Research On Chatter Identification And Suppression Method Of Three-Dimensional Elliptical Vibration Cutting

Three-dimensional elliptical vibration cutting(3D-EVC)is a kind of ultra-precision cutting technology with great potential.Its unique characteristics such as intermittent cutting,friction reversing,and convenient chip removal are concretely embodied in improving ultra-precision machining performance,creating complex free-form surfaces and improving machinability of difficult-to-cut materials.The research field was mainly focused on device design,system control,spatial ellipse path planning and 3D-EVC processing performance testing since the technique of 3D-EVC was developed.However,there is still a lack of research on the problem of chatter in the process of 3D-EVC processing.Therefore,the chatter phenomenon in the process of 3D-EVC is studied based on the non-resonant 3D-EVC apparatus developed by research group.The main contents are as follows:(1)A non-resonant 3D-EVC cutter location model is established to fit the spatial ellipse trajectory.The spatial elliptical motion locus of the cutter location is analyzed based on the non-resonant 3D-EVC apparatus developed by our research group.The elliptical motion locus of tool tip under different phase is fitted by changing the phase of driving signal in MATLAB software.And the initial three-dimensional elliptical motion trajectory is synthesized through specific tests.(2)A chatter identification method in non-resonant 3D-EVC process is proposed.The identification strategy mainly includes two parts: initial identification based on Fourier transform and characteristic value identification based on empirical mode decomposition.The 3D-EVC process is divided into three different cutting states(stable cutting state,transition state and flutter state)in initial identification.In the process of characteristic value identification,the characteristics extracted from the intrinsic mode function obtained decomposed by the empirical mode decomposition are used to analyze the chatter state.(3)A model between the cutting parameters and the characterization of chatter in the non-resonant 3D-EVC process is established.By the use of the relationship between the cutting parameters(the cutting speed,the depth of cut and feed rate)which mainly affect surface quality and the surface characteristics(mean value of vibration amplitude),the occurrence of chatter phenomenon in the process of 3D-EVC is described accurately,and providing a theoretical model for further chatter suppression.(4)A modified artificial bee colony algorithm based on particle swarm optimization algorithm is proposed,which is applied to the chatter model of 3D-EVC for parameter optimization.The PABC algorithm merges the cognitive part and the social part of the mobile operator in particle swarm optimization algorithm into the honeybee evolution strategy,and introduces inertia weight to improve the search ability and convergence performance near the global optimal solution.The benchmark test function test results show that the PABC algorithm has good convergence performance compared with the other optimization algorithms.Finally,the 3D-EVC chatter model is optimized using the PABC algorithm.The experimental results show that after the optimization of the cutting parameters in the 3D-EVC process by the PABC algorithm,the vibration amplitude of the tip point is obviously reduced,and the surface roughness of the workpiece is reduced by 57%-76%,which proves the effectiveness of the method.