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As the reduction of high -quality coastline at home and abroad and the worse sea conditions of new ports, which brings great challenges to the marine construction operations of ships. In order to explore the marine construction of ships under harsh sea conditions, based on a 3 850 DWT deck barge, considering cable dynamics, a mooring analysis model was and established by using time domain module, and the influence of ship positioning, mooring form, mooring radius, mooring angle, and mooring points on the motion response and cable tension of deck barge were analyzed. The analysis shows that the mooring system has a significant influence on the motion response and cable tension of deck barge, increasing mooring radius, mooring open angle and mooring points can effectively reduce motion response and mooring cable tension, which can provide reference for marine construction operations of ships. [ABSTRACT FROM AUTHOR]

The drum cable engines with DO/HBs (Draw off hold back gear) have been indispensable equipments to lay and recover the optical submarine cables and the optical submarine repeaters. When use them, the back tensions by the DO/HB have been set at relative high tensions because of the empirical knowledge to pass repeaters and cable couplings safely through the drum. However there had been no papers on the minimum back tensions for the DO/HB. If we could know them for the various kind of repeaters, the preparation and operations of the drum cable engines and DO/HBs would be improved and get security. Therefore the author solved forces and moments acting on the repeaters and the cable couplings on the rotated drum cable engines using the linear system of equations. And found that there were the negative longitudinal axial forces acting on the repeaters when the repeaters passed around 85 to 100 degrees from the top of the drum of the first turn in the lay, and around 80 to 110 degrees from the top of the drum of the last turn in the recovery if the back tensions by DO/HB were set below specific values. If there were the negative longitudinal forces, the repeaters would not face the drum and not be wound correctly on the drum. Then here the author clarified the minimum DO/HB back tensions for the drum cable engines based upon more than zero longitudinal axial forces acting on the optical submarine repeaters during lay and recover. These calculations can apply to almost all kind of repeaters if they are connected to the cable coupling with the gimbals joints.

The cables are extremely important and vulnerable components in the cable-stayed bridges. Because cable tension is one of the most crucial structural health indicators, therefore, assessing the cable condition based on the cable tension is a major interest in the structural health monitoring (SHM) of the cable-stayed bridges. This paper aims to develop a deep convolutional neural network (DCNN)-based transfer learning method that is integrated with a continuous wavelet transform (CWT) for the health condition identification of the cables in a cable-stayed bridge using the one-dimensional time series cable tension data. For this purpose, the CWT is adopted to convert the cable tension to the images of a time-frequency representation. The last three new layers emerged in the pre-trained DCNN model, which is called AlexNet, as a new learning framework to use for the identification of the cable condition. The performance of the proposed DCNN model is examined using several statistical measures that include accuracy, sensitivity, specificity, precision, recall, and the F-measure. The results show that the proposed DCNN model gives superior accuracy (100%) for the identification of the undamaged cables and the damaged cables based on the cable tension data.

Since all structures vibrate due to external loads, measuring and analyzing vibration data is a representative method of structural health monitoring. In this paper, we propose a non-contact cable estimation method using a vision sensor mounted on an unmanned aerial vehicle. A target cable among many cables can be identified through marker detection. In addition, the motion of the structure can be quickly captured using the extracted feature points. Although computer vision can be used to transform displacements of multiple axis, in this study, only the vertical displacement is considered to estimate tension. Finally, the cable tension can be estimated via the vibration method using the modal frequencies derived from the cable displacement. To verify the performance of the proposed method, lab-scale experiments were carried out and the results were compared with the conventional method based on the accelerometer. The proposed method showed a 3.54% error compared with the existing method and confirmed that the cable tension force can be estimated quickly at low cost. [ABSTRACT FROM AUTHOR]

Estimation and monitoring of cable tension is of great significance in the structural assessment of cable-supported bridges. For short cables, the traditional cable tension identification method via frequency measurement has large errors due to the influence of complex boundaries, which affect the accuracy of estimation. A new cable tension estimation method based on mode shape identification with a multiple sensor arrangement on the cable can take the influence of boundary conditions into account and its accuracy has been verified. However, it requires more sensors compared to the traditional frequency-based method, which will significantly increase the cost of long-term monitoring in practice. Therefore, a novel approach for cable tension monitoring considering both cost and accuracy is further proposed in this study. The approach adopts multiple sensors to measure the influence of boundary conditions. Then, only a single sensor is required for long-term monitoring of the cable. In this paper, an analytical model of the cable is firstly established. The influence of boundary conditions is calculated, which ensures the accuracy of mode shape identification. Furthermore, a field experiment is carried out to verify the effectiveness of the new approach. The results have demonstrated the effectiveness and accurateness of the proposed method in long-term short cable tension monitoring. [ABSTRACT FROM AUTHOR]

