Research On Reproducible Hole Position Accuracy Of AGV Mobile Robot In Aircraft Assembly

As one of the technique in aircraft manufacturing,some connecting holes should be drilled,disassembled,glued and become glulam members finally.Then the process of enlarging,reaming and lamaging the holes is necessary.For this kind of connecting holes,the technique is named as repeated drilling holes.Due to the positioning error of AGV and the robot,the existing robot automatic drilling system can only be used in the process of making the final hole with one knife,which cannot meet the requirements of repeated drilling.To solve this problem,this paper studies the positioning accuracy of the AGV mobile robot system,including the research on the absolute positioning accuracy and the correction and compensation of the error caused by AGV entering its position again.In general,the robot can be seen as a set of rigid links connected by two adjacent joints driven by the electric machinery on the joint.Because of the error between manufacturing and assembly,there are some difference of the robot position and orientation from theoretically to practically,which called absolute positioning error.Under the condition of full load,the absolute positioning error is generally 3 to 4 millimeters.The error analysis of the robot is essentially the use of the corresponding mechanism motion analysis method,by seeming the error factors as the corresponding parameters of the variable.This paper establishes an optimization model of link parameters of a robot based on the industrial robot named KUKA KR500-L340.It draws the conclusion that the error between theoretically and practically is below 0.3 millimeter by using Newton method for robot link parameter calibration,and then the simulation verification,finally by the measurement of 40 geo-spatial points with Leica laser tracker.The position and orientation error of AGV caused by entering again and again is essentially due to the change of base coordinates of the robot.Thus this paper puts forward that the repeated drilling error of AGV can be equivalent to a small translation rotation change between two robot coordinate systems.The base coordinate is set to the initial coordinate system when AGV enters its actual position firstly.Then the position and orientation error can be calculated by using the differential kinematics equations and the different coordinates of the hole used to convert coordinate system shot by industrial camera.After that,the deviation can be compensated to the initial base coordinate system so that we can get the actual base coordinate system after AGV entering secondly.Finally,the reference hole of product can be calibrated by using industrial camera again.It attaches huge effect to the calculation of error between theoretical and actual hole position.Based on the error of reference hole,all the connecting holes within the space formed by the reference holes get the error compensation after using the inverse distance weighting model.Analyzing the data of repeated drilling holes,the maximum aperture is 6.005 millimeters,the minimum is 5.999 millimeters,and the aperture deviation is ±0.01mm,which reach the specifications for drilling holes of aircraft manufacturing.