Modeling Machine-Stand Vibration Based on Multibody Dynamics Analysis Considering Contact in Support Mechanisms

Abstract

Machine-stand vibrations often occur in industrial machines with table-positioning systems during the high acceleration/deceleration motions of the table, which deteriorate positioning performance. To enhance the performance, the mechanism and control system of the equipment should be effectively designed using a simulator that can adequately simulate machine-stand vibrations. Machine-stand vibrations exhibit strictly nonlinear characteristics, but the underlying mechanism remains unclear. Therefore, it is difficult to construct a model that can accurately reproduce the vibration characteristics. In this study, a prototype with a machine stand and support mechanisms used in actual industrial machines was modeled using multibody dynamics software while considering contact as a nonlinear element. As an element of contact in the support mechanism model, a nonlinear contact force was defined between the leveling bolt and leveling plate based on Hertz’s contact theory. Furthermore, linear spring forces between the leveling plate and floor surface were used to reproduce the contact effect between them. The frequency characteristics of the drive systems with a basic closed-loop control system were measured using sinusoidal sweeps, and the dependence of the machine-stand vibration and its characteristics on the disturbance amplitude were investigated. The model was validated by comparing the experimental and simulation results. The results revealed that it is possible to reproduce the softening-spring characteristics of machine-stand vibrations by properly incorporating the contact between the bolt and plate into the model.