交会对接航天员训练电视图像实时高动态范围渲染

应用基于人眼视觉系统的高动态范围实时渲染技术处理交会对接仿真场景,可以为航天员手控交会对接训练提供高逼真度的电视图像.文中结合交会对接电视图像的特点,分析了交会对接航天员训练电视图像高动态范围实时渲染的关键技术;根据两航天器相对距离,将交会对接过程分为远、中和近3个距离段,采用S-curve算法、自适应对数算法和Reinhard算法分别对每个距离段进行调和映射处理;改进了自适应对数算法和Reinhard算法,并基于GPU处理技术实现仿真电视图像的实时显示.实验结果表明,采用基于距离变化调整调和映射算法的方法处理交会对接仿真电视图像可以高逼真地模拟实录视频场景,为航天员手控交会对接训练提供了视景支持.     

交会对接仿真电视图像TMO算法主观评价

通过对实时渲染仿真交会对接电视图像的主观评价,指出调和映射处理(TMO)算法的修正是提高仿真场景逼真度的方法.基于交会对接仿真电视图像TMO算法应用,分别针对S-curve算法、自适应对数算法和Reinhard算法设计了基于静态图像对比的亮度调和因子评价实验和基于动态场景对比的算法应用距离段评价实验,并对实验结果的均值、标准差以及HSD值进行了计算与分析;上述3种算法亮度调和因子分别为6.0,0.6和2.2,依次应用于远距离,中、近距离和靠拢距离时仿真电视图像有最佳评价和显示效果.实验结果表明,采用同种TMO算法处理的交会对接仿真图像动态场景真实感效果优于静态图像;在交会对接不同距离段内,仿真场景需要采用不同的TMO渲染方法.     

实时数据驱动的交会对接仿真平台设计与实现

航天器地面综合测试时,为了在测试数据显示基础上,动态展示航天器交会对接过程,验证交会对接飞行方案的正确性,为航天员手控交会对接训练提供支持,设计航天器交会对接仿真系统,给出交会对接仿真平台设计架构。通过对航天器建模、虚拟场景装配、模型驱动方法、阳照区/阴影区绘制、姿态和星下点轨迹计算方法研究,开发实现航天器交会对接仿真平台。平台由实时测试数据驱动,在航天器地面静态测试下,可以实时显示航天器三维飞行状态及星下点轨迹。目前,仿真平台已经应用于航天器地面综合测试过程中,同时,平台可以扩展支持航天器在轨飞行动态展示,丰富了航天器测试和监视手段,具有较高工程应用价值。     

基于超二次曲线障碍描述的航天器交会对接地面实验研究

航天器交会对接技术是众多空间任务得以开展的关键性技术,在进行空间在轨飞行任务之前,需开展相应的地面实验研究.首先,基于二维交会对接模型,提出了一种基于势函数法的交会对接控制方法.其次,考虑与类矩形障碍物的避撞约束以及与心形目标航天器的安全对接区域约束,并采用超二次曲线去描述该障碍物外形.然后,基于花岗岩气浮平台搭建了二维交会对接地面实验系统,设计了航天器气浮模拟器以及电磁对接机构,并开展了交会对接地面实验研究.实验结果表明了所搭建实验系统的可行性,同时也验证了所提出交会对接控制方法的有效性.     

空间对接仿真试验台对接机构测控系统设计

为实现空间两飞行器的交会对接,需要对空间交会对接过程进行仿真调试。为此,构建空间对接半实物仿真试验台,克服无实物仿真环境的局限性,再现2个空间飞行器的交会对接过程。提出对接机构测控系统设计方案,描述其软件结构和控制流程,建立对接机构测控模型,通过RT-LAB实时仿真平台将模型下载到测控计算机上运行,实现对接机构传感器信号的采集和运动控制。试验结果表明,该系统模型能够模拟飞行器的交会对接过程,具有较好的实时性,系统运行稳定、可靠。     

基于RT-LAB的空间对接半实物仿真系统

针对当前实时仿真平台工具操作不便以及灵活性较差的缺点,介绍RT-LAB仿真平台的特点,分析其应用于大型控制系统中的优势,基于该平台设计空间对接半实物仿真系统并开发相应的仿真软件,将编写的Matlab/Simulink数学模型通过RT-LAB平台加载到目标机上,实现空间交会对接的模拟仿真。仿真结果表明,该系统能够真实模拟空间两飞行器交会对接的过程,验证数学模型的准确性及对接机构产品质量,具有较高的稳定性及可靠性。     

