Event-triggered model-free adaptive control for a class of surface vessels with time-delay and external disturbance via state observer

This paper provides an improved model-free adaptive control(IMFAC)strategy for solving the surface vessel trajectory tracking issue with time delay and restricted disturbance.Firstly,the original nonlinear time-delay system is transformed into a structure consisting of an unknown residual term and a parameter term with control inputs using a local compact form dynamic linearization(local-CFDL).To take advantage of the resulting structure,use a discrete-time extended state observer(DESO)to estimate the unknown residual factor.Then,according to the study,the inclusion of a time delay has no effect on the linearization structure,and an improved control approach is provided,in which DESO is used to adjust for uncertainties.Furthermore,a DESO-based event-triggered model-free adaptive control(ET-DESO-MFAC)is established by designing event-triggered conditions to assure Lyapunov stability.Only when the system’s indicator fulfills the provided event-triggered condition will the control input signal be updated;otherwise,the control input will stay the same as it is at the last trigger moment.A coordinate compensation approach is developed to reduce the steady-state inaccuracy of trajectory tracking.Finally,simulation experiments are used to assess the effectiveness of the proposed technique for trajectory tracking.

Interpolation Technique for the Underwater DEM Generated by an Unmanned Surface Vessel

High-resolution underwater digital elevation models(DEMs)are important for water and soil conservation,hydrological analysis,and river channel dredging.In this work,the underwater topography of the Panjing River in Shanghai,China,was measured by an unmanned surface vessel.Five different interpolation methods were used to generate the underwater DEM and their precision and applicability for different underwater landforms were analyzed through cross-validation.The results showed that there was a positive correlation between the interpolation error and the terrain surface roughness.The five interpolation methods were all appropriate for the survey area,but their accuracy varied with different surface roughness.Based on the analysis results,an integrated approach was proposed to automatically select the appropriate interpolation method according to the different surface roughness in the surveying area.This approach improved the overall interpolation precision.The suggested technique provides a reference for the selection of interpolationmethods for underwater DEMdata.

Robust Leader-Follower Formation Tracking Control of Multiple Underactuated Surface Vessels

This paper is concerned with the formation control problem of multiple underactuated surface vessels moving in a leader-follower formation. The formation is achieved by the follower to track a virtual target defined relative to the leader. A robust adaptive target tracking law is proposed by using neural network and backstepping techniques. The advantage of the proposed control scheme is that the uncertain nonlinear dynamics caused by Coriolis/centripetal forces, nonlinear damping, unmodeled hydrodynamics and disturbances from the environment can be compensated by on line learning. Based on Lyapunov analysis, the proposed controller guarantees the tracking errors converge to a small neighborhood of the origin. Simulation results demonstrate the effectiveness of the control strategy.

METHOD FOR CALCULATION AND SIMULATION ON PROPAGATION OF SURFACE CRACK ON SPHERICAL VESSELS MADE OF STEELS

To avoid leaking or bursing by crack on surface of preddure vessels made of streels,a method for analyzing the principle of propagation of a surface crack is established,and used on a spherical vessel with program calculation and simulation,the program is written in QBASIC and the reaults are provided and discussed.

Trajectory planning and tracking control for underactuated unmanned surface vessels

The trajectory planning and tracking control for an underactuated unmanned surface vessel(USV) were addressed.The reference trajectory was generated by a virtual USV,and the error equation of trajectory tracking for underactuated USV was obtained,which transformed the tracking and stabilization problem of underactuated USV into the stabilization problem of the trajectory tracking error equation.A nonlinear state feedback controller was proposed based on backstepping technique and Lyapunov's direct method.By means of Lyapunov analysis,it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property.Numerical simulation results are presented to validate the effectiveness and robustness of the proposed controller.

Robust Adaptive Path Following for Underactuated Surface Vessels with Uncertain Dynamics

柔韧的适应控制策略被开发强迫一个 underactuated 表面容器跟随一条引用路径，尽管有包括外长的骚乱和测量噪音的不明确的参数和未组织的无常的存在。参考路径能是一条曲线或一根直线。建议控制器被使用 Lyapunovs 直接方法和滑动模式控制和 backstepping 技术设计。因为容器的摇摆轴直接没被激活，二滑动表面被介绍，第一以追踪的巨浪运动，为 yaw 的错误和第二个错误打手势追踪错误。适应控制法律保证制服得到了追踪的错误的最终的固定。数字模拟结果被提供为路径列在后面 underactuated 表面容器验证建议控制器的有效性。

