Rope Model Research Articles

Development of a higher-order model for a roll simulator

A four degree-of-freedom model of a roll simulator is developed. The roll simulator consists of a sled-platform assembly, where a recreational off-highway vehicle (ROV) is mounted to the platform which has the freedom to rotate up to 90 degrees. The purpose of the roll simulator is to re-create rollover manoeuvres ascertained from in-field vehicle dynamic experiments. Previous studies developed a two degree-of-freedom model; one for translational and one for rotational motion. This study expands on that model and increases the number of degrees-of-freedom to more closely emulate the roll simulator. The model incorporates non-linear stiffness models of the wire ropes and enables the model to have three translational degrees-of-freedom and one rotational degree- of-freedom. The equations of motion (EOM) are numerically simulated using Matlab’s Simulink. Comparisons are made with experimental data derived from the roll simulator to validate the model.

Magnetic fields in a limb flare on July 19, 2012

The magnetic field intensity in the limb solar flare of July 19, 2012, was measured by the Zeeman bisector splitting in the Hα line. An average magnetic field is established to attain 200 G at a measurement error of ±100 G in the top of a radiant flare loop at a height of about 40 Mm. The confinement of a strong magnetic field in the high coronal arcade at a relatively weak external field of the corona (about 1–2 G) is considered using a model of a force-free magnetic flux rope with a fine magnetic structure at a scale of about 300 km.

Geometrical Modeling of Steel Ropes

Abstract The paper deals with the mathematical geometric modeling of the ropes of circular cross- section. Such rope can be formed from strands of different shapes. There is considered steel rope made up of six strands, whose crosssection has oval, triangular or circular profil in this paper. The wires of these types of the strands are presented by parametric equations of the wire axis. The equations are implemented in the Pro/Engineer Wildfire V5 software for creating the geometrical model of the strand.

THE FORMATION AND ERUPTION OF SOLAR QUIESCENT PROMINENCES

Following the two-stage catastrophic flux rope model presented by Zhang et al., we investigate how magnetic flux emergence affects the formation and evolution of solar quiescent prominences. The magnetic properties of the flux rope are described with its toroidal magnetic flux per radian Phi(p) and poloidal flux Phi(phi), and Phi(p) is defined as the emerging strength (ES) of the magnetic flux. After the first catastrophe, the quiescent prominences are supported by the vertical current sheet and located in cavities below the curved transverse current sheet in the inner corona, for which both ES and Phi(phi) are in the certain ranges. We calculate the strength range as 0.25 < ES < 0.50 for the quadrupolar field, and obtain the equation Phi(p)Phi(phi) = const., that is, the relationship between Phi(p) and Phi(phi) of the emerging flux for which the quiescent prominences are formed in the inner corona. After the second catastrophe, the quiescent prominences would either fall down onto the solar surface or erupt as an important part of coronal mass ejections. During the eruption of the quiescent prominences, most of the magnetic energy in the flux rope is lost, and less than half of the energy loss of the rope is released in the form of Alfven waves. We argue that there would be two important conditions required for the formation and eruption of solar quiescent prominences, a complicated source region and emerging toroidal magnetic flux that exceeds a critical strength.

Numerical simulation of a climber’s fall

This newly developed program gives predictions of a climber's fall in two dimensional space. It numerically calculates all forces acting on the climber, the belayer, the rope and various fix points. Also it shows the movement of both the climber and the belayer, taking air drag, friction, deformation of the climber, real rope and belay device characteristics into account. By using a 3-parameter viscoelastic rope model the different behaviour of the rope for dynamic and static loading is correctly simulated. The rope parameters are calibrated using actual rope values which are commonly available from product data sheets of rope manufacturers. A new concept is introduced to describe the rope forces due to the friction at the 1st protection. The climber is modelled with 2-masses to describe the body deformation. An energy analysis shows in detail the significance of all present mechanisms to absorb the fall energy compared to all others.

