Trajectory planning for multi-robot coordinated towing system based on stability

Given the unconstrained characteristics of the multi-robot coordinated towing system,the rope can only provide a unidirectional constraint force to the suspended object,which leads to the weak ability of the system to resist external disturbances and makes it difficult to control the trajectory of the suspended object.Based on the kinematics and statics of the multi-robot coordinated towing system with fixed base,the dynamic model of the system is established by using the Newton-Euler equations and the Udwadia-Kalaba equations.To plan the trajectories with high stability and strong control,trajectory planning is performed by combining the dynamics and stability of the towing system.Based on the dynamic stability of the motion trajectory of the suspended object,the stability of the suspended object is effectively improved through online real-time planning and offline manual adjustment.The effectiveness of the proposed method is verified by comparing the motion stability of the suspended object before and after planning.The results provide a foundation for the motion planning and coordinated control of the towing system.

Research on the Motion Track of Ocean Towing System

In this paper, a method for predicting the position of towline is presented. The location of the finite node is determined by installing fixed spaced attitude sensors in towline arrays, then the appropriate objective functions are selected for water depth profile and course profile respectively, and the interpolation fitting method is combined with the determined predicted positions. Through the hydrodynamic analysis of the existing towing cable’s underwater motion, the position of the towing cable under the steady state motion is obtained as the reference basis, and two methods are put forward, which are improved spline interpolation method, polynomial fitting method and multivariate nonlinear regression analysis. In the case of steady state motion, the two methods are compared and compared with the hydrodynamic simulation results. Finally, a more suitable method is selected as the basis of cable location inversion and applied to deep-sea towing operations.

Air-Floating Towing Behaviors of Multi-Bucket Foundation Platform

Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）.

Comparison of marine controlled-source electromagnetic data acquisition systems by a reservoir sensitivity index:analyzing the effect of water depths

During the past ten years, a marine controlled source electromagnetic（CSEM） method has been developed rapidly as a technology for hydrocarbon exploration. For shallow water environments, two CSEM data acquisition systems： Seabed Logging（SBL） and towed streamer electromagnetics（TSEM） have been developed in recent years. The purpose is to compare the performance of the SBL and TSEM systems at different water depths. Three different methods for the comparison are presented. The first method is a quick one dimensional sensitivity modelling. As a result, the sensitivity of marine CSEM data increases with water depth for the SBL system. Further, the sensitivity decreases with the increasing water depth for the TSEM system. The two other methods use two dimensional synthetic data from a simple 2-D isotropic model. The second method is a reservoir sensitivity index（RSI） method which has been developed to provide a quick comparison of the two systems. The RSI is calculated as the amplitude of the scattered field dividing by data uncertainty. From the calculations, it is found that with the increasing water depth RSI increases for the SBL system, while it decreases for the TSEM system. The third method uses Occam＇s inversion, and applies an anomaly transverse resistance（ATR） ratio for evaluating the resulting resistivity image. In shallow water environments, the resolution of the CSEM inversion results is good for both the SBL and TSEM systems. In deep water environments, the resolution of the CSEM inversion is better for the SBL system than for the TSEM system. The ATR ratios of the resistivity images show the similar conclusion. The SBL data acquisition system has an advantage in deep water environments. The TSEM system, on the other hand, is preferable for the shallow water environments.

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.

Influence of towing speed on effectiveness of rolling dynamic compaction

The influence of towing speed on the effectiveness of the 4-sided impact roller using earth pressure cells(EPCs)is investigated.Two field trials were undertaken;the first trial used three EPCs placed at varying depths between 0.5 m and 1.5 m with towing speeds of 9-12 km/h.The second used three EPCs placed at a uniform depth of 0.8 m,with towing speeds of 5-15 km/h.The findings from the two trials confirmed that towing speed influences the pressure imparted to the ground and hence compactive effort.This paper proposes that the energy imparted to the ground is best described in terms of work done,which is the sum of the change in both potential and kinetic energies.Current practice of using either kinetic energy or gravitational potential energy should be avoided as neither can accurately quantify rolling dynamic compaction(RDC)when towing speed is varied.

