An Integrated Dynamic Model of Ocean Mining System and Fast Simulation of Its Longitudinal Reciprocating Motion

An integrated dynamic model of China＇s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control.

Numerical Evaluation of Longitudinal Motions of Wigley Hulls Advancing in Waves by Using Bessho Form Translating-Pulsating Source Green's Function

In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green's function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green's function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption.

Analysis of Transverse Vibration of a Longitudinally Moving Fabric

Fabric moves along running direction continuously in the processing of weaving,dyeing and finishing and its dynamic behavior is very complex.Running at a high speed,the fabric vibrates,which has great influence not only on the performance of machine,but also on the fabric itself.Analysis of transverse free vibration of a longitudinally moving fabric is put forward in this paper and the calculating formula of natural frequencies of the fabric is introduced accordingly.Meanwhile the effects of several parameters on the first order natural frequency are also discussed.

列车作用下大跨径悬索桥纵向运动响应分析方法对比研究

随着我国铁路事业的发展,近年来设计和建造了一些大跨径铁路悬索桥。悬索桥属于典型的柔性结构,加之列车荷载大、运行速度快,列车过桥时加劲梁纵向运动问题突出。准确地计算出列车过桥时梁端纵向运动响应是进行悬索桥结构设计和梁端位移控制的前提。该文通过有限元仿真,采用4种不同的分析方法,对运行列车作用下大跨径铁路悬索桥纵向运动响应特征进行对比研究。首先,分别介绍移动静载法、移动荷载法、移动质量法、车-桥动力相互作用法的计算理论及其有限元实现方法;随后,以某主跨1060m铁路悬索桥为例,分别采用4种方法进行纵向运动响应计算;最后,对4种分析方法的计算结果进行对比分析。结果表明:大跨径铁路悬索桥纵向运动分析应考虑动力效应;通过移动荷载法、移动质量法及车-桥动力相互作用法分析得到的纵向运动响应接近;采用移动荷载法进行大跨径铁路悬索桥纵向运动响应分析可以简化计算且满足计算精度要求。

铁路悬索桥车致纵向运动混合阻尼减振研究

针对铁路悬索桥在列车过桥时梁端纵向运动响应控制问题,提出了一种创新的混合阻尼减振方案,采用多种类型的阻尼器控制梁端位移,以满足不同的减振需求.以某在建大跨铁路悬索桥为工程背景,建立了空间桁架精细模型和等效单梁简化模型,系统研究了混合阻尼减振方案不同阻尼器参数对减振效果的影响.该方案将低指数黏滞阻尼器纵向安装于桥塔与加劲梁之间,同时在桥台与加劲梁之间纵向安装电涡流阻尼器.鉴于桥台结构的特殊性,电涡流阻尼器被设计为仅能承受压力的装置,并通过样机试验进行了验证.为了进一步提升减振性能,电涡流阻尼器还配备了摩擦耗能元件.该混合阻尼减振方案能够有效控制列车过桥时梁端的纵向运动响应,显著提高桥梁结构的安全性和耐久性,在类似工程中具有重要的参考价值和借鉴意义.

基于计算流体动力学方法的两栖飞机规则波中运动特性研究

针对水陆两栖飞机加速起飞运动过程受波浪干扰问题,本文基于Star-CCM+平台数值模拟技术,引入SST k-ε湍流模型求解RANS方程,VOF方法捕捉自由液面,DFBI模块以及重叠网格技术模拟水上飞机六自由度运动,建立了一套波浪中水陆两栖飞机加速滑行起飞运动特性研究方案。以波长和波高为变量,探讨了加速滑行过程中上述变量对水上飞机升沉、纵摇运动响应以及机身重心处垂向加速度的影响规律。结果表明:随着波长增加,飞机升沉运动先增加后缓慢变化,飞机重心垂向加速度、纵摇角加速度和纵摇峰值集中在波长为2~3倍机身长度海况范围内;随着波高增大,飞机升沉、纵摇运动及重心垂向加速度最大值随之增大,且长波中的运动变化量较短波中更大;机翼气动升力数值模拟结果与计算值一致,该方案可用于水陆两栖飞机气动力相关计算。

