| As a typical rolling bearing-rotor system,the electro-magnetic eccentricity caused by the uneven distribution of air-gap between the rotor and stator of the built-in motor,as well as the loosening of the interference connection between the rolling bearing and the spindle as the speed increases,will cause nonlinear changes in the dynamic characteristics of the high-speed electric spindle(HSES),thus directly affecting the rotational accuracy of the spindle.This paper takes a high-speed electric spindle as the research object,considers the nonlinear influence of electromagnetic eccentricity and loosening fault on the dynamic characteristics of high-speed electric spindle rotor system,establishes the rotor system dynamics model with electromagnetic eccentricity and the rotor dynamics model with electromagnetic eccentricity-loosening coupling fault respectively,combines chaos theory and bifurcation theory,analyzes the influence of rotational speed,eccentricity and contact depth on the dynamic characteristics of high-speed electric spindle rotor system.The influence law of speed,eccentricity and contact depth on the dynamic characteristics of high-speed electric spindle rotor system is analyzed,and the correctness of the model built in this thesis is indirectly verified through the axis trajectory experiment.The main research contents are as follows:(1)Nonlinear dynamics model for rotor systems with electro-magnetic eccentricity is constructed.The non-linear factors affecting the dynamic characteristics of the HSES rotor system-the built-in motor rotor eccentricity and the rolling bearing support force-are analyzed;on the basis of the established air-gap model between the built-in motor stator and rotor,the unbalanced magnetic pull force of the motor rotor is solved by the Maxwell stress tensor method;the nonlinear support force of the rolling bearing is solved according to the Hertz contact theory;the above two The above two nonlinear factors are used as inputs to finally construct a nonlinear dynamics model of high-speed electric spindle rotor system with electromagnetic eccentricity.(2)The dynamic characteristics of the rotor system containing electro-magnetic eccentricity are analyzed.After solving the above nonlinear dynamics model numerically using the Runge-Kutta algorithm of order 4/5 with variable steps,the nonlinear effects of rotational speed,eccentricity and rolling bearing preload on the dynamic characteristics of the system are analyzed based on chaos theory and bifurcation theory,and the periodic motion law of the rotor system with electromagnetic eccentricity is obtained by combining the system time history diagram,phase diagram,spectrum diagram and bifurcation diagram;And the effects of unbalanced magnetic pull force and rolling bearing nonlinear support force on the nonlinear dynamic characteristics of the system are compared and analyzed.(3)Dynamic characteristics of a rotor system with electromagnetic eccentricity-loose coupling fault are analysed.Based on the established non-linear dynamics model of rotor system with electro-magnetic eccentricity,the rotor system dynamics model of coupled electro-magnetic eccentricity-loosening fault was constructed by taking the loosening fault of the interference connection between the rolling bearing and the spindle as a consideration as the rotational speed increases.change,and finally stay in the chaotic motion state.(4)Experimental verification.Through the high-speed electric spindle experimental platform,the axial trajectory of the high-speed electric spindle was collected,and after comparison and analysis,when the speed is low,the maximum radius of rotation of the axial trajectory of the numerical solution of the above model is basically the same as the maximum radius of rotation of the experimentally obtained axial trajectory,and when the speed is around 8000r/min,the difference between the two maximum radii of rotation is the largest,which indicates that the system is in the state of proposed cyclic non-stationary motion at this speed,and it is recommended that in It is suggested that this speed should be avoided as much as possible in the actual machining. |
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