基于GPU流计算模式的非凸体碰撞检测算法的研究

针对虚拟坐标测量系统中非凸物体间的碰撞检测问题,将非凸体分解为三角形面片,利用可编程图形处理单元(GPU)的流计算优势,将分离轴检测算法映射到图形硬件的片断着色器中,以计算三角形间的相交情况.结果表明,该算法在处理流数据时具有良好的实时性和稳定性.     

虚拟生产环境中的实时碰撞检验技术

针对由机床、机器人等成百上千个物体构成的虚拟生产环境澡的实时碰撞检验问题，提出了一个由数据结构支持的层次化紧符合碰撞检验算法，解决了含凹多面体的、复杂障碍空间中多移动物体的碰撞检验问题，算法能够自动报告将要发生和已经发生的几何接触，并精确检测出两个移动物体的最小欧氏空间距离和最大干涉量，它们是计算干涉力和机器人运动规划中罚函数的重要参数，算法能够快速收敛且鲁棒性好。     

基于可见性查询的凸体碰撞检测算法

虚拟制造、机器人路径规划等许多应用都需进行实时的碰撞检测.论文提出一种新的凸体碰撞检测算法,此算法基于主流图形硬件的可见性查询功能,克服了同类图像空间算法需从显存回读大量数据的缺点,并可一次提交多个物体对的碰撞检测.实验表明该算法有效提高了碰撞检测的效率.     

虚拟座舱设备碰撞检测算法实现技术研究

在虚拟现实技术中，人与虚拟空间物体的碰撞检测是非常重要的研究课题之一．在简要地介绍了某大型运输机空中加油虚拟仿真训练系统的基本结构和实现原理之后，给出了手的初始数据模型、坐标变换算法以及手的运动方向的定义．在此基础之上，给出了虚拟空间中手与机舱内的主要可操纵设备进行交互碰撞检测的主要算法．     

基于特征点的快速碰撞检测算法

在Lin-Canny算法的基础上,提出一种虚拟环境下面向凸体的动态、实时碰撞检测方法。该方法采用模型的特征点集合来描述其外部轮廓,通过改进的最近特征对获取方法和提出的中心定位算法来进行碰撞检测。实验给出了基于特征点的碰撞检测算法与基于包围盒算法的比较结果,证明了所提出算法的优越性。     

一维三体碰撞过程的数值实验研究

力学中常常将物体之间的相互作用描述为碰撞过程，两体碰撞模型广泛地运用于处理各种物理问题，然而现实世界中普遍存在着多体碰撞．文中建立了三体碰撞过程的动力学方程组，对一维完全弹性三体碰撞进行了数值实验研究．研究结果表明，三体碰撞物体的分离速度与物体之间相互作用过程的细节有关，一般情况下不能简化为相继的两次两体碰撞求解．     

基于OpenCasCade的虚拟三坐标测量机碰撞检测方法

为了解决三坐标测量机测量过程中可能出现的碰撞问题,提出将虚拟空间与实际空间相结合的防碰撞方法,同时提出一种基于OpenCasCade(OCC)的快速、准确的虚拟空间碰撞检测方法.防碰撞方法在虚拟空间中建立与实际空间具有一一对应关系的虚拟模型,从而在计算机向三坐标测量机发送运动指令时先在虚拟空间中检测该指令是否会造成碰撞,将有碰撞的指令修改为无碰撞的安全指令输出,以达到防碰撞的目的.根据OCC建模的特点,可以将虚拟空间碰撞检测方法分为2步,第1步利用包围盒法快速剔除不可能碰撞的部分,第2步利用三角面片相交检测法进行较为精确的碰撞检测.为了提高速度,利用OpenMP将碰撞检测程序的计算并行化.相关的碰撞检测实验验证了该碰撞检测方法的可行性,并根据记录的数据对碰撞检测时间和精度进行了分析,证明该碰撞检测方法具有一定的实用价值.     

