scholarly journals Dynamic Modeling and Analysis of Impact in Space Operation Tasks

Aerospace ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 381
Author(s):  
Yaxing Cai ◽  
Yujun Chen ◽  
Yazhong Luo ◽  
Xinglong Wang
Keyword(s):  
Dynamic Model ◽  
Dynamic Models ◽  
Wire Rope ◽  
Rigid Bodies ◽  
Modeling And Analysis ◽  
Flow Table ◽  
Model Foundation ◽  
Flexible Wire ◽  
The Impact ◽  
Space Operation

For the rigid impact and flexible impact in space operation tasks, impact dynamic models between two objects are established in this paper, laying the model foundation for controlling or suppressing the impact. For the capture task between a grapple shaft and a rigid body, the impact dynamic model is established based on the Zhiying–Qishao model. Moreover, by introducing a friction factor into the original impact model, an improved dynamic model between two rigid bodies is proposed. For the capture task with flexible impact, an impact dynamic model between the grapple shaft and a flexible wire rope is established based on the dynamic model of the flexible wire rope. The ground experiments and simulations are carried out with two objects on an air flow table. The experiment results validate the impact dynamic model proposed in this paper.

Co-Simulation Procedure for Multibody Reeving Systems

2018 ◽  
Author(s):  
Grzegorz Orzechowski ◽  
Aki M. Mikkola ◽  
José L. Escalona
Keyword(s):  
Multibody System ◽  
Wire Rope ◽  
Rigid Bodies ◽  
Arbitrary Lagrangian Eulerian ◽  
Transverse Deformation ◽  
Absolute Position ◽  
Eulerian Approach ◽  
Wire Ropes ◽  
Simulation Procedure ◽  
Flexible Wire

In this paper, co-simulation procedure for a multibody system that includes reeving mechanism will be introduced. The multibody system under investigation is assumed to have a set of rigid bodies connected by flexible wire ropes using a set of sheaves and reels. In the co-simulation procedure, a wire rope is described using a combination of absolute position coordinates, relative transverse deformation coordinates and longitudinal material coordinates. Accordingly, each wire rope span is modeled using a single two-noded element by employing an Arbitrary Lagrangian-Eulerian approach.

Pseudo-rigid-body dynamic modeling and analysis of compliant mechanisms

2017 ◽  
Vol 232 (9) ◽  
pp. 1665-1678 ◽  
Author(s):  
Yue-Qing Yu ◽  
Qian Li ◽  
Qi-Ping Xu
Keyword(s):  
Rigid Body ◽  
Dynamic Model ◽  
Dynamic Modeling ◽  
Dynamic Models ◽  
Compliant Mechanisms ◽  
Lagrange Equation ◽  
Dynamic Responses ◽  
Modeling And Analysis ◽  
Rigid Body Dynamic ◽  
Body Dynamic

An intensive study on the dynamic modeling and analysis of compliant mechanisms is presented in this paper based on the pseudo-rigid-body model. The pseudo-rigid-body dynamic model with single degree-of-freedom is proposed at first and the dynamic equation of the 1R pseudo-rigid-body dynamic model for a flexural beam is presented briefly. The pseudo-rigid-body dynamic models with multi-degrees-of-freedom are then derived in detail. The dynamic equations of the 2R pseudo-rigid-body dynamic model and 3R pseudo-rigid-body dynamic model for the flexural beams are obtained using Lagrange equation. Numerical investigations on the natural frequencies and dynamic responses of the three pseudo-rigid-body dynamic models are made. The effectiveness and superiority of the pseudo-rigid-body dynamic model has been shown by comparing with the finite element analysis method. An example of a compliant parallel-guiding mechanism is presented to investigate the dynamic behavior of the mechanism using the 2R pseudo-rigid-body dynamic model.

scholarly journals Price development on fluid milk processing market and level of final consumer demand for this product

2004 ◽  
Vol 52 (3) ◽  
pp. 59-68 ◽  
Author(s):  
Pavel Syrovátka
Keyword(s):  
Dynamic Model ◽  
Demand Function ◽  
Dynamic Models ◽  
Consumer Demand ◽  
Time Lag ◽  
Price Development ◽  
Milk Processing ◽  
The Impact ◽  
Final Consumer ◽  
Fluid Milk