Vessel fusion tracking with a dual-frequency high-frequency surface wave radar and calibrated by an automatic identification system

High-frequency surface wave radar（HFSWR） and automatic identification system（AIS） are the two most important sensors used for vessel tracking.The HFSWR can be applied to tracking all vessels in a detection area,while the AIS is usually used to verify the information of cooperative vessels.Because of interference from sea clutter,employing single-frequency HFSWR for vessel tracking may obscure vessels located in the blind zones of Bragg peaks.Analyzing changes in the detection frequencies constitutes an effective method for addressing this deficiency.A solution consisting of vessel fusion tracking is proposed using dual-frequency HFSWR data calibrated by the AIS.Since different systematic biases exist between HFSWR frequency measurements and AIS measurements,AIS information is used to estimate and correct the HFSWR systematic biases at each frequency.First,AIS point measurements for cooperative vessels are associated with the HFSWR measurements using a JVC assignment algorithm.From the association results of the cooperative vessels,the systematic biases in the dualfrequency HFSWR data are estimated and corrected.Then,based on the corrected dual-frequency HFSWR data,the vessels are tracked using a dual-frequency fusion joint probabilistic data association（JPDA）-unscented Kalman filter（UKF） algorithm.Experimental results using real-life detection data show that the proposed method is efficient at tracking vessels in real time and can improve the tracking capability and accuracy compared with tracking processes involving single-frequency data.

Dynamic Responses of Top Tensioned Riser Under Combined Excitation of Internal Solitary Wave, Surface Wave and Vessel Motion

An investigation on the dynamic response of a top tensioned riser (TTR) under combined excitation of internal solitary wave, surface wave and vessel motion is presented in this paper. The riser is idealized as a tensioned slender beam with dynamic boundary conditions. The KdV-mKdV equation is chosen to simulate the internal solitary wave, and the vessel motion is analysed by using the method proposed by Sexton. Using finite element method, the governing equation is solved in time domain with Newmark-β method. The computation programs for solving the differential equations in time domain are compiled and numerical results are obtained, including dimensionless displacement and stress. The action of internal solitary wave on the riser is like a slow powerful impact, and is much larger than those of surface wave and vessel motion. When the riser is under combined excitation, it vibrates at frequencies of both surface wave and vessel motion, and the vibration is dominated by internal solitary wave. As the internal solitary wave crest passes by the centre of the riser, the maximum displacement and stress along the riser occur. Compared to the lower part, the displacement and stress of the riser in the upper part are much larger.

Global Robust and Adaptive Output Feedback Dynamic Positioning of Surface Ships

A constructive method was presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind, and ocean currents. The ship's parameters were not required to be known. An adaptive observer was first designed to estimate the ship's velocities and parameters. The ship position measurements were also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control was then designed based on Lyapunov's direct method to force the ship's position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presented a new method to design an effective control system for dynamic positioning of surface ships.

基于ANSYS Workbench稳定性分析的大型真空容器优化设计

真空容器是石油、化工等行业中常见的设备之一,与内压容器不同,真空容器往往发生的是稳定性破坏。文中首先采用有限元软件ANSYS Workbench对DN22000 mm的真空容器进行了特征值屈曲分析,结果表明:其外压承载系数为17.427,远大于外压安全系数2.5。进而采用Response Surface Optimization模块对该真空容器进行优化设计,分析了外压承载系数、容器质量随穹顶壁厚和筒体壁厚的变化规律,以及外压承载系数、容器质量、应力随穹顶辐射筋数量的变化规律。最终确定穹顶壁厚取20 mm、筒体壁厚取22 mm、穹顶辐射筋取16个,优化后结构较最初结构质量减小了83140 kg,减小了17.02%,并且稳定性满足ASME规范要求,实现了容器轻量化的设计目标,从而显著降低制造成本。

带有状态/输入量化的无人艇航向跟踪控制

[目的]针对水面无人艇(USV)的海上通信受限的问题,提出一种带有状态/输入量化的USV航向跟踪控制方法。[方法]基于反步法设计系统控制律,结合动态面技术降低虚拟控制律的计算量膨胀问题。对于控制系统中存在的不确定项及外界干扰,利用扩张状态观测器(ESO)进行估计。采用均匀量化器分别对控制系统中的状态变量和控制输入进行量化,且量化后的状态反馈信息仅用于跟踪控制。利用量化状态递归设计基于ESO的USV航向控制器,证明闭环控制系统中量化变量和非量化变量间误差的有界性。[结果]基于李雅普诺夫稳定性理论,提出了量化误差考量及闭环系统稳定性判定方法,严格证明了所设计的带有状态量化和输入量化的USV航向跟踪控制系统的稳定性,仿真实验验证了该控制策略的有效性。[结论]结果表明,所提方法可为USV航向跟踪控制提供借鉴。

