Dynamic analysis and modeling of ball screw feed system with a localized defect on the support bearing

In this study, based on the motion characteristic of the feed system, two kinds of external excitation including harmonic excitation applied on screw nut and fault excitation caused by support bearing are considered. In addition, the stiffness of screw shaft is considered as time-varying. Based on which, a three-degrees-of-freedom dynamic model is proposed to investigate the dynamic characteristics of the system. The dynamics of the system are discussed under different system parameters by using amplitude-frequency curves. The results show that the defect induced abnormal resonances exists at some specific frequencies, and the harmonic excitation and bearing fault excitation act synergistically in affecting the dynamic behavior of the feed system. Furthermore, the amplitude of abnormal resonance is related to the geometric parameters of the local defect. The speed of motor determines the appearance of the abnormal resonance. Last, a series of experiments are conducted to obtain the system parameter and validate the proposed model.