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In this paper, boundary control of a marine installation system is developed to position the subsea payload to the desired set-point and suppress the cable's vibration. Using Hamilton's principle, the flexible cable coupled with vessel and payload dynamics is described as a distributed parameter system with one partial differential equation (PDE) and two ordinary differential equations (ODEs). Adaptive boundary control is proposed at the top and bottom boundaries of the cable, based on Lyapunov's direct method. Considering the system parametric uncertainty, the boundary control schemes developed achieve uniform boundedness of the steady state error between the boundary payload and the desired position. The control performance of the closed-loop system is guaranteed by suitably choosing the design parameters. Simulations are provided to illustrate the applicability and effectiveness of the proposed control.

In order to design the humanoid dual-arms high voltage transmission line inspection robot, the robot model is given and the working mechanism of the robot crossing obstacles is introduced, and the motion trajectory of the robot when it is moving is analyzed. The dynamic equations of the serial driven and the serial-parallel driven robotic arm are presented based on Lagrange equation and the dynamic characteristics of the wrist and elbow joint are simulated. The numerical simulation result of the serial driven robotic arm shows that the elbow joint has great torque when the robot moves horizontally and vertically. However, the numerical simulation result of the serial-parallel driven robotic arm shows that the elbow joint torque reduces greatly comparing with the serial driven arm. By analyzing the results of the simulation experiment, it can be seen that this serial-parallel combination driven joint with flexible-cable can reduce the elbow torque greatly and improve the load capacity of robotic arm comparing with the serial driven joint, which can solve the problem that the torque of serial driven joint in dual-arms inspection robot is too high.

In this paper a solution method is presented for the coupled problem of elastic flat or space membranes supported by elastic flexible cables. Both membrane and cable undergo large deflections. Starting from the minimal surface the membrane is prestressed by imposed boundary displacements under the self-weight. Then an iterative procedure is employed, which consists in solving the membrane and the cable large deflection problems separately in each iteration step and checking the continuity of displacements and forces between membrane and cable. The procedure is repeated until convergence is achieved. Both membrane and cable problems are solved using the analog equation method (AEM). The displacements as well as the stress resultants are evaluated at any point of the membrane and the cable from the integral representations of the solution of the analog equations, which are used as mathematical formulae. Example problems are presented, for both flat and space membranes, which illustrate the method and demonstrate its efficiency and accuracy.

According to the thought of beam string structure, pre-stressing structure was presented that it was joined by rigid grid and flexible cable by pole support. It was grid string branch structure. A calculation model of string branch grid was founded. Static and dynamic characteristics of the structure that it was acted by different pre-stress value were analyzed. Through the analysis, the structure displacement and internal forces of rod are improved obviously depending on pre-stress value. The pre-stress value is larger, structure displacement and internal forces of rod are lower. Natural vibration characteristics of the structure are almost not changing, while pre-stress value is changing. When the structure is time history analysis, its response curve accords with general law of structural vibration. Node displacement response of up and bottom chord nodes are not occurred retardation effect.

The Feed Support System (FSS) addressed here is the receiver carrier of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China. The FSS is a complex hybrid manipulator, which consists of a cable-driven Stewart manipulator, an A–B rotator and a rigid Stewart manipulator. The cable-driven Stewart manipulator, which is a long-span flexible cable structure, is sensitive to the wind disturbance and induces the FSS vibration. The rigid Stewart manipulator is designed to suppress the vibration and improve the terminal accuracy of the FSS. In the paper, the elastic dynamic model of the cable-driven Stewart manipulator is deduced by simplifying the flexible cable as the spring damping model, while the rigid-body dynamic model of the A–B rotator and the rigid Stewart manipulator is obtained in detail, using the Newton–Euler method. The internal coupling forces of the FSS are figured out. The wind disturbance model is established according to the Davenport spectrum. By adopting the kinematic and dynamic parameters of the FAST prototype, the simulation model of the FSS is completed. Kinematic and dynamic vibration control strategies are evaluated with simulations. Results show that the dynamic vibration suppression strategy well satisfies the FSS terminal accuracy requirement, keeps the rigid Stewart manipulator working with reasonable driving forces, and should be adopted in the control system of the FAST prototype.

