Research On Surface-normal Adjustment In Robotic Drilling For Aircraft Panel Assembly

Automatic drilling is an important technology in the aircraft digital assembly. The industrial robot, which has many advantages, develops rapidly. Mounting with an end effector, the robotic drilling system is built and it is replacing the traditional manual works gradually. In the field of aircraft assembly, holes quality has a significant influence on the life and safety of aircraft structures. Against this background, an intelligent surface-normal adjustment method, which is based on the robotic automatic drilling system, has been proposed to improve holes’ normal accuracy.The robotic automatic drilling system consists of hardware devices, control system and software system. The hardware devices include industrial robot, moving platform, end effector, laser tracker and control computer. The communication between the control computer and the robot is based on the technique of socket through the Ethernet network. The control of the moving platform and end effector is based on the SynqNet network, which is a high-performance centralized motion network constructed between control card and driver with high reliability. The automatic drilling software is the user interface for users to control all the devices to realize automatic drilling.In the robotic drilling system, four laser distance sensors are used to measure surface-normal vector. The laser distance sensor can measure distance without contacting workpiece. They are installed around the pressing foot on the end effector. At first, all the laser distance sensors should be calibrated, the origin coordinate and the direction of laser have to be achieved before they worked. A method by using standard plane to calibrate laser distance sensors is proposed. By changing the pose of standard plane more than six times and calculating the measure data, each sensor’s origin coordinate and direction can be achieved.After calibrated, each laser distance sensor can measure position near the holes to be drilled. The surface-normal vector near the holes can be achieved by using the four points’coordinates. Then the vector correction values can be calculated. Because the end effector is installed on the robot, so changing the pose of the robot can adjust the direction of drilling tool, and surface-normal adjustment can be realized. In the end, a robotic automatic drilling system which integrates the technology of laser measurement, computer control and robotics is established. Based on this system, the methods of calibration of laser distance sensors and surface-normal adjustment are tested. The results show that the methods work and the normal accuracy can be effectively controlled within0.5°. The holes’ quality is much better than that without surface-normal adjustment.