Intelligent surface normal measurement method of end effector for the aeronautical drilling robot

In order to solve the perpendicularity of robotic drilling in the aircraft assembly, this paper proposed a novel surface normal measurement method for the aeronautical drilling robot. Firstly, vision location module is used to mark the drilling point and get the coordinate of drilling point. Meanwhile, four laser range sensors start to measure the distance between the emitting laser points and their subpoints on the workpiece surface. Thus, the coordinates of four subpoints can be obtained. According to the four subpoints and drilling point, line or circle are used to approach two curves through the drilling point on the workpiece surface. Two tangent vectors of the two curves at drilling point can be obtained. Then the normal vector of drilling point can be calculated from the cross product of two tangent vectors. The angle between the normal vector and drill axis vector can be obtained. If the angle is greater than 0.5 degree, the two eccentric discs will rotate definite angles to meet the requirement. Finally, the simulation results and experimental results on the aeronautical drilling robot show that the surface normal measurement method is valid and effective to meet the requirement in aircraft assembly.