DLO is a railroad industry designation given to flexible cable certified for use in Diesel Locomotives. For use outside the railroad industry, these cables may be labeled with a UL insulation type certification such as RHW-2. Carried over from the cables' railroad lineage are sizes such as 535 kCMIL that are absent from National Electrical Code (NEC) tables. While interpolation of NEC tables may appear a logical means of calculating ampacity, the NEC limits ampacity calculation options to the formula provided in 310.15(C). Applications of the 310.15(C) formula for cables in underground duct banks are well documented, but constants for duplicating conditions of NEC Table 310.16 are absent from the NEC. For application of nonstandard cable sizes in conditions matching those of NEC Table 310.16, this paper provides ampacity calculations while also clarifying the delineation between permanent building wiring and temporary cords as defined by the NEC

In this paper, the coupled dynamics and control of the vessel, crane, flexible cable and payload under environmental disturbances with attached thrusters for subsea installation operations is investigated. For the practical system with physical constraints, we employ Barrier Lyapunov Function in the design of positioning control for the flexible crane-cable-payload subsystem to ensure that the constraints are not violated. Uniform stability of the flexible subsystem is shown and asymptotic positioning of the boundaries is achieved. Next, we tackle the scenario where nonuniformity of the cable, uncertainties and environmental disturbances are considered. Boundary controls are formulated using the nonlinear partial differential equation of the cable. Numerical simulations are provided to illustrate the performance of the proposed controls.

In this paper, the vibration behavior of a suspension bridge due to moving vehicle loads with vertical support motions caused by earthquake is studied. The suspension bridge system is presented here by two coupled nonlinear cable–beam equations aiming to describe both the dynamic characteristics for the supporting cable and the roadbed, respectively. The dynamic effect of traffic vehicles are modeled as a row of equidistant moving forces, while the earthquake movement is simulated as the vertical oscillation of boundary supports. The governing integro-differential equations are transferred into a set of ordinary differential equations, which can be solved analytically in the present study. Furthermore, the world’s largest designed suspended bridge – Messina Bridge – is examined (central span of length 3.3 km) and the modified Kobe earthquake records is applied to the calculations in order to validate the present study and the proposed methodology. As a result, the deformation of the cable produces more oscillations than that of the beam since the material property of the cable is more flexible. It is shown that the interaction of both the moving loads and the seismic forces can substantially amplify the response of long-span suspension bridge system especially in the vicinity of the end supports.

Forklift truck is one of the most important tools in logistics. However, the general mast system of a forklift truck not only restrains the driver's vision, but also increases the whole weight of a truck and decreases the fuel economy. Therefore, this paper focuses on the innovative design of a new lifting mechanism for forklift truck. Firstly, a spatial multi-link lift-guidance mechanism is proposed. And then, under the constraints of this mechanism, the mobility of the fork and fork frame is investigated in theory. Lastly, a new lifting mechanism based on it is presented and computer simulation is used to demonstrate the feasibility of motion. This multi-link lifting mechanism takes advantage of flexible cable drive and rigid body guidance, which not only provides the operator with a wider field of vision but also reduces the equilibrate weight of a vehicle and therefore improves the fuel economy.

A new seismic isolation system,namely the prestress rubber isolator(PRI,Chinese patent application number:200910174415x),is introduced.The basic principle of this new isolator is: making all or part of vertical deformation of isolator be finished in advance by exerting a longitudinal pre-compressional stress on the rubber isolator with flexible cables, the prestress tension cables become loose because of unloading after the exerting of superstructure loads,and the loose cables can limit the horizontal displacement and resist the tension of isolator. The calculation formula of horizontal stiffness of isolator is derivated,and the mechanical properties are researched. The research results show that:besides the horizontal isolating property of common rubber isolators,the prestress rubber isolator has also properties of reducing vertical deformation, limiting horizontal displacement and resisting tension.Moreover,the prestress isolator has also a certain vertical isolating affect because of the improve of rubber thickness.

Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined.

The design method of μ-synthesis controller for the flexible cable-strut structure with mixed uncertainties was presented and verified by the simulation experiments. The uncertainties include model uncertainties caused by joint clearance and friction, and the uncertainties arising from the actuator range and sensor noise. Based on the structured singular value theory, the model of robust active vibration control for the flexible cable-strut structure was established. The robust performance of the external disturbance rejection is characterized by introducing a fictitious uncertainty block across the disturbance/error channels and carrying out a robust stability analysis. The controller was derived from minimizing the structured singular value. This method considers the structural characteristics of the mixed uncertainty block, so that the conservativeness of H∞ controller in dealing with the mixed uncertainty problem is avoided. The simulation results show that the method has good robustness and stability performances for the controlled system with mixed uncertainties and external disturbances.

