Modelling the dynamic behaviour of a ball-screw system taking into account the changing position of the ball-screw nut

摘要

An estimation of the dynamic behaviour of ball-screw systems is particularly important in the industrial processes where significant cost savings can be achieved by optimising the drive operation. The dynamic behaviour of a ball-screw system is modelled using a finite element approach in this paper. The nut exerts a significant lateral restraint on transverse vibration of the screw in the case of a ball-screw. The effect of this vibration varies with time as the nut moves. This implies that the natural frequencies of a ball-screw system change with time. The method described models the dynamic behaviour of a ball-screw taking the moving nut into account. The analysis accuracy was improved by integrating the accumulated data (damping ratios, natural frequencies, stiffness) acquired from evaluation experiments of each element and experimental modal analysis. The simulated results have been proved satisfactory when compared with measured data taken from a CNC machine tool. The model, which can simulate a variety of non-linear mechanical behaviour in a ball-screw system, also predicts the amount of heat generated. A better understanding of ball-screw dynamics was gained through the modelling process and it is hoped to use the energy dissipation features in predicting thermal behaviour of ball-screws.