RME:基于滑动窗口的实时人脸检测算法

研究了基于滑动窗口的视频实时人脸检测,提出了刚性运动估计(RME)算法.该算法以小尺度人脸瞬时刚性运动为假设,根据几何变换对窗口图像的运动进行描述,以光流代替运动矢量计算运动参数进而识别窗口图像的刚性、非刚性运动类型,通过排除非刚性窗口以提高人脸检测效率.对比实验与分析表明,该算法在准确率与时间效率方面具有优势.     

Developments in quantitative dimensional synthesis (1970-present): four-bar motion generation

Dimensional synthesis is a type of inverse problem in linkage kinematics where the objective is to calculate the linkage dimensions required to achieve prescribed linkage output motion. Motion generation is a particular category of dimensional synthesis where the objective is to calculate the linkage dimensions required to achieve a group of prescribed link positions. In motion generation for a four-bar linkage, positions are prescribed for the coupler link. While early motion generation methods were primarily qualitative, ongoing advancements in computing hardware and software continue to make quantitative motion generation more practical. By providing overviews of works representative of developments in quantitative four-bar motion generation since 1970, this work is essentially an overview that spans over 40 years of developments in quantitative four-bar motion generation.     

一种具有力检测机制的新型血管介入手术机器人

为了在机器人辅助远程介入手术中实现向医生提供高精度的力反馈,设计了一种具有力检测机制的新型血管介入手术机器人,其是一个主从控制系统,包括一个操作方便的主端装置和一个递送导丝/导管的从端装置。首先,设计了血管介入手术机器人的力检测机制,以实现轴向近端力的精准测量和径向夹紧力的感知。然后,基于血管介入手术机器人的动力学分析,设计了具有在线整定参数功能的模糊PID (proportional integral derivative,比例积分微分)控制器,以提高从端装置的递送精度和抗干扰能力,同时选择阶跃信号对所设计的模糊PID控制器进行仿真验证。最后,搭建血管介入手术机器人物理样机,并开展主从运动跟踪实验和轴向近端力、径向夹紧力检测评估实验。实验结果表明,该血管介入手术机器人具有[-0.31, 0.25] mm的运动跟踪误差,可检测平均误差为0.12 N的轴向近端力以及可感知0.47～4 N的径向夹紧力。研究结果验证了所设计血管介入手术机器人的鲁棒性以及其力检测机制的可行性,可为同类产品的设计和改进提供参考依据。     

Contact Stability Analysis of a One Degree-of-Freedom Robot

The aim of this note is to examine the conditions of stability of a simple robotic task: we consider a one degree-of-freedom (dof) robot that collides with a spring-like environment with stiffness k, the goal being to stabilize the system in contact with the environment. We study conditions on the feedback gains that guarantee quadratic Lyapunov stability of the task with a well-conditioned solution to the Lyapunov equation. It is shown that when the environment's stiffness k grows unbounded, those conditions yield unbounded values of the gains. Motivated by the stability analysis of the impact Poincaré map in the perfectly rigid case ( ), we propose an analysis that is independent of k. It enables us to conclude on global asymptotic convergence of the system's state towards the equilibrium point. This work can also be seen as the study of stability of a contact (force control) phase, taking into account the unilateral feature of the constraint.     

复杂背景下跌落试验件的图像测试技术研究

为实现复杂背景条件下跌落试验件运动姿态参数的自动测试,采用数字图像处理技术提取复杂背景中的试验件特征图像,并利用计算机分析提取后的特征图像,实现了试验件姿态参数的计算机自动识别;实践表明,文中研究的图像处理方法可有效提取复杂背景下的目标试验件,此研究是计算机图像处理技术在武器工程自动化测试领域应用的有益尝试。     

A dynamic priority-based approach to concurrent toolpath planning for multi-material layered manufacturing

This paper presents an approach to concurrent toolpath planning for multi-material layered manufacturing (MMLM) to improve the fabrication efficiency of relatively complex prototypes. The approach is based on decoupled motion planning for multiple moving objects, in which the toolpaths of a set of tools are independently planned and then coordinated to deposit materials concurrently. Relative tool positions are monitored and potential tool collisions detected at a predefined rate. When a potential collision between a pair of tools is detected, a dynamic priority scheme is applied to assign motion priorities of tools. The traverse speeds of tools along the x-axis are compared, and a higher priority is assigned to the tool at a higher traverse speed. A tool with a higher priority continues to deposit material along its original path, while the one with a lower priority gives way by pausing at a suitable point until the potential collision is eliminated. Moreover, the deposition speeds of tools can be adjusted to suit different material properties and fabrication requirements. The proposed approach has been incorporated in a multi-material virtual prototyping (MMVP) system. Digital fabrication of prototypes shows that it can substantially shorten the fabrication time of relatively complex multi-material objects. The approach can be adapted for process control of MMLM when appropriate hardware becomes available. It is expected to benefit various applications, such as advanced product manufacturing and biomedical fabrication.     

3D Human model adaptation by frame selection and shape–texture optimization

We present a novel approach for 3D human body shape model adaptation to a sequence of multi-view images, given an initial shape model and initial pose sequence. In a first step, the most informative frames are determined by optimization of an objective function that maximizes a shape–texture likelihood function and a pose diversity criterion (i.e. the model surface area that lies close to the occluding contours), in the selected frames. Thereafter, a batch-mode optimization is performed of the underlying shape- and pose-parameters, by means of an objective function that includes both contour and texture cues over the selected multi-view frames.Using above approach, we implement automatic pose and shape estimation using a three-step procedure: first, we recover initial poses over a sequence using an initial (generic) body model. Both model and poses then serve as input to the above mentioned adaptation process. Finally, a more accurate pose recovery is obtained by means of the adapted model.We demonstrate the effectiveness of our frame selection, model adaptation and integrated pose and shape recovery procedure in experiments using both challenging outdoor data and the HumanEva data set.     

基于流场的爆炸分裂效果模拟

通过分析冲击波气流的运动特点,对Navier-Stokes方程进行合理简化。根据简化后的方程所反映出的气流速度变化规律,提出描述冲击波气流运动的扩散模型。基于该模型所定义的流场,对碎片的运动进行控制,实现对冲击波作用下物体碎片飞散效果的模拟。实验结果表明,该方法具有较强的真实感,能够满足实时性要求。     

基于双向运动补偿的帧速率上变换算法

针对不同帧速率视频之间的转换问题,提出一种改进的基于双向运动补偿的帧频提升算法,通过边缘加权获取高精度的双向运动向量,利用可变尺寸块运动向量场估计逐级对运动向量求精,采取自适应重叠块补偿方法解决帧频提升过程中产生的重叠及空洞问题,提高双向运动向量的精度,减小块效应。实验结果表明,与传统的帧频提升算法相比,该算法在内插图像主、客观质量方面都有较大提升。     

基于XvMC的MPEG-2硬件解码的研究与实现

研究了如何利用GPU来加速视频解码,概述了MPEG-2视频解码的系统框架,论述了MPEG-2视频解码在Linux下以XvMC(X video motion compensation)为API并基于通用可编程GPU的实现过程,重点讨论了MPEG-2视频解码中IDCT(inverse discrete cosine transform)和运动补偿的实现,提出了新的优化算法.MPEG-2视频解码算法具有一定的通用性,实验结果表明,与传统的解码方式相比,该解码器不仅能加速视频解码,还能有效降低CPU的利用率和电脑的功耗.