Digital design and assembly of cables is a most important and difficult problem in mechanical industry. The paper solved the problem through the CAD/CAE software. Firstly, 3-D model of electrical bundle was built in the digital mock-up. The model reflected the parameters of the bundle exactly. After the design of cables, the simulation of cable moving was developed. The flexible feature of cable was displayed in the animation. It was an exciting achievement of this article, which can be used in the virtual assembly of cables to detect design problems. Besides the maintenance process containing cable plug and pull was simulated. The ergonomics was then tested in the form of virtual maintenance.

In this paper dynamic load carrying capacity (DLCC) of a cable robot equipped with a closed loop control system based on feedback linearization, is calculated for both rigid and flexible joint systems. This parameter is the most important character of a cable robot since the main application of this kind of robots is their high load carrying capacity. First of all the dynamic equations required for control approach are represented and then the formulation of control approach is driven based on feedback linearization method which is the most suitable control algorithm for nonlinear dynamic systems like robots. This method provides a perfect accuracy and also satisfies the Lyapunov stability since any desired pole placement can be achieved by using suitable gain for controller. Flexible joint cable robot is also analyzed in this paper and its stability is ensured by implementing robust control for the designed control system. DLCC of the robot is calculated considering motor torque constrain and accuracy constrain. Finally a simulation study is done for two samples of rigid cable robot, a planar complete constrained sample with three cables and 2 degrees of freedom and a spatial unconstrained case with six cables and 6 degrees of freedom. Simulation studies continue with the same spatial robot but flexible joint characteristics. Not only the DLCC of the mentioned robots are calculated but also required motors torque and desired angular velocity of the motors are calculated in the closed loop condition for a predefined trajectory. The effectiveness of the designed controller is shown by the aid of simulation results as well as comparison between rigid and flexible systems.

SummaryThe catenary is usually introduced as the solution to the hanging flexible cable problem. This is a physical description of a catenary. In this article we give a geometrical description of a...

The dynamic characteristics of slender cable often present serried modes with low frequencies due to large structure flexibility resulted from high aspect ratio (ratio of length to diameter of cable), while the flow velocity distributes non-uniformly along the cable span actually in practical engineering. Therefore, the prediction of the vertex-induce vibration of slender cable suffered from multi-mode and high-mode motions becomes a challenging problem. In this paper a prediction approach based on modal energy is developed to deal with multi-mode lock-in. Then it is applied to the modified wake-oscillator model to predict the VIV displacement and stress responses of cable in non-uniform flow field. At last, illustrative examples are given of which the VIV response of flexible cable in nonlinear shear flow field is analyzed. The effects of flow velocity on VIV are explored. Our results show that both displacement and stress responses become larger as the flow velocity increasing; especially higher stress response companied with higher frequency vibration should be paid enough attention in practical design of SFT because of its remarkable influence on structure fatigue life.

The problem of stabilizing vibrations of flexible cable related to an overhead crane is considered. The cable vibrations are described by a hyperbolic partial differential equation (HPDE) with an update boundary condition. We provide in this paper a systematic way to derive a boundary feedback law which restores in a closed form the cable vibrations to the desired zero equilibrium. Such a control law is explicitly constructed in terms of the solution of an appropriate kernel PDE. The pursued approach combines the “backstepping method” and “semigroup theory”.

A polymer-based flexible tactile sensor array integrated with interconnection terminals was fabricated with polymer MEMS technologies and electroplating. The tactile sensing arrays were made as 4 × 4, 8 × 8, 16 × 16 and 32 × 32 sensing elements connected with a pluggable connector. Both the tactile sensor arrays and the interconnection terminals were fabricated together on the same polymer substrate in order to integrate them as a sensor module. The tactile sensor array with FFC (flexible flat cable) can be easily connected with the sensor array mounting PCB board by inserting the flexible cable into the pluggable connector socket on the board. The number and pitch of the fabricated interconnection terminals for 32 × 32 arrays were 68 and 500 μm, respectively. Continuous normal force ranging 0–1 N was applied to a unit tactile sensor for evaluating the tactile sensor characteristics through the integrated interconnection terminals. The measured resistance increased linearly with normal force in the range of 0–0.6 N but the resistance variation rate decreased above 0.6 N. The variation rate of the resistance is about 2.0%/N in the range of 0–0.6 N and 1%/N in the range of 0.6–1 N. The characterization of the tactile sensor array for the rod bar and a fingertip was successfully evaluated using the custom designed controller and the window-based 3D display software.

