Towed System Research Articles

Hydrodynamic Response of Ocean-Towed Cable-Array System under Different Munk Moment Coefficients

The ocean towing system plays an important role in the ocean development process. The motion of a towed body is closely coupled with the motion of a towing cable. In this paper, the lumped mass method is used to discrete a towing cable into a lumped mass model. At the same time, on the basis of some assumptions, the relationship between the expression of Munk moments in the classical towed body kinematics and the expression of the Munk moments in the hydrodynamic analysis software OrcaFlex is established. Based on the above assumptions and the derivation, combined with the specific parameters of a certain sea state and a certain towing system, the dynamic simulation of the towing system is made by OrcaFlex. By changing the different Munk moment coefficients, the real-time response of the cable tension and the towed underwater body under different Munk moments is achieved. The effects of different Munk moment coefficients on the change of the tension are obtained; the six degrees of freedom of the towed body under the action of different Munk moment coefficients are shown. To obtain the spectral density of the six degrees of freedom of the towed body under the action of different Munk moment coefficients, Fast Fourier Transform is performed on the calculated results of the towed body in the time domain. The results provide a theoretical basis for the optimal design of a cable and towed body.

Dynamic analysis of underwater towed system under undulating motion mode of towed vehicle

This study analyzed the dynamic characteristics of an entirely underwater towed system functioning under the undulating motion mode of the underwater towed vehicle. The motions of the towing ship and underwater towed vehicle were simulated using Computational Fluid Dynamics (CFD) method. The towing cable connecting the unmanned surface vehicle (USV) and the underwater towed vehicle was divided into elastic segments, and the influence of flow on the towing cable was determined by the real-time velocities of the flow field at the nodes connecting the cable segments. The numerical results show that external and internal forces of the system and position and posture of the components of the towed system exhibit periodic change under a periodic control action, and the amplitude of the depressing force acting on the vehicle increases with the increase in the towing speed. Further, the hydrodynamic forces acting on the towing cable attain minimum and maximum values when the shifting weight passes its equilibrium position from back to front and vice versa, respectively. In addition, the undulating motion of the towed vehicle exerted no significant effect on the trimming angle of the USV.

The development of a concept of an unmanned glider-tug and cargo unmanned aerial vehicle with electric drive

The development of a concept of an unmanned glider-tug and cargo unmanned aerial vehicle with electric drive Abstract: The article presents a few selected ideas for AUV usage which are being developed in Poland as well as the description of a project of an unmanned tug, a new technological solution which was submitted to the Patent Office in December 2017 and which has been being developed since then. The proposed towing system consists of a universal ground-based air traffic control station for unmanned flights, an AUV-tug and an additional control system placed on the towed object. The proposed solution aims at maintenance costs reduction and increase of performance of aircrafts with electric drive. Keywords: UAV; Tug; Global Positioning System (GPS); Galileo

Acute effects of overspeed stimuli with towing system on athletic sprint performance: A systematic review with meta-analysis

ABSTRACT Overspeed-based training is widely used to improve athletes’ maximum running speed and towing systems are one of the most frequently employed methods for this purpose. However, the effectiveness of this modality has not been thoroughly determined. This review analyzes the acute effects of overspeed conditions with towing systems in sprinters. The articles were searched, analysed and selected following the PRISMA methodology in the PubMed, SPORTDiscus and Google Scholar databases. Sixteen studies were included, with a total sample of 240 men and 56 women (14 to 31y; 1.73 to 1.82 m; 66.2 to 77.0 kg). The main acute responses found were: 1) an increase in maximum running speed (ES = 1.54, large), stride length (ES = 0.92, moderate), flight time (ES = 0.28, small) and stride rate (ES = 0.12, trivial); and, 2) a decrease in contact time (ES = 0.57, small). However, analysis of the reported ground reaction forces and electromyography data did not provide enough consistent evidence to conclusively determine whether the changes are due to a greater muscular response of the athlete or the effect of the towing system. Future research should focus on studying the mechanisms responsible for the observed acute effects.

