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Alternative TitleResearch on detection collision for robot arms using hierarchical OBB-tree
Thesis Advisor李斌
KeywordObb包围盒 碰撞检测 主从遥操作机器人 虚拟现实
Call NumberTP241.3/J69/2014
Degree Discipline控制工程
Degree Name硕士
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract伴随着全球人口的增长,能源危机问题将变得日益严峻。为解决这一问题,中、美、俄等七国对核聚变能的研究与应用展开了广泛的合作,这一合作计划又称“国际热核聚变实验堆(ITER)计划”。聚变能具有资源能够无限利用,不对环境造成污染等一系列优点,是目前人类所能认知的可以解决社会环境问题、能源问题并保证社会能够可持续发展的主要方法之一。核聚变反应会释放具有高放射性的中子,这将会导致托卡马克装置的部件丧失应有的功能,因此需要定期对其进行维护。但是反应堆内部显然是不适合操作人员工作的环境,为保证核聚变反应装置能够长期稳定、安全的运行,需要主从遥操作机器人对其进行定期的维护,主要的任务有:瓦片更换、气体检漏、切割、焊接、与吸尘等。机器人在核环境下维护作业,需要保证其双臂不发生干涉碰撞,否则将会带来巨大的安全隐患。由此可见,对从机械臂进行碰撞检测对整个系统具有重要的意义。本文的研究工作源于国家科技部“ITER计划专项”中的子课题“精细遥操作主从机器人与人机交互控制系统”(Y2D1153101)。主要有以下几个研究内容:首先分析、比较了国内外碰撞检测算法的研究现状,给出了属于时间域和图像空间一类的碰撞检测算法不适用于本课题的科学依据。并针对本课题中机械臂模型已知、可视为刚体的特点,选取了基于OBB包围盒的碰撞检测算法。面向机械臂作业时关于实时性与安全阈值的需求,对算法做出了一定的调整:利用三角形做权重计算包围盒以改进包围盒的紧密性;只对进行碰撞检测的包围盒做位姿更新;在满足作业安全阈值的前提下,只检测包围盒间是否发生碰撞,不再计算其内部的三角形,大大提高了算法的实时性。最后分析了安全阈值对机器人作业空间的影响,通过计算临界包围内部凸多面体的间距得出了安全阈值满足作业需求的结论。其次详细研究并分析了机器人运动学的基本原理并以本课题中的从机械臂为研究对象,利用D-H方法对其建立了运动学模型,保证了机器人双臂调整位姿时,各关节的包围盒能够更新到正确的位置,并在仿真平台下对运动学模型的正确性进行了验证。最后利用OpenGL与Visual C++6.0搭建了虚拟现实仿真平台,为算法的有效性和相关理论的验证提供了可靠的依据。仿真平台能够验证机械臂各关节包围盒树建立、更新与碰撞检测的正确性以及机器人运动学模型的正确性;并通过网络与从机械臂实体通信实现了虚拟现实技术,借此还可验证机器人力位控制、运动规划的正确性。本文最后还介绍了算法所依托的硬件环境,并通过实验验证了基于OBB包围盒的碰撞检测算法的实时性与安全阈值能够满足从机械臂的作业需求,也即能够保证其执行任务时的安全性。
Other AbstractWith the growth of population in the world, the problem of energy dilemma will be more serious day by day. In order to solve this problem, China, the United States, Russia and other four countries launch a wide range of cooperation for researching and applying on nuclear fusion energy. This cooperation also called “International Thermonuclear Experimental Reactor”. Nuclear fusion energy has the advantages of infinite energy, non-environmental pollution. It is one of the major energy in the future and one of the important ways to solve the energy problem, the environment problem and the sustainable development problems finally for human beings. Nuclear fusion reaction can release high activity neutron, this will lead to the parts of tokomak lose its functions, so we need to maintain it on a regular basis. But the internal of reactor is unfit environment for human working obviously. To ensure the device for nuclear fusion can work long, steady and safely, it needs to be maintained termly by the master-slave tele-robot. The major jobs of the robot are replacing the tiles, gas leak detection, incision, soldering, dust absorption and so on. When working under the nuclear environment, the arms of robot cannot collide each other. Otherwise the collision will bring the great safety loophole. It follows that detection collision for dual-arms robot has the great significance. In this paper, the research work is the sub-topic from the special project “ITER” of National Ministry of Science and Technology. And this sub-topic called “the master-slave tele-robot and the human-computer interaction control system” (Y2D1153101). This research has the following several aspects. Firstly, this paper analysis and compares the domestic and foreign research status about the detection collision algorithm. Giving the reason that we don’t use the algorithm which belong to Time Domain and Image Domain. Because the robot arms’ model is known and it can be regarded as rigid body, we select the collision detection algorithm based on OBB bounding box. In consideration of the robot’s operation target, we improve the algorithm with the following three aspects: using the triangle as weighting to increase tightness of OBB; Only updating the boxes that are used for collision detection; On the premise of meet the safe threshold, only testing collision between the bounding boxes. Thus, it makes the algorithm faster. At last we analyze how safe threshold effects the work space of robot and prove that the algorithm can meet needs of safe threshold by computing the distance between the convex polyhedron in boxes. Secondly, we analysis and expound the basic principle of robot kinematics in detail. Then using D-H method, the kinematics model is established on the robot arm that is used for “ITER”. In this way, we can ensure the bounding boxes of each joint can be updated to the right position, when the robot’ pose has changed. And then we check the correctness under the simulation platform. At last, we use OpenGL and Visual C++ 6.0 to build the virtual reality simulation platform, and provide a reliable guarantee for the effectiveness and validation of the related theory. Simulation platform can verify that the building, updating and checking collision for bounding-box tree of each joint and robot kinematics model are correct; Realizing the communication between robot and simulation platform through the network. Based on the virtual reality technology, we can also verify the correctness of the position and force control, motion planning. Finally this paper introduces the hardware platform which the algorithm based on, then the real time and detection error of collision detection algorithm based on OBB bounding box is verified by the experiment and it can satisfy the demand from robot work, which is to ensure the safety on its mission.
Contribution Rank1
Document Type学位论文
Recommended Citation
GB/T 7714
晋爱元. 基于OBB层次包围盒树的机械臂碰撞检测算法研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2014.
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