频响函数估计是多输入多输出随机振动试验控制算法中的必要环节.在振动环境试验中,通常不采集振动台的实际激励信号,而用实测的响应信号和计算机内存中的激励信号来进行系统频响函数估计.由于计算机内存中的激励信号与实际振动台上的激励信号之间在相位上存在着差异,从而导致实测的响应信号和计算机内存中的激励信号不同步.这给系统频响函数的估计带来了较大困难.为此,根据线性系统中激励和响应之间的关系,结合随机减量法,提出了一种二次相关法用于系统频响函数的估计,用该方法进行频响函数估计只需要采集响应信号.在三轴振动台上进行了对比试验,结果验证了所提出的二次相关法的正确性.%The estimation of frequency response functions ( FRFs) is unavoidable in MIMO ( multiple input and multiple output) random vibration test control. The actual excitation signals on the shaker tables are always not sampled during the vibration test. So, the FRFs are usually estimated by the response signals acturally measured and the excitation signals stored in the computer memory. Because there is a phase lag between the signal in the memory and the actual signal on the shaker table, the response signal is not synchronous with the memory excitation signal, which makes difficulty to estimat FRFs. Based on the relationship between the excitation and response in linear system and utilizing the random decrement technique, a dual correlation method ( DCM) was presented to estimate FRFs without measuring the actual driving force signals. A comparison test between DCM and the conventional method which needs to sample the excitation and response signals simultaneously was accomplished on a 3-axis vibration table. The result shows the correctness of the presented DCM.
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