Controlling the stiffness of cable-driven parallel mechanisms (CDPM) is of great significance for improving performance in different tasks. A method for stiffness control of a redundant CDPM is presented in this paper. The stiffness matrix of the redundant CDPM is established. On this basis, considering the effect of coupling stiffness, a complete analytical formula for stiffness in different directions is established. Then, the influence of the vector λ on the stiffness of the CDPM in different directions is analyzed, and a method to control the stiffness of the CDPM through adjusting the vector λ is proposed. To avoid traversing the value of λ in the polygon formed by the set of λ to obtain the appropriate cable tension and keep the cable tension away from the upper and lower limit values, a change path of the vector λ is designed. When the vector λ changes along the path, the stiffness of the mechanism can be changed from the minimum value to the maximum value. This method has high computational efficiency and safety. Finally, the correctness and effectiveness of the stiffness control method are verified by experiments. The stiffness control method proposed in this paper can be used to control the stiffness in different directions, and can also be used for different types of redundant CDPMs. [ABSTRACT FROM AUTHOR]

Forest operations are one of the most dangerous jobs in all fields of industrial production. Studies have shown that cable logging accidents are frequently caused by inadequate safety factors. Due to the limited reliability of theoretical models of cableway installations and the inefficacy of load limiters of existing machines, technical solutions for continuous skyline tensile force monitoring should be developed. This work proposes a novel concept and model to determine the skyline tensile force in real time, based on a non-invasive measurement and evaluation system built into the carriage. This information can be harnessed to improve the logging operational safety automatically and dynamically. The concept was tested with the help of a miniature cableway setup. The mean absolute error between the predicted and measured skyline tension for a total of 55 measurements was 14 %, and the maximum error was 29 %. This confirms the validity of the proposed approach. • In 55 % of cable logging cycles, safe skyline force limits are exceeded. • The proposed concept computes the skyline force in real time based on a few sensors. • Some variations even work in dynamic situations and with partial load suspension. • A test setup revealed a mean error of 14 % with respect to measured data. • The concept is ready to be employed in all types of horizontally suspended equipment. [ABSTRACT FROM AUTHOR]

Since all structures vibrate due to external loads, measuring and analyzing vibration data is a representative method of structural health monitoring. In this paper, we propose a non-contact cable estimation method using a vision sensor mounted on an unmanned aerial vehicle. A target cable among many cables can be identified through marker detection. In addition, the motion of the structure can be quickly captured using the extracted feature points. Although computer vision can be used to transform displacements of multiple axis, in this study, only the vertical displacement is considered to estimate tension. Finally, the cable tension can be estimated via the vibration method using the modal frequencies derived from the cable displacement. To verify the performance of the proposed method, lab-scale experiments were carried out and the results were compared with the conventional method based on the accelerometer. The proposed method showed a 3.54% error compared with the existing method and confirmed that the cable tension force can be estimated quickly at low cost.

The dynamics of the gravitational lifting system of the deep sea mining industry is demonstrated in this article. A simplified dynamic model is obtained when gravity, buoyancy and drag force are the major concerns. By quantitative analysis, different variables like bucket size, distribution distance, and filling rate are considered to measure their influence on lifting speed and production rate, which ends up with that the most influential factor is the bucket size, and it has a positive correlation with both the two targets: lifting speed and production rate. Due to the breaking strength of the cable wire rope, a feasible design of such a lifting system should take the tension force into consideration. Hence, the feasibility is also examined and a conclusion is summarized that a combination of the bucket size and the distribution distance should be optimized according to the concrete working conditions.

