We address the theoretical and practical problems related to the trajectory generation and tracking control of tail-sitter UAVs. Theoretically, we focus on the differential flatness property with full exploitation of actual UAV aerodynamic models, which lays a foundation for generating dynamically feasible trajectory and achieving high-performance tracking control. We have found that a tail-sitter is differentially flat with accurate aerodynamic models within the entire flight envelope, by specifying coordinate flight condition and choosing the vehicle position as the flat output. This fundamental property allows us to fully exploit the high-fidelity aerodynamic models in the trajectory planning and tracking control to achieve accurate tail-sitter flights. Particularly, an optimization-based trajectory planner for tail-sitters is proposed to design high-quality, smooth trajectories with consideration of kinodynamic constraints, singularity-free constraints and actuator saturation. The planned trajectory of flat output is transformed to state trajectory in real-time with consideration of wind in environments. To track the state trajectory, a global, singularity-free, and minimally-parameterized on-manifold MPC is developed, which fully leverages the accurate aerodynamic model to achieve high-accuracy trajectory tracking within the whole flight envelope. The effectiveness of the proposed framework is demonstrated through extensive real-world experiments in both indoor and outdoor field tests, including agile SE(3) flight through consecutive narrow windows requiring specific attitude and with speed up to 10m/s, typical tail-sitter maneuvers (transition, level flight and loiter) with speed up to 20m/s, and extremely aggressive aerobatic maneuvers (Wingover, Loop, Vertical Eight and Cuban Eight) with acceleration up to 2.5g.
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在本文中,我们解决了未知和非结构化环境中在线四型全身运动计划(SE(3)计划)的问题。我们提出了一种新颖的多分辨率搜索方法,该方法发现了需要完整的姿势计划和仅需要位置计划的正常区域的狭窄区域。结果,将四型计划问题分解为几个SE(3)(如有必要)和R^3子问题。为了飞过发现的狭窄区域,提出了一个精心设计的狭窄区域的走廊生成策略,这大大提高了计划的成功率。总体问题分解和分层计划框架大大加速了计划过程,使得可以在未知环境中进行完全的板载感应和计算在线工作。广泛的仿真基准比较表明,所提出的方法的数量级比计算时间中最先进的方法快,同时保持高计划成功率。最终将所提出的方法集成到基于激光雷达的自主四旋转器中,并在未知和非结构化环境中进行了各种现实世界实验,以证明该方法的出色性能。
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由于空间和时间变化的模糊,视频脱毛是一个高度不足的问题。视频脱毛的直观方法包括两个步骤:a)检测当前框架中的模糊区域; b)利用来自相邻帧中清晰区域的信息,以使当前框架脱毛。为了实现这一过程,我们的想法是检测每个帧的像素模糊级别,并将其与视频Deblurring结合使用。为此,我们提出了一个新颖的框架,该框架利用了先验运动级(MMP)作为有效的深视频脱张的指南。具体而言,由于在曝光时间内沿其轨迹的像素运动与运动模糊水平呈正相关,因此我们首先使用高频尖锐框架的光流量的平均幅度来生成合成模糊框架及其相应的像素 - 像素 - 明智的运动幅度地图。然后,我们构建一个数据集,包括模糊框架和MMP对。然后,由紧凑的CNN通过回归来学习MMP。 MMP包括空间和时间模糊级别的信息,可以将其进一步集成到视频脱毛的有效复发性神经网络(RNN)中。我们进行密集的实验,以验证公共数据集中提出的方法的有效性。
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Neural architectures can be naturally viewed as computational graphs. Motivated by this perspective, we, in this paper, study neural architecture search (NAS) through the lens of learning random graph models. In contrast to existing NAS methods which largely focus on searching for a single best architecture, i.e, point estimation, we propose GraphPNAS a deep graph generative model that learns a distribution of well-performing architectures. Relying on graph neural networks (GNNs), our GraphPNAS can better capture topologies of good neural architectures and relations between operators therein. Moreover, our graph generator leads to a learnable probabilistic search method that is more flexible and efficient than the commonly used RNN generator and random search methods. Finally, we learn our generator via an efficient reinforcement learning formulation for NAS. To assess the effectiveness of our GraphPNAS, we conduct extensive experiments on three search spaces, including the challenging RandWire on TinyImageNet, ENAS on CIFAR10, and NAS-Bench-101/201. The complexity of RandWire is significantly larger than other search spaces in the literature. We show that our proposed graph generator consistently outperforms RNN-based one and achieves better or comparable performances than state-of-the-art NAS methods.
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The emergence of low-cost, small form factor and light-weight solid-state LiDAR sensors have brought new opportunities for autonomous unmanned aerial vehicles (UAVs) by advancing navigation safety and computation efficiency. Yet the successful developments of LiDAR-based UAVs must rely on extensive simulations. Existing simulators can hardly perform simulations of real-world environments due to the requirements of dense mesh maps that are difficult to obtain. In this paper, we develop a point-realistic simulator of real-world scenes for LiDAR-based UAVs. The key idea is the underlying point rendering method, where we construct a depth image directly from the point cloud map and interpolate it to obtain realistic LiDAR point measurements. Our developed simulator is able to run on a light-weight computing platform and supports the simulation of LiDARs with different resolution and scanning patterns, dynamic obstacles, and multi-UAV systems. Developed in the ROS framework, the simulator can easily communicate with other key modules of an autonomous robot, such as perception, state estimation, planning, and control. Finally, the simulator provides 10 high-resolution point cloud maps of various real-world environments, including forests of different densities, historic building, office, parking garage, and various complex indoor environments. These realistic maps provide diverse testing scenarios for an autonomous UAV. Evaluation results show that the developed simulator achieves superior performance in terms of time and memory consumption against Gazebo and that the simulated UAV flights highly match the actual one in real-world environments. We believe such a point-realistic and light-weight simulator is crucial to bridge the gap between UAV simulation and experiments and will significantly facilitate the research of LiDAR-based autonomous UAVs in the future.
