Cable Dynamics Research Articles

Parameters influence on maneuvered towed cable system dynamics

The dynamic response of a towed cable system to ship maneuver is parametrically simulated. Three dimensionless parameters influence on towed cable system maneuverability is investigated. They are ratio of total length to turning radius R/L, ratio of cable mass to vehicle mass σ, and ratio of mass unit length to hydrodynamic force w/r. An oscillatory motion of towed vehicle is found in simulation of spiral towed courses. Features of this oscillation in different spiral courses are compared. The sharp turns, gradual turns and their transient states of towed cable dynamics for different course directions are discussed extensively. According to the characters of transient states and horizontal trajectories evolution of maneuvered cable system, the dynamic behaviors can be divided into three situations in Fig. 8 turning maneuvers. The behavior of towed cable system during a zigzag turning course is simulated in the end. Two ingredients of heave motion are found during small ratio of turning radii to length in this course. The primary damp to initial turning becomes weak and the response to alternative turns plays a more and more important role. The damping properties of the transient behavior in different maneuvers show a periodical invariance to σ during some turning maneuvers.

Numerical investigation of the dynamics for low tension marine cables

This paper presents a numerical investigation into the dynamics of marine cables which are extensively used in offshore industry. In this numerical study, the Euler-Bernoulli beam model is adopted to develop the governing equations of the cable. Bending stiffness is considered to cope with the low tension problem in local area of towing cable, and thus a more accurate solution with the consideration of the axial elongation can be given. The derived strongly-coupled and nonlinear governing equations are solved by a second-order accurate, implicit, and large time step stable central finite difference method. The quadratically convergent Newton-Raphson iteration method is applied to solving the discrete nonlinear algebraic equations. Then a towed array sonar system (TASS) problem is studied. The numerical solutions agree reasonably well with the experimental data and the simulated results of the references. The specified program of the present paper shows great robustness with high efficiency.

Vibration Dynamics of an Inclined Cable Excited Near Its Second Natural Frequency

Inclined cables are essential structural elements that are used most prominently in cable-stayed bridges. When the bridge deck oscillates due to an external force, such as passing traffic, cable vibrations can arise not only in the plane of excitation, but also in the perpendicular plane. This undesirable phenomenon can be modeled as an auto-parametric resonance between the in-plane and out-of-plane modes of vibration of the cable. In this paper, we consider a three-mode model, capturing the second in-plane, and first and second out-of-plane modes, and use it to study the response of an inclined cable that is vertically excited at its lower (deck) support at a frequency close to the second natural frequency of the cable. Averaging is applied to the model and then the solutions and bifurcations of the resulting averaged differential equations are investigated and mapped out with numerical continuation. In this way, we present a detailed bifurcation study of the different possible responses of the cable. We first consider the equilibria of the averaged model, of which there are four types that are distinguished by whether each of the two out-of-plane modes is present or not in the cable response. Each type of equilibrium is computed and represented as a surface over the plane of amplitude and frequency of the forcing. The stability of the equilibria changes and different surfaces meet along curves of bifurcations, which are continued directly. Overall, we present a comprehensive geometric picture of the two-parameter bifurcation diagram of the constant-amplitude coupled-mode response of the cable. We then focused on bifurcating periodic orbits, which correspond to cable dynamics with varying amplitudes of the participating second in-plane and second out-of-plane modes. The range of excitation amplitude and frequency is determined where such whirling cable motion can occur. Further bifurcations — period-doubling cascades and a Shilnikov homoclinic bifurcation — are found that lead to a chaotic cable response. Whirling and chaotic cable dynamics are confirmed by time-step simulations of the full three-mode model. The different cable responses are characterized, and can be distinguished clearly, by their motion at the quarter-span and by their frequency spectra.