A design of a miniature lightweight multichannel preamplifier for recording electrophysiological activity in freely moving small animals is presented. The advantages of this construction include the possibility to obtain differential multichannel recording of neuronal activity, EEG and evoked potentials, relatively simple fabrication and exploitation. If necessary, the preamplifier may be easily disassembled for repair. Fine and flexible cable and "soft" hanger do not disturb free movement of an animal. The lightweight construction may be used for recording neuronal activity even in mice performing spatial task in Morris water maze.

The active scope camera we proposed has active mobility using a ciliary vibration drive mechanism for long flexible cables. The physical details have yet to be clarified. We determined it based on detailed physical phenomena to design an optimal ciliary vibration drive. We discuss the reasons for design efficiency based on the analysis of dynamic models of ciliary parts, focusing on (1) the characteristic vibration of the cilia and (2) stick-slip contact. We constructed a pseudo linear spring model and a stick-slip friction model to evaluate these phenomena. We determined optimal driving vibration frequencies and the inclined angle of cilia through experiments and analysis. Qualitative comparisons with the dynamic models and the results of experiments indicated the effective physical factors of the activation mechanism. A prototype of the active scope camera showed good performance in practical rescue activities.

In this paper, a formulation for a spatial sliding joint is derived using absolute nodal coordinates and non-generalized coordinate and it allows a general multibody move along a very flexible cable. The large deformable motion of a spatial cable is presented using absolute nodal coordinate formulation, which is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. And the nongeneralized coordinate, which is related to neither the inertia forces nor the external forces, is used to describe an arbitrary position along the centerline of a very flexible cable. Hereby, the non-generalized coordinate represents the arc-length parameter. The constraint equations for the sliding joint are expressed in terms of generalized coordinate and nongeneralized coordinate. In the constraint equations for the sliding joint, one constraint equation can be systematically eliminated. There are two independent Lagrange multipliers in the final system equations of motion associated with the sliding joint. The development of this sliding joint is important to analyze many mechanical systems such as pulley systems and pantograph-catenary systems for high speed-trains.

The cable which transfers the signal and power in an industrial robot has a problem of fatigue fracture like steel components. Since the cable is very flexible compared to other components of the system, it is difficult to estimate its motion numerically. Some studies have been done on a large deformation problem, especially in a cable, and a few attempts have been made to apply the absolute nodal coordinate formulation (ANCF), which can simulate a large deformation. Only researches about the fatigue life of structural cables or comparative studies of FEM and ANCF simulations can be found. This paper presents a method to simulate the behavior of the cable harness using the ANCF and to predict the fatigue life while computing the strain time history of the point of interest. Rigid body dynamics is applied for the robot system, while ANCF is used for the cable harness. The simulation is performed by using the dynamic analysis process. The material property of the cable is obtained by a test. A simplified model is prepared. With these data, the behavior of the cable is simulated and the fatigue life is predicted.

Monolayer cable nets have been widely applied in point-supported glass facades in recent years because of transparency, light weight and flexibility of construction. In this paper, work on the static load bearing performance of this type of cable net is described through the use of finite element analysis (FEA) and tests on a 1/10–scale model of a real project in P.R. China under construction. Firstly a method of analysis inverse to the sequence of erection and much different from conventional methods, is used to model the pre-stretching of cables with the aid of FEA to provide guidelines for the tests. Cable pre-stretching proceeds by three stages, then load bearing behaviour tests on the cable net are carried out both before and after the installation of glass panels. The agreement between the pre-stretching tests and the FEA analysis indicates that the inverse analysis method is convenient in calculation, and provides useful references for the pre-stretching of similar types of cable net in practical engineering. The nonlinear relationship found between loads and displacements just indicates the nonlinear properties of flexible cable nets. Before the installation of glass panels, the structural stiffness actually increases slowly with increasing external loads, and greater initial pre-tension is more beneficial to load bearing capacity of the structure. But too large an initial pre-tension may overload the supporting structures of the cable net. The increase in cable force due to external loads is small. Nevertheless, the stiffness of the glass panels themselves make a significant contribution to the overall structural stiffness, the contribution which becomes less obvious as the stiffness of the cable net itself increases.

