On the Impedance of Statically-Balanced Mechanisms

2011 ◽  
Author(s):  
Qi Lu ◽  
Wenwu Xiu ◽  
Ou Ma
Keyword(s):  
Dynamic Effect ◽  
Gravity Force ◽  
Mechanical Resistance ◽  
Zero Gravity ◽  
Reduced Gravity ◽  
Simulation Fidelity ◽  
Input Motion ◽  
Optimal Set ◽  
Inertia Forces ◽  
Impedance Property

Statically-balanced technology is often used to compensate partial or full gravity force exerting on a mechanism in order to reduce the effort of driving the mechanism. Since such compensation is static, when a statically-balanced mechanism is used for dynamic applications, it will still have impedance (mechanical resistance to input motion) because the mechanism still subjects to the inertia forces although the gravity force has been compensated. Such a dynamic effect is undesirable for many applications, especially for those required to physically interact with humans and hence, the impedance property needs to be fully understood and possibly minimized in the design and/or operation of a statically-balanced mechanism. This paper studies the impedance property of passive statically-balanced mechanisms. Based on the study result, optimization strategies are proposed in order to optimize the operation of a statically-balanced mechanism. The strategies are then applied to a spring-based reduced-gravity simulation mechanism to figure out an optimal set of configurations in the workspace where the mechanism has the lowest impedance and the highest zero-gravity simulation fidelity.

scholarly journals EMBODIED CARBON EFFICIENT INDUSTRIAL BUILDINGS WITH OPTIMIZED LONG SPAN SANDWICH PANELS

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Martin D. Heywood ◽  
Dimitrios Moutaftsis ◽  
Raymond G. Ogden
Keyword(s):  
Sandwich Panels ◽  
Structural Testing ◽  
Mechanical Resistance ◽  
Long Span ◽  
Pareto Optimal Set ◽  
Embodied Carbon ◽  
Industrial Buildings ◽  
Portal Frame ◽  
Frame Construction ◽  
Optimal Set

A series of studies have been undertaken to quantify potential steelwork and embodied carbon savings in single-storey industrial buildings with long span sandwich panel roof cladding. It was found that trussed-roof frames with north lights offer the greatest potential steelwork saving (38%-60%) against traditional portal frame construction when used with long span panels. However, in order to achieve the necessary span between adjacent frames, the structural performance of the sandwich panels needed to be improved. A subsequent study was undertaken to develop revised specifications for long span roof sandwich panels to increase their spanning capability, while minimizing the increase in embodied carbon. The mechanical resistance of the panels was evaluated using a combination of theoretical analysis and structural testing and a Pareto-optimal set of solutions was found. Finally, the optimized structure-envelope assembly was reviewed holistically in terms of its embodied carbon. The results showed that savings of up to 7.3% may be achieved for the frame when compared against traditional portal frame construction.

The mechanism of bubble detachment from a wall at zero and negative gravity

1976 ◽  
Vol 77 (2) ◽  
pp. 313-320 ◽  
Author(s):  
G. Malcotsis
Keyword(s):  
Surface Tension ◽  
Vertical Wall ◽  
Two Dimensions ◽  
Gravity Force ◽  
Zero Gravity ◽  
Air Bubbles ◽  
Subcooled Boiling ◽  
Vapour Bubble ◽  
Approximate Representation ◽  
Bubble Detachment

An experiment has been carried out in which air bubbles were caused to grow isothermally at a vertical wall between two closely spaced horizontal plates. The experiment gives an approximate representation in two dimensions for the growth of a vapour bubble at a wall under some conditions of subcooled boiling in zero gravity. Although the effect of gravity was virtually eliminated in the experiment, it was found that a bubble could still detach itself from the wall, apparently owing to the effects of surface tension and inertia.Also, bubbles were seen to detach from a wall despite the presence of a slight gravity force directed to oppose such detachment.