任意形状工件的二维视觉定位和定向的研究

利用计算机视觉技术对任意形状的工件可以进行快速的定位定向．例如：被测工件在CMM工作台上放置状态的确定；机器人抓起生产线传送带上的工件等等．本文利用物体影像的转动惯量对物体进行定位和定向，对空间物体的位置和方向给出了利用物体影像的转动惯量确定的严格定义．文中对利用物体影像的转动惯量对物体进行视觉定位定向的原理给出了详细的叙述，并给出了便于计算机编程的定位定向公式，同时给出了该方法的实验数据．     

动态织物仿真与碰撞响应算法

针对织物动态仿真粒子系模型做了深入的研究。为了解决织物仿真中的非线性碰撞约束问题，笔者提出了新的碰撞检测及相应的碰撞反应算法。该算法不仅在直观上有很好的物理解释，而且简单易行，计算量小，可以适用于实时模拟，对于很多复杂的碰撞情况具有处理上的统一。另外，笔者提出用显式积分方法来求解模型建立起来的微分方程，该方法的优点是不需解线性方程组，处理碰撞问题时，可以直接求出非常精确的碰撞时刻，从而达到了提高计算效率的目的。     

鳞状因子循环矩阵方程解的条件与求解的快速算法

利用多项式快速算法,给出了鳞状因子循环矩阵方程AX=b可解的条件与求解的快速算法.当鳞状因子循环矩阵非奇异时,该快速算法求出线性方程组的唯一解;当鳞状因子循环矩阵奇异时,该快速算法求出线性方程组的特解与通解.该快速算法仅用到鳞状因子循环矩阵的第一行元素及对角矩阵中的对角上的常数进行计算.在计算机上实现时只有舍入误差.特别地,在有理数域上用计算机求得的结果是精确的.     

机器人关节间的碰撞检测

将多臂机器人各运动关节简化为具有一定直径的圆柱体,通过计算两圆柱体中心线间最短距离来进行机器人的碰撞检测研究.在此过程中,首先通过总结提炼两空间线段间的相互位置关系,在进行解析,推导的基础上,提出了7个有意义的解析几何推论,直接可得出两空间线段间的最短距离,然后根据得出的结果,设计了一个机器人运动关节间的碰撞检测算法.该算法程序设计简单,计算量小,能有效地满足实际应用需要.     

Exact collision detection for a virtual manufacturing simulator

Collision detection is a critical aspect of Virtual Reality (VR)-based simulation of manufacturing processes. Despite the significant progress that has been made in developing efficient, exact collision detection algorithms for convex objects, limited and slow progress has been reported in developing collision detection algorithms for general, nonconvex objects. To narrow this gap we introduce the concept of virtual objects which extends the applicability of exact collision detection algorithms to nonconvex objects. The outcome of our methodology is the fast creation of convex objects for a class of frequently encountered nonconvex manufacturing objects that can be used in any existing collision detection approach. The collision detection technique described in this paper is best suited for interactive simulation and animation applications where a high accuracy of object contact modeling is required. Examples include virtual assembly; mobile robot simulation; robotic painting; robotic welding; and coordinate measuring processes.     

Geometric approach for designing optical binary amplitude and binary phase-only filters

An analytic solution for real optimal filters is known, and the special case of optimal binary phase-only filters can be solved by a fast binning algorithm but no analytic solution is known. We establish a geometric solution for the design of optimal binary amplitude filters (OBAF's) and optimal binary phase-only filters (OBPOF's) for any object. The optimal filter is found in terms of maximizing the field strength at the origin in the correlation plane. We found that it is possible to construct a unique convex polygon by using an ordered set of phasors from the filter object's Fourier transform. This process leads eventually to an exact solution for the filter-design problem. We show that the maximum distance across the polygon divides the phasors into two groups: For the OBAF, it determines the group that is passed or blocked; for the OBPOF, it determines which group is passed with a zero or a pi phase shift. The shape of the convex polygon gives qualitative information on the criticalness and the tightness needed in the design process. It provides good insight into the binning-process algorithm and permits us to bound the error in the binning process. Design examples through computer simulation and applications in fingerprint identification are presented.     

