在飞机自动化装配中,机器人制孔技术由于其高度柔性和相对低成本而倍受关注。然而,机器人本身的动、静态误差及制孔过程大量坐标系标定和坐标转换会引起难以补偿的残留误差,为提高机器人制孔的位置和姿态精度,构建一种基于激光跟踪仪闭环反馈的机器人辅助飞机装配制孔系统。本文首先论述应用激光跟踪仪建立系统中关键坐标系的方法,并分析了机器人制孔过程中残留误差的构成因素。然后通过机器人末端制孔工具在加工位置处的理论位姿与实际位姿匹配运算,为修正机器人制孔过程中由机器人动静态误差、机械加工、坐标转换算法、测量仪器等因素引起的残留误差提供依据,以提高机器人制孔系统的相对定位精度。并通过仿真实验验证上述算法修正残留误差的可行性。最后,对壁板类零件进行实际加工试验。试验表明,针对具体的制孔系统和对象,采用激光跟踪仪闭环反馈补偿后,可将机器人末端工具的相对位置精度、角度精度分别提高至±0.2 mm和±1″以内。这种技术有效抑制了制孔过程中由于机械加工、坐标转换算法、测量仪器等复杂组合因素所带来的残留误差,满足飞机装配中法向制孔的精度要求。
In automatic aircraft assembly, one focus of attention is robotic drilling technology with its high flexibility and relatively low cost. However, pose errors hard to compensate of the robotic end tool may exist which are caused not only by the dynamic and static error of the robot, but also by errors in the calibration and transformation of the coordinate frames. To improve the accuracy of the position and orientation of the robotic end tool, a robot-aided aircraft assembly drilling system is constructed based on laser tracker closed-loop feedback. Methods to build key coordinate frames of the system using the laser tracker are first discussed. Then, the constitutive factors of the robotic tool pose error are analyzed. A pose difference matrix between the theoretical pose and actual pose of the robotic tool in the drilling position is evaluated to eliminate remnant errors caused by the robotic dynamic error, static error, machining error, matching error and measuring error, etc. Finally, a simulation test for validating the feasibility of the above algorithm and a drilling test of ribbed-plate parts is executed. For a robotic drilling prototype system, by introducing the laser tracker closed-loop feedback compensation, the robotic drilling error is such that the position precision is effectively controlled within ±0.2 mm and the orientation precision of the normal angle is within ±1". The accuracy and quality obtained by the above robot-aided drilling method can satisfy the requirements of aircraft assembly.
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