基于激光SLAM辅助的陆用惯导行进间粗对准方法

目前常见的陆用惯导系统的行进间对准方法往往存在一些各自的问题,如GPS辅助时容易受到信号遮蔽影响;而里程计辅助时往往会受到机动路线约束的限制。针对这些问题,提出了一种激光SLAM系统信息辅助的陆用惯性导航系统(SINS)行进间粗对准算法,推导了基于激光SLAM系统视在速度观测矢量的姿态矩阵更新算法,利用基于REQUEST的双矢量定姿方法,实现初始常值姿态矩阵C_(b)^(n)(0)的求取,完成行进间的姿态粗对准和定位导航。在实验室无人车实验中,所提方法的对准姿态误差比里程计辅助的方法减小了约56%;同时与合作单位的综合实验验证结果表明,在进行250 s的行进间粗对准时,最终时刻的航向角误差为-0.0088°,实现5 min内达到1 mil的粗对准精度,所提算法可以有效实现激光SLAM信息辅助下的陆用惯导的行进间粗对准,并具有较快的收敛速度。

Ship Hull Slamming Analysis with Nonlinear Boundary Element Method

A boundary element method is developed for calculating the flare ship hull slamming problem. The nonlinear free surface elevation and the linear element assumption are employed. The method has been verified by comparisons with results for the water entry of wedges with various deadrise angles. Numerical results show that the pressure distribution varies greatly with the ship hull with different curvilinear equations, and the slamming features are also different; From the numerical simulation, the authors found that the structural damage of the flare hull might be caused by the increasing hydrodynamic pressure over an extensive area on the flare when the upper part of the flare comes into contact with water.

昏暗环境下自适应ORB-SLAM2算法研究

本文针对ORB-SLAM2算法在黑暗环境或纹理较少的环境下提取特征点少,从而导致SLAM系统定位精度不高、匹配对数较少,进而导致系统崩溃的问题,提出了一种基于自适应阈值的特征点提取算法与改进的四叉树均匀化策略。首先基于图像的亮度进行基于自适应阈值的FAST特征点提取,之后通过改进的四叉树均匀化策略对图像的特征点进行剔除与补偿,完成特征点选取。实验结果表明,与原算法相比,改进后的特征点提取算法在黑暗环境与纹理较少的环境下,匹配对的数量提升了17.6%,SLAM轨迹精度提升了49.8%,有效的提升了SLAM系统的鲁棒性和精度。

动态场景下基于YOLOv5和几何约束的视觉SLAM算法

目的移动智能体在执行同步定位与地图构建(Simultaneous Localization and Mapping,SLAM)的复杂任务时,动态物体的干扰会导致特征点间的关联减弱,系统定位精度下降,为此提出一种面向室内动态场景下基于YOLOv5和几何约束的视觉SLAM算法。方法首先,以YOLOv5s为基础,将原有的CSPDarknet主干网络替换成轻量级的MobileNetV3网络,可以减少参数、加快运行速度,同时与ORB-SLAM2系统相结合,在提取ORB特征点的同时获取语义信息,并剔除先验的动态特征点。然后,结合光流法和对极几何约束对可能残存的动态特征点进一步剔除。最后,仅用静态特征点对相机位姿进行估计。结果在TUM数据集上的实验结果表明,与ORB-SLAM2相比,在高动态序列下的ATE和RPE都减少了90%以上,与DS-SLAM、Dyna-SLAM同类型系统相比,在保证定位精度和鲁棒性的同时,跟踪线程中处理一帧图像平均只需28.26 ms。结论该算法能够有效降低动态物体对实时SLAM过程造成的干扰,为实现更加智能化、自动化的包装流程提供了可能。

Approximation Method for Flare Slamming Analysis of Large Container Ships in Parametric Rolling Conditions

Since the research of flare slamming prediction is seldom when parametric rolling happens, we present an efficient approximation method for flare slamming analysis of large container ships in parametric rolling conditions. We adopt a 6-DOF weakly nonlinear time domain model to predict the ship motions of parametric rolling conditions. Unlike previous flare slamming analysis, our proposed method takes roll motion into account to calculate the impact angle and relative vertical velocity between ship sections on the bow flare and wave surface. We use the Wagner model to analyze the slamming impact forces and the slamming occurrence probability. Through numerical simulations, we investigate the maximum flare slamming pressures of a container ship for different speeds and wave conditions. To further clarify the mechanism of flare slamming phenomena in parametric rolling conditions, we also conduct real-time simulations to determine the relationship between slamming pressure and 3-DOF motions, namely roll, pitch, and heave.