难加工材料纵扭超声振动辅助铣削加工研究进展

纵扭复合超声振动辅助铣削(LTUVAM)是在刀具轴向与扭转方向上施加高频微幅振动的一种辅助铣削技术,具有降低切削力与切削热、提高工件表面质量、提高表面残余压应力、减少刀具磨损等诸多优点。本文围绕难加工材料的铣削加工进行了系统综述。在设备制造方面,阐述了纵扭复合超声振动系统的结构设计方法与工作原理;在工艺开发方面,从LTUVAM的切削刃运动轨迹及切削特性入手,分析各类材料的切削加工性能,并总结了LTUVAM的优势及应用。最后,本文对LTUVAM的未来发展趋势进行展望。

隧道纵向地震易损性分析

为研究隧道纵向抗震性能,使用改进的地基梁-弹簧非线性分析模型计算隧道纵向地震响应,其中采用PQ-Fiber纤维梁模型模拟隧道纵向的非线性行为,并施加弯矩来考虑隧道与场地之间的切向相互作用。随后,将基于增量动力分析(IDA)方法的结构地震易损性分析方法应用于隧道结构,探究适用于隧道结构的地震动强度指标(IM)。选取12条近场地震记录,用于IDA分析隧道纵向的抗震性能水平。将概率地震需求模型与工程需求参数相结合,建立结构的地震易损性曲线。结果表明,峰值速度(PGV)是适用于隧道纵向抗震性能的地震动强度指标;场地类型对隧道纵向损伤程度的影响最为深远,其中Ⅰ类场地在地震作用下损伤概率最大。此外,将计算所得易损性曲线与经验易损性曲线和横向易损性曲线进行对比分析,验证了模型的可行性,为隧道结构的抗震设计提供了一定的参考。

磁共振增强T1 mapping和IVIM-DWI技术评估乙型肝炎肝硬化患者肝脏储备功能价值研究

目的分析应用磁共振(MR)体素内不相干运动扩散加权成像(IVIM-DWI)和钆塞酸二钠增强T1 mapping参数评估乙型肝炎肝硬化患者肝脏储备功能的价值。方法2020年3月~2022年3月我院诊治的乙型肝炎肝硬化患者60例,接受吲哚菁绿15 min滞留率检测和MR增强扫描,测量增强前20 min和增强后20 min T1弛豫时间,计算肝细胞增强分数,并应用Mltalytics 1.0.1软件自动测算表观扩散系数(ADC)和真性水分子扩散系数(D)。应用受试者工作特征(ROC)曲线分析参数评估肝储备的效能。结果在60例肝硬化患者中,吲哚菁绿15 min滞留率<10%者30例(A组),≥10%但<30%者16例(B组),≥30%者14例(C组);C组增强前T1弛豫时间和增强后T1弛豫时间分别为(700.5±71.2)ms和(324.1±99.6)ms,显著长于A组【分别为(612.2±28.3)ms和(148.3±51.9)ms,P<0.05】或B组【分别为(682.5±73.1)ms和(256.2±88.1)ms,P<0.05】,而ADC、D和肝细胞增强分数分别为(0.5±0.1)×10^(3)、(0.5±0.1)×10^(3)和(50.2±11.6)%,均显著低于A组【分别为(1.2±0.1)×10^(3)、(1.0±0.4)×10^(3)和(80.8±10.9)%,P<0.05】或B组【分别为(0.8±0.2)×10^(3)、(0.7±0.2)×10^(3)和(59.4±19.7)%,P<0.05】;ROC曲线分析显示,增强前和增强后20 min T1弛豫时间、ADC、D和肝细胞增强分数评估乙型肝炎肝硬化患者肝脏储备功能均具有较高的价值(灵敏度均在70.0%以上,特异度均在76.7%以上)。结论应用MR IVIM-DWI和T1 mapping参数评估乙型肝炎肝硬化患者肝脏储备功能具有很大的临床价值,可为临床决策提供影像学依据。