The article is focused on the analysis of impact of the final consumer for milk on the price development on the fluid milk processing market. The impact research was based on the dynamic model of intermediate demand function in inverse form. There were examined two approaches for the dynamisation of developed models – the implicit and explicit approach. Implicit dynamic model, which was developed on the base of linear inverse demand function with time lag explanatory variable, wasn’t acceptable in the view of the achieved results of statistical and economical verification. According to this developed model, the quarterly lag in the examined vertical demand linkage did not play statistically significant role. Among explicit dynamic models, the best model with respect to results of T-test of B2 parameter got the following form:pt = +18.8854 – 0.8636 · qt* + 0.1783 · t – 2.7336 · 10–3 · t2; (t = 1, 2, ..., 32).This developed model with the explicit dynamisation fit theoretical economical condition of Law of diminishing demand and its transmission in the researched section of the product vertical – milk. The intensity of the impact of final consumer demand for milk on the price development on the market for fluid milk processing was evaluated on the base of value of B2 and on base of elasticity coefficient FPt(qt*). In view of B2, the rise of the consumer demand for milk by 1 litre implied the decrease in the prices of litre of milk on the market for fluid milk processing approximately by 0.90 CZK. According to FPt(qt*), the increase of the consumer demand for milk by 1 % bring out in average the fall of the prices per litre of milk on the fluid milk processing market by almost 0.60 %.

scholarly journals Is modelling complexity always needed? Insights from modelling PrEP introduction in South Africa

2020 ◽  
Vol 42 (4) ◽  
pp. e551-e560 ◽  
Author(s):  
Hannah Grant ◽  
Anna M Foss ◽  
Charlotte Watts ◽  
Graham F Medley ◽  
Zindoga Mukandavire
Keyword(s):  
South Africa ◽  
Condom Use ◽  
Dynamic Model ◽  
Hiv Risk ◽  
Dynamic Models ◽  
Static Model ◽  
Hiv Intervention ◽  
Time Horizons ◽  
Static Models ◽  
The Impact

Abstract Background Mathematical models can be powerful policymaking tools. Simple, static models are user-friendly for policymakers. More complex, dynamic models account for time-dependent changes but are complicated to understand and produce. Under which conditions are static models adequate? We compare static and dynamic model predictions of whether behavioural disinhibition could undermine the impact of HIV pre-exposure prophylaxis (PrEP) provision to female sex workers in South Africa. Methods A static model of HIV risk was developed and adapted into a dynamic model. Both models were used to estimate the possible reduction in condom use, following PrEP introduction, without increasing HIV risk. The results were compared over a 20-year time horizon, in two contexts: at epidemic equilibrium and during an increasing epidemic. Results Over time horizons of up to 5 years, the models are consistent. Over longer timeframes, the static model overstates the tolerated reduction in condom use where initial condom use is reasonably high ($\ge$50%) and/or PrEP effectiveness is low ($\le$45%), especially during an increasing epidemic. Conclusions Static models can provide useful deductions to guide policymaking around the introduction of a new HIV intervention over short–medium time horizons of up to 5 years. Over longer timeframes, static models may not sufficiently emphasise situations of programmatic importance, especially where underlying epidemics are still increasing.

Dynamic Modeling and Analysis of an Origami-Inspired Optical Shield for the Starshade Spacecraft

2016 ◽  
Author(s):  
Landen Bowen ◽  
Brian Trease ◽  
Mary Frecker ◽  
Timothy Simpson
Keyword(s):  
Dynamic Model ◽  
Dynamic Models ◽  
Joint Stiffness ◽  
Design Requirement ◽  
Deployable Structures ◽  
Design Decisions ◽  
Modeling And Analysis ◽  
Critical Design ◽  
Joint Forces ◽  
Shield Design

The Starshade is a future exoplanet discovery mission consisting of a satellite and a 34 meter diameter starshade used to block the light of a star of interest, enhancing visualization of the orbiting planets. The starshade itself is composed of a number of 7 meter long petals surrounding a 20 meter diameter optical shield. A critical design requirement of the optical shield is stowage in a 3 meter diameter area during launch. Origami has been investigated as a means of collapsing the optical shield, specifically a family of action origami models known as “flashers.” In this paper a dynamic model of an optical shield design candidate based on a flasher pattern is created in Adams 2014. As these patterns can have many parts and joints, a method for the automatic creation of dynamic models using information about the geometry of the crease pattern is utilized. As the fabricated optical shield panels will be somewhat flexible, each quadrilateral panel is modeled as two rigid triangles connected with a joint. The effect of joint stiffness on the forces and torques developed during deployment is investigated. It is found that the optical shield design is rigid foldable if the panel flexibility is taken into account by additional joints, which are found to bend from 10° – 40°. Joint forces are predicted over the deployment, and maximum and average joint forces are tabulated. These and other insights gained from the dynamic model can help guide future Starshade design decisions, and similar analyses can be performed for other origami-inspired deployable structures.

