Cable Force Research Articles

Initial-Pose Self-Calibration for Redundant Cable-Driven Parallel Robot Using Force Sensors Under Hybrid Joint-Space Control

This letter investigates initial-pose estimation (Cartesian position and orientation) for redundant cable-driven parallel robots (CDPRs). As the forward kinematics cannot be performed if the robot is equipped with incremental sensors, a calibration method using force sensors is proposed. The self-calibration problem is formulated as a non-linear least-squares optimization problem based on the hybrid joint-space control strategy. The redundant cables are tension-controlled; the other cables are maintained at a fixed length in the joint space. A position-determined cable adjustable force (P-CAF) performance index and the concept of calibratable space were proposed to maintain the quasi-static conditions. A simulated case study was used to validate the calibration process.

Comparison of cable tension force prediction using effective length with linear regression and two-mode combination method

ABSTRACT The development of vibration-based tension determination has increased in recent years. The effective vibration length concept is one of the most robust methods in dealing with various end-rotational support stiffness. Recently, a two-mode combination approach by compelling multiple frequencies and effective lengths has been developed to replace the bending rigidity from the cable relationship so the tension can be solved explicitly. This paper aims to compare the tension prediction using the effective length concept with two existing methods: linear regression and the two-mode combination. Three cases of cable support: hinged-hinged (Case 1), hinged-fixed (Case 2), and fixed-fixed (Case 3), are studied through numerical simulation. The cable is vibrated under random excitation, and its dynamical properties are extracted through the SSI method. Equivalent frequencies and equivalent-effective lengths are computed to perform the two-mode approach. The study shows that linear regression produces more minor errors than the two-mode combination method, either for Cases 1, 2, or 3. The theoretical results are presented to figure out the cause of errors. However, linear regression and the two-mode method both produce promising results in calculating the cable tension in these three cases. Similar results are also shown in the study using experimental laboratory test data.

Cable Force Optimization of Cable-Stayed Bridge Based on Multiobjective Particle Swarm Optimization Algorithm with Mutation Operation and the Influence Matrix

To compensate the incapability of traditional cable force adjustment methods to automatically optimize cable forces, this paper proposes Midas/Civil and MATLAB as a structure calculator and a cable force optimizer, and external memory as a data transfer. Initial solutions from conventional methods can be optimized by internalizing the influence matrix into the multiobjective particle swarm optimization algorithm with mutation operation and constructing the mathematical model of cable force optimization, and then, a series of Pareto frontier solution sets are obtained. For the first time, fuzzy set theory is introduced for selecting Pareto presolution set for the optimization of cable-stayed bridges, to solve the final reasonable dead load state of bridges. By using this method, the peak vertical displacement of a main girder of the optimized cable-stayed bridge decreased from −11 mm to −6 mm, with a reduction of 45%. Before and after optimization, the difference of peak negative bending moment at the top of the pier was 34.8%, indicating that the main beam was more evenly stressed and the alignment was more reasonable.

Pre-stressed anchor cable force evolution laws of plane sliding bedding slopes

This paper aims to understand how anchor cable force evolution laws can improve reinforcement designs. The self-developed weak plane sustained deterioration technology was conducted in the indoor test on the reinforced bedding rock slope containing a linear type weak plane. The force evolution laws of anchor cables with the weak plane sustained deterioration was studied. Furthermore, the theoretical equations were derived on the basis of the rigid assumption of the rockmass and the limit equilibrium method, and the equations have been verified to be reliable through comparison with the test results. The numerical simulations in different rockmass mechanical parameters reveal that the theoretical equations are suitable for hard rockmass. The results indicate that, with the weak plane sustained deterioration, the anchor cable axial forces increase gradually, and the axial force increase is inversely proportional to the length of the free sections. The findings could provide the theoretical guideline for the pre-stress safety reserves during the reinforcement designs of anchor cables in different positions of bedding rock slopes.