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公平的聚类旨在将数据分为不同的簇,同时防止敏感属性(例如性别,种族,RNA测序技术),而不是主导聚类。尽管最近已经进行了许多作品并取得了巨大的成功,但其中大多数是启发式的,并且缺乏算法设计的统一理论。在这项工作中,我们通过开发一种相互信息理论来填补这一空白,以实现深度公平的聚类,并因此设计出一种称为FCMI的新型算法。简而言之,通过最大化和最大程度地减少共同信息,FCMI旨在通过深度公平的聚类(即紧凑,平衡和公平的簇)以及信息丰富的特征来实现四种特征。除了对理论和算法的贡献外,这项工作的另一个贡献是提出了一个基于信息理论的新颖的公平聚类指标。与现有的评估指标不同,我们的指标以整体而不是单独的方式来衡量聚类的质量和公平性。为了验证拟议的FCMI的有效性,我们对六个基准进行了实验,包括单细胞RNA-seq Atlas,而与11种最先进的方法相比,就五个指标而言。认可后将发布代码。
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准确的自我和相对状态估计是完成群体任务的关键前提,例如协作自主探索,目标跟踪,搜索和救援。本文提出了一种全面分散的状态估计方法,用于空中群体系统,其中每个无人机执行精确的自我状态估计,通过无线通信交换自我状态和相互观察信息,并估算相对状态(W.R.T.)(W.R.T.)无人机,全部实时,仅基于激光惯性测量。提出了一种基于3D激光雷达的新型无人机检测,识别和跟踪方法,以获得队友无人机的观察。然后,将相互观察测量与IMU和LIDAR测量紧密耦合,以实时和准确地估计自我状态和相对状态。广泛的现实世界实验显示了对复杂场景的广泛适应性,包括被GPS贬低的场景,摄影机的退化场景(漆黑的夜晚)或激光雷达(面对单个墙)。与运动捕获系统提供的地面真相相比,结果显示了厘米级的定位精度,该精度优于单个无人机系统的其他最先进的激光惯性射测。
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现有的源单元手机识别方法缺乏源设备的长期特征表征,从而导致与源单元相关特征的不准确表示,从而导致识别精度不足。在本文中,我们提出了一种基于时空表示学习的源细胞手机识别方法,其中包括两个主要部分:提取顺序高斯平均矩阵特征和基于时空表示学习的识别模型的构建。在特征提取部分中,基于对记录源信号的时间序列表示的分析,我们通过使用高斯混合模型对数据分布的灵敏度提取具有长期和短期表示能力的顺序高斯平均矩阵。在模型构建部分中,我们设计了一个结构化的时空表示网络C3D-BILSTM,以充分表征时空信息,结合3D卷积网络和双向长期短期记忆网络,用于短期光谱信息和长期的长期记忆网络波动信息表示学习,并通过融合记录源信号的时空特征信息来准确识别细胞手机。该方法的平均准确性为99.03%的封闭设置识别在CCNU \ _Mobile数据集中的45个手机识别,而在小样本尺寸实验中的平均识别率为98.18%,识别性能优于现有的最新目前的识别性能方法。实验结果表明,该方法在多级细胞手机识别中表现出出色的识别性能。
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学习辐射场对新型视图综合显示出了显着的结果。学习过程通常会花费大量时间,这激发了最新方法,通过没有神经网络或使用更有效的数据结构来通过学习来加快学习过程。但是,这些专门设计的方法不适用于大多数基于辐射的方法的方法。为了解决此问题,我们引入了一项一般策略,以加快几乎所有基于辐射的方法的学习过程。我们的关键想法是通过在多视图卷渲染过程中拍摄较少的射线来减少冗余,这是几乎所有基于辐射的方法的基础。我们发现,在具有巨大色彩变化的像素上的射击不仅显着减轻了训练负担,而且几乎不会影响学到的辐射场的准确性。此外,我们还根据树中每个节点的平均渲染误差将每个视图自适应地细分为Quadtree,这使我们在更复杂的区域中动态射击更多的射线,并具有较大的渲染误差。我们在广泛使用的基准下使用不同的基于辐射的方法评估我们的方法。实验结果表明,我们的方法通过更快的训练获得了与最先进的可比精度。
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节点注入对图神经网络(GNN)的攻击已作为一种实际的攻击场景而引起了人们的注意,攻击者会注入恶意节点,而不是修改节点功能或边缘以降低GNN的性能。尽管节点注射攻击最初取得了成功,但我们发现,通过防御方法,可以通过防御方法和限制其在实践中限制其攻击性能,从而很容易将注射的节点与原始正常节点区分开。为了解决上述问题,我们致力于伪装节点注入攻击,即伪装注入恶意节点(结构/属性)是对防御方法似乎合理/不察觉的普通淋巴结。图形数据的非欧亚人性质和缺乏人类的先验性质给伪装上伪装的形式化,实施和评估带来了巨大挑战。在本文中,我们首先提出并制定了从注射节点围绕的自我网络的忠诚度和多样性中注入的节点的伪装。然后,我们为节点注射攻击(即Cana)设计了一个对抗性伪装框架,以改善伪装,同时确保攻击性能。进一步设计了几种用于图形伪装的新型指标,以进行全面的评估。实验结果表明,当将现有的节点注入攻击方法与我们提出的CANA框架配置时,针对防御方法的攻击性能以及节点伪装将显着改善。
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