A STUDY OF A FAILED CORONAL MASS EJECTION CORE ASSOCIATED WITH AN ASYMMETRIC FILAMENT ERUPTION

We present the multi-wavelength observations of asymmetric filament eruption, associated CME and coronal downflows on 2012 June 17-18 during 20:00-05:00 UT. We use SDO/AIA, STEREO-B/SECCHI observations to understand the filament eruption scenario and its kinematics. While LASCO C2 observations have been analyzed to study the kinematics of the CME and associated downflows. SDO/AIA limb observations show that the filament exhibits whipping like asymmetric eruption. STEREO/EUVI disk observations reveal a two ribbon flare underneath the south-eastern part of the filament that is most probably occurred due to reconnection process in the coronal magnetic field in the wake of the filament eruption. The whipping like filament eruption later gives a slow CME in which the leading edge and the core propagate respectively with the average speed of $\approx$ 540 km s$^{-1}$ and $\approx$ 126 km s$^{-1}$ as observed in the LASCO C2 coronagraph. The CME core formed by the eruptive flux-rope shows the outer coronal downflows with the average speed of $\approx$ 56 km s$^{-1}$ after reaching up to $\approx$4.33 $R_{\sun}$. Initially, the core decelerates with $\approx$ 48 m s$^{-2}$. The plasma first decelerates gradually up to the height of $\approx$4.33 $ R_{\sun}$ and then starts accelerating downward. We suggest a self-consistent model of a magnetic flux rope representing the magnetic structure of the CME core formed by eruptive filament that lost its previous stable equilibrium when reach at a critical height. With some reasonable parameters, and inherent physical conditions the model describes the non-radial ascending motion of the flux rope in the corona, its stopping at some height, and thereafter the downward motion, which are in good agreement with the observations.

The Formation of a Cavity in a 3D Flux Rope

AbstractThere are currently no three dimensional numerical models which describe the magnetic and energetic formation of prominences self-consistently. Consequently, there has not been significant progress made in understanding the connection between the dense prominence plasma and the coronal cavity. We have taken an ad-hoc approach to understanding the energetic implications of the magnetic models of prominence structure. We extract one dimensional magnetic field lines from a 3D MHD model of a flux rope and solve for hydrostatic balance along these field lines incorporating field-aligned thermal conduction, uniform heating, and radiative losses. The 1D hydrostatic solutions for density and temperature are then mapped back into three dimensional space, which allows us to consider the projection of multiple structures. We find that the 3D flux rope is composed of several distinct field line types. A majority of the flux rope interior field lines are twisted but not dipped. These field lines are density-reduced relative to unsheared arcade field lines. We suggest the cavity may form along these short interior field lines which are surrounded by a sheath of dipped field lines. This geometric arrangement would create a cavity on top of a prominence, but the two structures would not share field lines or plasma.

Axis and velocity determination for quasi two‐dimensional plasma/field structures from Faraday's law: A second look

[1] We re-examine the basic premises of a single-spacecraft data analysis method, developed by Sonnerup and Hasegawa (2005), for determining the axis orientation and proper frame velocity of quasi two-dimensional, quasi-steady structures of magnetic field and plasma. The method, which is based on Faraday's law, makes use of magnetic and electric field data measured by a single spacecraft traversing the structure, although in many circumstances the convection electric field, − v × B, can serve as a proxy for E. It has been used with success for flux ropes observed at the magnetopause but has usually failed to provide acceptable results when applied to real space data from reconnection events as well as to virtual data from numerical MHD simulations of such events. In the present paper, the reasons for these shortcomings are identified, analyzed, and discussed in detail. Certain basic properties of the method are presented in the form of five theorems, the last of which makes use of singular value decomposition to treat the special case where the magnetic variance matrix is non-invertible. These theorems are illustrated using data from analytical models of flux ropes and also from MHD simulations as well as a 2-D kinetic simulation of reconnection. The results make clear that the method requires the presence of a significant, non-removable electric field distribution in the plane transverse to the invariant direction and that it is sensitive to deviations from strict two-dimensionality and strict time stationarity.

