【作者】 于野；

【导师】 刘宇；

【作者基本信息】 东北大学 ， 机械工程（专业学位）， 2021， 硕士

【摘要】 随着工业制造向智能制造方向发展,工业机器人凭借着其工作空间大、灵活性高和成本低等优势逐渐被应用在铣削加工领域,且常被用于复杂零件的加工上。因此,对编程效率和加工轨迹精度都具有较高要求。然而,目前机器人编程方式还多采用现场示教编程,不仅编程效率和轨迹精度低,而且难以胜任复杂的铣削加工任务。另一方面,工业机器人一般都采用串联结构,其刚度远低于传统数控机床,铣削加工精度低且加工稳定性差,容易导致颤振的发生。因此,本文开发了一种机器人铣削离线编程仿真软件,提高编程效率和加工轨迹精度。同时对六轴工业机器人执行5轴铣削加工任务时存在的冗余度进行优化,提高机器人铣削加工的稳定性和精度。本文主要研究内容及相关工作如下:(1)机器人铣削离线编程仿真软件整体设计。通过对软件进行需求分析,确定了以Python、Qt和OpenGL作为开发平台,以机器人铣削加工仿真模块、机器关节运动规划模块和离线编程后处理模块为三个主要功能模块,并对软件的整体架构进行了设计。(2)机器人铣削加工仿真模块开发。利用OpenGL搭建三维可视化仿真环境,实现对机器人连杆等三维模型的加载。通过对机器人进行正向运动学建模在仿真环境中实现了对机器人正向运动学仿真。利用解析法对机器人逆运动学进行了求解,在运动学算法实现的基础上,通过对关节空间轨迹规划、笛卡尔空间直线轨迹规划、笛卡尔空间圆弧轨迹规划和位姿插补算法实现了对机器人铣削加工中常用的运动指令的仿真。(3)机器人关节运动规划模块开发。通过灵活性指标来表示机器人距离奇异点的远近程度。通过开发碰撞检测功能实现了对机器人关节运动过程中的碰撞问题进行检测,并通过对关节角度转动范围的限制来避免机器人连杆自身发生碰撞。以灵活性、无碰撞和关节角度极限为约束,以全部机器人刀位点的冗余度为变量建立关节运动规划模型,并通过离散搜索方法确定可用冗余度,为离线编程时冗余度的选取提供了依据,并在实验中进行了应用和验证。(4)离线编程后处理模块开发及实验验证。针对复杂铣削加工任务的编程效率和加工轨迹精度问题,采用了将3轴和5轴双摆头型机床的数控程序转换为机器人程序的方法。通过定义数控程序和机器人程序转换的规则,利用程序转换算法对数控程序中的关键指令和位姿数据进行提取并计算,从而转换为机器人程序。利用机器人铣削加工仿真和实际加工实验验证了转换程序的可行性和正确性。(5)基于刚度性能指标的冗余度优化。对六轴工业机器人执行五轴铣削加工任务时存在的冗余度进行优化,提高机器人铣削加工的稳定性和精度。首先,建立机器人铣削系统动力学模型,利用零阶近似法和频响实验获得了冗余度与极限稳定切深之间的关系,并通过实验验证了冗余度变化对加工稳定性的影响。然后,基于机器人刚度模型提出了以冗余度为变量的全局刚度性能指标。最后,以全局刚度指标最大化为目标,在保证加工稳定的情况下,建立了优化模型,并利用离散寻优法来优化冗余度,并通过实验验证了方法的有效性。更多还原

【Abstract】 With the development of industrial manufacturing to intelligent manufacturing direction,industrial robot with its large workspace,high flexibility and low cost advantages are gradually applied in the field of milling processing,and is often used in the processing of complex parts,so the programming efficiency and machining traj ectory accuracy have higher requirements.However,at present,the robot programming methods mostly adopt the field teaching programming,which not only has low programming efficiency and traj ectory accuracy,but also can not be qualified for complex milling tasks.On the other hand,industrial robots are generally used in series structure,whose stiffness is far lower than the traditional CNC machine tools,low milling accuracy and poor machining stability,easy to lead to the occurrence of chatter.Therefore,this paper developed a robot milling offline programming simulation software to improve the programming efficiency and machining trajectory accuracy.At the same time,the redundancy existed in the 5-axis milling task of the six-axis industrial robot was optimized to improve the stability and accuracy of robot milling.The main research contents and related work of this paper are as follows:(1)Overall design of offline programming simulation software for robot milling.By analyzing the requirements of the software,three main functional modules were determined,including Python,Qt and OpenGL as the development platform,robot milling simulation module,machine joint motion planning module and off-line programming post-processing module,and the overall architecture of the software was designed.(2)Development of robot milling simulation module.OpenGL is used to build a threedimensional visual simulation environment to realize the loading of the robot connecting rod and other three-dimensional models.By modeling the forward kinematics of the robot,the forward kinematics simulation of the robot is realized in the simulation environment.The inverse kinematics of the robot was solved by the analytical method.On the basis of the kinematics algorithm,the simulation of the motion instructions commonly used in robot milling was realized by using the trajectory planning in joint space,the linear trajectory planning in Cartesian space,the circular are trajectory planning in Cartesian space and the pose interpolation algorithm.(3)Development of off-line programming post-processing module and experimental verification.In order to solve the problems of programming efficiency and machining trajectory precision of complex milling tasks,a method of converting 3-axis and 5-axis double swing head numerical control program into robot program was adopted.By defining the rules of conversion between the numerical control program and the robot program,the key instructions and pose data in the numerical control program are extracted and calculated by the program conversion algorithm,and then converted into the robot program.The feasibility and correctness of the conversion program are verified by robot milling simulation and actual machining experiments.(4)Redundancy optimization based on stiffness performance index.In order to improve the stability and precision of the six-axis industrial robot,the redundancy of a six-axis industrial robot in five-axis milling was optimized.Firstly,a dynamic model of robot milling system was established,and the relationship between redundancy and ultimate stable cutting depth was obtained by zero-order approximation method and frequency response experiment.The influence of redundancy on machining stability was verified by experiments.Then,based on the robot stiffness model,a global stiffness performance index with redundancy as a variable is proposed.Finally,with the objective of maximizing the global stiffness index,the optimization model was established under the condition of ensuring the machining stability,and the discrete optimization method was used to optimize the redundancy,and the effectiveness of the method was verified by experiments.更多还原