改进RRT^(*)算法的无人艇局部路径规划方法

文中提出一种改进RRT^(*)算法,该算法依据国际海上避碰规则计算本船与他船间DCPA与TCPA并判断会遇场景,限制采样空间.通过偏置采样在采样空间中选取采样点,增强目的性,加快搜索速度.依据线段公理和锚点采样的方式重新选择父节点,去除中间冗余的节点,减少路径转向次数和路径长度,使得最终生成的路径相对平滑.结果表明:改进RRT^(*)算法减少了81%以上的转向点和5%以上的路径长度.

土耳其武装无人艇发展

近年来,土耳其武装无人艇发展迅速,已成为世界无人艇装备领域重要的力量,从作战概念设计、装备发展、技术实现和试验验证等方面梳理了土耳其武装无人艇的发展。首先总结了土耳其武装无人艇作战概念和主要武装无人艇发展现状,归纳了各主要武装无人艇的作战用途、平台特点、作战能力和任务载荷搭载情况;其次介绍了各武装无人艇搭载的模块化导弹武器载荷、反潜任务载荷等无人任务载荷,讨论了各任务载荷的主要技术和战术指标;然后分析了土耳其武装无人艇开展的自主航行试验、导弹实弹射击试验、遥控武器站实弹射击试验、反潜作战试验等,重点指出了各项试验的显著特点;最后进行了土耳其武装无人艇与世界典型无人艇的对比,进一步概括了土耳其武装无人艇的主要发展特点。系统性地对土耳其武装无人艇发展进行分析总结,可为无人艇论证和研制提供一定的借鉴。

基于输入饱和的欠驱动水面舰艇预定义时间跟踪控制

[目的]为解决欠驱动水面舰艇(USV)在模型不确定性、强耦合特性和控制器输入饱和情况下的轨迹跟踪问题,提出基于输入饱和的USV预定义时间跟踪控制方法。[方法]针对USV模型具有非零对角项和强耦合特性问题,引入坐标变换,将系统模型转变为斜对角形式;将预定义时间性能函数与障碍Lyapunov函数(BLF)结合,保证瞬态和稳态的跟踪性能;利用自组织神经网络(SSNN)降低未知外部环境扰动和复杂的连续未知非线性项以及输入饱和产生的影响,以保证控制系统的跟踪精度,并且在线调整优化SSNN的神经元数目,减少控制系统的计算负担。[结果]基于Lyapunov稳定性理论,证明了闭环系统在预定义时间内是有界稳定的,跟踪误差始终保持在约束范围内。[结论]仿真结果表明,所提控制策略是有效的,其具有良好的跟踪性能。

基于智能预测控制的鱼雷状小型无人艇轨迹跟踪研究

[目的]针对无人艇(USV)在狭窄湖泊、涵洞作业时存在精度保持难和航迹控制难的问题,以自主研制的一款鱼雷状小型USV为对象,提出一种轨迹跟踪智能预测控制方法。[方法]首先,构建自主研制的欠驱动USV非线性状态空间模型;然后,设计智能预测控制器,该控制器基于模型预测控制的设计思想并结合改进的粒子群算法,在线决策、优化每一时刻的性能指标并纠正预测状态;最后,开展仿真和湖试试验测试系统对参考轨迹的跟踪性能,并与线性模型预测控制器的跟踪性能进行比较。[结果]结果表明,所设计的智能预测控制器超调小、抗干扰性好。[结论]所提方法不仅能运用于鱼雷状小型USV跟踪系统,也能对其他USV跟踪系统起到很好的借鉴作用。

复杂海洋环境下无人船仿真教学平台设计

针对机器人工程专业在移动机器人控制领域的理论与实践相结合的教学需求,利用机器人操作系统和Gazebo物理仿真引擎以及USVSim仿真平台,开发复杂海洋环境下无人船仿真教学平台。该平台实现了无人船的模型搭建、海洋环境扰动模拟、模型动力学参数辨识以及控制算法验证等功能。通过无人船仿真场景实验,表明了该仿真教学平台的可靠性与有效性,可弥补实验教学的不足,培养学生应对现实工程挑战的能力。