Strength Capabilities While Performing Torquing Tasks in Weightlessness

1994 ◽  
Vol 38 (10) ◽  
pp. 593-596
Author(s):  
Jeff Poliner ◽  
Robert P. Wilmington ◽  
Glenn K. Klute
Keyword(s):  
Design Tool ◽  
Test Stand ◽  
Mission Planning ◽  
Zero Gravity ◽  
Tool Development ◽  
Reduced Gravity ◽  
Workplace Design ◽  
Maximum Torque ◽  
Male Volunteers ◽  
Total Effort

Knowledge of individuals' strength capabilities in weightlessness is of interest within many areas of NASA, including workplace design, tool development, and mission planning. This study was a generic examination of the loads produced by individuals performing maximal efforts with a torquing tool in zero-gravity. The study also examined the effects of orientation and direction of rotation of the tool on strength effectiveness. An experiment was conducted aboard NASA's reduced gravity aircraft which simulates brief periods of weightlessness. A test stand was developed and instrumented to measure the loads applied to fixed fittings. Eight male volunteers participated in this study in which they used a wrench to apply a maximum torque to fittings oriented along each of three orthogonal axes. It was seen that these subjects could produce approximately 400 to 750 N of force, depending on the orientation of the tool and the direction of effort. The most force could be produced when pushing the tool upwards. A force effectiveness ratio (FER) was defined as an indication of how much of the subject's total effort actually went into performing the desired task. Values of FER ranged from 0.55 to 0.90, with the greatest FER occurring with UP and DOWN efforts, and the lowest with AWAY and LEFT efforts. Designers can use these results to set specifications for craft structures; tools can be developed based on the known strength of the tool users; and tasks can be developed to not exceed the crewmembers' capabilities.

scholarly journals Zero-gravity wardrobes: The behaviour of costume in weightless environments

2020 ◽  
Vol 9 (1) ◽  
pp. 5-21
Author(s):  
Barbara Brownie
Keyword(s):  
Science Fiction ◽  
Real Life ◽  
Fashion Design ◽  
Music Video ◽  
Zero Gravity ◽  
Reduced Gravity ◽  
Special Effects ◽  
Clothing Design ◽  
Commercial Space ◽  
Inside Out

Abstract In this commercial space age, audiences increasingly expect realism in science fiction. Weightlessness is commonly simulated through physical or virtual special effects, but reduced gravity aircraft offer opportunities for capturing the effects of microgravity more authentically. While this poses practical challenges for costume designers, it also invites the possibility of creative engagement with weightlessness. Costume can be employed to visibly evidence the effects of weightlessness, but to take advantage of this opportunity, designers must discard many of the fundamental principles of fashion design. This article examines the effects of weightlessness on costume in sequences shot on board reduced gravity aircraft, from Apollo 13 (Howard, 1995), The Mummy (Kurtzman, 2017), and the music video for OK Go's 'Upside Down & Inside Out' (Kulash and Sie, 2016), as well as footage of real-life astronauts. It then identifies those features of clothing design which must be reconsidered when designing costume for microgravity.

Observation of the Sulphur Atoms in Cu2S Using HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 38-39
Author(s):  
Y.D. Yu ◽  
R. Guan ◽  
K.H. Kuo ◽  
H. Hashimoto
Keyword(s):  
Electron Diffraction ◽  
Tube Wall ◽  
Present Report ◽  
Dynamic Effect ◽  
Glass Tube ◽  
Fluorite Structure ◽  
Point Of View ◽  
Electron Diffraction Analysis ◽  
Sulphur Atom ◽  
Copper Thin Film

We have indicated that the lighter atoms such as oxygen in Cu2O can be observed at the specimen with optimal thicknesses based on the dynamic effect of electron diffraction(1). This rule in principle should hold good for the imaging of other lighter atoms such as sulphur atom in Cu2S. However, this point of view needs further experimentally confirm because up to now only oxygen atoms have been observed in Cu2O and a series of new suboxides of copper and nickel (2). In addition, the sulphur atom is much heavier than oxygen one though is still lighter than copper atom. In the present report we provide such a confirmation.The crystallites of Cu2S shown in Fig.l were obtained by sulfurizing at 300°C of the copper thin film which was sealed in a glass tube with mg sulphur left on the tube wall in a vacuum of about 10-2 Pa. The energy dispersive spectrocscopy analysis indicated that they are the sulfides and the electron diffraction analysis indicated they have anti-fluorite structure.

The limits of human performance

2008 ◽  
Vol 44 ◽  
pp. 11-26 ◽  
Author(s):  
Ralph Beneke ◽  
Dieter Böning
Keyword(s):  
Human Performance ◽  
Safety Margin ◽  
Afferent Input ◽  
Metabolic Energy ◽  
Human Organism ◽  
Mechanical Resistance ◽  
As Doping ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms ◽  
Biochemical Research

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

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