Stability analysis of wheeled mobile multi-robot coordinated towing system

Stability analysis of wheeled mobile multi-robot coordinated towing system

Review of Nodule Mineral Image Segmentation Algorithms for Deep-Sea Mineral Resource Assessment

A large number of nodule minerals exist in the deep sea. Based on the factors of difficulty in shooting, high economic cost and high accuracy of resource assessment, large-scale planned commercial mining has not yet been conducted. Only experimental mining has been carried out in areas with high mineral density and obvious benefits after mineral resource assessment. As an efficient method for deep-sea mineral resource assessment, the deep towing system is equipped with a visual system for mineral resource analysis using collected images and videos, which has become a key component of resource assessment. Therefore, high accuracy in deep-sea mineral image segmentation is the primary goal of the segmentation algorithm. In this paper, the existing deep-sea nodule mineral image segmentation algorithms are studied in depth and divided into traditional and deep learning-based segmentation methods, and the advantages and disadvantages of each are compared and summarized. The deep learning methods show great advantages in deep-sea mineral image segmentation, and there is a great improvement in segmentation accuracy and efficiency compared with the traditional methods. Then, the mineral image dataset and segmentation evaluation metrics are listed. Finally, possible future research topics and improvement measures are discussed for the reference of other researchers.

Course stability analysis for towing system of a gravity-based structure in managed ice fields

ABSTRACT Compared to open water, the presence of ice floes in ice-covered water may pose additional challenges to the towing operations of offshore platforms. This paper proposes a numerical model for analyzing course stability of a gravity-based structure during towing operation in managed ice fields, considering coupled motions of tugs, towed platform, and ice floes. A discrete element method is applied to simulate interaction between drifting ice floes and structures, and verified by existing model tests. The motions of tug and towed platform are coupled through a catenary towline model. A proportional-differential controller is employed to adjust heading and lateral position of tug. The effects of main factors, such as tugs’ number, towline length, ice concentration, rudder area and controller gains on course stability are discussed through numerical case studies. The presented numerical approach is expected to provide practical guidance for towing design, and ensure safety of towing operation.

A homogenization-planning-tracking method to solve cooperative autonomous motion control for heterogeneous carrier dispatch systems

Taxiing aircraft and towed aircraft with drawbar are two typical dispatch modes on the flight deck of aircraft carriers. In this paper, a novel hierarchical solution strategy, named as the Homogenization-Planning-Tracking (HPT) method, to solve cooperative autonomous motion control for heterogeneous carrier dispatch systems is developed. In the homogenization layer, any towed aircraft system involved in the sortie task is abstracted into a virtual taxiing aircraft. This layer transforms the heterogeneous systems into a homogeneous configuration. Then in the planning layer, a centralized optimal control problem is formulated for the homogeneous system. Compared with conducting the path planning directly with the original heterogeneous system, the homogenization layer contributes to reduce the dimension and nonlinearity of the formulated optimal control problem in the planning layer and consequently improves the robustness and efficiency of the solution process. Finally, in the tracking layer, a receding horizon controller is developed to track the reference trajectory obtained in the planning layer. To improve the tracking performance, multi-objective optimization techniques are implemented offline in advance to determine optimal weight parameters used in the tracking layer. Simulations demonstrate that smooth and collision-free cooperative trajectory can be generated efficiently in the planning phase. And robust trajectory tracking can be realized in the presence of external disturbances in the tracking phase. The developed HPT method provides a promising solution to the autonomous deck dispatch for unmanned carrier aircraft in the future.

Development of a Concept of an Unmanned Glider-tug. Part 2

The article presents the development of the unmanned glider tug project, a description of the stages of a new technical solution, submitted to the patent office in December 2017 and developed to date. The proposed towing system consists of a universal drone ground control station and a tugboat rigidly connected to the sailplane. The proposed solution is aimed at reducing operating costs and limiting the number of people necessary to service sailplane flights.

Development of a Concept of an Unmanned Glider-tug. Part 1

The article presents the development of the unmanned glider tug project, a description of the stages of a new technical solution, submitted to the patent office in December 2017 and developed to date. The proposed towing system consists of a universal drone ground control station and a tugboat rigidly connected to the sailplane. The proposed solution is aimed at reducing operating costs and limiting the number of people necessary to service sailplane flights.

Functional and performance test of modified lug wheel on two wheels tractor with pivot type trailer