Alternation of Flex Cable Vibration Modes in High Precision Hard Disk Drives

For fast and accurate data accessing operations, flex cable's vibratory response has been identified to be the key development focus for magnetic hard disk drives to meet near nanometer precision accuracy. Dampening the cable's dynamics with damper layers and revising the seek servo designs have been the common approaches found in the literature to reach the requirement. In this paper, vibrations of nonuniform flex cable, which is composed of baseline flex cable layers and addition of piezoelectric layer such as polyvinylidene fluoride film, are investigated through experiments and non-classical, reduced-order finite element analysis. It is found that the addition of the piezofilm changes the cable's natural frequencies only within 3% error range but alters the cable's bending vibration mode shapes significantly. The change in the cable's mode shapes leads to change of the known cable/actuator dynamic coupling reported in the literature. Results presented in this paper establish mechanical framework for active control of the flex cable onto the rotary actuator.

Extending the Benchmark Cable-Stayed Bridge for Transverse Response under Seismic Loading

AbstractAn updated version of the ASCE benchmark on controlled cable-stayed bridges has been recently developed in the ANSYS framework. It includes new aspects in the relative transversal motion of the main girder with respect to the towers in the simulation of the stay cable dynamics with respect to the coupled motion of the main girder in the soil-structure interaction and the numerical formulation by assuming full geometric nonlinearities. Analyses are carried out in a multiple support framework in a time domain by using the earthquake records as collected from the benchmark original statement. The original benchmark configuration considered earthquake restrainers in the transverse direction. The proposed updated bridge model first reproduces this kinematic arrangement, and a new configuration with transversal releases is subsequently implemented. The control strategies consist of passive and decentralized semiactive systems working in the horizontal plane and are also those studied in a previous inves...

Preliminary Assessment of the Importance of Platform–Tendon Coupling in a Tension Leg Platform

This paper presents performance metrics that can be used to evaluate the response sensitivity of a tension leg platform (TLP) to its tendons. An uncoupled TLP model ignores the intrinsic dynamics and environmental loads on the cables by treating each tendon as an ideal massless spring. A coupled TLP system, in contrast, considers the effects of distributed mass and drag along the tendon. Under certain operating conditions, an uncoupled dynamics model can produce results comparable to its coupled counterpart. This paper defines the conditions under which it is acceptable to model a TLP tendon as a linear spring, as opposed to one that considers the cable dynamics. The analysis is performed in the frequency domain and, for generality, the results are nondimensionalized. The findings indicate that a more elaborate set of conditions than the platform–to–cable mass ratio must be satisfied for the two models to provide similar results. To conclude this study, two simulations are performed and compared against the performance metrics derived in this paper.

Performance evaluation of active wireline heave compensation systems in marine well logging environments

The basic functionality and performance of a new Schlumberger active wireline heave compensation system on the JOIDES Resolution was evaluated during the sea trial and a 3-year period of the IODP Phase II operations. A suite of software programs was developed to enable real-time monitoring of the dynamics of logging tools, and assess the efficiency of wireline heave compensation during downhole operations. The evaluation of the system effectiveness was performed under normal logging conditions as well as during stationary tests. Logging data were analyzed for their overall quality and repeatability, and to assess the reliability of high-resolution data such as formation microscanner (FMS) electrical images. This revealed that the system reduces 65–80 % of displacement or 88–98 % variance of downhole tool motion in stationary mode under heave conditions of ±0.2–1.5 m and water depths of 300–4,500 m in open holes. Under similar water/heave conditions, the compensator system reduces tool displacement by 50–60 %, or 75–84 % variance in downhole tool motion during normal logging operations. Such compensation efficiency (CE) is comparable to previous compensation systems, but using advanced and upgradeable technologies, and provides 50–85 % heave motion and heave variance attenuation. Moreover, logging down/up at low speeds (300–600 m/h) reduces the system’s CE values by 15–20 %, and logging down at higher speeds (1,000–1,200 m/h) eliminates CE values by 55–65 %. Considering the high quality of the logging data collected, it is concluded that the new system can provide an improved level of compensation over previous systems. Also, if practically feasible, future integration of downhole cable dynamics as an input feedback into the current system could further improve its compensation efficiency during logging operations.

