| This dissertation is supported by the National Natural Science Foundation’Uncertain Nonparametric Modeling and Dynamic Prediction of High Speed Motorized Spindles for CNC Machine’(11172260)and focused on the dynamic modeling of a high speed motorized spindle and vibration characteristic analysis.Combining typical faults with uncertainties,the dynamics model of a high-speed motorized spindle is established,and a uncertain nonparametric modeling method for rotating machinery is studied.The dynamic evolution law of the motorized spindle is studied theoretically and numerically.The nonlinear time series analysis and the phase space reconstruction technique are utilized and developed to reconstruct the one-dimensional time series signal into a higher dimensional phase space.The disordered vibration signals are identified and classified through the different topological manifold structures of the vibration signals in the reconstructed high-dimensional phase space.Experiments are complemented to validate the numerical results.This study is organized as follows.The importance and significance of the dynamic modeling and characteristic analysis of the high speed motorized spindle are outlined in Chapter 1.The research status of the dynamics modeling method of the motorized spindle,the uncertain nonparametric modeling method and the vibration signal feature extraction method are reviewed.Important problems which need be further studied are summarized therein.Finally the content of this study is proposed.In Chapter 2,a pseudo-static model of the angular contact ball bearing in a motorized spindle is built in the case of the high speed rotation,from which the impacts of the bearing radial force and the speed of motorized spindle on the contact angle and the contact force between the ball and the bearing race are discussed.According to the force equilibrium condition of the bearing and the ball,the impact of the bearing preload on the bearing stiffness is studied.Then,the finite element models of the bearing and the spindle are set up based on the Timoshenko beam theory,from which the influence of preload from the bearing on the critical speed of the motorized spindle is discussed in more detail.In Chapter 3,the models of the ball bearing contact force,the unbalanced magnetic pull caused by rotor eccentricity and the rolling bearing surface defect are presented,respectively.Based on the finite element model of the high-speed motorized spindle,the bifurcation diagrams of vibration response of the motorized spindle are obtained numerically for different rotation speed,bearing clearance and initial eccentricity distance,from which the dynamic bifurcation phenomena caused by the ball bearing contact force and the unbalanced magnet pull are analyzed in detail.Moreover,the fault features of the rolling bearings are discussed through the vibration response of the faulty bearings.A nonparametric model of the motorized spindle system is established in Chapter 4,where the bearing restoring force,the unbalanced magnetic pull,and the external bounded noise excitation are also taken into account.Based on the Monte Carlo simulation,several numerical examples are used to study the effect of dispersion parameters from model uncertainty and external bounded noise excitation on the whirl frequency and the vibration behavior of the spindle.In Chapter 5,the phase space reconstruction technique is used to reconstruct the one-dimensional vibration signal of the electric spindle into the high-dimensional phase space,and the influences of uncertainties in the spindle is identified by comparing the phase space trajectories of the reconstructed deterministic system and the uncertain system.Aiming at the rolling bearing faults,the vector angle method based on phase space reconstruction is proposed.The effectiveness of the method is verified by numerical simulation and experimental verification.Conlusions of this work are summarized in Chapter 6,and in which some advanced topics for future work could also be found. |
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