Service performance evaluation is of great significance to the safety, durability, and reliability of bridge engineering. Over the last decade, structural health monitoring (SHM) systems have been widely used for condition monitoring of cable-stayed bridges, massive monitoring data are measured and stored by the sensing subsystems, which provides the basis for service performance evaluation of bridge engineering. Meanwhile, the load test is a common method to assess the construction and service performance of bridges. Combined the SHM systems and a load test of a thousand-meter level cable-stayed bridge after ten years of service, this paper investigates the operating conditions of main structures, including bridge towers, main girders, and steel cables. 52 trucks were used to conduct a quasi-static load on three key sections of bridges. Meanwhile, the GPS displacement of towers and main girders, stress of the main girders and acceleration responses of cables were measured synchronously by the SHM systems. Based on the health monitoring data, the dynamic responses, structural deformation, and cable tension of the bridge were investigated and evaluated by comparing with the finite element (FE) model load test at construction stage. The results show that the service performance of the bridge is basically within the designed conditions. [ABSTRACT FROM AUTHOR]

The rotating mechanism is a significant procedure in swing bridges. In this paper, the Nandu River swing bridge is taken as an engineering case study to exhibit the critical technology of the monitoring process and the construction method of the swing bridge. The research focuses on the central load-bearing control system used to guarantee the security of the construction process. The mechanical problems during the construction process are discussed. Simultaneously, the cable tension and gravity center test are introduced. The non-Hertz contact theory is utilized to calculate the stress distribution of the spherical joint. Furthermore, the overturning moment is computed to monitor the stability of the rotating system based on the stress distribution calculation of the spherical joint. The monitoring process of central load-bearing control is entirely exhibited and discussed. Concurrently, the calculating result of the real-time overturning moment reflects the stability of the rotating construction process, and adjustments are made to ensure the safety of construction. The results show that, during the cable tension process, the middle position of the main arch exhibited 162.3 mm maximum vertical displacement. Meanwhile, the fraction moment was greatly larger than the unbalanced moment. Furthermore, the maximum overturning moment value was 2094.38 kN·m, which was smaller than the resistance of the overturning moment. The present research demonstrates that the non-Hertz contact theory fits the calculation of spherical joint stress distribution. Simultaneously, the middle position of the main arch should be monitored to control the vertical displacement at the cable tensioning stages. The gravity center test and stability control of the rotating construction are the key steps to reaching central load-bearing control. [ABSTRACT FROM AUTHOR]

Featured Application: The method proposed in this paper can quickly identify the time-varying cable tension and have the potential for condition monitoring and performance evaluation of cables under special events, such as typhoons, earthquakes and heavy traffic. Cables have been increasingly utilized in modern long-span or tied-arch bridges as the main bearing structures. Real-time identification of time-varying cable tension is essential for assessing the service performance of bridges. Vibration-based methods have been an increasing research focus in recent decades. However, a long time interval is needed to estimate structural frequency using vibration-based methods, increasing the calculating time of cable tension. The time-varying cable tension is thus difficult to extract. This study proposes a time-frequency reassignment-based algorithm to reduce the detection time to address this issue. Combined with a time-frequency analysis tool and vibration theory of cables, the algorithm can identify the time-varying frequency and further quickly calculate the time-varying cable tension within 12.8 s. The features of the proposed algorithm are mainly threefold: identifying the time-varying frequencies with high precision; without some prior knowledge of vibration; having no other requirements for sensor modes. Moreover, the experimental validation is conducted using a quasi-static loading in a workshop and a dynamic field test on Sutong Bridge, respectively. The results show that the proposed algorithm can be used to identify time-varying tension and assess the service performance of cables, providing a new path for real-time condition monitoring of bridges in service. [ABSTRACT FROM AUTHOR]

• Measured cable tension using the indirect method of vibration analysis. • Cable tension measured using a vision-based system. • Dynamic response measured using cable shape. • Cable shape extracted using Canny edge detection. • Similarities observed between tensions measured by vibration and lift-off test. Cables transfer the primary load of cable-stayed bridges and are necessary for examining the integrity and safety of bridges. In this study, we used images obtained from a vision-based system to estimate cable tension using a vibration method and proposed a method to measure the dynamic response required for cable tension estimation. The method does not require a target attachment and can be used on cables without feature points; it involves extracting the edge of a cable shape from acquired images and measuring the cable's dynamic response by determining the center of the extracted edge. The measured dynamic response is analyzed to extract the natural frequencies of vibration modes, which are then applied to the vibration method using the least squares approach. To verify the reliability of the proposed method, we measured the dynamic response of cables in a state of ambient vibration on an operating cable-stayed bridge. [ABSTRACT FROM AUTHOR]

