An improved dynamic model of preloaded ball screw drives considering torque transmission and its application to frequency analysis

A dynamic model of the ball screw drive is proposed in this article. It is revealed that when axial thrust is transmitted between the ball screw and the nut, extra torque is generated synchronously which is not proposed in existing dynamic models. And a physical model for studying the relationship between the thrust and the torque is proposed. A lumped dynamic model is established, and a kinematic compatibility equation describing motion transmission between rotary displacement and axial displacement is established. Then a preload model of a double-nut for analyzing the force and the deformation is built. An approach to analyze the first resonant frequency of the proposed model is described. Meanwhile, a tested bench with a novel preload-adjustable double-nut and two novel loading mechanisms is constructed. The axial stiffness of the supporting bearings and the preloaded double-nut is tested based on a measurement system. Then vibration tests are carried out to measure the first resonant frequency of the ball screw drive. Finally, contrastive analysis between experimental results and simulated results of three models is conducted. The results show that the proposed model agrees much better with the experimental results than the discrete model and the hybrid model do.