轴承间隙及柔性特征对机构动态误差的影响分析

为能够准确、有效地揭示轴承间隙与柔性特征对机构动态误差的影响规律,基于多体动力学理论与Hertz接触理论,提出一种计及轴承间隙与柔性特征影响的多体系统建模方法。该方法采用力约束替代运动约束,构建多体系统环境下的轴承精细化模型。基于该方法,可深入揭示轴承微观动力特性与多体系统宏观动态性能及运动精度之间的映射关系。在此基础上,以含深沟球轴承的曲柄滑块机构为仿真算例,分析轴承间隙与柔性特征对该机构运动位置与速度误差的影响规律。研究表明,轴承内外圈中心形成的相对偏心轨迹的变化特征是由多体系统动态环境下的轴承受载特性决定的;在轴承偏心影响下的机构运动位置与速度误差大小会随曲柄转角位置不同而变化。

Effects of Bearing Clearance and Flexibility on the Dynamic Errors of Mechanisms

In order to reveal the influence of the bearing clearance and flexibility on the dynamic errors of mechanisms accurately and efficiently,a methodology for dynamic modeling of multibody systems with bearing clearance and flexibility is presented based on the theories of multibody dynamics and Hertz contact.The detailed bearing joint in the multibody system is modeled by introducing a constraint force system instead of the kinematic constraints.The presented methodology provides a foundation for in-depth revealing the relationships between the bearing micro dynamic characteristics and the multibody system macro dynamic performance and kinematic accuracy.A crank slider mechanism including a deep groove ball bearing is used as a numerical example application to analyze the effects of the bearing clearance and flexibility on the position and velocity errors of the mechanism.The results indicate that the variation of the eccentric trajectory of the bearing inner race center with respect to the outer race center is determined by the loading characteristic of the bearing joint in the context of dynamic analysis of multibody system.Under the influence of the bearing eccentricity,the position and velocity errors of the mechanism are usually different with the variation of crank angle position.