基于激光SLAM的矿用巡检装置控制系统设计

为了实现煤矿井下综采工作面的无人化开采,代替工作人员监测危险的开采环境,设计了一款基于激光SLAM的矿用巡检装置控制系统。针对低功耗、并行处理快速等需求,选择NVIDIA Jetson AGX作为主控模块,并采用WiFi和LoRa双通信方式以满足不同的数据传输需求;驱动系统核心采用STM32F103C8T6微控制器,通过接收主控模块指令驱动直流无刷电机;算法采用非极大值抑制精细化特征提取,以实现局部最大搜索,从而更精准地定位和识别目标。在室内实验室场景与煤矿井下综采工作面2种不同的实验环境中对巡检装置控制系统的建图清晰度、精确定位和标靶识别效果进行了样机测试。试验结果表明,设计的建图效果在特征提取等算法方面表现出色,具有较高的定位精度,满足了实际应用需求。

基于SLAM激光扫描的建筑物建模方法研究与应用

激光雷达技术的突破与惯性导航系统的完善使激光扫描设备在测绘领域表现出色。该设备已成为构建高效、精准三维模型的关键工具,广受认可,被广泛应用于各类工程测绘项目。它能迅速捕获三维坐标点、反射率及纹理等关键信息,以点云形式存储,为构建建筑物三维模型提供坚实数据。针对市场局限,研发了即时定位与建图(Simultaneous Localization and Mapping,SLAM)方法,实现大型异构建筑室内外三维建模,并通过案例验证其高度可行性与可靠性,为相关行业提供技术支持,为类似工程提供全面解决方案,对测绘行业产生深远影响。

基于SLAM中视觉与IMU传感器融合方法综述

同步定位与建图(Simultaneous Localization And Mapping,SLAM)技术已经成为移动机器人领域重要的导航方式,视觉传感器由于便宜的价格和丰富的图像信息,让视觉同步定位与建图(Visual Simultaneous Localization And Mapping,V-SLAM)技术受到研究者广泛关注。为提升V-SLAM的综合性能,多种传感器信息融合的V-SLAM得到了快速发展。归纳并整理几何变换法的V-SLAM中各关键环节,详细阐述了SLAM中视觉与IMU传感器融合方法,对松融合与紧拟合两种主流方法进行论述,并对一些具有代表性的传统视觉惯性融合的SLAM方案进行讨论分析。最后,总结了视觉惯性融合的SLAM方案的关键问题和未来的发展方向。

基于视觉SLAM和光流法的无人施药船定位精度研究

随着农业自动化技术的不断发展,无人施药船作为先进的水生养殖设备,逐渐得到广泛应用。文章采用视觉同步定位与建图(Simultaneous Localization and Mapping,SLAM)和光流法相结合的方法,提出一种提高无人施药船定位精度的方法。该方法能够有效提高无人施药船的定位精度和自主导航能力,具有广阔的应用前景,有助于提升农业生产的效率。

基于融合改进RANSAC光流法的无人机视觉SLAM研究

针对同时定位与建图(SLAM)中存在定位精度不足、匹配特征点误差累积和特征匹配时间较长,提出了一种融合改进RANSAC光流法的优化算法。该方法基于传统RANSAC算法,加入最小二乘法对模型进行迭代优化来估计最优模型,对光流法的误匹配点进行剔除,大量减少图像误匹配特征点;把融合改进后的RANSAC光流法与特征点通过卡尔曼滤波进行融合,最后使用改进后的算法在公开的EuRoC MAV数据集中进行SLAM定位精度实验。实验结果表明:该改进算法能够有效减小光流法特征匹配的误差,从而提高无人机视觉SLAM的定位精度。

基于SLAM的井筒倾斜变形监测方法研究

针对传统矿山井筒安全监测方法中存在效率低(需停产监测)、数据量少、误差大等问题,提出利用激光SLAM(Simultaneous Localization and Mapping实时定位与建图)技术监测井筒倾斜变形的方法。以峰峰集团牛儿庄矿主井为研究对象,设计监测方案并利用激光SLAM技术感知井筒的内部信息,采用K′-means算法提取井筒边界点云,建立马尔可夫数学模型得到点云切片的中心,进而建立井筒中心基准线,根据整体和分段的方法分析了井筒倾斜变形。结果表明:井筒整体竖向倾斜1.99‰,上部井筒(距井口0~100 m)竖向倾斜3.06‰,下部井筒(距井口150~205 m)竖向倾斜1.85‰;相对于传统监测方法,激光SLAM工作时长由1 d甚至更长时间缩短至1 h,在井筒罐笼检修时间内即可完成监测工作,不需要停产的同时工作效率显著提高。

