码盘偏心对扭振测试影响的研究

扭振测试对旋转机械的故障诊断具有十分重要的意义,当测速码盘存在偏心时,会给扭振测试带来很大的误差。在轴实际存在扭振的情况下,由理论推导,得到在码盘偏心时测量转速与轴实际转速之间的关系式,从而得到测量扭振角速度,分析出测量扭振的组成成分并得到了其数学表达式。讨论影响扭转各成分幅值大小的因素,偏心比越大,测量扭振的误差越大;偏心比相同时,转速越高,扭振角速度的误差也越大;任一阶测量扭振均受到分布在其两边的轴实际扭振的所有阶次的影响,在幅值相同情况下,距离越远的阶次影响越小。仿真和试验验证了理论推导的正确性,仿真中的最大误差为2.83%,试验中的最大误差为5.6%。

A Research on the Effect of Encoder Eccentricity on Torsional Vibration Test

Torsional vibration measurement is important to the fault diagnosis of rotating machinery, and a big measuring error would be caused when the speed encoder is eccentric. The relationship between the actual speed and the measured speed from eccentric encoder is theoretical deduced, and the measured torsional angular velocity is derived accordingly. The components of torsional vibration are found out and whose mathematics expression are obtained. The factors influencing the amplitude of each component of the torsional vibration are discussed. It is found that the bigger the eccentricity ratio, the larger the measuring error of torsional vibration; and the measuring error increase with the rotating speed when the eccentricity ratio is constant. The measuring error of any order of torsional vibration is influenced by all the harmonic of the torsional vibration, and the bigger the interval the smaller the influence. The simulation and experimental result verified the effectiveness of the theoretical derivation, and the largest errors of the simulation and experiment are 2.83% and 5.6%, respectively.