Durability of Bridge Pavement Using a High-Modulus Asphalt Mixture

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1449
Author(s):  
Wenfeng Wang ◽  
Shaochan Duan ◽  
Haoran Zhu
Keyword(s):  
Construction Industry ◽  
Mechanical Response ◽  
Design Method ◽  
Asphalt Mixture ◽  
Field Tests ◽  
Bottom Layer ◽  
High Modulus ◽  
Practical Applications ◽  
Depth Prediction ◽  
Pavement Structure

In order to improve the durability of the asphalt pavement on a cement concrete bridge, this study investigated the effect of the modulus of the asphalt mixture at the bottom layer on the mechanical response of bridge pavement, along with a type of emerging bridge pavement structure. In addition, the design method and pavement performance of a high-modulus asphalt mixture were investigated using laboratory and field tests, and the life expectancy of the deck pavement structure was predicted based on the rutting deformation. The results showed that the application of a high-modulus asphalt mixture as the bottom asphalt layer decreased the stress level of the pavement structure. The new high-modulus asphalt mixture displayed excellent comprehensive performance, i.e., the dynamic stability reached 9632 times/mm and the fatigue life reached 1.65 million cycles. Based on the rutting depth prediction, using high-modulus mixtures for the bridge pavement prolonged the service life from the original 5 years to 10 years, which significantly enhanced the durability of the pavement structure. These research results could be of potential interest for practical applications in the construction industry.

scholarly journals Galloping Stability and Wind Tunnel Test of Iced Quad Bundled Conductors considering Wake Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Mengqi Cai ◽  
Guangyun Min ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Aerodynamic Coefficients ◽  
Wake Effect ◽  
Aerodynamic Coefficient ◽  
Set Up ◽  
The Stability ◽  
Three Degrees Of Freedom

A new quad bundle conductor galloping model considering wake effect is proposed to solve the problem of different aerodynamic coefficients of each subconductor of iced quad bundle conductor. Based on the quasistatic theory, a new 3-DOF (three degrees of freedom) galloping model of iced quad bundle conductors is established, which can accurately reflect the energy transfer and galloping of quad bundle conductor in three directions. After a series of formula derivations, the conductor stability judgment formula is obtained. In the wind tunnel test, according to the actual engineering situation, different variables are set up to accurately simulate the galloping of iced quad bundle conductor under the wind, and the aerodynamic coefficient is obtained. Finally, according to the stability judgment formula of this paper, calculate the critical wind speed of conductor galloping through programming. The dates of wind tunnel test and calculation in this paper can be used in the antigalloping design of transmission lines.

Design and Analysis of Motion Mechanism Driven by Several IDMs in Parallel

2012 ◽  
Vol 197 ◽  
pp. 55-59 ◽  
Author(s):  
Nan Jiang ◽  
Jun Biao Liu
Keyword(s):  
Degrees Of Freedom ◽  
Design Method ◽  
Piezo Actuator ◽  
Motion Mechanism ◽  
Spherical Motor ◽  
Drive Mechanism ◽  
Follow Up Study ◽  
Analysis Of Motion

As a kind of piezo actuator, impact drive mechanism (IDM) has advantages in precision machinery and instruments. Several IDMs are used in parallel to realize some motion mechanisms which have multi degrees of freedom (DOF). Two motion mechanisms are designed subsequently, and a spherical motor is designed and assembled in principle based on one of them. Experiment results reveal that this design method is feasible, but some problems exist, for example, vibration is serious. These problems should be solved in follow-up study.