Multi-thermal dynamics and energetics of a coronal mass ejection in the low solar atmosphere

The aim of this work is to determine the multi-thermal characteristics and plasma energetics of an eruptive plasmoid and occulted flare observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). We study an event from 03-Nov-2010 (peaking at 12:20UT in GOES soft X-rays) of a coronal mass ejection and occulted flare which demonstrates the morphology of a classic erupting flux rope. The high spatial, and time resolution, and six coronal channels, of the SDO/AIA images allows the dynamics of the multi-thermal emission during the initial phases of eruption to be studied in detail. The Differential Emission Measure (DEM) is calculated, using an optimised version of a regularized inversion method (Hannah & Kontar 2012), for each pixel across the six channels at different times, resulting in emission measure maps and movies in a variety of temperature ranges. We find that the core of the erupting plasmoid is hot (8-11, 11-14MK) with a similarly hot filamentary "stem" structure connecting it to the lower atmosphere, which could be interpreted as the current sheet in the flux rope model, though is wider than these models suggest. The velocity of the leading edge of the eruption is 597-664 km s$^{-1}$ in the temperature range $\ge$3-4MK and between 1029-1246 km s$^{-1}$ for $\le$2-3MK. We estimate the density (in 11-14 MK) of the erupting core and stem during the impulsive phase to be about $3\times10^9$ cm$^{-3}$, $6\times10^9$ cm$^{-3}$, $9\times10^8$ cm$^{-3}$ in the plasmoid core, stem and surrounding envelope of material. This gives thermal energy estimates of $5\times10^{29}$ erg, $1\times10^{29}$ erg and $2\times10^{30}$ erg. The kinetic energy for the core and envelope is slightly smaller. The thermal energy of the core and current sheet grows during the eruption, suggesting continuous influx of energy presumably via reconnection.

Hydrogel fibers for ACL prosthesis: Design and mechanical evaluation of PVA and PVA/UHMWPE fiber constructs

Prosthetic devices for anterior cruciate ligament (ACL) reconstruction have been unsuccessful due to mechanical failure or chronic inflammation. Polymer hydrogels combine biocompatibility and unique low friction properties; however, their prior use for ligament reconstruction has been restricted to coatings due to insufficient tensile mechanics. Here, we investigate new constructs of polyvinyl alcohol (PVA) hydrogel fibers. In water, these fibers swell to an equilibrium water content of 50% by weight, retaining a tensile modulus greater than 40MPa along the fiber axis at low strain. Rope constructs were assembled for ACL replacement and mechanical properties were compared with data from the literature. Pure PVA hydrogel constructs closely reproduce the non-linear tensile stiffness of the native ACL with an ultimate strength of about 2000N. An additional safety factor in tensile strength was achieved with composite braids by adding ultrahigh molecular weight polyethylene (UHMWPE) fibers around a core of PVA cords. Composition and braiding angle are adjusted to produce a non-linear tensile behavior within the range of the native ligament that can be predicted by a simple rope model. This design was found to sustain over one million cycles between 50 and 450N with limited damage and less than 20% creep. The promising mechanical performances of these systems provide justification for more extensive in vivo evaluation.

Advancing in situ modeling of ICMEs: New techniques for new observations

It is generally known that multispacecraft observations of interplanetary coronal mass ejections (ICMEs) are more likely to reveal their three‐dimensional structure than single‐spacecraft observations. The launch of STEREO in October 2006 has greatly increased the number of multipoint ICME studies, but the field is still in its infancy. To date, many studies still use flux rope models that rely on single track observations through a vast, multifaceted structure, which oversimplifies the problem and hinders interpretation of the large‐scale geometry. This oversimplification is especially problematic for multispacecraft ICME observations in which only one spacecraft observes a flux rope structure. To tackle these complex problems, we describe two new techniques and combine them to analyze two ICMEs observed at the twin STEREO spacecraft on 22–23 May 2007, when the spacecraft were separated by ∼ 9∘. We find a combination of non–force‐free flux rope multispacecraft modeling, together with a new non–flux rope ICME plasma flow deflection model, better constrains the large‐scale structure of these ICMEs. We also introduce a new spatial mapping technique that allows us to put multispacecraft observations and the new ICME model results in context with the convecting solar wind. What is distinctly different about this analysis is that it reveals aspects of ICME geometry and dynamics in a far more visually intuitive way than previously accomplished. In the case of the 22–23 May ICMEs, the analysis facilitates a more physical understanding of ICME large‐scale structure, the location and geometry of flux rope substructures within these ICMEs, and their dynamic interaction with the ambient solar wind.

