scholarly journals Analysis and control of state jump in space deployable structures under alternating temperature loads

2021 ◽  
Vol 12 (1) ◽  
pp. 59-67
Author(s):  
Congcong Chen ◽  
Tuanjie Li ◽  
Yaqiong Tang ◽  
Zuowei Wang
Keyword(s):  
Influence Factors ◽  
Stable State ◽  
Variable Stiffness ◽  
Equivalent Model ◽  
Deployable Structures ◽  
Deployable Structure ◽  
Structure Changes ◽  
Alternating Temperature ◽  
Space Deployable Structures ◽  
And Control

Abstract. State jump has been experimentally observed in space deployable structures working in alternating temperature environments. State jump is a phenomenon in which the geometric shape of the structure changes after the temperature loading and unloading process, which makes the working accuracy of the space deployable structure intrinsically unpredictable. This paper aims to investigate the causes of this state jump phenomenon and seek measures to reduce its effect. Firstly, the static multiple-stable-state phenomenon resulting in state jump is analyzed for clearance joints in deployable structures. Then, an equivalent model consisting of a variable stiffness spring and a contact element for state jump analysis is proposed, which is verified by a finite element simulation. Influence factors and control methods of state jump are further explored. Finally, numerical results of a space deployable structure of an umbrella-shaped antenna show the effectiveness of the developed analytical method.

Dynamics of Space Deployable Structures

2015 ◽  
Author(s):  
Qiang Tian ◽  
Jiang Zhao ◽  
Cheng Liu ◽  
Chunyan Zhou ◽  
Haiyan Hu
Keyword(s):  
Equations Of Motion ◽  
Scientific Basis ◽  
Advanced Technology ◽  
Space Structures ◽  
Deployable Structures ◽  
Large Space ◽  
Modeling Analysis ◽  
High Efficient ◽  
Space Deployable Structures ◽  
And Control

The space industry is eager to have the advanced technology of large space structures composed of trusses, cables and meshes. These space structures will deploy on orbit for different space missions. The important scientific basis of the technology is the nonlinear dynamic modeling, analysis and control of those space structures during their deployment and service. In this study, many space deployable structures (such as satellites antenna and spinning solar sail) are described by using the absolute nodal coordinate formulation (ANCF), and the huge set of equations of motion are solve by high efficient parallel generalized-alpha method. Some numerical results are also validated by experiment results.

scholarly journals Research on influence factors and control methods of backfill compactness

2021 ◽  
Vol 787 (1) ◽  
pp. 012027
Author(s):  
Yudian Li ◽  
Jiajie Dong ◽  
Kai Fei ◽  
Hao Song ◽  
Zeyi Li ◽  
...  
Keyword(s):  
Influence Factors ◽  
Control Methods ◽  
And Control

Study on Dynamic Accuracy of CNC in Aviation Part

2011 ◽  
Vol 314-316 ◽  
pp. 1717-1720
Author(s):  
Li Du ◽  
Wei Wang ◽  
Zhi Yong Song ◽  
Jie Xiong Ding
Keyword(s):  
High Speed ◽  
Influence Factors ◽  
Maximum Error ◽  
Error Sources ◽  
Dynamic Accuracy ◽  
Cutting Test ◽  
Manufacture Process ◽  
Shape Precision ◽  
Dynamic Errors ◽  
And Control

Thin-walled parts are widely used in aerospace engineering. For their complexity under loading and the higher shape precision, it’s difficult for their manufacturing on high speed machine. In order to understand manufacture process, characteristic of aviation part in high speed machining is investigated. Error sources on parts are classified and the maximum error, dynamic errors are studied on its main influence factors, such as cutting force and vibration. Finally, useful method on cutting test part is proposed, which can observe and control dynamic accuracy of aviation part and ensure effective manufacture.

scholarly journals Simultaneous position and stiffness control of a revolute joint using a biphasic media variable stiffness actuator

2019 ◽  
Vol 1 (2) ◽  
pp. 80-97
Author(s):  
Jesus H Lugo
Keyword(s):  
Control Method ◽  
Variable Stiffness ◽  
Industrial Processes ◽  
Revolute Joint ◽  
Additional Information ◽  
Physical Prototype ◽  
Stiffness Control ◽  
Variable Stiffness Actuator ◽  
Control Fluid ◽  
And Control

Safe interactions between humans and robots are needed in several industrial processes and service tasks. Compliance design and control of mechanisms is a way to increase safety. This article presents a compliant revolute joint mechanism using a biphasic media variable stiffness actuator. The actuator has a member configured to transmit motion that is connected to a fluidic circuit, into which a biphasic control fluid circulates. Stiffness is controlled by changing pressure of control fluid into distribution lines. A mathematical model of the actuator is presented, a model-based control method is implemented to track the desired position and stiffness, and equations relating to the dynamics of the mechanism are provided. Results from force loaded and unloaded simulations and experiments with a physical prototype are discussed. The additional information covers a detailed description of the system and its physical implementation.

