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基于绳索驱动的蛇形机械臂运动控制研究
Alternative TitleResearch on motion control of snake-like manipulator based on rope driving
王轸
Department机器人学研究室
Thesis Advisor李斌
Keyword蛇形机械臂 运动学 脊线模态法 轨迹规划
Pages77页
Degree Discipline机械电子工程
Degree Name硕士
2021-05-21
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract本文的研究内容主要围绕非结构环境下机器人的运动控制展开。随着科技进步,工业技术的发展,出现了越来越复杂的工作环境,这些工作环境对机器人自身条件更加苛刻。在非结构化工作环境中,例如太空探索,资源勘探,管道检查,水下工作等等,要求机器人具有适应复杂环境,完成特定任务的能力。仿生机器人通过模仿生物界动物的特征,使机器人获得更好的性能。根据蛇蜿蜒灵活的特点,衍生出了具有高自由度高灵活性的蛇形机械臂。蛇形机械臂凭借其良好的灵活性,可以应用于非结构环境内的清洁、检测、维修、探测等等。因此本文针对基于绳索驱动的蛇形机器臂在复杂环境下工作的情况进行运动学模型的建立,逆运动学的求解,避障轨迹规划,以及软硬件平台的搭建,实验验证等一系列内容的研究。首先对蛇形机械臂的整体构型进行介绍。蛇形机械臂的灵活性体现在电机驱动器与机械臂主体的分离。通过绳索驱动,机械臂的所有电机驱动器后置。通过控制绳索长短的变化,来控制机械臂各个自由度的变化。通过改进 D-H 法,建立蛇形机械臂的正运动模型,包括各个关节对应的坐标系以及 D-H 参数表。通过 MATLAB 机器人工具箱进行验证和可视化。此外,研究蛇形机械臂关节角度变化与绳索长度变化的关系。蛇形机械臂的控制机理是电机旋转带动丝杠移动副移动,带动绳索运动,促使机械臂关节发生角度变化。确定绳索长度与关节角度变化的关系是研究蛇形机械臂运动控制的基石。在建立蛇形机械臂正运动模型之后,对蛇形机械臂的逆运动学进行研究。通过调研国内外研究者对冗余机械臂逆解的研究,结合蛇形机械臂自身的特性——一个关节可以向两个方向旋转,多个关节串联的特点,采用脊线模态法进行逆解求解。针对脊线模态法存在的一些问题进行改进。将模态协同参数的求解方法由迭代法转化为方程组求解。在得到满足期望目标的空间脊线之后,通过关节映射将蛇形机械臂的各个关节点映射到空间脊线上以完成逆解,最终得到各个自由度的期望角度。随后对蛇形机械臂的避障轨迹规划进行研究。通过将非结构环境下的障碍简化为圆球或圆柱,对障碍建立模型。将障碍转化成空间中规则的几何体,虽然扩展了障碍的空间,但是简化了计算,提高了计算效率。蛇形机械臂转化为串联的圆柱,则机械臂的碰撞检测转化为圆柱与圆球或圆柱与圆柱之间的碰撞检测。根据蛇形机械臂具有冗余自由度的特性,保持指定的机械臂关节点不动,通过调整冗余自由度避过障碍。同时采用 RRT 算法生成从起点到终点无碰撞的轨迹。之后针对传统 RRT 算法的局限性,对 RRT 算法进行改进,使蛇形机械臂在复杂的环境中较快生成无碰撞轨迹。最终对实验室样机,进行软硬件平台的搭建,使蛇形机械臂具备运动控制的功能。上位机在 MATLAB 环境中搭建,下位机基于 VxWorks 嵌入式操作系统。完成上位机与下位机之间的通信,上位机进行机械臂正运动学和逆运动学的求解,轨迹规划方面的运算仿真,以及下位机与电机驱动之间的通信。之后通过实验对蛇形机械臂的研究内容进行验证。单关节的角度变化实验以及多关节的角度变化实验以验证蛇形机械臂的正运动学分析以及绳索角度变化关系的正确性。进行逆解实验和避障实验以验证改进脊线模态法和避障轨迹规划算法的准确性和实用性,验证蛇形机械臂的灵活性和良好的适应能力。
Other AbstractThe research content of this paper focused on robot motion control in unstructured environment. Nowadays more and more complex working environments have emerged, and higher requirements have been placed on the working content of robots. In unstructured working environments, such as space exploration, resource exploration, pipeline inspection, underwater work, etc. Robots are required to have the ability to deal with complex environments and accomplish goals. The biomimetic robot imitates the characteristics of animals in the biological world to make the robot achieve better performance. According to the flexible characteristics of snakes, the snake-like manipulator with high degree of freedom and flexibility is derived. With its good flexibility, the snake-like manipulator can be used for cleaning, inspection, maintenance, detection and other functions in non-structural spaces. Therefore, this article aims at the establishment of kinematics model, the solution of inverse kinematics, obstacle avoidance trajectory planning, the construction of software and hardware platforms, and the experimental verification for the snake-like manipulator based on rope driving in the complex environment. First, the overall structure of the snake-like manipulator is introduced. The flexibility of the snake-like manipulator lies in the separation of the driver and the main body . Driven by ropes, all the drives of the manipulator are rear-mounted. By controlling the change of the rope, the change of each degree of freedom of the snake-like manipulator is controlled. Using the improved D-H method, the forward kinematics of the snake-like manipulator is established, including the coordinate system corresponding to each joint and the D-H parameter table. It can be verified and visualized through the MATLAB Robot Toolbox. In addition, the relationship between th the angle of the snake-like manipulator’s joint and the rope length is studied. The control of the snakelike manipulator is that the rotation of the motor drives the movement of the lead screw, which