Frequency-Based Cable Tension Identification Using a Nonlinear Model with Complex Boundary Constraints

Accurate estimation of the cable force affects the bridges’ long-term integrity and serviceability directly. The frequency method is often used for cable tension testing in bridge engineering. However, the generally used cable tension calculation formulae are based on “ideal hinge” or “ideal fixed” boundary conditions. The inclination, bending stiffness, and sag-extensibility of the cable are not properly considered, which results in non-negligible errors. A frequency-based method for precisely determining the tensile force of a cable with unknown rotational and support constraint stiffnesses at the boundary was proposed. A nonlinear mathematical model of the vibration of the cable was established. In addition to parameters such as inclination, sag, and bending stiffness, the effects of unknown rotational and support constraint stiffnesses at both ends of the cable were also considered. The finite difference method was employed to discretize and solve the mode equation of the cable vibration. A frequency-based sensitivity-updating algorithm was applied that can identify simultaneously several system parameters using multiorder measured natural frequencies. Calculation of the matrix eigenvalue derivatives was the key to obtaining the system sensitivity matrix. Numerical examples indicated that the algorithm can be used efficiently and precisely to identify multiple system parameters of the cable, including its tension, bending stiffness, and boundary constraint stiffnesses.

Condition Assessment of Grouped Cable Forces of Cable-Stayed Bridge Using Deflection Data

The stress state of the cable group in a cable-stayed bridge directly affects the overall performance. A novel method for assessing grouped cable forces using deflection data is proposed in this article. Firstly, a simplified equation between the variation in cable forces and the girder deflection was built according to the geometric relationship of the deformation. Secondly, the threshold value of cable force change rate for a single cable can be determined by the proposed theoretical equation and the deflection limit in the specification. On this basis, the evaluation standard of single cable force of piecewise linear mode was established. Thirdly, considering the uniform and non-uniform changes in the cable forces, the condition assessment method of grouped cable forces was established based on the variable weight synthesis method and the gray correlation degree theory. Finally, a case study of a real bridge was undertaken. The results show that the case data validate the correctness of the proposed theoretical equation. The threshold of change rate for long cable is 30%. Six-year assessment scores of grouped cables are generally decreasing, which also reflects the development of other component defects from the side.

Simultaneous Estimation of Submerged Floating Tunnel Displacement and Mooring Cable Tension through FIR Filter-Based Strain and Acceleration Fusion

A submerged floating tunnel (SFT) is a tunnel structure that floats approximately 50 m below the water surface and is anchored to the seabed by mooring cables. It is a new alternative to conventional bridges and immersed tunnels. There have been ongoing efforts to construct SFTs worldwide, and the integrity of these SFTs needs to be monitored throughout their lifespan. This study simultaneously estimated the tunnel displacement and mooring cable tension force using acceleration and strain measurements to assess the integrity of an SFT. First, strain measurements were transformed to displacement using simplified mode shapes and mode-scaling factors, which did not require the true mode shapes of the SFT. The mode-scaling factors were automatically estimated using initial strain and acceleration measurements. Then, the strain-based displacement was combined with the acceleration measurement using a finite impulse response filter to improve the displacement estimation accuracy. In addition, the tension force of a mooring cable was estimated from the displacement at the connection between the tunnel and mooring cable. The feasibility of the proposed technique was examined through a series of numerical simulations and laboratory tests on an 8 m-long aluminum SFT mock-up structure.

Structural Response of an Extra-Wide Concrete Self-Anchored Suspension Bridge under Static Vehicle Loads: Testing and Numerical Simulations

The finite element (FE) analysis by ANSYS software based on field test was used to study the structural performance of an extra-wide concrete self-anchored suspension bridge under static vehicle loads. The longitudinal, transverse and vertical stresses of the extra-wide girder were analyzed, and the changing criteria of girder stresses induced by vehicle loads were presented. Additionally, the effects of the shear lag on extra-wide box girders were investigated. The results showed that the maximum shear lag coefficient was 1.89 at the junction of bottom plate and outer web at the middle of midspan. Moreover, the non-uniformity of cable force is perceptible under eccentric load. Furthermore, an optimization measure for comparable bridges and essential health monitoring locations were outlined.

