Development Of Robotic End Effector For Automatic Drilling And Drilling Process Control

Nowadays,oriented to the development in flex and automotive aircraft manufacturing and assembly,robotics drilling systems have contributed a lot to the manufacturing tasks of wings and wallboard,taking advantages in good flexibility,high integration,low space occupation but large action range.As the first progress in aircraft assembly,drilling is the key point,since the quality of drilling has a crucial impact on the lifetime of an airplane.This paper based on the development of a multifunction drilling end effector for the robotics drilling systems,and focused on some significant parameters of the drilling quality,such as countersink precision,holes perpendicularity and burrs decreasing in multi-layered drilling to improve the quality stability and optimize the performance of the drilling machine.The key contents of this thesis are as follows:The frame and module development of the drilling end effector.Firstly,based on the characteristics of the robotics drilling systems and the drilling technology of aircraft parts,the function requirements have been discussed and summarized.Then the frame design and function integration have been finished,resulting in a lightweight,module,and multifunction drilling end effector successfully.PLC control system building and optimization of countersink precision.Under the decomposing and analyzing on the procedure of robotics drilling,the PLC control system for the end effector has been built.With the help of the variable table for Modbus/TCP,the three parts of the whole system can communicate with each other in an Ethernet.By optimal design,closed-loop feed control and error compensation,the requirement for countersink precision has been met.Normal vector detection and error analysis.Based on flexible press foot nose-piece and contact type displacement sensors,a novel normal vector detection structure installed in the drilling end effector is proposed.The error sources including the sensor error,installation position,initial angle and undesirable orientation have been discussed.Then predicted error is calculated,approaches aimed to eliminate or diminish error is proposed and validation tests are conducted to measure the error precisely,the result of which shows the validity of the model.PID control on press force and validation of its inhibitory action on interlayer burrs.The PID control system and programs have been built,also with the PID self-tuning.The wave and instability of the press force control in the press and drilling procedure have been analyzed,which contributes to the optimization of press force control.With the multilayered Al-alloy sheets drilling experiments,the press force's inhibitory action on interlayer burrs has been validated.The drilling end effector prototype has been used in drilling tests to further validation.Its weight is less than 50 kg,and the drilling efficiency is almost 3-4 holes per minute.The strategy on improve the quality stability has been proposed,and the results show that the countersink precision is less than 0.02 mm,the measurement error of hole perpendicularity is less than 0.1 ° and burrs and vibration in drilling have been controlled successfully,which has met the requirement on the quality and efficiency in the manufacturing and assembly of aircraft parts.