摘要
由通用工业机器人和视觉传感器组成的柔性坐标测量系统是视觉检测技术在工业在线测量领域的重要应用。工业机器人的机械结构和控制过程复杂,因此其定位误差成为影响系统测量精度的最主要因素,但可以通过修正连杆参数的方式加以补偿。以MD-H运动学模型为基础,建立机器人工具中心点(Tool center point,TCP)的基于相对定位精度的定位误差补偿模型,避免坐标在不同坐标系转换过程中产生精度损失。对与机器人测量姿态有关的柔度误差进行针对性补偿,通过建立柔性关节的弹性扭簧模型,将柔度误差分解为外加负载柔度误差和机械臂自重柔度误差分别进行补偿。标定过程中使用激光跟踪仪作为外部高精度测量设备,只需在单点测量模式下就能实现对TCP的三维坐标采集,大大简化数据采集过程。经过补偿后,标定点处的方均根误差由之前的1.230 2 mm降至0.428 8 mm,验证点处的则由0.723 6 mm降至0.505 4 mm。
The flexible coordinate measurement system which consists of universal industrial robot and visual sensor is a very important application of visual inspection technology in the area of industrial online measurement.The positioning error of the industrial robot is the most major factor which affects system measurement accuracy due to robot＇s complex mechanical structure and control process,but it can be compensated by modifying the link parameters.The positioning error compensation model of tool center point（TCP） on the basis of the relative positioning accuracy is derived by means of modified Denavit-Hartenberg kinematics convention,which can avoid accuracy loss in the transformation among different coordinate frames.Pertinent study on compliance errors related to robot＇s postures is carried out.By establishing the elastic torsion spring model of flexible joints,compliance errors are divided into two parts,the compliance error from external load and that from manipulator gravity,to be compensated separately.A laser tracker is used as high precision measurement equipment in the calibration process to simplify the operation so that the three dimension coordinates of TCP can be acquired in the single point measurement mode.After compensation,the root-mean-square error of calibration points is reduced from 1.230 2 mm to 0.428 8 mm and that of validation points from 0.723 6 mm to 0.505 4 mm.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2011年第15期31-36,共6页
Journal of Mechanical Engineering
基金
国家高技术研究发展计划(863计划
2008AA042407)
国家自然科学基金(50805105)资助项目
关键词
工业机器人
定位误差
相对定位精度
柔度误差
激光跟踪仪
Industrial robot Positioning error Relative positioning accuracy Compliance error Laser tracker