This paper investigates the control of a single degree of freedom flexible cable-driven parallel manipulator (CDPM) with a focus on maintaining positive cable tensions. A control architecture that uses a particular saturation prevention function is used to force the control torques to remain within limits that maintain positive cable tensions. The maximum and minimum allowable control torque limits are calculated by solving a linear programming problem on an element-wise inequality involving the equations of motion of the system. It is shown that the controller is input strictly passive and the closed-loop system is input-output stable. Numerical simulation results compare the performance of the proposed controller to that of an existing controller from the literature.

This paper is focused on the dynamics and control of arbitrary number of quadrotor UAVs transporting a rigid body payload. The rigid body payload is connected to quadrotors via flexible cables where each flexible cable is modeled as a system of serially-connected links. It is shown that a coordinate-free form of equations of motion can be derived for arbitrary numbers of quadrotors and links according to Lagrangian mechanics on a manifold. A geometric nonlinear controller is presented to transport the rigid body to a fixed desired position while aligning all of the links along the vertical direction. Numerical results are provided to illustrate the desirable features of the proposed control system., Comment: arXiv admin note: text overlap with arXiv:1403.3684

In deep lunar soil sampling, the drilling mechanism is driven by the loading wire rope through a driving mechanism. This paper is aimed at establishing an accurate dynamic model of the removable loading wire rope and analyzing its influence on the drilling process. In the process of drilling, there exists material transportation at the boundaries, so the length and mass of the upper and lower wire ropes are time-varying. Using absolute nodal coordinate formulation (ANCF), the model of variable-length flexible cable element which considers the preload is derived by combining Euler and Lagrange nodes. Compared to traditional ANCF cable element, a material transportation item which is associated with the moving velocity is added up to the new element. The variable-length and traditional cable are respectively used to establish the boundary and internal elements. The simulation results prove that the movement and vibration of the variable-length wire ropes can be well simulated by the length variable flexible cable model. Then the influences of preload and impact frequency are studied. The greater the preload, the larger the natural frequency and smaller the vibration amplitude will be. When the impact frequency approaches the natural frequency, the resonance occurs, and the vibration amplitude increases.

We demonstrate the design and implementation of hybrid optical-electrical probes (`optrodes') for high resolution electrophysiology and optogenetic stimulation of neurons in multiple brain areas. Our 64-channel implantable optrodes are minimally invasive (50 μm × 20 μm) and span 1~2 mm. To minimize tethering forces on the brain tissue a monolithic high-density flexible cable (6 μm thin) connects the probe to a lightweight headstage (1.3 gr, 256 channel configuration) designed for awake, freely-behaving small animals. A polymer-based multi-channel photonic light delivery system is integrated on shank in a separate layer, providing local optogenetic stimulation of the neural population adjacent to the probe. The entire manufacturing process, including the nanofabrication of the optrodes, post-fabrication assembly, and surgical implantation procedures are designed to be scalable, high-yield, and high-throughput.

As energy and signal transmission medium, cable harness is widely used in complex mechatronic products, and cable harness information are the basis and premise conditions of the flexible cable harness assembly simulation of complex mechatronic products system. To retrieve cable harness information from the information management system or repository effectively, a push method of cable harness information for complex mechatronic products based on variable precision rough sets (VPRS) was proposed in this paper. By using the cable harness information reduction method, the cable harness information repository is simplified, and rules which can support the precise push also be distilled from the reduct cable harness information repository. On the basis of the above approach, cable harness wiring designers, assembly process planners and assembly process simulation designers can efficiently share cable harness information during all design processes. Finally, a case is employed to validate the proposed method of this paper.

Based on the nonlinear geometric relation between strain and displacement for flexible cable, the equilibrium equation under self-weight and influence of temperature was established and an analytical solution of displacement and tension distribution defined in Eulerian coordinate system was accurately obtained. The nonlinear algebraic equations caused by cable structure were solved directly using the modified Powell hybrid algorithm with high precision routine DNEQNE of Fortran. For example, a cable structure consisting of three cables jointly supported by a vertical spring and all the other ends fixed was calculated and compared with various methods by other scholars.

