摄像机旋转运动下的快速目标检测算法

论文提出了一种摄像机旋转运动下的快速目标检测算法。首先为图像的全 局运动建立旋转参数模型,然后基于运动预测在相邻帧之间建立SIFT 特征点对,利用 RANSAC 去除外点的影响,结合最小二乘法求解全局运动参数进行运动补偿,基于残差图 像的更新策略实时更新特征点集,以适应背景的变化,最后使用帧差法获得运动目标。该算 法不仅保持了SIFT 本身的优越性能,而且极大地提高了检测速度。实验结果表明该算法可 以实时准确的检测出运动目标。     

基于角度补偿的手机多传感器数据融合测距算法

在惯性测量领域,单纯利用加速度二次积分的方法并不能准确感知目标对象移动的距离.加速度传感器在感知呈线性运动的目标对象时较为准确和实用,但在三维空间运动时它的坐标轴会随物体发生方向的改变而不断漂移.为解决该问题,提出了一种基于角度补偿的手机多传感器数据融合测距算法(ADC-R),使用加速度传感器测量物体运动的加速度,作为计算位移的原始数据;采用手机陀螺仪传感器测量运动物体的角速度,并以旋转矢量传感器输出的数据作为参数把手机动态坐标系下测得的加速度值空间坐标转换到静态的参考坐标系下,然后进行数据融合完成角度补偿计算;最后根据物理学加速度和位移的关系运用数学积分方法和进一步修正误差的技术得到最终移动的距离.实验结果表明此方法在近距离测距方面精度较高,优于加速度积分算法和加速度与陀螺仪融合算法.     

运动矢量加速度预测起始搜索点的块匹配算法

块匹配运动估计是去除图像序列时间冗余的重要手段,在MPEG-4、H.264/AVC等视频编码标准中都得到了应用,但消耗了巨大的运算量.论文阐述了块匹配算法原理,归纳了当前运动估计中采用的各种手段,建议使用一种运动矢量加速度预测搜索起点的算法,利用相邻的若干参考帧中对应块的运动加速度来预测待编码块的起始运动矢量.仿真结果证明该方法效果明显,减少了搜索次数且准确度高.     

Optimal Shock Isolation of a Two-Component Elastic Object

We consider the problem of the optimal shock isolation of an object whose mechanical model is described by two masses with a linear elastic connection between them. The object is situated on a base whose movement is considered as a shock load. The base acceleration law (shock action) is given. For the sake of safety, the object is fastened to the base by a special device—an shock isolator. The isolator is characterized by the force of the action on the object. We pose the problem of constructing the force law of the isolator such that the stroke of the isolator (the maximum change in the distance between the fastening points of the isolator on the object and on the base) is minimal under the condition that the force of the elastic connection between the masses of the object does not exceed the given admissible value. We obtain approximate solutions of the problem, as well as exact solutions for various classes of shock actions. We provide examples. We show that the solutions include the summands that are the impulse functions. The results can be used to create highly effective devices to protect against shock of technical systems and humans in industry and in transport.     

Optimal shock isolation of a two-component viscoelastic object

A limiting performance of shock isolation is studied for an object modeled by two rigid bodies connected by a viscoelastic element with a linear characteristic. The object is attached to a movable base by means of a shock isolator, which is regarded as a device that produces a control force between the base and the object. The base and the object move along the same straight line. The base is subject to an external shock excitation that is characterized by the time history of the acceleration of the base. A control law is defined for the shock isolator to minimize the maximum magnitude of the displacement of the object relative to the base, provided that the force of interaction between the components of the object does not exceed a prescribed value. An algorithm for constructing the exact solution of the problem under certain assumptions is presented. A technique for constructing an approximate solution for an object having high stiffness is described. The optimal control is shown to have impulse components. Examples are given. The two-component model considered in the paper is known to have been utilized to describe the mechanical response of a human body to a shock load along the spine or from thorax to back. Therefore, the problem under consideration can be regarded as a benchmark optimal control problem for a system that protects from injuries cased by shock loads. Solution of such problems is highly topical for development of safety systems for vehicles.     