scholarly journals The effect of sludge retention time (SRT) on the Nitrifier typical kinetics at ambient temperature under the low ammonia density

2021 ◽  
Author(s):  
Yifan Li ◽  
Jinzhu Wu ◽  
Yongjie Liu ◽  
Feiyong Chen ◽  
Jie Guan ◽  
...  
Keyword(s):  
Growth Rate ◽  
Ambient Temperature ◽  
Retention Time ◽  
Stable State ◽  
Species Structure ◽  
Maximum Reaction Rate ◽  
Sludge Retention Time ◽  
Structure Changes ◽  
Nitrification Process ◽  
D 20

Abstract Sludge retention time (SRT) regulation is one of the essential management techniques for refined control of the main-sidestream treatment process under the low ammonia density. It is indispensable to understand the effect of SRTs changes on the Nitrifier kinetics to obtain the functional separation of the Nitrifier and the refined control of the nitrification process. In this study, Nitrifier was cultured with conditions of 35 ± 0.5 °C, pH 7.5 ± 0.2, DO 5.0 ± 0.5 mg-O/L, and SRTs was controlled for 40 d, 20 d, 10 d, and 5 d. The net growth rate (), decay rate (), specific growth rate (), the yield of the Nitrifier (), temperature parameter (), and inhibition coefficient () have been measured and extended with the SRT decreases. Instead, the half-saturation coefficient () decreased. In addition, the limited value of pH inhibition occurs (), and the pH of keeping 5% maximum reaction rate () was in a relatively stable state. The trade of kinetics may be induced by the species structure of Nitrifier changed. The Nitrosomonas proportion was increased, and the Nitrospira used to be contrary with the SRT decreasing. It is a match for the functional separation of Nitrifier when SRTs was 20 d at ambient temperature under the low ammonia density. The kinetics of ammonia-oxidizing organism (AOO) and nitrite-oxidizing organism (NOO) in Nitrifier under different SRT conditions should be measured respectively to the refined control of the partial nitrification process in the future study. HIGHLIGHT The Nitrifier typical kinetics used to be affected notably by way of SRTs changes. The species structure of the Nitrifier was recognized beneath distinctive SRTs. The change of Nitrifier kinetics with SRTs used to be estimated by the species structure changes.

Germination, Growth, Development, and Control of Galinsoga

Weed Science ◽  
1973 ◽  
Vol 21 (1) ◽  
pp. 41-45 ◽  
Author(s):  
J. A. Ivany ◽  
R. D. Sweet
Keyword(s):  
New York ◽  
New York State ◽  
Main Axis ◽  
Fresh Weight ◽  
York State ◽  
Total Percentage ◽  
Growth Development ◽  
Alternating Temperature ◽  
And Control ◽  
Galinsoga Ciliata

Hairy galinsoga [Galinsoga ciliata (Raf.) Blake] and smallflower galinsoga [G. parviflora Cav.] are widespread weeds in New York State. Freshly harvested achenes (seed) are not dormant and germinate in the field from early May until frost. Rate of germination but not final total percentage was stimulated by alternating temperature, with the fastest rate being at 30 C day and 20 C night and with a 16-hr photoperiod and 11,000 lux of light. Some seed in each seed-lot required light for germination. Both species were day-neutral with respect to flowering. Smallflower galinsoga produced its first flower after node seven and hairy galinsoga after node six on the main axis 6 to 8 weeks after germination. Decreasing light intensity 83% decreased fresh weight.

Analysis and Control of Layer Deformation Induced by the Densely Arranged Large Diameter Underground Steel Tubes Jacking with NTR Method

2015 ◽  
Vol 744-746 ◽  
pp. 1010-1014
Author(s):  
Chun Fu Jin ◽  
Peng Niu ◽  
Yong Sheng Zhao ◽  
Xuan Wang
Keyword(s):  
Surface Deformation ◽  
Large Diameter ◽  
Influence Factors ◽  
Surface Subsidence ◽  
The Finite Element Method ◽  
Steel Tubes ◽  
Steel Pipes ◽  
Pipe Jacking ◽  
And Control ◽  
Layer Deformation

Combined with the finite element method (FEM) and the field data of Shenyang Metro NTR engineering for pipe jacking process, the variation of surface deformation and influence factors of NTR construction are systematically analyzed. The result is shown that the curves of the lateral surface subsidence produced by pipe jacking process are accord with the normal distribution curves put forward by Peck .When the top steel pipes are jacked , the surface subsidence develops rapidly and the rate of deformation is larger. In addition , grouting behind the wall and the sequence of the pipe jacking all have a greater impact on the deformation of the layer.

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