Dimensional Design on the Six-Cable Driven Parallel Manipulator of FAST

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Xiaoqiang Tang ◽  
Rui Yao
Keyword(s):  
Radio Telescope ◽  
Parallel Manipulator ◽  
Optimization Design ◽  
Design Method ◽  
Guizhou Province ◽  
Large Span ◽  
Similarity Model ◽  
Dimensional Parameters ◽  
Set Up ◽  
Design Result

China is now building the world’s largest single dish radio telescope in Guizhou province, which is called Five-hundred meter Aperture Spherical radio Telescope (FAST). The main purpose of this paper is to present an effective dimensional design method on the six-cable driven parallel manipulator of FAST. Sensitivity design method is adopted for the six-cable driven parallel manipulator of FAST. Cable has the capability to bear tension but not compression, so that cable driven parallel manipulator may not be controlled as expected if tension of one cable is small or zero. Therefore, for dimensional design of the six-cable driven parallel manipulator, three functions to evaluate tension performance were proposed. The tension performance functions can reflect the uniformity of cable tension and controllability of the six-cable driven parallel manipulator. According to the sensitivity design method and tension performance evaluating functions, a set of optimized dimensional parameters is calculated for constructing the six-cable driven parallel manipulator of FAST. In order to verify the optimization design result, a similarity model of the six-cable driven parallel manipulator was set up in Beijing. A serial of experiments shows that tension performance of the six-cable driven parallel manipulator satisfies the system’s requirement. More importantly, it provides a theoretical reference for further study on dimensional design of a cable driven parallel manipulator with large span.

Systematic Synthesis and Applications of Novel Multi-Degree-of-Freedom Differential Systems

1992 ◽  
Author(s):  
Sridhar Kota ◽  
Srinivas Bidare
Keyword(s):  
Degrees Of Freedom ◽  
Building Blocks ◽  
Degree Of Freedom ◽  
Differential Systems ◽  
Practical Applications ◽  
Epicyclic Gear ◽  
Differential Mechanism ◽  
Long Time ◽  
Gear Trains ◽  
Drive Systems

Abstract A two-degree-of-freedom differential system has been known for a long time and is widely used in automotive drive systems. Although higher degree-of-freedom differential systems have been developed in the past based on the well-known standard differential, the number of degrees-of-freedom has been severely restricted to 2n. Using a standard differential mechanism and simple epicyclic gear trains as differential building blocks, we have developed novel whiffletree-like differential systems that can provide n-degrees of freedom, where n is any integer greater than two. Symbolic notation for representing these novel differentials is also presented. This paper presents a systematic method of deriving multi-degree-of-freedom differential systems, a three and four output differential systems and some of their practical applications.

Application of Tree Graph Method for Reducing the Total Time of Tool Changing in Milling and Boring Machine Tools

2013 ◽  
Vol 371 ◽  
pp. 431-435 ◽  
Author(s):  
Claudiu Obreja ◽  
Gheorghe Stan ◽  
Lucian Adrian Mihaila ◽  
Marius Pascu
Keyword(s):  
Machine Tools ◽  
Design Method ◽  
Machining Process ◽  
Cnc Machine Tools ◽  
Tree Graph ◽  
Cnc Machine ◽  
High Productivity ◽  
Automatic Tool Changer ◽  
Automatic Tool ◽  
Set Up

With a view of increasing the productivity on CNC machine tools one of the main solution is to reduce, as much as possible, the auxiliary time consumed with the set-up and replacement of the tools and work pieces engaged in the machining process. Reducing the total time of the tool changing process by the automatic tool changer system can be also achieved through minimizing the number of movements needed for the actual exchange of the tool, from the tool magazine to the machine spindle (the optimization of the tool changing sequences). This paper presents a new design method based on the tree-graph theory. We consider an existing automatic tool changing system, mounted on the milling and boring machining centre, and by applying the new method we obtain all the possible configurations to minimize the tool changing sequence of the automatic tool changer system. By making use of the method proposed we obtain the tool changing sequences with minimum necessary movements needed to exchange the tool. Reconfiguring an existing machine tool provided with an automatic tool changer system by making use of the proposed method leads to obtaining the smallest changing time and thus high productivity.