drives the rope to move, and promotes the angle change of the manipulator joint. Determining the relationship between the rope change and the joint angle change is the cornerstone of studying the motion control of the snake-like manipulator. After establishing the forward kinematics model of the ssnake-like manipulator, the inverse kinematics of the snake-like manipulator is studied. By investigating the research on the inverse solution of redundant manipulators by domestic and foreign researchers, combined with the characteristics of one joint with two degrees of freedom of the snake-like manipulator itself and the characteristics of multiple joints in series, the inverse solution is solved by the backbone mode method. In view of some problems existing in thebackbone mode method, improvements are made. The solution of modal parameters is transformed into calculation of equations by iterative method. After obtaining the spatial backbone curve that meets the desired goal, through joint mapping, each joint point of the snake-like manipulator is mapped to the spatial backbone curve to complete the inverse solution, and finally obtain the desired angles. Then the obstacle avoidance trajectory planning of the snake-like manipulator is studied. By simplifying the obstacles in the unstructured environments into spheres or cylinders, the obstacles are modeled and the obstacles are transformed into regular geometric bodies in the space. Although the obstacle space is expanded, the calculation is simplified and the calculation efficiency is improved. The snake-like manipulator is transformed into a series of cylinders, and the collision detection of the snake-like manipulator is transformed into the collision detection between the cylinder and the sphere or the cylinder and the cylinder. According to the characteristics of the snake-like manipulator with redundant degrees of freedom, it is studied to keep the designated joint points of the manipulator still and avoid obstacles by adjusting the redundant degrees of freedom. At the same time, the RRT algorithm is used to generate a collision-free trajectory from the start point to the end point. Afterwards, in view of the limitations of the traditional RRT algorithm, the RRT algorithm was improved to enable the snake-like manipulator to generate a collision-free trajectory faster in a more complex environment. Finally, the software and hardware platform is built to make the snake-like manipulator have the necessary functions. The upper computer program is built in the MATLAB environment, and the lower computer program is based on the VxWorks embedded operating system. Complete the communication between the upper computer and the lower computer. The upper computer performs the calculation of the robot’s forward kinematics, inverse kinematics, trajectory planning, and the communication between the lower computer and the motor drive. Afterwards, the experimental research on the snake-like manipulator was carried out. Single joint angle change experiment and multi-joint angle change experiment to verify the correctness of the forward kinematics calculation of the snake-like manipulator and the rope angle change relationship. The inverse solution experiment and obstacle avoidance experiment have verified the accuracy and practicability of the improved backbone mode method and obstacle avoidance trajectory planning algorithm so as to verify the flexibility and good adaptability of the snake-shaped manipulator.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/28957
Collection机器人学研究室
Affiliation中国科学院沈阳自动化研究所
Recommended Citation
GB/T 7714
王轸. 基于绳索驱动的蛇形机械臂运动控制研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2021.
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