基于COSMOSMotion插秧机纵向进给机构的运动分析

为得到合理的纵向进给机构的结构参数,为插秧机纵向进给机构的设计提供依据,对两种水稻插秧机纵向进给机构的运动方式进行了分析。分析中应用SolidWorks软件对两种机构的零件进行三维设计,并将零件按装配关系装配成装配体,并应用COSMOSMotion对两种不同形式的机构进行运动模拟,分别得到两种机构的角速度图。结果表明,直线形棘轮的进给更为合理。

海上风电某大型稳桩平台运输船选型分析

针对海上桩基施工所需的大型稳桩平台的运输驳船选型、稳桩平台位置选择、绑扎设计、舱室调载的合理规划问题,以北方海域某风电项目为背景,对驳船进行完整稳性分析、总纵强度分析和运动响应分析。发现中拱对该驳船总纵强度的影响要大于中垂,重物装载位置合理可以减小中拱影响,3~9 s周期的横浪对该驳船航行最为不利。结果表明,该驳船稳性、总纵强度的安全裕度较大,运动响应安全合理,具备运输该大型稳桩平台的能力。

穿浪双体船纵向减摇策略麻雀搜索优化

为了改善穿浪双体船恶劣工况下的纵向稳定性,本文基于T型水翼及尾板设计了综合姿态控制系统。同时,对该系统相关控制参数的优化策略进行研究,以更好地实现减摇目标。采用了线性二次调节器和混合麻雀算法相结合的策略来设计控制器,将一种新型群智能算法(麻雀算法)及其改进算法应用于线性二次调节控制器权重矩阵寻优。通过两者对比,不仅验证了所设计姿态控制系统的有效性,也验证了该智能算法改进策略的高效性。结果表明:基于混合麻雀算法的控制器具有很好的自适应能力,且寻优过程收敛速度快,精度高,对工程实践具有一定的参考价值。

考虑道路因素的智能车辆纵向运动决策与控制研究

针对智能车辆纵向运动时的交通道路适应性问题,考虑路面附着系数和前车运动速度等因素,研究了智能车辆纵向运动决策与控制方法。基于车头时距的纵向运动决策方法,建立不同驾驶行为的目标车速模型,运用变论域模糊推理算法设计了目标加速度模型。基于纵向动力学模型,运用自适应反演滑模控制算法建立了驱动控制器和制动控制器。对高附着系数路面和低附着系数路面的行驶工况进行仿真试验验证,结果表明,在不同的附着系数路面和前车变速行驶条件下,智能车辆能实时、合理地决策目标车速和目标加速度,实现安全、高效、稳定的跟驰。

Longitudinal and lateral control methods from single vehicle to autonomous platoon

To successfully implement the platoon control of connected and automated vehicles,it is necessary to address motion control issues to achieve longitudinal and lateral collaborative control.However,due to traffic capacity limitations and the complex traffic environment in which autonomous and human-driven vehicles coexist,autonomous platoon faces significant risks and challenges.This paper investigates longitudinal and lateral control issues from the perspective of a single vehicle up to a platoon,simulating the performance and suitability of various controllers.First,a longitudinal controller based on fuzzy logic and PID control is employed for speed tracking control of a single vehicle,followed by the adoption of an MPC controller based on the vehicle kinematics model to realize the lateral motion of a single vehicle.Second,the communication methods of the autonomous platoon are discussed,and the longitudinal controller that considers the platoon's various communication topologies is developed.Thirdly,a framework for robust integrated motion control is established,which combines the robust H-infinity longitudinal controller and the APF-based MPC lateral controller.Simulation results validate the effectiveness of the aforementioned controllers and reveal their limitations.