Full-Scale Vertical Combustion Test of PVC Cable and Computational Fluid Dynamics Study

Full-Scale Vertical Combustion Test of PVC Cable and Computational Fluid Dynamics Study

The Non-Linear Analysis of Cable

The paper reports an investigation on a continuous model for dynamics of cables, taking bending stiffness and sag extensibility into account. The new approach involves the use of derived sensitivity coefficients associated with various cable parameters of interest, and use these coefficients to achieve optimal cable performance. The fatigue damage is calculated in the time domain through an adequate cycles counting method. A discussion of the influence of the Irvine parameter on the total fatigue damage is then performed. A Monte Carlo parametric analysis on a case-study,representative of a suspended cable typical of overhead power-line applications, especially in cyclic exposure, exceeds the present chromate-based systems.introduces a discussion on the convergence of the modal expansions and highlights the respective importance of the different classes of non-linear terms included in the model.

An Analytic-Iterative Redundancy Resolution Scheme for Cable-Driven Redundant Parallel Manipulators

In this paper, redundancy resolution of a cable-driven parallel manipulator is performed through an analytic-iterative scheme. The redundancy resolution scheme is formulated as a convex optimization problem with inequality constraints that are imposed by manipulator structure and cable dynamics. The Karush-Kuhn-Tucker theorem is used to analyze the optimization problem and to draw an analytic-iterative solution for it. Subsequently, a tractable and iterative search algorithm is proposed to implement the redundancy resolution of such redundant manipulators. Furthermore, it is shown through simulations that the worst case and average elapsed time that is required to implement the proposed redundancy resolution scheme in a closed-loop implementation is considerably less than that of other numerical optimization methods.

Motility and Segregation of Hsp104-Associated Protein Aggregates in Budding Yeast

During yeast cell division, aggregates of damaged proteins are segregated asymmetrically between the bud and the mother. It is thought that protein aggregates are cleared from the bud via actin cable-based retrograde transport toward the mother and that Bni1p formin regulates this transport. Here, we examined the dynamics of Hsp104-associated protein aggregates by video microscopy, particle tracking, and image correlation analysis. We show that protein aggregates undergo random walk without directional bias. Clearance of heat-induced aggregates from the bud does not depend on formin proteins but occurs mostly through dissolution via Hsp104p chaperon. Aggregates formed naturally in aged cells also exhibit random walk but do not dissolve during observation. Although our data do not disagree with a role for actin or cell polarity in aggregate segregation, modeling suggests that their asymmetric inheritance can be a predictable outcome of aggregates' slow diffusion and the geometry of yeast cells.

Dynamic analysis of cable-driven parallel manipulators with time-varying cable lengths

In conventional researches, cables of cable-driven parallel manipulators are treated as simple linear elements that can only work in tension. This results in the fact that the effect of cable dynamics on the positioning precision of the end-effector is not adequately taken into account. To overcome this shortcoming, a dynamic model for cable-driven parallel manipulators with cables of slowly time-varying length is presented in this paper. The partial differential equation characterizing the dynamics of a cable with varying-length is deduced, and converted into ordinary differential equations through spatial discretization by finite difference approximation. Then, the dynamic model for cable-driven parallel manipulators is achieved considering the relationship between the motion of the end-effector and the cable end force, in which the degrees of freedom of cables and the end-effector are all involved. Two numerical examples are demonstrated to validate the dynamic model, and also show that it is necessary to take into consideration the cable dynamics for manipulators of long-span cables.

Cotranslational transport of ABP140 mRNA to the distal pole ofS. cerevisiae

In budding yeast, several mRNAs are selectively transported into the daughter cell in an actin-dependent manner by a specialized myosin system, the SHE machinery. With ABP140 mRNA, we now describe the first mRNA that is transported in the opposite direction and localizes to the distal pole of the mother cell, independent of the SHE machinery. Distal pole localization is not observed in mutants devoid of actin cables and can be disrupted by latrunculin A. Furthermore, localization of ABP140 mRNA requires the N-terminal actin-binding domain of Abp140p to be expressed. By replacing the N-terminal localization motif, ABP140 mRNA can be retargeted to different subcellular structures. In addition, accumulation of the mRNA at the distal pole can be prevented by disruption of polysomes. Using the MS2 system, the mRNA was found to associate with actin cables and to follow actin cable dynamics. We therefore propose a model of translational coupling, in which ABP140 mRNA is tethered to actin cables via its nascent protein product and is transported to the distal pole by actin retrograde flow.