Early Warning for Abnormal Cable Forces of Cable-Stayed Bridges Considering Structural Temperature Changes

The deterioration or damage of stay cables can threaten the safety of bridges. It is difficult to judge whether a stay cable is deteriorated only by the variation in cable force because cable force also varies with temperature. Therefore, an early warning method for abnormal cable forces of cable-stayed bridges considering structural temperature changes is proposed in this paper. In the proposed method, a baseline model is established to characterize the normal relationship between the healthy cable force and structural temperatures, so the abnormal cable force can be detected by inspecting the residual between the identified cable force to be detected and the cable force predicted by the baseline model. First, the frequency–temperature relationship (FTR) model obeyed by a healthy cable is established by analyzing the mechanism of cable force change caused by structural temperature changes in bridge components from the perspective of deformation coordination. Then, the prediction error is inspected by constructing a mean value control chart of the modeling error generated from the baseline FTR model. An early warning will be triggered when the prediction error exceeds the control limits. Finally, the proposed method is applied to an actual cable-stayed bridge to verify its effectiveness. The results show that the modeling and prediction capabilities of the established FTR model are satisfactory and that the abnormal changes in cable forces can be detected by the proposed early warning method with satisfactory accuracy.

Final-State Structural Behavior of the Long-Span Kömürhan Cable-Stayed Bridge under Torsional and Bending Loadings

Final-state field load testing is an effective method for understanding the real behavior of a bridge before it opens to traffic. The paper presents the procedure and the results of final-state static field tests on the new long span Kömürhan cable-stayed bridge with a single pylon and back span anchorage block under torsional and bending loadings. A total of six static loading cases were conducted to investigate real structural behavior of the bridge having a back span anchorage block and main span deck connected to the pylon with 42 tensioned cables in the deck center. Measured results have been obtained from the surveys and sensors while theoretical results have been calculated from the three-dimensional finite element model of the bridge final-state geometry. The results of final-state static load tests include the main span deck deflections, pylon horizontal displacements, the strains of the main span deck and the pylon, and the cable forces. A good agreement has been achieved between the experimental and theoretical results. Both experimental and theoretical results have shown that the real bridge behavior is in the elastic state under the planned test loads and supplies the design requirements. It is also observed that the results from the torsional and bending load cases positioned in the same sections are close to each other.

Numerical analysis of a slope stabilized with piles and anchor cable frame beams

A landslide located in northern Sichuan Province, China was investigated. A series of numerical models of the landslide stabilized with piles and anchor cable frame beams were developed using a three-dimensional finite-element method. The Strength Reduction Method was employed to investigate the stability of slopes, the internal forces of piles, and the axial forces of anchor cables. A parametric study consisting of pile position, pile length, and pile spacing was carried out. The results show that compared to anchor cable frame beams, the combination of piles and anchor cable frame beams is a more effective retaining structure to improve slope stability. During slope destabilization, the proportion of thrust shared by piles gradually increases, while the proportion of thrust shared by anchor cables gradually decreases. Piles installed on the leading edge of a trail-mode landslide can make the slope mostly stable. As the piles move from the leading, middle, and trailing edges of the slope, the proportion of thrust shared by the anchor cables gradually increases, while local instability may occur in front of the pile. Increasing the pile length can improve the stability of the slope. However, excessive embedded length of piles has little effect on further improving the slope stability. The critical embedment length of piles found in this study is 1/3 of the total length of the pile. The critical pile spacing found in this study is 2.5 times the width of the pile section. Beyond this spacing, the effective soil arch between the piles is difficult to develop and the anchor cables may share more proportion of the landslide thrust. This study provides a reference for reinforcement system design of engineering projects considering piles and anchor cable frame beams.

Fully automated and non-contact force identification of bridge cables using microwave remote sensing

Efficient force identification of bridge cables is important to the performance evaluation of cable-supported bridges. For this purpose, sensors are conventionally installed on the cables to record vibration responses, which is nevertheless time-consuming and labor-intensive. This study develops a fully automated and noncontact cable force identification method using microwave radar sensing, enabling forces of a group of cables to be identified simultaneously and thus largely improving the efficiency. The fast sieve method with a linear time complexity is proposed to find the local maxima of the Fourier spectrum of the displacement measurements. Subsequently, the weighted hash voting is presented to identify the mode orders of the picked frequencies. An appropriate cable vibration model can then be used to compute the tension force. The proposed method has been validated in cable force identification of a newly constructed railway cable-stayed bridge during loading tests. Cable force variations in the loading tests are discussed.

