Improved Screw–Nut Interface Model for High-Performance Ball Screw Drives

Abstract

Emerging applications of ball screw drives such as semiconductor inspection, fiber optic alignment, medical equipment, and miniature robotic actuators typically make use of ball screws that are compact, stiff, and precise. Existing models for the screw–nut interface stiffness of ball screw drives are however unable to accurately describe the dynamics of compact and stiff ball screws because they are derived based on the assumption that the portion of the screw within the nut is rigid. This paper proposes a new screw–nut interface stiffness model, which incorporates the elastic deformation of the screw within the nut using Timoshenko beam shape functions. The new model is shown, via simulation and experiments, to provide more accurate predictions of the natural frequencies of compact and stiff ball screw/nut assemblies compared to the existing models. It is therefore more suitable for use in the design simulation/evaluation of high-performance ball screw drives where compactness and rigidity are required.