空间交会对接过程的动力学模型与仿真

在空间交会对接过程中．从首次接触碰撞到完成捕获与捕获后的缓冲校正这两个阶段是对接动力学研究的重点。建立动力学模型进行仿真是研究的一个有效途径．以有内导向办异体同构周边式对接机构为研究对象．从机构的物理模型出发建立了对接捕获阶段与缓冲校正阶段的动力学模型。在动力学仿真软件DADS的接口上开发相应的用户模块．完成交会对接过程的动力学仿真．     

基于立体视觉的非合作目标位姿测量

非合作航天器间相对位姿(位置和姿态)测量,是实现非合作目标的交会与捕获等在轨服务的前提。本文研究一种基于立体视觉的位姿测量方法,包括图像采集、图像滤波、边缘检测、特征提取、目标识别、3D重建、相对位姿计算等步骤,并分别进行计算机仿真和在自制物理平台上的验证实验。仿真实验结果验证了该方法的准确性和有效性。     

全向立体成像系统场景深度估计

基于单相机双抛物面反射镜设计了一种共轴结构的折反射全向立体成像装置,给出了针对相应展开柱面全景立体图像对深度估计的应点匹配方法,最后通过3D Max构造相应虚拟装置和虚拟场景进行了仿真实验,初步证明了该结构设计和对应深度估计方法的有效性。     

基于雷达测距的飞行器交会对接误差补偿控制技术

为解决由视线倾角、视线偏角过大造成的飞行器对接存在误差的问题,实现飞行器交会轨迹的精准对接,提出基于雷达测距的飞行器交会对接误差补偿控制技术。建立空间参考坐标系,根据轨道根数计算结果,推导动力学状态方程,实现对飞行器交会对接过程中的动力学作用分析。按照雷达测距原理,计算飞行器的理论飞行时长及雷达装置作用距离,再联合相关参数指标,确定精度极限的取值范围,实现基于雷达测距的对接误差控制。在三坐标测量机结构模型中,定义飞行位姿拟合条件,再根据位姿误差求解结果,实现对误差参数的补偿修正处理,完成基于雷达测距的飞行器交会对接误差补偿控制方法的设计。对比实验结果表明,应用所提方法可以同时将视线倾角、视线偏角的取值控制在0°-45.0°的数值范围之内,能够较好解决飞行器错误对接的问题,符合精准对接飞行器交会轨迹的实际应用需求。     

基于直线间结构信息的立体视觉图像动态匹配方法

针对立体视觉匹配问题，介绍一种改进的动态规划图像匹配方法，它将边缘直线相似测度分为局部相似测度和全局相似测度，在后者中加入图像边缘直线之问的结构关系信息，并在动态搜索最优匹配路径的过程中利用结构关系约束删除不合理的匹配路径。仿真实验结果证明，采用该方法解决立体视觉中边缘线段的匹配问题，不仅提高了匹配的准确率，而且大大减少了匹配时间。     

基于Creator/Vega的虚拟场景设计与实现

阐述了基于Creator/Vega的虚拟场景仿真系统的设计过程.结合虚拟场景系统开发实例,从视景建模角度,详细分析了纹理贴图得几何尺寸和模型多边形数量,对系统运行性能的影响,并提出了利用纹理贴图、LOD和网格等建模技术提高系统运行性能的方法.在虚拟场景驱动中,实现了利用键盘、鼠标等一般输入输出设备,进行步行、鸟瞰等多种方式的漫游,增进了人机交互性能.为使系统支持立体显示,运用了Vega提供的立体显示技术.文中涉及的技术对其它虚拟场景仿真系统的开发具有重要参考价值.     

A setup for panoramic stereo imaging

In this paper, based on the proposed basic implementation of circular projection, a multi-camera setup which can be used for panoramic stereo imaging is presented. Firstly, we get multiple stereo pairs instantly by fixing multiple cameras on the proposed setup, which is an approximate implementation of circular projection. We then prove that the influence on the resultant stereo pairs generated by this approximate setup is slight based on similar triangles and structural similarity (SSIM). With these stereo pairs, the automatic panoramic image stitching algorithm is applied to generate panoramas for both eyes. In addition, with reasonable distance between cameras and the scene, physical dimensions of this setup are given. Finally, experimental results demonstrate that our scheme can be used to generate cylindrical stereo panoramic image with proper scene depth, which can provide viewers with distinguishing stereoscopic experience. The device can be installed on the mobile equipment and captures panoramic stereo image in a moment without stopping. In the future, the proposed setup can be used in the field of network navigation, video monitor and virtual reality.     