Palm oil fields with slopes require special wheels for transportation for transporting fresh fruit bunches (FFB), the special wheels in question are modified wheels from the existing cage wheel, the modified wheels can adjust the slope conditions on the land with the lug angle adjustment mechanism. The objective of this study was to test the functional and performance of the modified lug wheel as a means of transporting FFB on sloping land using a hand tractor on a pivot type trailer. Functional testing on the modified lug wheel was carried out by observing changes in the angle of the lugs (0, 15, 30, 45)0 by lifting one of the tractor shafts first using a jack, after which the locking pins were released. The angle change rim can be moved clockwise or anticlockwise by hand according to the desired lug angle. Performance testing on the modified lug wheel is carried out by observing and calculating the slip on the wheel. Functional testing on trailer pivots is carried out by observing all components of the towing system when installed and operated, to determine whether the trailer towing system can function properly. Performance testing on the pivot trailer is done by observing and calculating the turning radius when the tractor turns. Performance testing is also carried out by observing the stability of the two-wheel tractor and trailer. The slope of the land and the angle of the lugs greatly affect wheel slip, the higher the slope on a land, the higher the possibility of wheel slippage during operation. The test results show that the use of modified lug wheels shows better performance at 30° lug angle, as seen from the smaller slip value at 30° lug angle.

Spatial Rigid-Flexible-Liquid Coupling Dynamics of Towed System Analyzed by a Hamiltonian Finite Element Method

An effective Hamiltonian finite element method is presented in this paper to investigate the three-dimensional dynamic responses of a towed cable-payload system with large deformation. The dynamics of a flexible towed system moving in a medium is a classical and complex rigid-flexible-liquid coupling problem. The dynamic governing equation is derived from the Hamiltonian system and built-in canonical form. A Symplectic algorithm is built to analyze the canonical equations numerically. Logarithmic strain is applied to estimate the large deformation effect and the system stiffness matrix will be updated for each calculation time step. A direct integral solution of the medium drag effect is derived in which the traditional coordinate transformation is avoided. A conical pendulum system and a 180° U-turn towed cable system are conducted and the results are compared with those retraced from the existing Hamiltonian method based on small deformation theory and the dynamic software of Livermore software technology corp. (LS-DYNA). Furthermore, a circularly towed system is analyzed and compared with experimental data. The comparisons show that the presented method is more accurate than the existing Hamiltonian method when large deformation occurred in the towed cable due to the application of logarithmic strain. Furthermore, it is more effective than LS-DYNA to treat the rigid-flexible-liquid coupling problems in the costs of CPU time.

Featured Cover

The cover image is based on the Research Article An intelligent course keeping active disturbance rejection controller based on double deep Q-network for towing system of unpowered cylindrical drilling platform by Yuemin Zheng et al., https://doi.org/10.1002/rnc.5740.

Dynamics and workspace analysis of a multi-robot collaborative towing system with floating base

Dynamics and workspace analysis of a multi-robot collaborative towing system with floating base

An intelligent course keeping active disturbance rejection controller based on double deep Q‐network for towing system of unpowered cylindrical drilling platform

AbstractTowing is a widely used mode of transportation in offshore engineering, and towing of unpowered platforms is of particular significance. However, the addition of unpowered facilities has increased the difficulty of ship maneuvering. Moreover, the marine environment is complex and changeable, and sudden winds or waves can have unpredictable effects on the towing process. Therefore, it is of great significance to overcome the influence of the harsh marine environment while navigating the towing system following a planned course to a target sea area. To tackle the time‐varying disturbances, a course control method for a towing system of unpowered cylindrical drilling platform is designed based on double deep Q‐network (DQN) optimized linear active disturbance rejection control (LADRC). To be specific, to tackle the difficulty of LADRC tuning, double DQN is applied to select the best parameters of the LADRC at any time according to the states of the system, without relying on the specific information of the model and the controller. The course control performance of the towing system is evaluated in a simulation environment under various disturbances. Moreover, the Monte Carlo experiment is used to test the robustness of the controller when the ship's mass changes and the robustness of the proposed method is verified by testing with various heading angles. The results show that the LADRC with adaptive parameters optimized by double DQN performs well under external interference and inherent uncertainty, and compared with the traditional LADRC, the proposed method has better course control effects.

Numerical Simulation of Depth Tracking Control of an Underwater Towed System Coupled with Wave–Ship Interference

This paper presents a numerical study of the depth tracking control for an underwater towed system under wave–ship interference condition. To overcome the laminations of ignoring the hydrodynamic factors and wave–ship interference in the existing simulation model for the depth tracking operation of the underwater towed system, a numerical model combining the control system with the computational fluid dynamics (CFD) method based on the overset mesh technique is explored and constructed; the influence of towing ship and head waves is introduced into the numerical analysis of the underwater towed system; a depth control system based on the center of gravity adjustment is proposed and its control characteristics are discussed. The fluid motion around the towed vehicle and the towing ship is governed by the Navier–Stokes equations, and the overset mesh technique is applied for the numerical solution of the equations. The towing cable connecting the towed vehicle and towing ship is governed by the quasi-steady-state catenary equations. The depth tracking controller adjusting the longitudinal position of a shifting weight is constructed based on the proportional–integral–derivative (PID) algorithm. The simulation results show that the numerical simulation system is practicable, and the depth tracking control system is feasible, effective, and robust.