Integrated Towing Transportation Technique for Offshore Wind Turbine with Composite Bucket Foundation

Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine construction and installation has been largely reduced.Foundation stability is the key technology in the process of towing transportation.Field observation data can reflect the real state of the foundation.In this paper,the influence of water depth and towing speed on liquid level,the compartment pressure,and the pitch angles during towing of composite bucket foundation are studied.These data are analyzed based on the field measurements data from a 3.3 MW offshore wind power project in China.The results show that with varied water depths and towing speeds,the compartment pressure changes are small during the bucket foundation towing process.The offshore wind turbine composite bucket foundation is stable while being towed in the ocean.

Mechanical Analysis of Submarine Pipeline During off-Bottom Towing Operation

The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction force of seabed, pontoon buoyancy, and tow force of tugboat can cause large deformation and fatigue damage to the pipeline. In order to keep the pipeline in safety, the lateral and vertical defomlations of pipeline must be controlled within an appropriate range. Theoretical study is carried out in the paper on the environmental forees acting on pipeline, pontoons and chaias, and the confimation of tow parameters including tow forces of tugboat, number of pontoons and length of chains. Then the pipeline in the off-bettom towing process may be simplified into a continuous beam with elastic supports under the concentrated and distributed forces. A finite element method is applied to achieve numerical solutions describing the distributions of deformation and stress along the pipeline. The results show that the lateral shape of the pipeline is like an arc with the maximal deformation appearing at the middle of the pipeline. The distributions of stress are similar between two arbitrary pontoons. Moreover, both deformation and stress have the inverse relation with the tow forces of tugboat.

Numerical Simulation of Dynamic Response of Towed Systems

In this paper, the dynamic response of undersea -+towed systems is numerically simulated. A two body towed system is especially considered in detail. The factors influencing the heave of towed-bodies, such as the weight of the towed-body (in sea water), the length and the weight (in sea water) per unit length of the cable between towed-bodies and towing ship, are investigated in detail. Calculations show that the two-body towed system can greatly increases the stability of the towed system.

Test Research on Influence of Draft on Towing Behaviors of 3-Bucket Foundation Platform

To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.

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.

Analysis of the Dynamic System of Wave Glider with a Towed Body

Mobile observation platforms are widely used in oceanographic and marine resource exploration and other applications. Wave Glider is a mobile platform that can transform wave energy into locomotion power and overcome the bottleneck of low energy supply. Wave Glider has recently been applied to tow underwater sensors fulfilling observation tasks. In this paper, the dynamic system of Wave Glider with a towed body is studied by applying multibody mechanics, and the relevant motion conditions of the system are investigated. Dynamic models of Wave Glider with a towed body and tether are first developed individually and then integrated into a whole model. The numerical method is used to obtain the dynamic responses and assess performance of the towed body pulled by the submerged glider of Wave Glider. The effects of sea state, mass of the towed body, and length of the towed cable are investigated on the basis of simulation results. This work can be used for the design and analysis of Wave Glider-towed body systems.

武夷山朱子文化旅游发展与路径

随着观光发展与旅游型态的进化,乡贤文化旅游已成为国人选择旅游方式之一,亦是全国旅游发展的重点领域。透过乡贤文化传播,不仅可起到乡贤文化资源保护与传承,还可运用其乡贤话题发展旅游观光,提升城市知名度,达到文化传承、资源共享,更能带动地方经济的发展。本研究之目的在找出武夷山朱熹文化旅游发展与创新的策略,透过对文献、案例的探讨与SWOT分析,再以TOWS矩阵匹配战略掌握竞争优势,形成最适合武夷山朱子文化旅游的建设路径。研究结果提出以下四个方面:朱子文化推进文旅合作发展;跨区域性的策略联盟;产业发展定位,形塑特色的区域产业;推动朱子文创园区,打造武夷优质城市。