Truck adaptive following distance based on threat assessment under variable conditions

Vehicle-stopping distance and recommended following distance are important factors for heavy-duty truck safety. The practical vehicle stopping-distance is affected by several factors beside vehicle dynamics: current speed, braking system retardation force, road slip and road grade. One of the purposes of truck onboard monitoring is to provide real-time feedback to the driver that could have two forms: a warning to the driver for any threat of frontal collision; or advisory information. Both are based on threat assessment and thus are equivalent in theory. Most previous work in the literature only provides threat assessment and warning under ideal cases that is, flat, straight, dry and concrete road surface conditions. The authors systematically investigate vehicle stopping distance under variable conditions, based on which the corresponding recommended following distance is generated. Although it is difficult for the driver to estimate the following distance visually, sensor detection plus appropriate feedback to the driver can achieve the same goal. Practical implementation issues and field test results are also presented. They show how significantly the environmental factors affect the threat assessment and the recommended following distance. The results are readily applicable to the development of safety systems for other types of vehicles.     

Collision avoidance timing analysis of DSRC-based vehicles

Dedicated short-range communication (DSRC) has been used in prototyped vehicles to test vehicle-to-vehicle communication for collision avoidance. However, there is little study on how collision avoidance software should behave to best mitigate accident collisions. In this paper, we analyse the timing of events and how they influence software-based collision avoidance strategies. We have found that the warning strategies for collision avoidance are constrained by the timing of events such as DSRC communication latency, detection range, road condition, driver reaction and deceleration rate. With these events, we define two collision avoidance timings: critical time to avoid collision and preferred time to avoid collision, and they dictate the design of software-based collision avoidance systems.     

A swept volume approach based on hermite interpolation for optimization in collision‐free motion planning

Abstract

The recursive quadratic programming (RQP) technique has been successfully applied for the motion planning problem. This paper inherits the RQP optimization formulation to solve collision‐free motion planning problems. The focus of the paper is to develop a more accurate approach to represent the swept volume based on Hermite interpolation. The non‐convex swept volume may be described by parametric representation. Based on this idea, the non‐convex limitation of the motion planning by the previous RQP technique can be overcome and it has yielded accurate answers in distance calculation. Also, have been presented to illustrate and demonstrate this approach in the paper.     

Terrain and Model Queries Using Scalar Representations With Wavelet Compression

In this paper, we present efficient height/distance field data structures for line-of-sight (LOS) queries on terrains and collision queries on arbitrary 3-D models. The data structure uses a pyramid of quad-shaped regions with the original height/distance field at the highest level and an overall minimum/maximum value at the lower levels. The pyramid can compactly be stored in a wavelet-like decomposition but using max and plus operations. Additionally, we show how to get minimum/maximum values for regions in a wavelet decomposition using real algebra. For LOS calculations, we compare with a kd-tree representation containing the maximum height values. Furthermore, we show that the LOS calculation is a special case of a collision detection query. Using our wavelet-like approach, even general and arbitrary collision detection queries can efficiently be answered.      

Simultaneous detection of molecular oxygen and water vapor in the tissue optical window using tunable diode laser spectroscopy

We report on a dual-diode laser spectroscopic system for simultaneous detection of two gases. The technique is demonstrated by performing gas measurements on absorbing samples such as an air distance, and on absorbing and scattering porous samples such as human tissue. In the latter it is possible to derive the concentration of one gas by normalizing to a second gas of known concentration. This is possible if the scattering and absorption of the bulk material is equal or similar for the two wavelengths used, resulting in a common effective pathlength. Two pigtailed diode lasers are operated in a wavelength modulation scheme to detect molecular oxygen ~760 nm and water vapor ~935 nm within the tissue optical window (600 nm to 1.3 mum). Different modulation frequencies are used to distinguish between the two wavelengths. No crosstalk can be observed between the gas contents measured in the two gas channels. The system is made compact by using a computer board and performing software-based lock-in detection. The noise floor obtained corresponds to an absorption fraction of approximately 6x10(-5) for both oxygen and water vapor, yielding a minimum detection limit of ~2 mm for both gases in ambient air. The power of the technique is illustrated by the preliminary results of a clinical trial, nonintrusively investigating gas in human sinuses.     

碰撞检测技术及在桥梁视景仿真中的应用

碰撞检测（Collision Detection）及优化是视景仿真技术中一项非常重要的技术,文中通过对碰撞检测理论的论述,概要介绍了碰撞检测算法关于时间域与空间域的不同分类方法,并讨论如何优化碰撞检测的方法,以减少运算时间与复杂度。通过视景仿真中桥梁碰撞检测的实例对碰撞检测理论及优化算法进行了验证。