In this paper, we study the stabilization problem of a flexible cable with two rigid loads which is described by two kinds of hyperbolic equations. From the engineering point of view, the model can be regarded as a distributed parameter overhead crane which conveys two loads simultaneously. After deriving a control law which does not increase an energy defined for the model, we prove the asymptotic stability of the closed-loop system, using the LaSalle's invariance principle. Finally, we show that the control law works effectively through a numerical simulation.

Recently, the finite element absolute nodal coordinate formulation(ANCF) was developed for large deformation analysis of flexible bodies in multi-body dynamics. This formulation is based on finite element procedures and the general continuum mechanics theory to represent elastic forces. In this paper, a computational method, which predicts the dynamic and structural properties of a very flexible beam in a multibody system, is presented based on Euler-Bernoulli beam theory and ANCF. In order to consider the dynamic interaction between a continuous large deformable beam and a rigid multibody system, a combined system equations of motion was derived by adopting absolute nodal coordinates and rigid body coordinates. The efficiency and reliability of the computational results are verified by comparison with a commercial program. These methods can be applied for predicting the dynamic stress and fatigue life of the wire harness used in a robot system. The process of predicting the fatigue life using the proposed method in this paper may be applied to continuous mechanical parts of various dynamic systems.

This work considers the control problem of overhead cranes with flexible cable and load hoisting or lowering during crane travel. The objective is to drive the overhead crane to its final desired position while suppressing the payload swing. The proposed control strategy is based on three fuzzy logic controllers where the control action is based on expert knowledge. These controllers are a trolley motion controller, payload hoist controller and payload anti-swing controller. Numerical simulations are provided to show the effectiveness of the proposed fuzzy control scheme.

In this paper, we present direct numerical simulation (DNS) of the transient dynamics of single-molecule DNA by modeling it as a highly flexible cable. Fully nonlinear dynamic equations are derived from the principles of conservation of momentum and angular momentum, and solved via numerical means. Compared to previous models, this cable-dynamics model enables direct physical simulation of an individual biopolymer string rather than a random-walk style statistical modeling. To validate this DNS modeling approach, the canonical DNA stretching problem is simulated. The DNS solutions are compared with published benchmark results. The DNS model is further deployed to investigate the Brownian motion of single DNA molecule, and the translocation process of a DNA molecule through a nanopore induced by the presence of an external electric field. In the latter case, our simulations have exhibited good agreement with experimental observations, including the linear dependence of the translocation time on the contour length of the molecule, the formation of "hairpins" during translocation, and back-and-forth molecule motions

For the slender and flexible cable supported bridges, identification of all the flutter derivatives for the vertical, lateral and torsional motions is essential for its stability investigation. In all, eighteen flutter derivatives may have to be considered, the identification of which using a three degree-of-freedom elastic suspension system has been a challenging task. In this paper, a system identification technique, known as covariance-driven stochastic subspace identification (COV-SSI) technique, has been utilized to extract the flutter derivatives for a typical bridge deck. This method identifies the stochastic state-space model from the covariances of the output-only (stochastic) data. All the eighteen flutter derivatives have been simultaneously extracted from the output response data obtained from wind tunnel test on a 3-DOF elastically suspended bridge deck section-model. Simplicity in model suspension and measurements of only output responses are additional motivating factors for adopting COV-SSI technique. The identified discrete values of flutter derivatives have been approximated by rational functions. rnKeywords: flutter derivative; wind tunnel test; stochastic subspace identification; rational function approximation.

Modeling and Lyapunov controller design for transverse vibration of a flexible cable transporter system with arbitrarily varying lengths are presented using Hamilton's principle and Lyapunov theory. The axial velocity of the system is assumed to be unknown in the model. This is different from existing literature where the axial velocity is assumed either to be constant or prescribed. The governing equations include two coupled non-linear Partial Differential Equations (PDEs) and boundary conditions. The interactions between the cables and the slider, pulleys, and motors are included in the model. Numerical solution of the derived governing equations is obtained using Galerkin's method. Based on the Lyapunov theory, we propose two boundary controllers and one domain point-wise controller, which suppress the transverse vibration of the cables effectively while assuring the attainment of the slider goal. The proposed controllers dissipate the vibration energy and guarantee the stability of the closed-loop system in Lyapunov sense. Simulation results demonstrate the effectiveness of the proposed controllers.