基于可视点法剔除动态目标的激光-惯导SLAM

针对传统激光同时定位与建图在动态环境中位姿估计累计误差大、地图中存在动态目标错误点云的问题,本文提出了一种基于可视点法实时剔除动态目标的激光-惯导SLAM方法(DM-LIO)。该方法使用IMU测量值为基于可视点法的动态目标剔除模块提供先验位姿,并引入基于弯曲体素空间的点云聚类方法,以解决在低分辨率可视点法下动态点不能被完全捕捉的问题,从而实现了在算法前端剔除激光点云中的动态目标。本文通过自主搭建室内真机实验平台和使用公开数据集两种方式对算法性能进行评估。真机实验结果表明本文提出的DM-LIO能够对多个动态目标以及非先验动态目标进行实时剔除;在公开数据集Urbanloco上的测试结果表明,在高动态的环境下DM-LIO的绝对轨迹误差相较于LIO-SAM减少了60%以上,验证了该算法在高动态环境中具有良好的定位精度。

Wave Slamming on An OWSC Wave Energy Converter in Coupled Wave-Current Conditions with Variable-Depth Seabed

Coastal wave energy resources have enormous exploitation potential due to shorter weather window,closer installation distance and lower maintenance cost.However,impact loads generated by depth variation from offshore to nearshore and wave-current interaction,may lead to a catastrophic damage or complete destruction to wave energy converters(WECs).This objective of this paper is to investigate slamming response of a coastal oscillating wave surge converter(OWSC)entering or leaving water freely.Based on fully nonlinear potential flow theory,a time-domain wave-current-structure interaction model combined with higher-order boundary element method(HOBEM),is developed to analyze the coupled hydrodynamic problem.The variable-depth seabed is considered in the model to illustrate the shallow water effect on impact loads and free surface profiles in coastal zone.A domain decomposition approach is utilized to simulate the overlapping phenomenon generated by a jet falling into water under gravity effect.Through a series of Lagrangian interpolation methods,the meshes on boundaries are rearranged to avoid the mismatch between element size on free surface and body surface.The present model is validated against the existing experimental and numerical results.Simulations are also provided for the effects of wave-current interaction and uneven local seabed on the slamming responses.It is found that the length of the splash jet increases for a following current and decreases for an opposing current,and that the slamming response of the OWSC device is sensitive to the geometric features of the uneven seabed.

Hydroelastic Analysis of a Rectangular Plate Subjected to Slamming Loads

A hydroelastic analysis of a rectangular plate subjected to slamming loads is presented. An analytical model based on Wagner theory is used for calculations of transient slamming load on the ship plate. A thin isotropic plate theory is considered for determining the vibration of a rectangular plate excited by an external slamming force. The forced vibration of the plate is calculated by the modal expansion method. Analytical results of the transient response of a rectangular plate induced by slamming loads are compared with numerical calculations from finite element method. The theoretical slamming pressure based on Wagner model is applied on the finite element model of a plate. Good agreement is obtained between the analytical and numerical results for the structural deflection of a rectangular plate due to slamming pressure. The effects of plate dimension and wave profile on the structural vibration are discussed as well. The results show that a low impact velocity and a small wetted radial length of wave yield negligible effects of hydroelasticity.

基于稀疏直接法的特征增强视觉SLAM算法

针对基于特征点的视觉同步定位与建图(SLAM)算法在低纹理环境下特征提取能力弱、定位精度降低和鲁棒性差的问题,本文提出了一种基于稀疏直接法的特征增强视觉SLAM算法。首先对图像序列进行预处理,提高算法的特征提取能力;然后融合基于图优化的稀疏直接法和特征点法求解位姿,在保证算法定位精度的前提下,提高算法的运行效率和鲁棒性。由TUM数据集的实验结果表明,本文提出的算法定位精度优于当前SLAM算法,在TUM数据集中纹理稀疏的场景下,该算法提取的特征点数目是ORB-SLAM2算法的9.6倍,平均每帧跟踪耗时减少了58%。