基于TOWS理论审视我国体育旅游发展战略——以河南省体育旅游开发为例

将战略规划的系统方法——TWOS分析引入河南省体育旅游发展战略规划实践。研究认为,区域体育旅游的发展战略关系到体育旅游发展的全局性、根本性问题,是区域体育旅游取得持续发展的决定性因素。据此认为,河南省体育旅游的开发应围绕特色文化、区域合作、体制创新、产品整合、相对优势、品牌和形象主导制定战略规划。

基于TOWS分析的区域旅游发展战略规划——以辽宁鞍山为例

发展战略在区域旅游开发和规划中至关重要,它关系到旅游发展的全局性和战略性问题,是区域旅游业取得长期绩效的决定性因素。目前,区域旅游发展战略规划,基本上依赖于专家的经验和直觉,随意性和主观性较强,给区域旅游发展系统带来莫大的风险。为此,本文以辽宁鞍山为实例,将TOWS分析方法引入旅游发展战略的制定过程,以增强区域旅游发展战略规划的客观性、系统性和可靠性,降低旅游系统所面临的风险,旨在促进区域旅游持续发展。

大同市旅游发展战略的TOWS分析

利用TOWS分析法对大同市旅游发展的优势、劣势、机遇与威胁进行了综合分析评价,得到以云冈石窟为代表的人文旅游资源优势明显、旅游产品结构单一、旅游交通的极大改善为旅游业发展提供了机遇、对重点文物和环境保护的压力大等关键的内外部因素,最后提出了如特色文化、完善交通、区域联合等适合大同市旅游发展的六个战略.

基于SWOT-TOWS分析区域竞技体育发展的战略规划——以辽宁省竞技体育发展为例

运用文献资料、数理统计、逻辑分析、SWOT分析等方法,对辽宁竞技体育发展过程中所面临的内外部环境进行探讨,进而引入战略规划的系统研究方法—TWOS分析对未来辽宁竞技体育发展的战略规划进行研究。表明:区域竞技体育发展的战略规划是关系到竞技体育发展的全局性和根本性的问题,是区域竞技体育取得可持续发展的决定性因素。因此,辽宁竞技体育的发展应以特色文化战略、相对优势战略、区域联盟战略、体制创新战略和整合发展战略为重点制定战略规划。

TOWS分析方法在公路交通发展战略制定中的应用

从公路交通与企业发展所而临的环境的相似性出发,将社会经济系统作为公路交通发展的外部环境,用TOWS分析方法对公路交通与经济发展的适应性进行了分析,提出了与之相适应的发展战略.

高校发展战略选择的影响因素--兼论TOWS矩阵和博弈论的应用

本文借助波特的产业分析思想,全面分析了高校所面临的竞争环境,指出了与高校发展密切相关的五种作用力,探讨影响高校发展战略选择的相关因素,并给出战略选择的一般流程。本文另运用TOWS矩阵分析方法以实例分析了高校所面临的外部威胁和机遇,内部的弱势和优势,从而做出具体的战略选择。继而,本文还论述了博弈论的思想在制定高校发展战略时的价值,指出高校盲目扩张策略的"囚徒困境"。

企业市场适应性分析模式──介绍一种新的市场环境分析矩阵

在企业市场战略外部环境与内部资源环境适应性分析的过程中，将企业有可能遇到的外部机会与威胁和内部优势与劣势等四种主要因素进行综合思考，在立体交叉作用下，可能产生四种新的战略结果或效应。这八种要素构成了一种新的企业战略内外环境适应性分析的基本管理模式。这八种要素分析矩阵或模式不仅有助于企业更好地分析和理解市场环境状况，而且也可作为企业的一种市场战略决策技术。