Modeling and Analysis of Piezo-Elastica Energy Harvester in Computer Hard Disk Drives

In this paper, design and analysis of an energy harvester named piezo-elastica energy harvester (PEEH) to harvest wasted mechanical energy generated by flex cable kinetic and vibratory motions are presented. A coupled piezo-elastic model is developed for the harvester with focus given to understanding piezoelectricity generated by its PVDF layer over its underlying largely deformed flex cable elatica structure. Design for manufacturing for the proposed harvester is detailed in this work. Numerical finite element simulations and laboratory measurements using noncontact laser interferometry validate the mode with respect to the PEEH's profiles, natural frequencies and mode shapes as well as electric energy generated resulted from flex cable's dynamics. It is observed that about 25% of the power consumed by disk drive's voice coil motor can be harvested by the proposed design. Among harvested energy, it is found that 58% comes from significant change of PEEH's profile when rotary actuator swings between disk's outer diameter and inner diameter regions, 33% from PEEN's 2nd bending mode, and 9% from its 1st bending mode. The work presented in this paper suggests the possibility of scavenging and converting flex cable's mechanical vibrations and dynamics into electrical form for power conservation inside computer hard disk drives.

Cortical actin dynamics

The actin cytoskeleton plays essential roles in cell polarization and cell morphogenesis of the budding yeast Saccharomyces cerevisiae. Yeast cells utilize formin-generated actin cables as tracks for polarized transport, which forms the basis for a positive feedback loop driving Cdc42-dependent cell polarization. Previous studies on cable organization mostly focused on polarized actin cables in budded cells and their role as relatively static tracks for myosin-dependent organelle transport. Using quantitative live cell imaging, we have recently characterized the dynamics of cortical actin cables throughout the yeast cell cycle. Surprisingly, randomly oriented actin cables in G(1) cells exhibited the highest level of dynamics, while cable dynamics was markedly slowed down upon cell polarization. We further demonstrated that the rapid dynamics of randomly oriented cables were driven by the formin Bni1 and Myosin V. Our data suggested a precise spatio-temporal regulation of the two yeast formins, as well as an unexpected mechanism of actin cable rearrangement through myosins. Here we discuss the immediate significance of these findings, which illustrates the importance of generating randomness for cellular organization.

The Calcium-Sensing Receptor-Dependent Regulation of Cell–Cell Adhesion and Keratinocyte Differentiation Requires Rho and Filamin A

Extracellular Ca(2+) (Ca(2+)(o)) functioning through the calcium-sensing receptor (CaR) induces E-cadherin-mediated cell-cell adhesion and cellular signals mediating cell differentiation in epidermal keratinocytes. Previous studies indicate that CaR regulates cell-cell adhesion through Fyn/Src tyrosine kinases. In this study, we investigate whether Rho GTPase is a part of the CaR-mediated signaling cascade regulating cell adhesion and differentiation. Suppressing endogenous Rho A expression by small interfering RNA (siRNA)-mediated gene silencing blocked the Ca(2+)(o)-induced association of Fyn with E-cadherin and suppressed the Ca(2+)(o)-induced tyrosine phosphorylation of β-, γ-, and p120-catenin and formation of intercellular adherens junctions. Rho A silencing also decreased the Ca(2+)(o)-stimulated expression of terminal differentiation markers. Elevating the Ca(2+)(o) level induced interactions among CaR, Rho A, E-cadherin, and the scaffolding protein filamin A at the cell membrane. Inactivation of CaR expression by adenoviral expression of a CaR antisense complementary DNA inhibited Ca(2+)(o)-induced activation of endogenous Rho. Ca(2+)(o) activation of Rho required a direct interaction between CaR and filamin A. Interference of CaR-filamin interaction inhibited Ca(2+)(o)-induced Rho activation and the formation of cell-cell junctions. These results indicate that Rho is a downstream mediator of CaR in the regulation of Ca(2+)(o)-induced E-cadherin-mediated cell-cell adhesion and keratinocyte differentiation.