Dynamic modeling and simulation of impact in hydraulic cylinders

2020 ◽  
pp. 095440622098047
Author(s):  
Osama Gad
Keyword(s):  
Contact Force ◽  
Dynamic Models ◽  
Maxwell Model ◽  
Hydraulic Cylinder ◽  
Rigid Bodies ◽  
Solid Model ◽  
Contact Period ◽  
Suitable Model ◽  
Hydraulic Cylinders ◽  
The Impact

In this paper, modeling impact dynamics of a piston and its cylinder body in a hydraulic cylinder is investigated. The studied system consists of two identical hydraulic cylinders controlled by a pressure sequence valve. The impact is assumed as a linear one dimensional and purely translational viscoelastic impact of rigid bodies. Four impact models, the Kelvin-Voigt, the Maxwell, the standard-solid, and the Hunt-Crossley, are considered. Measurements of the transient variations of the cylinders operating pressures and both pistons strokes, at different loading conditions, are conducted. A comprehensive dynamic model of the studied system, considering the four models, is deduced. The Kelvin-Voigt model produced tensile forces by the end of the contact period and it resulted in discontinuities in the contact force during its steady state period. Both results are physically impossible in rigid bodies impacting. In the Maxwell model, large amount of discontinuities appeared in the contact force, which causes the piston to make an infinite number of rebounds during the contact period. In the standard-solid model, the discontinuities in the contact force were found to be much less than those of the Maxwell model. As a result, when the impact occurs, the cylinder pressure gets an overshoot accompanied with large oscillations when the Maxwell model is applied, however, these oscillations do not approximately appear when the standard-solid model is applied. The simulation results showed also that the Hunt-Crossley nonlinear model presented very high penetration depth, which is certainly unrealistic in rigid bodies impacting. The validation of the proposed dynamic models showed that the standard-solid is the most suitable model that may represent the impact in the studied cylinders.

Modeling of impact of the poppet element on its seat body in pressure relief valves

2020 ◽  
pp. 095965182094547
Author(s):  
Osama Gad
Keyword(s):  
Dynamic Model ◽  
Tensile Force ◽  
Dynamic Performance ◽  
Maxwell Model ◽  
Rigid Bodies ◽  
Operating Pressure ◽  
Pressure Relief ◽  
Pressure Relief Valves ◽  
The Impact ◽  
Impact Models

This article deals with modeling of the impact between the moving elements and their seats bodies in pressure relief valves. Four different impact models, such as the Kelvin–Voigt, the Maxwell, the standard-solid and the Hunt–Crossley models, are considered. A comprehensive dynamic model of the studied valve, considering the four models, is deduced. The simulation results show that the Kelvin–Voigt model cannot be used to represent the impact in pressure relief valves because, by the end of impact period, the model results in a tensile force, which is physically impossible in rigid bodies impacting. In the Maxwell model, a considerable number of discontinuities appeared in the impact force, which causes the poppet element to make a number of rebounds with the seat body during the impact period. However, in the standard-solid model, the poppet element barely rebounds. In the Hunt–Crossley nonlinear model, a certain penetration distance between the poppet element and the seat body occurs, which is certainly unrealistic in rigid bodies impacting. The validation of the impact models showed that the Maxwell model is the suitable impact model that can be used to represent the impact in pressure relief valves. However, the validation of the proposed dynamic model proved that the impact has no significant effect on the dynamic performance of pressure relief valves. The main reason behind this is that the impact occurs when the operating pressure has fallen down (the valve is out of operation).

Monetary policy and the effect of the transfer of oil prices to inflation

2020 ◽  
pp. 41-50
Author(s):  
Ph. S. Kartaev ◽  
I. D. Medvedev
Keyword(s):  
Monetary Policy ◽  
Inflation Targeting ◽  
Dynamic Models ◽  
Oil Prices ◽  
Oil Price ◽  
Oil Price Shocks ◽  
Negative Effects ◽  
Price Shocks ◽  
Policy Regime ◽  
The Impact

The paper examines the impact of oil price shocks on inflation, as well as the impact of the choice of the monetary policy regime on the strength of this influence. We used dynamic models on panel data for the countries of the world for the period from 2000 to 2017. It is shown that mainly the impact of changes in oil prices on inflation is carried out through the channel of exchange rate. The paper demonstrates the influence of the transition to inflation targeting on the nature of the relationship between oil price shocks and inflation. This effect is asymmetrical: during periods of rising oil prices, inflation targeting reduces the effect of the transfer of oil prices, limiting negative effects of shock. During periods of decline in oil prices, this monetary policy regime, in contrast, contributes to a stronger transfer, helping to reduce inflation.

332-OR: Determining the Impact of Additional Macronutrients on the Glycemic-Insulin Dynamic Model

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 332-OR
Author(s):  
BOYI JIANG ◽  
YUXIANG ZHONG ◽  
PRATIK AGRAWAL ◽  
TONI L. CORDERO ◽  
ROBERT VIGERSKY
Keyword(s):  
Dynamic Model ◽  
The Impact
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