Research On Dynamic Characteristics Of Hybrid Robot Based On CFRP Milling

Carbon Fiber Reinforced Plastic(CFRP)has a lot of advantages such as light weight,high strength and high resistance to corrosion.However,difficult machining property creates a series of problems during milling of CFRP.Compared with traditional serial robot,hybrid robot presents high stiffness and good accuracy.Nevertheless,dynamic characteristics of robot during robotic milling become significant influence factors of machined quality.Therefore,the studies based on TriMule hybrid robot,focus on modelling of milling force of different fiber angles,dynamic characteristics of robot and the dynamic responses of tool center point and corresponding machined quality of different fiber angles during robotic milling of CFRP.The research content is as follow:(1)A set of experiments of UD-CFRP milling for multiple helix tools has been carried out based on hybrid robot with different fiber angle and cutting force coefficients in tangential and radical directions are calculated.The results demonstrate that cutting force coefficients can be presented as a sine function of fiber cutting angle.The force model is capable of predicting cutting forces during milling of CFRP under different fiber angle.(2)Drawing heavily on finite element method,Langrange and modal analysis theory,the elastodynamic model of TriMule robot is established.The dynamic characteristics include the natural frequencies,mode shapes and frequency response functions(FRFs)over the entire workspace are estimated in a very efficient way based on obove model.Combined with modal test experiments,we find that the dynamic characteristics obtained by the elastodynamic model have good agreement with those obtained by experiments.(3)Based on the dynamic model of robotic milling system,the robotic milling stability is studied.The dynamic response characteristics of TriMule robot during robotic milling of CFRP are studied based on theories on dynamic response analysis under dynamic loading.The sensitivity of different assessment indicators of milled quality are studied by comparing the machined quality of CFRP milling of TriMule robot and five-axis CNC machine tool under different fiber angles,and the corresponding indicators are selected to assess milled quality.Based on the above indicators,the relationships between the dynamic responses of tool center point and indicators are established.This paper can provide an important reference for improving the machined quality of CFRP milling based on hybrid robot and the application of hybrid robot in the aeronautics manufacturing industry.