Load distribution strategy for multi-lift system with helicopters based on power consumption and robust adaptive game control

It is of great significance to reasonably distribute the slung load to each helicopter while considering difference in power consumption, relative position and interaction comprehensively. Therefore, the load distribution strategy based on power consumption and robust adaptive game control is proposed in this paper. The study is on a “2-lead” multi-lift system of four tandem helicopters carrying a load cooperatively. First, based on the hierarchical control, the load distribution problem is divided into two parts: the calculation of expected cable force and the calculation of the anti-disturbance cable force. Then, aimed at minimizing the maximum equivalent power of helicopter, an optimization problem is set up to calculate the expected cable force. Specially, the agent power model is trained by BP neural network, the safe distance constraint between helicopters is set to 2.5 rotor diameters to reduce aerodynamic interference, and the helicopters with different performance can be considered by introducing the equivalent power factor into the objective function. Next, considering the difference and interaction between helicopters, the robust adaptive differential game control is proposed to calculate the anti-disturbance cable force. Particularly, to solve the coupled Hamiltonian equations, an adaptive solving method for value function is proposed, and its stability is proved in the sense of Lyapunov. The simulation results indicate that the proposed load distribution method based on power consumption is applicable to the entire flight trajectory even there are differences between helicopters. The game control can consider interaction between helicopters, can deal with different objective functions, and has strong robustness and small steady-state error. Based on the entire strategy, the cable force can be reasonably allocated so as to resist disturbance and improve the flight performance of the whole system.

Load–deflection of flexible ring-net barrier in resisting debris flows

Quantitative understanding of the load–deflection mechanisms of a flexible barrier in intercepting debris flows is critical for barrier design, but remains practically challenging due to the difficulties involved in capturing multi-phase, multi-way interactions. This study employs a physics-based coupled computational fluid dynamics and discrete-element method (CFD–DEM) to simulate a flexible ring-net barrier as a permeable, deformable multi-component system by DEM and model a debris flow as a mixture of discrete particles and a continuous slurry by DEM and CFD, respectively. The CFD–DEM coupling framework offers a unified treatment of in-flow solid–fluid interaction, flow–barrier interaction and interactions among barrier components. Numerical predictions of key flow–barrier interactions and cable forces show reasonable consistency with large-scale experiments. Systematic simulations with varying flow–barrier height ratios ε and flow dynamics are performed to examine the evolving mechanisms of load sharing and transmission and quantify the ε-dependent load–deflection modes. The ratio ε is found to bear a strong, positive correlation with the key barrier response in three typical modes. The post-peak barrier deformations experience shrinkages with ε ≤ 0·6 and expansions when ε > 0·6. This study helps to improve understanding of the load–deflection mechanisms for practical design of flexible barriers in mitigating debris flows.

Learning for Precision Motion of an Interventional X-ray System: Add-on Physics-Guided Neural Network Feedforward Control

Tracking performance of physical-model-based feedforward control for interventional X-ray systems is limited by hard-to-model parasitic nonlinear dynamics, such as cable forces and nonlinear friction. In this paper, these nonlinear dynamics are compensated using a physics-guided neural network (PGNN), consisting of a physical model, embedding prior knowledge of the dynamics, in parallel with a neural network to learn hard-to-model dynamics. To ensure that the neural network learns only unmodelled Effects, the neural network output in the subspace spanned by the physical model is regularized via an orthogonal projection-based approach, resulting in complementary physical model and neural network contributions. The PGNN feedforward controller reduces the tracking error of an interventional X-ray system by a factor of 5 compared to an optimally tuned physical model, successfully compensating the unmodeled parasitic dynamics.

Dynamic model of a tendon-actuated snake robot using the Newton-Euler formulation

Dynamic models are necessary when dealing with robotic applications where requirements of dexterity, manipulability, payload and compliance have to be satisfied at the same time. This work considers a particular design of tendon-actuated snake-like robots in which links are not coupled through mechanical joints but are free to roll between each other under the effect of cable tension forces. The state of the art in modeling these tendon-actuated rolling-joints systems is limited to kinematic and quasi-static models. In order to simultaneously guarantee modeling accuracy and suitability for model-based control, the Newton-Euler (NE) formulation has been adopted, by taking into account the forces and moments generated by cable tensions, links interactions, inertias, and friction between the rolling surfaces.