Periodic Tail Motion Linked to Wing Motion Affects the Longitudinal Stability of Ornithopter Flight

During slow level flight of a pigeon, a caudal muscle involved in tail movement, the levator caudae pars vertebralis, is activated at a particular phase with the pectoralis wing muscle. Inspired by mechanisms for the control of stability in flying animals, especially the role of the tail in avian flight, we investigated how periodic tail motion linked to motion of the wings affects the longitudinal stability of ornithopter flight. This was achieved by using an integrative ornithopter flight simulator that included aeroelastic behaviour of the flexible wings and tail. Trim flight trajectories of the simulated omithopter model were calculated by time integration of the nonlinear equations of a flexible multi-body dynamics coupled with a semi-empirical flapping-wing and tail aerodynamic models. The unique trim flight characteristics of ornithopter, Limit-Cycle Oscillation, were found under the sets of wingbeat frequency and tail elevation angle, and the appropriate phase angle of tail motion was determined by parameter studies minimizing the amplitude of the oscillations. The numerical simulation results show that tail actuation synchronized with wing motion suppresses the oscillation of body pitch angle over a wide range of wingbeat frequencies.

Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

To investigate the longitudinal motion stability of aircraft maneuvers conveniently, a new stability analysis approach is presented in this paper. Based on describing longitudinal aerodynamics at high angle-of-attack （a ＆lt; 50 ） motion by polynomials, a union structure of two-order differential equation is suggested. By means of nonlinear theory and method, analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight. Applying the theories of bifurcations, many kinds of bifurcations, such as equilibrium, Hopf, homoclinic （heteroclinic） orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived. The bifurcation curves divide the parameter plane into several regions; moreover, the complete bifurcation diagrams and phase portraits in different regions are obtained. Finally, our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium. The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.

纵波运动方程的分支分析和行波解

本文应用动力系统分支方法研究纵波运动方程,建立一个与该方程相对应的平面系统,并给出该平面系统的分支相图,最后通过相图中的一些特殊轨道获得方程的精确行波解的参数表示,得出行波解之间的联系.

小水线面双体船纵向运动控制系统的试验研究

提出了小水线面双体船纵向运动控制系统的数学模型,并建立了该系统的试验平台,开展了前后鳍静态和动态水动力特性试验,分别进行了无控船模和前后鳍控制船模在规则波中的耐波性试验。试验结果表明,所设计的前后鳍对该小水线面双体船具有可控性;由确定控制矩阵K的方法获得了初步优化的控制规律;经初步优化控制后的实船,在不规则波上的升沉和纵摇有义值分别下降26.9%和32.0%。

用于汽车纵向运动控制的传动系统模型简化与分析

针对汽车纵向运动控制系统特点,采用线性化方法对比分析传动系统各部件对系统传递性的影响,总结出适合汽车纵向运动控制的简化数学模型。并基于简化模型,应用灵敏度理论分析了系统传递特性对模型中各参数的敏感性。

高速滑行艇在规则波中的纵向运动数值研究

为准确评估滑行艇在波浪中的运动特性、寻找运动规律,应用基于VOF RANS求解器的CFD方法对高速滑行艇在规则波浪中的迎浪运动进行数值计算。在纵摇和升沉两自由度模型下对滑行艇进行数值模拟,得到了滑行艇在迎浪运动中的无跳跃、规则跳跃和不规则跳跃3种运动形式。对3种运动形式发生的条件,即波长、波高和航速进行了研究,得到运动发生的条件区间,并分析了跳跃的发生对纵向运动幅度规律的影响。计算结果表明,规则跳跃和不规则跳跃的发生均会改变无量纲化纵向运动幅值随波高的变化规律。其中,不规则跳跃对滑行艇运动幅值的影响较规则运动更为强烈。