Robust SLAM localization method based on improved variational Bayesian filtering

Aimed at the problem that the state estimation in the measurement update of the simultaneous localization and mapping(SLAM)method is incorrect or even not convergent because of the non-Gaussian measurement noise,outliers,or unknown and time-varying noise statistical characteristics,a robust SLAM method based on the improved variational Bayesian adaptive Kalman filtering(IVBAKF)is proposed.First,the measurement noise covariance is estimated using the variable Bayesian adaptive filtering algorithm.Then,the estimated covariance matrix is robustly processed through the weight function constructed in the form of a reweighted average.Finally,the system updates are iterated multiple times to further gradually correct the state estimation error.Furthermore,to observe features at different depths,a feature measurement model containing depth parameters is constructed.Experimental results show that when the measurement noise does not obey the Gaussian distribution and there are outliers in the measurement information,compared with the variational Bayesian adaptive SLAM method,the positioning accuracy of the proposed method is improved by 17.23%,20.46%,and 17.76%,which has better applicability and robustness to environmental disturbance.

Mitigating check valve slamming and subsequentwater hammer events for PPFS using MOC

The method of characteristic(MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System(PPFS) during the alternate startup process.The motion of check valve disc was simulated using inertial valve model.Transient parameters including the pressure oscillation,local flow velocity and slamming of the check valve disc etc.have been obtained.The results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps.The induced maximum pressure vibration amplitude is up to 5.0 MPa.The scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water hammer.It has been numerically approved to be an effective approach.

移动机器人SLAM发展现状综述

SLAM通过传感器进行环境感知,可以实现移动机器人的实时定位与建图,并且可以在没有地标的情况下引导机器人。针对移动机器人使用激光雷达进行建图与定位的应用,围绕SLAM技术发展调研分析及近年来在此基础上演变而来的LIO-SAM技术的基本特点及优势进行介绍,并对基于激光雷达的SLAM算法的发展前景进行展望。

基于优化Hector-SLAM算法的机器人自主导航系统设计

针对机器人在复杂地形环境下定位不准确、建图精度不高和误差堆积等问题,设计了一种基于优化Hector-SLAM(simultaneous localization and mapping,实时定位与建图)算法的自主导航系统,以实现机器人在及时躲避障碍物的同时准确到达目标点。首先,采用双三次插值法代替原有插值法,以解决Hector-SLAM算法在使用低精度激光雷达数据建图时易出现地图不清晰等问题,从而提升扫描匹配的精准度。其次,采用扩展卡尔曼滤波算法对里程计和惯性测量单元的数据进行融合,以提高定位的准确性。再次,针对激光点数据无法瞬时获得而机器人持续运动所导致的运动畸变问题,结合里程计辅助法与PL-ICP(point to line iterative closest points,点到线迭代最近点)配准法,以实现运动畸变的校正;同时,设置倾斜角阈值以消除地图重影,并利用A*算法和动态窗口法规划最优路径。最后,以AGV(automated guided vehicle,自主导引车)为例,在实际场景中开展建图实验和自主导航实验。结果表明,优化后自主导航系统的平均建图相对误差约为0.44%,最小建图误差为0.236 m,较优化前减小了0.041 m,有效地解决了因误差堆积和运动畸变而导致的建图不清晰问题,增强了AGV在复杂地形环境中的适应能力,实现了高精度定位。研究结果对提高移动机器人在室内多障碍物环境下的自主导航能力具有一定的理论和工程意义。

A Hybrid Particle-Grid Scheme for Computing Hydroelastic Behaviors Caused by Slamming

Capable and accurate predictions of some effects of strongly nonlinear interaction wave-ship associated with hydroelastic behaviors are very required for simulation tool in naval architect and ocean engineering. It can guarantee ship safety at the sea state by producing proper design. Therefore, we have developed a hybrid scheme based on both grid and particle method. In order to clarify hydroelastic behaviors of a ship, a dropping test of a ship with elastic motion has been performed firstly. The developed scheme has been then validated on ship dropping case under the same conditions with experiment. The comparisons showed consistently in good agreement. Furthermore, evaluation on hydroelastic behaviors of ship motion under slamming, the impact pressure tends to increase in increasing Froude number. （Fn） The bending moment and torque defined at the centre gravity due to hogging and sagging events can be predicted well, and their effects on the ship increase in increasing wave length even though the impact pressure decreases in increasing wave length after wave length λ/L, where L is ship length, is equal to 1.0. Moreover, hydroelastie behaviors affect the large heave and pitch amplitudes. Finally, the developed scheme can predict simultaneously hydrodynamic and hydroelastic with a strongly nonlinear interaction between wave and ship.