长蛇灸调节阳虚体质的体表温度特征

目的探讨长蛇灸调节阳虚体质施灸时体表温度特征。方法将80例阳虚体质受试者以1∶1比例随机分为督脉组和膀胱经组各40例。督脉组取背部督脉为施灸部位,膀胱经组取膀胱经〔据后正中线10 cm(3寸)处〕为施灸部位,进行长蛇灸治疗,1次/w,每次3壮(约45 min),共治疗12次。观察两组治疗前、后阳虚体质评分,评估临床疗效;运用温度测试探头采集施灸时体表温度,对比不同经脉施灸、不同疗效程度受试者的体表温度特征。结果治疗后督脉组总有效率明显高于膀胱经组(P<0.05)。治疗后,督脉组和膀胱经组阳虚体质转化分均明显低于治疗前;且督脉组阳虚体质转化分明显低于膀胱经组(P<0.05)。督脉组总平均体表温度明显高于膀胱经组(P<0.05);不同测量时间对经脉体表温度的影响差异有统计学意义(P<0.05);不同测量时间对体表温度的影响存在经脉之间的显著差异(P<0.05);第3、5、7、12次治疗的督脉组平均温度明显高于膀胱经组(P<0.05)。膀胱经组中治疗有效者的体表温度明显高于治疗无效者(P<0.05);所有受试者中治疗有效者的体表温度显著高于治疗无效者(P<0.05)。结论长蛇灸可有效调节阳虚体质,督脉是优选治疗部位;长蛇灸疗效与体表温度呈现出督脉温度高于膀胱经温度、灸效越好温度更高的特征。

基于单目视觉的无人艇海面目标实时测距方法

针对无人艇海面航行场景中单目图像测距难的问题,本文采用Yolov8模型检测海面目标,设计基于类别先验划分的双模型测距算法。针对中小型海面目标测距引入目标画面偏航角修正和海天线修正,针对货船目标测距引入基于检测框高的回归策略;构建多场景海面目标测距数据集,对测距算法进行定量评估。实验结果表明,中小型船舶测距中,引入画面偏航角修正测距的相对误差均值减小3.53%,引入海天线优化测距的相对误差均值减小30.89%;货船目标测距中,拟合法测距误差收敛,在实船测试中基本满足无人艇多传感器感知融合的要求。

虚假数据注入式攻击下无人水面船舶自适应神经输出反馈轨迹跟踪控制

本文主要研究网络环境下无人水面船舶(Unmanned surface vessels,USVs)遭受虚假数据注入式(False-data-injection,FDI)攻击的跟踪控制问题.其中,内部和外部不确定以及输入饱和约束等实际因素均考虑在设计中.在控制设计过程中,为避免将船舶速度的攻击信号引入闭环系统,采用分类重构思想,构造一种新的神经网络(Neural network,NN)状态观测器,同时重构船舶速度和攻击信号.进一步,在backstepping设计框架下,利用重构的攻击信号补偿USVs运动学通道因虚假数据注入式攻击引起的非匹配不确定项.在动力学设计通道中,利用自适应神经技术和单参数学习法,重构由内部和外部不确定组成的复合不确定部分,进而提出自适应神经输出反馈控制方案.理论分析表明,即便在FDI攻击、内外不确定以及执行器饱和约束的情况下,所提控制方案仍能迫使USVs跟踪给定的参考轨迹.同时,仿真和比较结果证实了所提控制方案的有效性和优越性.

多无人艇固定时间自适应分布式协同编队控制

针对在实际海洋环境中由复杂恶劣海况导致的局部通讯条件下多无人艇协同编队控制问题,本文提出一种固定时间自适应分布式控制策略.首先,考虑只有部分跟随无人艇能够直接获取虚拟领航者的状态信息,为每艘跟随无人艇设计固定时间分布式观测器,在固定时间内实现对虚拟领航者位置和速度的估计.然后,在估计信息的基础上,采用反步法为每艘跟随无人艇设计固定时间自适应局部控制器,在固定时间内实现对由虚拟领航者产生的期望轨迹的跟踪.特别地,在局部控制器设计过程中,采用参数自适应机制对模型不确定和外界扰动进行补偿,在保证控制精度的同时避免抖振现象.同时,本文给出了所提出的固定时间观测器与局部控制器的稳定性分析,经数学证明,所提出的观测器和控制器能够保证每艘跟随无人艇均能够在固定时间内完成对虚拟领航者的位置和速度的估计并使位置和速度跟踪误差在固定时间内收敛至零的邻域内.最后,设计对比仿真,将本文所提控制策略和目前常用的PD控制器的控制性能进行对比,仿真结果表明所提出的控制策略在控制精度和收敛速度上具有更优越的表现.