基于XML面向Agent的视景仿真开发技术

提出基于XML面向Agent的视景仿真开发技术,用面向Agent的方法描述各个仿真实体的动作行为,将对各个仿真实体的动作行为描述存储到XML文件中,将仿真实体动作行为的描述控制与仿真软件分开。将该视景仿真开发技术应用于援潜救生视景仿真系统的开发能够提高系统的健壮性和开发效率。     

BRDF invariant stereo using light transport constancy

Nearly all existing methods for stereo reconstruction assume that scene reflectance is Lambertian and make use of brightness constancy as a matching invariant. We introduce a new invariant for stereo reconstruction called light transport constancy (LTC), which allows completely arbitrary scene reflectance (bidirectional reflectance distribution functions (BRDFs)). This invariant can be used to formulate a rank constraint on multiview stereo matching when the scene is observed by several lighting configurations in which only the lighting intensity varies. In addition, we show that this multiview constraint can be used with as few as two cameras and two lighting configurations. Unlike previous methods for BRDF invariant stereo, LTC does not require precisely configured or calibrated light sources or calibration objects in the scene. Importantly, the new constraint can be used to provide BRDF invariance to any existing stereo method whenever appropriate lighting variation is available.     

Fluid in Video: Augmenting Real Video with Simulated Fluids

We present a technique for coupling simulated fluid phenomena that interact with real dynamic scenes captured as a binocular video sequence. We first process the binocular video sequence to obtain a complete 3D reconstruction of the scene, including velocity information. We use stereo for the visible parts of 3D geometry and surface completion to fill the missing regions. We then perform fluid simulation within a 3D domain that contains the object, enabling one‐way coupling from the video to the fluid. In order to maintain temporal consistency of the reconstructed scene and the animated fluid across frames, we develop a geometry tracking algorithm that combines optic flow and depth information with a novel technique for “velocity completion”. The velocity completion technique uses local rigidity constraints to hypothesize a motion field for the entire 3D shape, which is then used to propagate and filter the reconstructed shape over time. This approach not only generates smoothly varying geometry across time, but also simultaneously provides the necessary boundary conditions for one‐way coupling between the dynamic geometry and the simulated fluid. Finally, we employ a GPU based scheme for rendering the synthetic fluid in the real video, taking refraction and scene texture into account.     

An improved graph cut algorithm in stereo matching

In stereo matching tasks, the matching effect is often very poor when the texture of the region is weak or repeated. To solve this problem, an improved Graph Cut stereo matching algorithm based on Census transform is proposed. The Hamming distance of the corresponding pixels in the left and right images after Census transform is introduced as the similarity measure in the data term of the energy function. In this way, the dependence on the pixel value is reduced. The stereo matching experiments are implemented on the standard images of Middlebury stereo benchmark and the real scene images, and it demonstrates that our algorithm is robust and can obtain better performance in weak texture or repeated texture region.     

Attention-Aware Disparity Control in interactive environments

Our paper introduces a novel approach for controlling stereo camera parameters in interactive 3D environments in a way that specifically addresses the interplay of binocular depth perception and saliency of scene contents. Our proposed Dynamic Attention-Aware Disparity Control (DADC) method produces depth-rich stereo rendering that improves viewer comfort through joint optimization of stereo parameters. While constructing the optimization model, we consider the importance of scene elements, as well as their distance to the camera and the locus of attention on the display. Our method also optimizes the depth effect of a given scene by considering the individual user’s stereoscopic disparity range and comfortable viewing experience by controlling accommodation/convergence conflict. We validate our method in a formal user study that also reveals the advantages, such as superior quality and practical relevance, of considering our method.     

目标三维场景建模与实时红外仿真技术研究

针对景象匹配系统对红外图像实时性的要求越来越高的特点,提出了基于目标三维场景的实时红外仿真方法。首先,设计了红外场景仿真的总体方案;其次,对材质红外图像计算、红外图像数据库建立、基于全球三维场景的实时红外场景建模三个关键技术做了初步实现;最后,结合红外场景仿真方案完成了系统。实验结果表明：该方法生成的红外图像与实拍红外图像的变化规律基本一致,从而为实时制备红外基准图提供了一种有效途径。     

立体图像对的生成

获取同一场景的立体图像对是实现双目立体成像的一个关键问题。提出了一种在三维场景已经建好的情况下生成立体图像对的方法。该方法根据双目立体视觉的原理，利用3DS MAX中的摄像机对象对场景中的物体进行坐标变换和透视投影变换，分别生成左眼视图和右眼视图。实验结果表明，两个目标摄像机与三维模型的位置关系以及基线长度是影响立体效果的重要因素，改变目标摄像机与三维模型的位置，可以分别生成正视差、负视差的立体图像对，当AB与CO的比例参数为0.05时，生成的立体图像对的立体效果较佳。