Mechanical design and feasibility of a finger exoskeleton to support finger extension of severely affected stroke patients.

In this paper we presented the mechanical design and evaluation of a low-profile and lightweight exoskeleton that supports the finger extension of stroke patients during daily activities without applying axial forces to the finger. The exoskeleton consists of a flexible structure that is secured to the index finger of the user while the thumb is fixed in an opposed position. Pulling on a cable will extend the flexed index finger joint such that objects can be grasped. The device can achieve a grasp size of at least 7 cm. Technical tests confirmed that the exoskeleton was able to counteract the passive flexion moments corresponding to the index finger of a severely affected stroke patient (with an MCP joint stiffness of k = 0.63Nm/rad), requiring a maximum cable activation force of 58.8N. A feasibility study with stroke patients (n=4) revealed that the body-powered operation of the exoskeleton with the contralateral hand caused a mean increase of 46° in the range of motion of the index finger MCP joint. The patients (n=2) who performed the Box & Block Test were able to grasp and transfer maximally 6 blocks in 60 sec. with exoskeleton, compared to 0 blocks without exoskeleton. Our results showed that the developed exoskeleton has the potential to partially restore hand function of stroke patients with impaired finger extension capabilities. An actuation strategy that does not involve the contralateral hand should be implemented during further development to make the exoskeleton suitable for bimanual daily activities.

Sensitized Fiber Bragg Grating Anchor Cable Force Sensor

Sensitized Fiber Bragg Grating Anchor Cable Force Sensor

Study on Key Technology of Assembling Installation of Long-Span Composite Girder Cable-Stayed Bridge

PDF HTML XML Export Cite reminder Study on Key Technology of Assembling Installation of Long-Span Composite Girder Cable-Stayed Bridge DOI: 10.59238/j.pt.2023.01.007 Author: Affiliation: (Sichuan Highway Planning, Survey, Design and Research Institute Ltd. , Chengdu 610041, China) Clc Number: Fund Project: Article | Figures | Metrics | Reference | Related | Cited by | Materials | Comments Abstract:The Nanxi (Xianyuan) Yangtze River Bridge in Yibin is a composite beam cable-stayed bridge with twin towers and double cable planes and a main span of 572 m. The superstructure is erected by the assembly method. In order to ensure the precise installation and control of internal forces for steel girders and bridge deck slabs of composite beams while also considering the construction efficiency of composite beams, a control method for the installation and erection of the superstructure has been proposed. This method is based on optimizing the internal force and geometric states of segments throughout the entire process, achieved by establishing finite element calculation models for both the full bridge and segmented sections and combining these with comparative studies of on-site monitoring data. With the installation stress and precision of composite beams properly controlled, construction efficiency has been enhanced through the optimization of the pouring process for wet joints between steel girders and concrete bridge deck slabs, as well as the tensioning process for stay cables. The equivalent tension method is applied to the tension process of the stay cable, thus ensuring the uniformity of the cable force of the steel strand. The relevant conclusions are applicable to the same type of composite girder cable-stayed bridge erection construction. Reference Related Cited by

Производительность сил траловой системы – VI: математическое моделирование (часть III)

Performance of external longitudinal and transverse forces developed in the course of towing the trawl systems, namely, the tension and compression forces of cables, ropes and yarns of the rope-net gears in commercial fishing of the longitudinal modulus of elasticity and the transverse modulus of elasticity in the cordage products. Physical and mechanical properties of the synthetic nylon threads, ropes and nylon cords, from which most trawl systems are made, are considered. Analysis of the physical and mechanical properties of synthetic rope products and cords based on the specified parameters for possible static and dynamic loads is proposed. Algorithms for calculating the physical and mechanical properties of threads, ropes and nylon cords are proposed under the condition of constant volume and mass. Method of calculating physical and mechanical properties of the nylon threads and ropes under the condition of uncertainty gives an error not exceeding 0.4% in calculating the relative elongation δε, but the maximum error δμ in calculating Poisson's ratio μ reaches 7.12%. This proves that the formula for calculating the Poisson's ratio μ for anisotropic bodies does not allow estimating this ratio at low loads and constant volume.