时延对ITD法模态参数识别精度的影响

摘要

ITD method used the free vibration response of structure,through three different time delay of sampling to establish the characteristic equation and sovle the modal parameters of structure.In the process of delay sampling,Time delay is related to the identification precision of modal parameter,so it is necessary to research the time delay of ITD.h is deduced by theoretical analysis that the multiple of the time delay relative to the sampling interval shall be less by half than the multiple of the sampling frequency relative to the system maximum intrinsic frequeney.Through numerical simulation and cantilever beam test to confirm the conclusion and analyse the influence of time delay on modal parameter identification.It turned out that proper increase of time delay can improve the modal parameter identifwation precision of ITD method and reduce the influence of noise mode.%ITD(Ibrahim Time Domain)法利用结构自由振动响应,通过3次不同延时的采样,建立特征方程,求解结构的模态参数.延时采样过程中,时延的取值与模态参数识别精度息息相关,因此需要对ITD法的时延展开研究.通过理论分析推导出时延为采样间隔的倍数应小于采样频率为系统最大固有频率的倍数的一半.利用数值仿真及悬臂梁实验验证了该理论,分析了噪声环境下时延变化对模态参数识别的影响规律.结果表明,适当增大时延能提高ITD法的模态参数识别精度,降低噪声模态的影响.