Cortical actin dynamics driven by formins and myosin V

Cell morphogenesis requires complex and rapid reorganization of the actin cytoskeleton. The budding yeast Saccharomyces cerevisiae is an invaluable model system for studying molecular mechanisms driving actin dynamics. Actin cables in yeast are formin-generated linear actin arrays that serve as tracks for directed intracellular transport by type V myosins. Cables are constantly reorganized throughout the cell cycle but the molecular basis for such dynamics remains poorly understood. By combining total internal reflection microscopy, quantitative image analyses and genetic manipulations we identify kinetically distinct subpopulations of cables that are differentially driven by formins and myosin. Bni1 drives elongation of randomly oriented actin cables in unpolarized cells, whereas both formins Bnr1 and Bni1 mediate slower polymerization of cables in polarized cells. Type V myosin Myo2 surprisingly acts as a motor for translational cable motility along the cell cortex. During polarization, cells change from fast to slow cable dynamics through spatio-temporal regulation of Bni1, Bnr1 and Myo2. In summary, we identify molecular mechanisms for the regulation of cable dynamics and suggest that fast actin reorganization is necessary for fidelity of cell polarization.

A Bond Graph Model of an Electromagnetic Launcher—Part 2: Simulation Results

An electromagnetic launcher (EML) or railgun is a complex dynamically coupled system, with interacting electric, magnetic, mechanical, and thermal subsystems. Part 1 of this paper formulated a bond graph model of an EML system, including power supply, dynamics of power cables, electric dynamics of armature and rails, magnetic containment of flux, electric contact resistance between sliding armature and rails, generation of forward longitudinal motion, transverse contact mechanics of armature sliding on rails, thermal analysis of armature heating, and model of armature melt wear and plasma erosion. Using state equations extracted from the Part 1 paper, numerical simulation results of the Institute of Advanced Technology's MCL EML are presented. Simulated are rail current, armature forward motions, armature-rail contact normal approach, armature and interface temperatures, and material loss. Results are compared to MCL shot 185. The results suggest interface temperatures of thousands of kelvins, which can exceed 15 000 K under certain conditions, and an armature-rail sliding contact separation due to accumulated melt erosion, consistent with transition.

Simulation of Flow past Cable with Upper Rivulet on its Surface and Investigation of the Cable Dynamics

Rain-wind induced vibration (RWIV) is a violent oscillation that appears on cable stayed bridge under rainy weather. Many researchers agree that the rivulets (specially the upper one) play an important role during the vibration. In present work, the upper rivulet’s effect is focused. A circular cylinder with an arches attachment on its surface is modeled to take the place of cable- rivulets system section in RWIV. Using finite volume method (FVM), 3D Flow past the cylinder-arch model is simulated for subcritical Reynolds Number (Re, ≈6.8×104). Large Eddy Simulation (LES) method is drawn in as a closure of turbulence model. The attachment locating at different positions are calculated. The results show many differences between cylinder-arch model and bare circular cylinder, including force coefficients change dramatically and velocity distributions in wake zone vary remarkably. Responses of cylinder-arch system driven by aerodynamic forces are also studied. Fourth order Runge-Kutta Method is introduced to solve second order ODEs that describe the vibration of cylinder model. The first four modal response are calculated and then added to analyze cable oscillating properties.

Multi-pulse orbits and chaotic dynamics in a nonlinear forced dynamics of suspended cables

The global bifurcations in mode of a nonlinear forced dynamics of suspended cables are investigated with the case of the 1:1 internal resonance. After determining the equations of motion in a suitable form, the energy phase method proposed by Haller and Wiggins is employed to show the existence of the Silnikov-type multi-pulse orbits homoclinic to certain invariant sets for the two cases of Hamiltonian and dissipative perturbation. Furthermore, some complex chaos behaviors are revealed for this class of systems.