Analyses of the equilibrium conditions of an anchor and a cable of a ship at anchoring are presented. Three conditions are considered: (1) a part of the cable lies on the seafloor; (2) no part of the cable lies on the seafloor and rises from the seafloor with a zero gradient of the slope; and (3) a nonzero gradient of the slope. In the third condition, a coefficient is introduced to represent the effects of the vertical component of the cable tension on the holding force of an anchor while considering the decrease in the apparent anchor weight. Formulas of the holding force limit in each condition are presented by analyzing the parameters representing the three cable conditions. Numerical examples demonstrate the effects of extended cable length, water depth, soil properties of the seafloor, and the coefficient of upward cable tension on the holding force limit and parameters characterizing the three cable conditions. Measuring the safety of anchoring in terms of the extended cable length and the current cable conditions associated with the risk allowance for dragging anchors is discussed. [ABSTRACT FROM AUTHOR]

Cable tension monitoring is vital for the health monitoring of cable-stayed bridges. During the service of bridges, cable tension fluctuates rather than monotonously changes. However, existing research works pay little attention to the influence of tension history. In this article, the influence of the tension history on the monitoring of cable tension was studied. To guide the experiment, the magnetization theory of ferromagnetic materials and the electromagnetic induction principle were combined to analyze the theory of the magnetoelastic inductance method. The magnetoelastic inductance method characterized cable tension by sensor inductance. Based on the theoretical analysis, tension monitoring experiments were carried out to figure out the influences of design tension and tension variation. Experimental results showed the design tension and the tension variation influenced the relationship between the inductance and the tension. To monitor the fluctuating tension, a secant method was proposed. When the tension changed less than 30% of the design tension, the tension can be ascertained by the secant method. The experimental results demonstrated that the influence of the tension history should be considered when the design tension was different or the tension variation was large. Besides, the influence of the tension history analyzed in this article is suitable for other tension monitoring methods based on the magnetic properties of ferromagnetic materials. [ABSTRACT FROM AUTHOR]

Estimation and monitoring of cable tension is of great significance in the structural assessment of cable-supported bridges. For short cables, the traditional cable tension identification method via frequency measurement has large errors due to the influence of complex boundaries, which affect the accuracy of estimation. A new cable tension estimation method based on mode shape identification with a multiple sensor arrangement on the cable can take the influence of boundary conditions into account and its accuracy has been verified. However, it requires more sensors compared to the traditional frequency-based method, which will significantly increase the cost of long-term monitoring in practice. Therefore, a novel approach for cable tension monitoring considering both cost and accuracy is further proposed in this study. The approach adopts multiple sensors to measure the influence of boundary conditions. Then, only a single sensor is required for long-term monitoring of the cable. In this paper, an analytical model of the cable is firstly established. The influence of boundary conditions is calculated, which ensures the accuracy of mode shape identification. Furthermore, a field experiment is carried out to verify the effectiveness of the new approach. The results have demonstrated the effectiveness and accurateness of the proposed method in long-term short cable tension monitoring.

Cable-driven parallel robots (CDPRs) are a new type of parallel robots with a mobile platform driven by several cables. The flexibility of the structure not only helps them perform better than traditional parallel robots, but also brings about the issues of model uncertainty and multicable coordination. To handle these problems, a novel adaptive synchronization control (ASC) scheme is proposed to suppress the uncertainties of kinematics and dynamics simultaneously, regulate the coordination motion of multiple cables, and finish high-precision tracking tasks. In the proposed scheme, apart from tracking error, a new synchronization error is introduced to describe the coordination motion relationship between adjacent cables. According to these defined errors, the kinematic and dynamic adaptation laws are designed through the linear expressions of kinematic and dynamic models, respectively. Finally, the ASC scheme is presented as well as a tension distribution algorithm. The tracking experiments are implemented on a redundantly actuated 3-degree-of-freedom CDPR with four cables. The proposed ASC scheme can effectively complete the correction of the model parameters by using the feedback of errors and enhance the tracking accuracy of each cable and the synchronization accuracy between all the cables significantly, thereby ultimately improving the control performance of the mobile platform. [ABSTRACT FROM AUTHOR]

