Chatter Analysis And Identification In Industrial Robotic Fine Boring Of Aircraft Intersection Holes

The finish machining of the intersection holes of the aircraft is an important part of aircraft assembly,the machining quality and position accuracy have an important influence on the assembly quality of the aircraft and the interchangeablility and coordination of the aircraft parts.The traditional finish machining of the intersection holes of the aircraft always use machine tools.But the traditional machine tools which are inflexible and occupy large space are not suitable to be used in aircraft assembly site,because there are too many assembly toolings and the working space is narrow.Therefore,the robotic boring system which includes the industrial robot and the boring end-effector is designed to solve the problems of the finish machining of aircraft intersection holes.In the early research of robotic boring system,it has been found that it's easy to generate vibrations which are caused by the weak rigidity of the robotic boring system There are two kinds of vibrations:forced vibration and chatter.The forced vibration can be suppressed by pressure foot greatly,but the chatter can't be suppressed effciently because of its abruptness and complexity.The chatter of robotic boring system will be analyzed in this paper,a way of chatter identification will be introduced based on HHT and SVM,to avoid the chatter which may destroy the machining quality.Firstly,the research background and significance of the paper are elaborated,and the research status of the intersection holes machining are summarized.In addition,the research status of the mechanism of chatter and the identification of chatter are analyzed and summarized to solve the probem of chatter in robotic fine boring.Secondly,the characteristics of robotic boring system are analyzed.In the modal analysis of the boring bar,it has been found that the natural frequency of the boring bar is close to the frequency of chatter,so the main part of chatter may be the boring bar.In the modeling of the robotic foot system,it's found the dynamometer signal and the displacement signal are the input and output of the second-order underdamping system,and both of the signals are applicable to monitor the chatter.Thirdly,according to the effective decomposition ability,high time-frequency accuracy and self-adaptability of HHT,HHT is applied to the analysis of a non-stationary simulation signal and achieves a good effect,and the feasibility of HHT in the non-stationary signal processing like chatter is proved.Finally,a new method of chatter identification is introduced which is based on HHT and SVM.Through the analysis of pressure foot displacement signal and dynamometer signal by HHT,the instantaneous frequency's probability P is extracted as the characteristic of chatter,then P and the corresponding cutting states are input as SVM's input characteristics and input labels,to finish the design,training and application of SVM,and get the optimal SVM which can identify chatter correctly at last...