Cooperative Multi-Agent Control for Autonomous Ship Towing Under Environmental Disturbances

Among the promising application of autonomous surface vessels (ASVs) is the utilization of multiple autonomous tugs for manipulating a floating object such as an oil platform, a broken ship, or a ship in port areas. Considering the real conditions and operations of maritime practice, this paper proposes a multi-agent control algorithm to manipulate a ship to a desired position with a desired heading and velocity under the environmental disturbances. The control architecture consists of a supervisory controller in the higher layer and tug controllers in the lower layer. The supervisory controller allocates the towing forces and angles between the tugs and the ship by minimizing the error in the position and velocity of the ship. The weight coefficients in the cost function are designed to be adaptive to guarantee that the towing system functions well under environmental disturbances, and to enhance the efficiency of the towing system. The tug controller provides the forces to tow the ship and tracks the reference trajectory that is computed online based on the towing angles calculated by the supervisory controller. Simulation results show that the proposed algorithm can make the two autonomous tugs cooperatively tow a ship to a desired position with a desired heading and velocity under the (even harsh) environmental disturbances.

Lumped Mass Model for Flexible Cable: A Review

Model of a flexible cable plays a great role in the applications of underwater towing system, mooring line system, etc. A complete mathematical model is a basis to accurately describe the dynamic characteristics of flexible cable. This article presents a state of art comprehensive review of lumped mass model. First, the mathematical principle of the lumped mass model, including geometric simplification, force analysis, and solution, are systematically summarized.Second, the dynamic response of cable under different boundary conditions is introduced, and boundary conditions are categoried. Third, the numerical solution of the lumped mass model are assessed. Finally, based on the application of guide dog robot, the authors discussed the research future and trends. The authors aim to ealize human-robot interaction through a flexible cable.

Analytical and numerical study on underwater towing cable dynamics under different flow velocities based on experimental corrections

A relatively simple and fast mathematical analysis method is proposed to determine the position and posture of underwater towing cable under steady-state. The lumped mass method is used to discretize the towing cable into a series of finite segment elements connected by nodes. Based on the static analysis of Morrison equation and finite segment of the towing cable, the analytical formulas of the steady-state control equation of the underwater towing cable are obtained and solved. The numerical simulations and experiments are carried out for verification. As the drag coefficients have a great influence on the accuracy of the results of the mathematical analysis and numerical simulation, the influences of normal drag coefficient and tangential drag coefficient on the calculation result are discussed. The normal drag coefficient is corrected through the experiment to further improve the accuracy of mathematical analysis and numerical simulation, which is significant for the depth control of underwater towing system.

Towing Performance of the Submerged Floating Offshore Wind Turbine under Different Wave Conditions

One of the advantages of floating offshore wind turbines (FOWTs) is that they can be designed to be easily wet towed and installed to reduce the cost of offshore construction. In this paper, a fully coupled towing system numerical model is established for a novel 10 MW FOWT concept, namely, a submerged floating offshore wind turbine (SFOWT) to investigate the towing performance. Firstly, the numerical simulation is validated by comparison with model experiment results. Then, a series of numerical simulations are conducted to predict and compare the towing performance for a three-column SFOWT (TC-SFOWT) and a four-column SFOWT (FC-SFOWT) under different wave conditions. The results show that the two forms of SFOWT have good towing performance when the significant wave height is less than 5 m, which is the maximum wave height for the allowable towing condition. The FC-SFOWT shows relatively better performance in heave motion and roll motion, but the towing force is relatively larger compared with the TC-SFOWT under the same condition. When the significant wave height is 5 m, the maximum values of heave motion, pitch motion, and roll motion of the TC-SFOWT are 2.51 m, 2.14°, and 1.38°, respectively, while they are 2.25 m, 2.70°, and 1.21°, respectively, for the FC-SFOWT. Both the roll motion and the pitch motion are satisfied with the requirement that the roll and pitch are less than 5° during the towing process. The mean towing force of FC-SFOWT is 159.1 t at the significant wave height of 5 m, which is 52.8% larger than that of TC-SFOWT. The peak period mainly influences the frequency where the response peak appears in power spectra. The findings in this paper could provide some guidelines for wet towed operations.