Does spacecraft trajectory strongly affect detection of magnetic clouds?

Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) where a magnetic flux rope is detected. Is the difference between MCs and ICMEs without detected flux rope intrinsic or rather due to an observational bias? As the spacecraft has no relationship with the MC trajectory, the frequency distribution of MCs versus the spacecraft distance to the MCs axis is expected to be approximately flat. However, Lepping and Wu (2010) confirmed that it is a strongly decreasing function of the estimated impact parameter. Is a flux rope more frequently undetected for larger impact parameter? In order to answer the questions above, we explore the parameter space of flux rope models, especially the aspect ratio, boundary shape, and current distribution. The proposed models are analyzed as MCs by fitting a circular linear force-free field to the magnetic field computed along simulated crossings. We find that the distribution of the twist within the flux rope, the non-detection due to too low field rotation angle or magnitude are only weakly affecting the expected frequency distribution of MCs versus impact parameter. However, the estimated impact parameter is increasingly biased to lower values as the flux-rope cross section is more elongated orthogonally to the crossing trajectory. The observed distribution of MCs is a natural consequence of a flux-rope cross section flattened in average by a factor 2 to 3 depending on the magnetic twist profile. However, the faster MCs at 1 AU, with V>550 km/s, present an almost uniform distribution of MCs vs. impact parameter, which is consistent with round shaped flux ropes, in contrast with the slower ones. We conclude that either most of the non-MC ICMEs are encountered outside their flux rope or near the leg region, or they do not contain any.

THE DRIVER OF CORONAL MASS EJECTIONS IN THE LOW CORONA: A FLUX ROPE

Recent Solar Dynamic Observatory observations reveal that coronal mass ejections (CMEs) consist of a multi-temperature structure: a hot flux rope and a cool leading front (LF). The flux rope first appears as a twisted hot channel in the Atmospheric Imaging Assembly 94 A and 131 A passbands. The twisted hot channel initially lies along the polarity inversion line and then rises and develops into the semi-circular flux rope-like structure during the impulsive acceleration phase of CMEs. In the meantime, the rising hot channel compresses the surrounding magnetic field and plasma, which successively stack into the CME LF. In this paper, we study in detail two well-observed CMEs occurred on 2011 March 7 and 2011 March 8, respectively. Each of them is associated with an M-class flare. Through a kinematic analysis we find that: (1) the hot channel rises earlier than the first appearance of the CME LF and the onset of the associated flare; (2) the speed of the hot channel is always faster than that of the LF, at least in the field of view of AIA. Thus, the hot channel acts as a continuous driver of the CME formation and eruption in the early acceleration phase. Subsequently, the two CMEs in white-light images can be well reproduced by the graduated cylindrical shell flux rope model. These results suggest that the pre-existing flux rope plays a key role in CME initiation and formation.

Dynamic High-Speed Knotting of a Rope by a Manipulator

In this paper we suggest an entirely new strategy for the dexterous manipulation of a linear flexible object, such as rope or a cable, with a high-speed manipulator. We deal with a flexible rope as one example of the linear flexible object. The strategy involves manipulating the object at high-speed. By moving the robot at high-speed, we can assume that the dynamic behaviour of the flexible rope can be obtained by performing algebraic calculations of the high-speed robot motion. Based on this assumption, we derive a dynamic deformation model of the flexible rope and confirm the validity of the proposed model. Then we perform a simulation of dynamic, high-speed knotting based on the proposed model. We also discuss the possibility of forming the knot based on a simple analysis model. Finally, we show experimental results demonstrating dynamic, high-speed knotting with a high-speed manipulator.