一种插值与逼近运动物体活动标架的新方法

插值运动物体给定活动标架(原点位置和3个坐标轴朝向)是计算机图形学、机器人等领域的一个重要问题.该文提出一种采用B样条曲线插值与逼近运动物体活动标架的新方法.采用4个欧拉参数对正交活动标架的旋转变换矩阵进行参数化,得到了一个简单的优化方程.采用迭代法求解该优化方程来逼近运动轨迹任意处伪活动标架的旋转变换矩阵.还证明了插值和逼近所引起的误差是可控的.由于活动标架的计算只涉及2阶或3阶线性方程组,所以此方法具有很高的运行效率.     

一种光学式运动捕捉系统下的物体运动数据捕捉方法研究

多相机视觉运动捕捉系统能通过捕捉标记点的空间坐标来获得运动物体的运动学参数,文中提出了一种基于多相机运动捕捉系统下的通用物体运动数据捕捉方法;首先根据3个标记点组成固定模型获取物体运动过程中对应标记点的瞬时坐标,然后通过向量法求解出被测物体在运动过程中各采集点对应的物体位姿,然后通过卡尔曼滤波方法消除运动捕捉过程中的系统和环境误差的影响,获得平滑的物体位姿运动轨迹,并根据滤波数据计算出物体在各采集点对应的速度、加速度、角速度、角加速度;最后基于协作机器人进行物体的运动数据捕捉实验,验证了所提出物体运动数据捕捉方法的正确性。     

Video object tracking based on improved gradient vector flow snake and intra-frame centroids tracking method

Accurately tracking the video object in video sequence is a crucial stage for video object processing which has wide applications in different fields. In this paper, a novel video object tracking algorithm based on the improved gradient vector flow (GVF) snake model and intra-frame centroids tracking algorithm is proposed. Unlike traditional gradient vector flow snake, the improved gradient vector flow snake adopts anisotropic diffusion and a four directions edge operator to solve the blurry boundary and edge shifting problem. Then the improved gradient vector flow snake is employed to extract the object contour in each frame of the video sequence. To set the initial contour of the gradient vector flow snake automatically, we design an intra-frame centroids tracking algorithm. Splitting the original video sequence into segments, for each segment, the initial contours of first two frames are set by change detection based on t-distribution significance test. Then, utilizing the redundancy between the consecutive frames, the subsequent frames’ initial contours are obtained by intra-frame motion vectors. Experimental results with several test video sequences indicate the validity and accuracy of the video object tracking.     

图象序列运动目标特征点对应的极指数栅格方法

目前的图象序列特征点对应方法是建立在相邻图象间的特征点在运动形式上变化不大 ,即相邻两帧图象间的时间间隔较小这样的一个假设之上的 ,但当相邻图象间的时间间隔较大时 ,则这些方法很难找到对应的特征点 .为此 ,提出了一个由粗到细解决图象序列特征点对应的新方法 ,该方法首先进行粗定位 ,即利用极指数栅格方法来得到运动后目标特征点的大致范围 ;然后通过细定位来得到对应的特征点 .为了使人们对该方法有一全面了解 ,还介绍了该方法的原理 ,并给出了实验结果 .实验证明 ,该方法可以很好地解决时间间隔较大的两帧图象间的特征点对应问题 ,其最大的优点是比通常的方法简单有效 .     

A numerical study of the dimple/gimbal interface in a hard disk drive

A finite element (FE) model for the dimple/gimbal interface of a hard disk drive is developed as a function of normal load, friction coefficient, material properties and dimple geometry. The air bearing force is approximated as a normal load acting on the slider. A rotational acceleration was applied to the dimple to simulate accessing of a hard disk drive suspension during seeking. Results for the relative displacement between the dimple and the gimbal are determined for a typical suspension as a function of normal load, rotational acceleration, friction coefficient, material properties and geometrical parameters of suspension and flexure.     