The control of an aerial-towed flexible cable system for precision rendezvous and snatch pickup of payloads is considered. In past studies of related systems, optimal trajectories have been determined assuming that the cable remains straight. However, aerodynamic drag and deployment forces can cause bowing of the cable that can significantly alter the position of the cable tip relative to the aircraft. To account for this, the cable is modeled using lumped masses connected via rigid links. Multiple rendezvous sequences using only cable winch control and including features such as collision avoidance and variable winds are solved by multiple-phase direct transcription methods. Numerical results show that for some multiple rendezvous scenarios it is necessary to use the cable lateral dynamics and swing motion to avoid impact with elevated terrain. The effect of different wind speeds and directions are also studied.

This paper introduces control tests on a feed positioning system for a large radio telescope. The system is an integration of three subsystems, including a cable trolley subsystem, with a two-degrees-of-freedom orienting mechanism mounted on the trolley, which points a Gough-Stewart mechanism, the third subsystem. The first two subsystems provide a coarse control of the motion of the upper platform of the Gough-Stewart mechanism, while the Gough-Stewart mechanism gives a finer control of the feed-mounted lower platform by actively isolating the vibrations from the upper platform. Standard proportional-integral-derivative controllers with direct terminal feedback from the optical sensors are employed to control the system. Delay-induced dynamic instabilities encountered in the experiments are addressed. A simple error analysis on control with flexible cable is carried to validate the control of the cable-drive architecture. Tests are carried out on a field model of dimension 50 m/spl times/50 m/spl times/12 m. Typical experiments manifest remarkable positioning ability of the proposed system.

We design an adaptive controller for a quadrotor UAV transporting a point-mass payload connected by a flexible cable modeled as serially-connected rigid links. The mass of the payload is uncertain. The objective is to transport the payload to a desired position while aligning the links along the vertical direction from an arbitrary initial condition. A fixed-gain nonlinear proportional-derivative controller is presented to achieve the desired performance for a nominal payload mass, and a retrospective cost adaptive controller is used to compensate for the payload mass uncertainty.

In this paper, a formulation for a spatial sliding joint, which a general multibody can move along a very flexible cable, is derived using absolute nodal coordinates and non-generalized coordinate. The large deformable motion of a spatial cable is presented using absolute nodal coordinate formulation, which is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. And the non-generalized coordinate, which is neither related to the inertia forces nor external forces, is used to describe an arbitrary position along the centerline of a very flexible cable. In the constraint equation for the sliding joint, since three constraint equations are imposed and one non-generalized coordinate is introduced, one constraint equation is systematically eliminated. Therefore, there are two independent Lagrange multipliers in the final system equations of motion associated with the sliding joint. The development of this sliding joint is important to analyze many mechanical systems such as pulley systems and pantograph/catenary systems for high speed-trains.

A non linear FEA study has been performed on the modular coils of the National Compact Stellarator Experiment (NCSX). The modular coils provide the primary magnetic field within NCSX and consist of flexible cable conductor wound on a cast and machined winding form and vacuum impregnated with epoxy. Eighteen coils and associated winding forms are connected at assembly into a toroidal shell structure. The purpose of this study was to evaluate the structural response of the windings and shell structure during cooldown and normal operation. Two separate software packages were used for the study, and two independent analyses were undertaken. The first analysis performed with Pro/Mechanica, examined both the response of the modular coils to magnetic pressure and thermal effects during a 2 Tesla pulse. Modeled items included a portion of the shell structure the winding packs, and a set of 48 'pseudo clamps'. The so called 'pseudo clamps' are represented simply by blocks of material that are restrained in their respective normal directions and have properties which mimic the stiffness of the spring washers of the actual preload clamps. The winding pack is free to slide on the shell structure and is restrained only by the clamps. A secondmore » model, including the complete shell structure of all three coils, was studied with the FEA program ANSYS. Contact regions defined in both Pro/Mechanica and Ansys allow the winding to slide and detach form the shell structure. The two analyses are compared for parameters such as winding/structure gap, overall displacement, equivalent stress and principle strain values.« less

This work considers the modelling problem of the dynamics of overhead cranes with flexible cable and load hoisting or lowering during crane travel. The analysis includes the transverse vibrations of the flexible cable and trolley motion. A set of nonlinear ordinary differential equations governing the motion of the crane system with time-varying spatial domain is derived via the calculus of variation and Hamilton’s principle. A variable-domain finite element method is used to discretize the nonlinear system. A proportional -derivative controller is suggested to drive the crane to a desired destination. Numerical simulations are provided to show the effectiveness of the developed model and to illustrate the results.

