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Abstract <p>Motorized grinding spindle vibration is a critical factor limiting the surface quality in robotic grinding. To improve workpiece surface integrity, this study systematically investigates the dynamic characteristics of a grinding motorized spindle system. A 14-degree-of-freedom (14-DOF) dynamic model is established using the lumped mass method, incorporating unbalanced magnetic pull (UMP) of the permanent magnet synchronous motor (PMSM), nonlinear bearing restoring forces, and grinding wheel unbalance. The equations of motion are derived via Lagrange equation and solved numerically using the fourth-order Runge-Kutta method (RK4). Experimental validation confirms the model’s accuracy. Based on the validated model, the effects of spindle speed, bearing parameters, and air gap length on spindle vibration characteristics and stability are thoroughly investigated. The results demonstrate that the spindle system exhibits period-doubling bifurcation and chaotic motion within specific speed ranges. It was also observed that an increase in bearing clearance lowers the stability threshold, whereas appropriate bearing stiffness enhances the dynamic performance. Moreover, an increased number of bearing balls reduces the system’s sensitivity to speed-dependent vibration, while a moderate increase in the motor air gap effectively suppresses the vibration amplitude. Collectively, these findings provide a theoretical foundation for the structural design of spindles and the optimization of grinding processes, thereby offering valuable insights for improving machining accuracy and surface quality in robotic grinding applications.</p>

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Research on Vibration Characteristics of Robot Motorized Grinding Spindle Considering UMP and Nonlinear Bearing Restoration Forces

  • 期刊论文

  • 发表日期：

    2026年2月1日

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  • Shengkai Qi,
  • Yang Yang,
  • Zhengnan Li,
  • Lidong Ma

摘要

Abstract

Motorized grinding spindle vibration is a critical factor limiting the surface quality in robotic grinding. To improve workpiece surface integrity, this study systematically investigates the dynamic characteristics of a grinding motorized spindle system. A 14-degree-of-freedom (14-DOF) dynamic model is established using the lumped mass method, incorporating unbalanced magnetic pull (UMP) of the permanent magnet synchronous motor (PMSM), nonlinear bearing restoring forces, and grinding wheel unbalance. The equations of motion are derived via Lagrange equation and solved numerically using the fourth-order Runge-Kutta method (RK4). Experimental validation confirms the model’s accuracy. Based on the validated model, the effects of spindle speed, bearing parameters, and air gap length on spindle vibration characteristics and stability are thoroughly investigated. The results demonstrate that the spindle system exhibits period-doubling bifurcation and chaotic motion within specific speed ranges. It was also observed that an increase in bearing clearance lowers the stability threshold, whereas appropriate bearing stiffness enhances the dynamic performance. Moreover, an increased number of bearing balls reduces the system’s sensitivity to speed-dependent vibration, while a moderate increase in the motor air gap effectively suppresses the vibration amplitude. Collectively, these findings provide a theoretical foundation for the structural design of spindles and the optimization of grinding processes, thereby offering valuable insights for improving machining accuracy and surface quality in robotic grinding applications.