The Study On Motorized Spindle-Tool Holder End FRF Prediction And Joint Part Parameters Identification

As the key link of power source and power transmission in the machining center,the dynamic characteristics of motorized spindle-tool holder system have a direct impact on the machining accuracy of the machining center.Obtaining the FRF of the end of the motorized spindle-tool holder system and extracting the dynamic characteristic index are important means to realize the prediction and suppression of cutting vibration.The connection part between the motorized spindle and the tool holder is one of the weakest links in the cutting process,and its connection stiffness and damping directly affect the machining efficiency and stability of the machining center.Furthermore,accurate identification of the joint parameters lays the foundation for the modeling of the motorized spindle-tool holder system and even the cutting system.Therefore,it is of practical significance to study the prediction of the FRF of the end of the motorized spindle-tool holder system and the parameter identification of the joint part for improving the machining accuracy and stability of the machining center.In view of the lack of a unified modeling method for the motorized spindle-tool holder system and the need to improve the accuracy of the joint part parameters identification,this article combines the national science and technology major project to carry out the research on the prediction of the FRF of the end of the motorized spindle-tool holder system and the parameters identification of the joint part.This article takes the motorized spindle-tool holder system as the research object and uses a combination of theoretical modeling and experimental testing,to obtain the theoretical calculation results and experimental results of the system end FRF.Based on this,a joint part parameters identification model is established,and the stiffness and damping parameters of the joint are accurately obtained by using genetic algorithms.The main research contents of this article are as follows:The study on simplified method of the motorized spindle-tool holder model.By analyzing the structure of the motorized spindle-tool holder system,it is concluded that the bearing,rotor,and motorized spindle-tool holder joint part are the main structures that affect the dynamic characteristics of the motorized spindle-tool holder system.The bearing is simplified as a spring,and the rotor,bearing and other parts which are assumed to be the same material as the shaft are retained.In addition,the motorized spindle-tool holder joint part is simplified as stepped shafts.According to the principle of segmentation,the motorized spindle studied in this paper is divided into 29 stepped shafts and the tool holder is divided into 12 stepped shafts.The study on prediction model of motorized spindle-tool holder end FRF.The modeling method of the motorized spindle-tool holder system is analyzed,and the prediction model of the motorized spindle-tool holder system end FRF is proposed by combining Euler-Bernoulli beam,transfer matrix method,multi-point response coupling method,and substructure admittance coupling method.The motorized spindle-tool holder system is divided into three sub-structures: motorized spindle,motorized spindle-tool holder joint part and tool holder.Based on Euler-Bernoulli beam modeling,the transfer matrix method is used to calculate the endpoint FRF of the motorized spindle and tool holder.The multi-point response coupling method is used to solve the end FRF of the motorized spindle-tool holder joint part.The rigid coupling model in the substructure admittance coupling method is used to couple the three sub-structures to obtain prediction model of the motorized spindle-tool holder system end FRF.Experimental study on the FRF of the end of the motorized spindle-tool holder.The influencing factors of hammer test are analyzed and the test parameters are selected,such as sampling frequency,sensor range,hammer head material,etc.The FRF of the end of the motorized spindle-tool holder system was obtained by hammering test.In order to reduce the error caused by the test data,the peak picking method was chosen to reduce the noise of the test data.Combining the experimental data after noise reduction and the improved finite difference method,the complete FRF of the end of the motorized spindle-tool holder system is estimate.Parameters identification and verification of the motorized spindle-tool holder joint part.Combining the calculation results and test results of the FRF of the motorized spindle-tool holder end,the identification model of the parameters of the motorized spindle-tool holder joint part is established,and the genetic algorithm is used to optimize the identification of the joint part parameters.The influencing factors of the FRF of the motorized spindle-tool holder end are analyzed,and it is concluded that the motorized spindle-tool holder joint part mainly affects the third-order mode.The experimental data of the frequency range of the third-order mode is used to identify the parameters of the joint part,and the identification results are substituted into prediction model of motorized spindle-tool holder end FRF and the finite element model to verify the accuracy of the identified joint part stiffness and damping parameters.Through the research in this paper,the prediction model of the FRF of the motorized spindle-tool holder end and the more accurate parameters of the joint part are obtained,which lays the foundation for the dynamic characteristics of the motorized spindle-tool holder system,has certain theoretical research and engineering application value.