Research On Identification Method Of Joint Parameters Based On Finite-Difference And Residual Compensation

The high-speed processing is one of the high-tech manufacturing techniques,which can significantly improve processing efficiency, reduce the cutting force andcutting temperature, improve tool life and working accuracy. The chatter vibration inhigh-speed machining mostly originates from the flexible connection of spindle andtoolholder, which is highly concerned by scholars. Accurate identification of spindle-toolholder joint is crucial to predict machining stability of spindle system. Taking thehigh-speed double-sided locking BT (BTF) toolholder as the study object,Proposedan enhanced stiffness identification method based on frequency response function forthe spindle-toolholder joint, in which the rotational degree of freedom (RDOF) isincluded. RDOF frequency response functions (FRFs) are formulated based onfinite-difference technique to construct a completed spatial FRF for the joint, wherethe measured data can be obtained from the piezoelectric acceleration sensors. Inorder to depress the influence of―modal truncation‖and measurement noises, residualcompensation theory is introduced to regenerate the RDOF FRF. Experiments areconducted to demonstrate the efficiency of the proposed model in stiffnessidentification of spindle-toolholder.Many cutting tests were performed to verify theBTF is better.The main contents of the research are as following:（1）Study the finite-difference technique and the method to achieve rotationalFRFs.The frequency responses of substructure and assembly of spindle-toolholdersystem can be obtained by the hammer impact experiment, these accelerated FRFScan be used to estimated rotational FRFs through the finite-difference technique, andthese rotational FRFs can be used to identify the joint rotational stiffness.（2）Study the residual compensation method based on FRFs. Modal constantscan be calculated through the compensation formulation based on measured FRFs,which can be used to regenerate ideal FRFs without modal truncation andmeasurement noises, through the regenerate formulations. These regenerated FRFscould improve the identification accuracy.（3）Introduce the stiffness identification method based on FRFs for thetoolholder-spindle joint, in which the rotational degree of freedom (RDOF) isincluded. The structural coupling method is introduced to establish the stiffness identification model of dynamic joint. Combined with the proposed method, thedynamic parameters can be identified exactly. The finite element model is establishedto verify and analyze the validity of the identified results. Comparing the experimentand simulation results, the proposed method can exactly identify the joint parameters.Otherwise,identify the joint stiffness of BT40and BTF40type toolholder-spindlebased on the machine tool, which verify BTF type toolholder has better bendingcharacteristics.（4）Many cutting stets will be carry out under series cutting parameters to showthat BTF type toolholder is better than BT in every respect, including terms such asprocessing efficiency, cutter life and machining precision.