3-d motion estimation, understanding, and prediction from noisy image sequences

This paper presents an approach to understanding general 3-D motion of a rigid body from image sequences. Based on dynamics, a locally constant angular momentum (LCAM) model is introduced. The model is local in the sense that it is applied to a limited number of image frames at a time. Specifically, the model constrains the motion, over a local frame subsequence, to be a superposition of precession and translation. Thus, the instantaneous rotation axis of the object is allowed to change through the subsequence. The trajectory of the rotation center is approximated by a vector polynomial. The parameters of the model evolve in time so that they can adapt to long term changes in motion characteristics. The nature and parameters of short term motion can be estimated continuously with the goal of understanding motion through the image sequence. The estimation algorithm presented in this paper is linear, i.e., the algorithm consists of solving simultaneous linear equations. Based on the assumption that the motion is smooth, object positions and motion in the near future can be predicted, and short missing subsequences can be recovered. Noise smoothing is achieved by overdetermination and a leastsquares criterion. The framework is flexible in the sense that it allows both overdetermination in number of feature points and the number of image frames.     

Vision Based Neuro-Fuzzy Controller for a Two Axes Gimbal System with Small UAV

This paper presents the development of a vision-based neuro-fuzzy controller for a two axes gimbal system mounted on a small Unmanned Aerial Vehicle (UAV). The controller uses vision-based object detection as input and generates pan and tilt motion and velocity commands for the gimbal in order to keep the interest object at the center of the image frame. A readial basis function based neuro-fuzzy system and a learning algorithm is developed for the controller to address the dynamic and non-linear characteristics of the gimbal movement. The controller uses two separate, but identical radial basis function networks, one for pan and one for tilt motion of the gimbal. Each system is initialized with a fixed number of neurons that act as rules basis for the fuzzy inference system. The membership functions and rule strengths are then adjusted with the feedback from the visual tracking system. The controller is trained off-line until a desired error level is achieved. Training is then continued on-line to allow the system to accommodate air speed changes. The algorithm learns from the error computed from the detected position of the object in image frame and generates position and velocity commands for the gimbal movement. Several tests including lab tests and actual flight tests of the UAV have been carried out to demonstrate the effectiveness of the controller. Test results show that the controller is able to converge effectively and generate accurate position and velocity commands to keep the object at the center of the image frame.     

使用修改的豪氏道夫距离自动提取运动对象

新的视音频编码标准MPEG－4增加了支持基于内容的功能,它把视频序列分割成语义意义上的视频对象（VO）视频对象在某一瞬时的：“快照”称为视频对象平面（VOP）,且一系列VOP表示一个运动对象,VOP分割相当困难,这主要是因为物理对象通常不以亮度,彩色或光流等低级特征来表达,所以经典的分割方法无法获得有意义的分割结果,为了对这种视频运动图象进行有效的提取,提出了一种基于修改的豪氏道夫对象踊跃器的自动VOP分割方法,首先提取出初始模型,然后用跟踪器在序列中继帧中跟踪此对象,再对模型逐帧修改,以适应对象在后继帧中形状的旋转和变化,最后根据一系列二值模型来提取出视频对象,此外,为了提高分割效果帮减少复杂性,还使用了静 背景滤除技术来滤除静态背景,实验结果表明,该算法是有效的。     

Spatial camera orientation control by rotation‐minimizing directed frames

The use of rotation‐minimizing directed frames (RMDFs) for defining smoothly varying camera orientations along given spatial paths, in real or virtual environments, is proposed. A directed frame on a space curve is a varying orthonormal basis for ℝ³ such that coincides with the unit polar vector from the origin to each curve point, and such a frame is rotation‐minimizing if its angular velocity vector maintains a vanishing component along o . To facilitate computation of rotation‐minimizing directed frames, it is shown that the basic theory is equivalent to the established theory for rotation‐minimizing adapted frames—for which one frame vector coincides with the tangent at each curve point—if one replaces the given space curve by its anti‐hodograph (i.e., indefinite integral). A family of polynomial curves on which RMDFs can be computed exactly by a rational function integration, the Pythagorean (P) curves, is also introduced, together with algorithms for their construction. Copyright © 2009 John Wiley & Sons, Ltd.     