106 エレベーター釣合ロープの挙動解析

In recent years, the number of skyscraper is increasing. Since elevators which are installed in such high-rise building run fast and need long wire ropes and cables for operation, the wire ropes and cables might induce a lateral vibration while car running. Among the elevator ropes, it is important to clarify the relationship between vibration of compensation ropes and weight of compensation sheave, because the compensation sheave is applied to suppress the sway of compensation ropes. However, it is difficult to observe the rope behavior of the high-rise elevator in advance, due to the height limitation of the test-bed. Therefore a simulation model is necessary to evaluate the vibration of the ropes. In this paper, we describe the modeling and vibration analysis of the compensation ropes. Rope and sheave models are derived by using multi-body dynamics theory. Comparisons of the experiment and simulation results validate our simulation model. Influence of the compensation sheave weight to the rope vibration is shown by simulation results.

Implementation of Mathematical Modeling for Wire Rope Strands

Modeling for complex spiral wire rope structures, on which the mechanical performances largely depend, are paramount to finite element analysis application. Three mathematical modeling thoughts were brought out to create the geometric models of wire rope strands. The first one was presented based on the centerline times of the helical structures, as the centerline times can be decreased through transitional coordinate system. For the second, the centerlines of the wire rope were formed by the helical movement of predefined point. In the third one, a local coordinate system which can be transformed into the world coordinate system by their relationship was employed. The above three ideas were implemented by different kinds of derivation. The geometric parameter equations were presented to express the accurate wire rope models. These approaches are beneficial for parametric modeling and analysis of wire rope strands.

Parameter identification for a heavy rope with internal damping

AbstractA method is presented that allows for the identification of parameters in systems described by linear partial differential equations with spatially dependent coefficients. The approach uses operational calculus to generate equations that involve only convolution products of known (boundary) measurements and the system parameters. In particular, a heavy rope model with an internal damping and a horizontally moving suspension point is addressed. Knowledge of two trajectories at the suspension is sufficient to identify all physical parameters of the rope. This is also illustrated by a simulation result. (© 2012 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Stationary flux ropes at the southern terminator of Mars

Flux ropes have long been observed in the upper atmosphere of Venus and more recently at Mars. Here we present magnetic field measurements of flux ropes encountered at the southern terminator of Mars by Mars Global Surveyor and compare them to a flux rope model. This allows several parameters of each rope to be inferred. Remarkably similar flux ropes are met repeatedly at the southern terminator over a period of the Martian year, when strong crustal magnetic fields are upstream of their position, indicating that they are most likely stationary and attached to the upstream crustal fields. A mechanism is described that could produce the observed flux ropes.

Dynamic and Control Strategy of Payload Motion for Deployment System

The dynamic model of wire rope with contact is presented based on finite element method and the flexible multi-body dynamics theory by putting the contact force between the wire rope and drum. The unilateral anti-sway and tension control strategy is put forward, and the dynamic model and collaborative simulation of payload motion for deployment system is modeled by dynamic analysis software RecurDyn and control library Colink. The correctness of the collaborative simulation model and control strategy is validated by analysis and comparison , which lays the foundation for further research on dynamic simulation of virtual prototype in nonlinear and complex mechanical-control system.

Winding Modeling and Driving Method of Varying Length Rope Based on ADAMS

It is necessary to study the dynamics and load-bearing characteristics of ropes in order to guarantee the stability and reliability of hoisting equipments. Based on ADAMS, a parametric coupling model of rope winded along cylindrical helix is built by force field. An optimized simulation method, cooperating fixed joints with angle sensors under the control of script, is recommended. Studying on the construction system of deep vertical shaft wall, the bucket is placed at static equilibrium position by preload defined in force field and dynamics behaviors of the center of mass in bucket are researched. The results indicate that the displacement curve is successive and complete, thus it confirms that the driving method is reasonable and feasible. This method could not only guarantee the accuracy and stability but also increase simulation efficiency, providing a new simulation approach for one kind of flexible body such as ropes and cables.