Stress analysis of the components of a sheave used to transfer loads between the lift span and counterweight in a movable span bridge is investigated. Stress analysis is a requirement for properly designing such sheaves. Modeling of the mechanism of load transfer from the wire ropes to the sheave is accomplished in three ways: (1) the traditional manner using a uniform pressure distribution; (2) using a varying pressure distribution developed from belt/pulley theory; and (3) using the finite-element method with nonlinear contact elements between the wire rope and the sheave. Internal stresses in the sheave are calculated using uniform distributed pressure and a varying pressure distribution. It is determined that the load distribution on the sheave from the wire ropes is precisely the same for the nonlinear contact analysis and the belt/pulley analysis. The internal stress analysis results show that the traditional, uniformly distributed load representation is less conservative than the more realistic belt/pulley load representation. A methodology is developed that can be utilized to more accurately model the load transfer representation without the complexity of nonlinear analyses.

A transcutaneous energy transformer system (TETS) can provide power to an implanted ventricular assist device (VAD) across an unbroken layer of skin. A TETS includes a subcutaneous secondary coil, which traditionally connects to remote power conditioning circuitry located to avoid eddy current losses and heating that occur in metal near operating TETS coils. Litz wire, used to construct the coil and connect it to that circuitry, efficiently conducts the high frequency alternating current but is bulky and stiff. A novel concept (US Patent No. 6,327,504 B1) packages the secondary coil's output power conditioning circuitry within the unused aperture of the coil while minimizing eddy current losses. The concept allows use of a more flexible cable for its direct current power output. The result is improved reliability, functionality, and efficiency along with decreased implant volume and a thinner, more flexible lead system to interconnect to the VAD. This in turn enhances system versatility by expanding sites available for module implantation. A TETS using this concept has demonstrated efficiency exceeding 80% and peak power outputs of 45 W with good tissue compatibility in the bovine model after a 30 day implant.

The main building block and readout unit of the planned CDF Run IIb silicon detector is a "stave," a highly integrated mechanical, thermal, and electrical structure. One of its characteristic features is a copper-on-Kapton flexible cable for power, high voltage, data transmission, and control signals that is placed directly below the silicon microstrip sensors. The dense packaging makes deadtime-less operation of the stave a challenge since coupling of bus cable activity into the silicon sensors must be suppressed efficiently. The stave design features relevant for deadtime-less operation are discussed. The electrical performance achieved with stave prototypes is presented.

This paper studies the dynamics and control of the Gough–Stewart platform for vibration control of a flexible supporting structure. The problem arises from a large radio telescope in which the astronomical equipment is mounted on a platform to be stabilized by a Gough–Stewart platform, while the base platform of the mechanism itself is carried by a vibrating cable-car that moves along flexible cables. As the base platform is not fixed on the ground, the reaction force caused by the motion of the stabilized platform will lead to perturbation on the base platform, and will induce vibration of the whole system. To study the feasibility for vibration control, this paper models the Stewart parallel mechanism as a multi-body systems with an elastically restrained base platform by the Newton–Euler method and proposes a PD control law based on the position prediction of the two platforms. Control simulations are carried out with the simulated wind excitations. The control effects are evaluated by comparing the root-mean-square responses of the stabilized platform.

In this Letter, high-purity, KAuBr4-treated single-wall carbon nanotube (SWCNT) materials are utilised as outer conductors in coaxial cables. The attenuation/length is within Mil-C-17 specification and nearly equivalent to traditional copper outer conductors up to 3 GHz. The improved transmission performance is attributed to higher conductivity and density of the SWCNT network which creates enhanced nanoscale coverage to improve screening. The weight/length which can be achieved with SWCNT outer coaxial cables results in greater than 40% savings compared with conventional coaxial cables while maintaining a flexible cable design.