This paper focus on parameter identification of the main cables of cable suspension structures. Based on the dynamic stiffness theory, an inverse analysis characteristic function (IAC function) for identifying the main cable parameters (such as cable tension, moment of inertia, cable length, and mass per unit length) is established. This function allows for the consideration of cable flexural rigidity, sag, inclination, and additional lumped masses sustained by the suspender. The effects of the cable tension and moment of inertia on the IAC function are investigated via a numerical method. On this basis, a method for identifying the two parameters based on the peak-ridges of the IAC function is proposed. The method comprehensively utilizes measured multimode frequencies. It is unnecessary to determine the fundamental frequency and frequency order. A 20-m real cable test with suspended lumped masses is conducted to verify the correctness of the proposed methods. With the increase in the weight of suspended lumped masses, the advantages of the proposed method are more obvious. For operational cable tension less than 50% of the cable breaking tension, the cable moment of inertia is less affected by suspended lumped masses. [ABSTRACT FROM AUTHOR]

The rotating mechanism is a significant procedure in swing bridges. In this paper, the Nandu River swing bridge is taken as an engineering case study to exhibit the critical technology of the monitoring process and the construction method of the swing bridge. The research focuses on the central load-bearing control system used to guarantee the security of the construction process. The mechanical problems during the construction process are discussed. Simultaneously, the cable tension and gravity center test are introduced. The non-Hertz contact theory is utilized to calculate the stress distribution of the spherical joint. Furthermore, the overturning moment is computed to monitor the stability of the rotating system based on the stress distribution calculation of the spherical joint. The monitoring process of central load-bearing control is entirely exhibited and discussed. Concurrently, the calculating result of the real-time overturning moment reflects the stability of the rotating construction process, and adjustments are made to ensure the safety of construction. The results show that, during the cable tension process, the middle position of the main arch exhibited 162.3 mm maximum vertical displacement. Meanwhile, the fraction moment was greatly larger than the unbalanced moment. Furthermore, the maximum overturning moment value was 2094.38 kN·m, which was smaller than the resistance of the overturning moment. The present research demonstrates that the non-Hertz contact theory fits the calculation of spherical joint stress distribution. Simultaneously, the middle position of the main arch should be monitored to control the vertical displacement at the cable tensioning stages. The gravity center test and stability control of the rotating construction are the key steps to reaching central load-bearing control.

Cables have been increasingly utilized in modern long-span or tied-arch bridges as the main bearing structures. Real-time identification of time-varying cable tension is essential for assessing the service performance of bridges. Vibration-based methods have been an increasing research focus in recent decades. However, a long time interval is needed to estimate structural frequency using vibration-based methods, increasing the calculating time of cable tension. The time-varying cable tension is thus difficult to extract. This study proposes a time-frequency reassignment-based algorithm to reduce the detection time to address this issue. Combined with a time-frequency analysis tool and vibration theory of cables, the algorithm can identify the time-varying frequency and further quickly calculate the time-varying cable tension within 12.8 s. The features of the proposed algorithm are mainly threefold: identifying the time-varying frequencies with high precision; without some prior knowledge of vibration; having no other requirements for sensor modes. Moreover, the experimental validation is conducted using a quasi-static loading in a workshop and a dynamic field test on Sutong Bridge, respectively. The results show that the proposed algorithm can be used to identify time-varying tension and assess the service performance of cables, providing a new path for real-time condition monitoring of bridges in service.