LOWER LIMB REHABILITATION ROBOT FOR GAIT TRAINING

2014 ◽  
Vol 14 (06) ◽  
pp. 1440004 ◽  
Author(s):  
SHUAI GUO ◽  
JIANCHENG JI ◽  
GUANGWEI MA ◽  
TAO SONG ◽  
JING WANG
Keyword(s):  
Lower Limb ◽  
Degrees Of Freedom ◽  
Balance Training ◽  
Gait Training ◽  
Rehabilitation Robot ◽  
Stroke Patients ◽  
Motion Characteristics ◽  
Set Up ◽  
Limb Rehabilitation ◽  
Lower Limb Rehabilitation

After analyzing the rehabilitation needs of stroke patients and the previous studies on lower limb rehabilitation robot, our lower limb rehabilitation robot is designed for stroke patients' gait and balance training. The robot consists of the mobile chassis, the support column and the pelvis mechanism and it is described in detail. As the pelvis mechanism allows most of the patient's motion degrees of freedom (DOFs), the kinematics model of the mechanism is set up, and kinematics simulation is carried out to study the motion characteristics of the mechanism. After analyzing the calculation and simulation results, the pelvis mechanism is proven to measure up to the movement needs of the paralytic's waist and pelvis in walking rehabilitation process.

scholarly journals Study on Mix Proportion Optimization of Manufactured Sand RPC and Design Method of Steel Fiber Content under Different Curing Methods

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1845 ◽  
Author(s):  
Chunling Zhong ◽  
Mo Liu ◽  
Yunlong Zhang ◽  
Jing Wang
Keyword(s):  
Steel Fiber ◽  
Design Method ◽  
Fiber Content ◽  
Orthogonal Experimental Design ◽  
Curing Conditions ◽  
Practical Applications ◽  
Manufactured Sand ◽  
Binder Ratio ◽  
Curing Methods ◽  
Reactive Powder

This study investigated four factors (water/binder ratio, silica fume, fly ash, and sand/binder ratio) using the orthogonal experimental design method to prepare the mix proportions of a manufactured sand reactive powder concrete (RPC) matrix to determine the optimal matrix mix proportions. On this basis, we assessed the compressive and splitting tensile strengths of different steel fiber contents under natural, standard, and compound curing conditions to develop an economical and reasonable RPC for various engineering requirements. A calculation method for the RPC strength of the steel fiber contents was evaluated. The results showed that the optimum steel fiber content for manufactured sand RPC is 4% under natural, standard, and compound curing conditions. Compared with standard curing, compound curing can improve the early strength of manufactured sand RPC but only has a small effect on the enhancement of late strength. Although the strength of natural curing is slightly lower than that of standard curing, it basically meets project requirements and is beneficial for practical applications. The calculation formula of 28-day compressive and splitting tensile strengths of manufactured sand RPC steel fiber at 0%–4% is proposed to meet the different engineering requirements and the flexible selection of steel fiber content.

An investigation of the propositional calculus used in a particular system of logic

1954 ◽  
Vol 50 (4) ◽  
pp. 495-512 ◽  
Author(s):  
R. Harrop
Keyword(s):  
Decision Problem ◽  
Propositional Calculus ◽  
Alternative Form ◽  
Original Form ◽  
Free Logic ◽  
Complete Model ◽  
Model Reference ◽  
Proper Extension ◽  
Set Up

This paper contains a summary of some of the results obtained by the author during a study of the propositional part (denoted by A) of a system of free-from-contradiction, type-free logic set up in 1950 by Ackermann (1). It is shown that in its original form the calculus does not possess the desired properties with respect to equivalence of formulae. A calculus A′, which it is shown may be considered as a ‘minimal’ satisfactory extension of A, is constructed. A′ is compared and contrasted with an alternative form A″ of A given by Ackermann in a paper published in 1952 (2). It is proved that A″ is a proper extension of A′. Among the properties of A′ and A″ which are obtained is the resuit that neither calculus possesses a finite complete model. Reference is made to the solution of the decision problem for A, and it is indicated that it is thought that the corresponding problems can probably be solved for A′ and A″. The proofs of many of the results mentioned in the paper are, if given in detail, rather long. In such cases, from space considerations, only outline proofs are given. Complete proofs are contained in (5), which reference also contains several additional properties of the calculi considered.

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