三自由度载人离心机弹性边界下的模态测试研究

Modal testing study of three-axis manned centrifuge under elastic boundary conditions

目的:针对三自由度载人离心机系统结构复杂、转动惯量高等特点,探讨其在弹性边界下的模态测试方法。方法:以三自由度载人离心机为测试对象,参照GJB 2706A—2008《航天器模态试验方法》和GB/T 11349.3—1992《机械导纳的试验确定冲击激励法》在离心机弹性边界下使用力锤作为激励源开展模态测试。每个激励位置锤击4次,对4次锤击数据进行线性平均计算后得出结果。利用三自由度加速度传感器、64通道数据采集仪收集数据,基于Test.Lab模态测试分析软件,采用频率响应函数对模态数据进行分析。结果:激励信号在30 Hz频段内相干系数不低于0.8;系统前3阶固有频率分别为9.15、15.66、19.22 Hz,均为扭转振型;在Z18和Z21激励位置下,系统一阶频率均为9.15 Hz左右,二阶和三阶频率也一致。结论:力锤测试法可用于三自由度载人离心机的模态测试,能够保障设备运行的安全性、提高受试者的舒适性,对指导后续的结构优化设计具有借鉴意义。

Objective To explore the modal testing method for the three-axis manned centrifuge under elastic boundary conditions with considerations on its complicated structure and high rotational inertia.Methods Modal testing was carried out with a three-axis manned centrifuge under elastic boundary conditions as the subject and a force hammer as the excitation source according to GJB 2706A—2008 Modal tests method for spacecraft and GB/T 11349.3—1992 Experimental determination of mechnical mobility measurements using impact excitation.Four times of hammering were carried out at each excitation position,and the data of the four times of hammering underwent linear average computation.Data acquisition was implemented with a three-axis accelerometer and a 64-channel data collector,and the modal data were analyzed using a frequency response function based on the Test.Lab modal test and analysis software.Results The coherence coefficient of the excitation signal was not lower than 0.8 in the 30 Hz band;the first three orders of the system's intrinsic vibrations were all torsional vibrations,with the frequencies of 9.15,15.66 and 19.22 Hz,respectively;the first order frequency of the system was about 9.15 Hz for both Z18 and Z21 excitation positions,and each of the second and third order frequencies similar situations were observed for also had a roughly equal value for the two excitation positions.Conclusion The force hammer testing method is applicable for the modal testing of the three-axis manned centrifuge,ensuring equipment safety and subject comfort.Referen-ces are provided for the following structural optimization design.