基于Rodrigues参数交互模型航天器相对位姿测量技术

针对传统测量技术测量航天器相对位姿准确度较低的问题,引用Rodrigues参数交互模型研究了一种新的航天器相对位姿测量技术。利用Rodrigues参数建立航天器位姿采集模型,通过原向量、旋转轴、原向量和旋转轴的交叉积等向量作为标架,获得航天器旋转以后得向量组,利用四元数定理来减少计算航天器旋转向量的计算量,在观察三维空间内的坐标系间的向量变化曲线规律后,测量出交互模型的航天器相对位姿,得出基于罗德里格旋转参数交互模型结构图,确定罗德里格旋转参数模型与航天器的距离H和地面接收到的航天器相位位姿的误差。通过Harris角点检测方法计算航天器模拟图像的每个像素和灰度,通过像素和灰度信息进行条件随机场计算,分析航天器相对位姿特征,在多次寻找三维坐标系中查找相似的最近临近点和次临近点后,合理匹配,确定航天器相对位姿。实验结果表明,基于Rodrigues参数交互模型航天器相对位姿测量技术测量的精准度比传统技术高出25.88%,实用性更强。     

Base frame calibration for coordinated industrial robots

To solve the problem of base frame calibration for coordinated multi-robot system, a new method is proposed in this paper. It is carried out through a series of “handclasp” manipulations between two coordinated robots, then a preliminary result can be reached by the calibrating equation. After that, in order to make sure that the calibrated rotation matrix is orthonormal, an optimal estimation of the relative rotation between the base frames of coordinated manipulators is solved out under the criterion of optimal Frobenius norm approximation. By the quaternion representation for rotation matrix and the Lagrange Multiplier method, an orthonormal matrix can be reached which is just the unknown calibrating result for base frames of the coordinated robots. Simulation and experiment results have verified the validity and effectiveness of the proposed method.     

基于FPGA/DSP的捷联惯导系统设计

介绍了一种基于FPGA/DSP的捷联惯导系统的软硬件设计;详细提供了系统的硬件架构(包括系统框图、基于CPLD的六通道V/F采集电路、DSP芯片自举系统的基本连接框图)、各模块的设计方案和软件流程图,选用了四元素和旋转矢量相结合的方法解算姿态矩阵,并且在计算旋转矢量的同时计算加速度,进一步提高了导航系统的精度;系统导航试验结果表明,该系统精度高,动态特性好,可靠性高。     

Electrohydraulic thrust vector control of twin rocket engines with position feedback via angular transducers

The thrust vector control (TVC) of rocket engines is used when the aerodynamic surfaces are inadequate to control vehicles or when a greater agility may be required of a missile. Traditionally, in all spacecraft to date actuators used to gimbal the engine have been hydraulic. The subject of this paper is the TVC with gimballed nozzle assembly controlled by an electrohydraulic servosystem, where two linear hydraulic servoactuators gimbal the engine. Each servoactuator is controlled by an electrohydraulic servovalve. The thrust vector direction is a result of the motion of both servoactuators. In this paper the TVC system is treated as a robotic system that allows developing the procedure of solving an inverse kinematics problem as well as the control of the robotic system in the output space instead of in the space of internal dynamics. The position feedback is provided by measuring the direction of the thrust vector, instead of measuring the displacements of the servoactuators. A linear model of the servosystem has been developed and simulated. The proposed control concept has experimentally been validated in the TVC test bench.     

Quaternion calculus as a basic tool in computer graphics

Quaternions, although not well known, provide a fundamental and solid base to describe the orientation of an object or a vector. They are efficient and well suited to solve rotation and orientation problems in computer graphics and animation. This paper describes two new methods for splining quaternions so that they can be used within a keyframe animation system. We also show that quaternions, although up to now solely used for animation purposes, can be used successfully in the field of modelling and rendering and we prove that we can speed up the rendering algorithm by using quaternions.