Summary: Structural health monitoring (SHM) systems have been widely implemented in long‐span bridges to measure various structural responses. It is difficult to directly perform condition assessment from the variations in structural responses because of initial residual stress and defaults, coupling effects of structure damage and external loads, and others. To fix these problems, this study proposes global and partial bidirectional long short‐term memory (BiLSTM) models to establish a relationship between girder vertical deflection (GVD) and cable tension (CT). First, a global BiLSTM model is built using all the measured signals of GVD and CT, and the test results show that the average root mean square error (RMSE) and relative RMSE (RRMSE) between the predicted and ground‐truth CTs are 1.83 kN and 3.19%, respectively. Second, the effects of both traffic volume and noise level on the model prediction error are investigated, indicating that the proposed method is robust to different noise levels and traffic volumes under normal operational conditions. Finally, to customize a prediction model for a certain CT, a group of partial BiLSTM models is further constructed with only a few GVDs as inputs and a single CT as output. Sobol's sensitivity index is adopted as the indicator to select the most significant inputs among all the GVD sensors. The partial model is more efficient for training because of significantly fewer channels in each layer and model parameters. The prediction results show that the partial models can achieve an average RMSE and RRMSE of 1.86 kN and 3.24%, respectively, which are similar to the prediction accuracy of the global model. In addition, the partial model can be applied if certain sensors are out of order when compared to the global model. [ABSTRACT FROM AUTHOR]

Ground based forest harvesting machines are being used on steeper slopes with the aid of tethers to help maintain traction and stability. It is common to position a base machine containing the tether winch above the forest harvesting machine. This configuration is termed a live tether. The live tethers may be run around rub trees to reduce the time required to reposition the tether. This study developed a new model that includes both friction and cutting forces to estimate cable tension on either side of the rub tree. A dataset collected in the field was used to estimate the parameters in the model. The model appears to be promising; however, further work is required on the interaction of the cable cutting surfaces and the surface toughness of the wood. In general, it was found that the difference in the tension on either side of the rub tree increased with increasing change in angle, that the cable on average cut 3 mm deeper with each 10 m of the cable travel, and that the difference in tension was not correlated with the depth cut into the wood. • This study develops a new model that includes friction and cutting forces to estimate cable tension around a rub tree. • Data was collected and used to estimate the friction coefficient and cutting deformation coefficient in the new model. • The change in tension is independent of the depth the cable cut into the tree. • Interaction between the surface toughness of the wood and the frictional surfaces of the cable requires further study. [ABSTRACT FROM AUTHOR]

Summary: In suspension bridges, hanger cables are the main load‐supporting members. The tension of the hanger cables of a suspension bridge is a very important parameter for assessing the integrity and safety of the bridge. In general, indirect methods are used to measure the tension of the hanger cables of a suspension bridge in use. A representative indirect method is the vibration method, which extracts modal frequencies from the cables' responses and then measures the cable tension using the cables' geometric conditions and the modal frequencies. In this study, ambient vibration tests were conducted on a suspension bridge in use to verify the validity of the image‐based back analysis method, which can estimate the tension of remote hanger cables using the modal frequencies as a parameter. The tension estimated through back analysis, which was conducted to minimize the difference between the modal frequencies calculated using finite element analysis of the hanger cables and the measured modal frequencies, was compared with that measured using the vibration method. It was confirmed that reliable tension estimation is possible even with low‐order modal frequencies when the image‐based back analysis method is used. [ABSTRACT FROM AUTHOR]

Minimally invasive surgical robotic systems established the foundation for precise and refined surgery, and the intelligentization of robotic systems is an important direction for future development. Among the methods of intelligentization, microinstrument external force sensing is an open and challenging research area. Force sensing information is used not only to ensure that surgeons apply the appropriate amount of force but also to prevent unintentional tissue damage. Because a microinstrument is a compact and small-sized construction, indirect force sensing method instead of the integration of sensors into the microinstrument is used, yielding better biocompatibility, sterilizability and monetary cost savings. This paper focuses on microinstrument-tissue contact force sensing, and the microinstrument used is a three degrees of freedom cable-driven manipulator. A contact force estimation strategy based on the differences in cable tension is established with consideration of the kinematics, dynamics and friction of the manipulator. A principle prototype of a surgical microinstrument force measurement system is developed, and then zero-drift, hysteresis and force loading experiments are studied. Based on the experimental data of the force loading experiments, the relationship between cable tension and contact forces is established by using a bidirectional long short-term memory plus multilayer perceptron network. The results show that the L2 cost of the network in the training set converges to 0.006 and that the RMSE of the network in the testing set converges to 0.053, and the network can meet the measurement requirements without overfitting. Therefore, the indirect force estimation method is a viable method of measuring forces of cable-driven microinstrument and can be used to integrate force sensing information into surgical robotic systems to improve the operability of surgical robots. [ABSTRACT FROM AUTHOR]