Multi-body Dynamics Modeling And Prediction Of Five-axis Machine Tool With Milling Load Related To Pose

Manufacturing industry development is a manifestation of our country’s power,especially since the Made in China 2025 initiative,manufacturing has been raised to new heights.In the manufacturing industry,because the machine tool has many advantages,higher requirements are also put forward.In previous studies,applying excitation to static and idling machine tools and processing the signal to obtain modal parameters,there is a big gap with the actual situation and the current modeling method is difficult to realize the efficient dynamic analysis of all working spaces of machine tools.In this thesis,considering milling conditions,machining positions,machine posture and contact stiffness of joint,a multi-body dynamic model of machine tool with low degree of freedom is established.In the actual working state of the machine tool,experiments are carried out to verify the accuracy of the model.Design well-distributed experiments to analyze the main and secondary effects of different conditions on the dynamic characteristics of machine tools and build support vector regression prediction model to analyze machine tool performance.This thesis is mainly as follows:The contact characteristic parameters of the interface were obtained by the established dynamic model of the interface.Carry out force analysis on the spindle system,establish the expression of surface pressure and calculate the internal deformation to get the corresponding stiffness value.By establishing the stress balance formula of the bearing system,newton iteration method is used to calculate the resultant force between the rolling body and the rails on both sides,and contact rigidity of bearing joint surface was obtained by derivation of displacement.The contact stiffness of the guideway-slider interface was obtained by analyzing stress on guide rail and calculating the deformation of ball body using Hertz contact theory.Through the force analysis of nut pair and bearing pair,Hertz theory is used to calculate the axial deformation of ball screw pair and calculate the corresponding stiffness value urface was derived by combining the axial force of the joint surface.The dynamic model of machine tool related to milling force and pose is established based on multi-body dynamics theory.The motion model of the machine tool is obtained according to its position,motion mode and D-H method.By dividing the machine tool into seven elastically connected sub-components and establishing a3-d model,the characteristic parameters of each component were obtained,and the position Jacobian matrix related to the machine position and pose under milling conditions was derived by combining the kinematic model.The complete multi-body dynamics model of dual-turntable five-axis was derived by introducing the joint surface stiffness.Through the dynamic characteristic experiment of milling machine tool,the actual milling load is used as the input signal,and the vibration acceleration signal is used as the output signal.The harmonic component of milling load was eliminated by singular guide way and the dynamic parameters of the machine tool were obtained by designing three groups of milling experiments under different working conditions to ensure the model is correct.Design well-distributed experiments and the dynamic characteristics of the machine were predicted by changing the position Jacobian matrix parameters to transform the machine pose,machining position,different pendulum angles and different milling loads to analyze the main and secondary effects of different conditions on the dynamic characteristics of machine tools.On this basis,build SVR prediction model to analyz machine tool performance.