模态测试中力传感器附加质量辨识及消除方法研究

摘要

针对激振器激励方式在模态测试中因力传感器附加质量影响会使测量频响函数不准确、附加质量大小难以准确获知等问题，提出基于测量的频响函数辨识力传感器附加质量方法，为消除该附加质量影响提供依据。分析附加质量对结构频响函数的修改，并推导用测量频响函数表达附加质量的通用公式；通过数值仿真验证方法的可行性；采用激振器＋激光测振仪方案对简支梁进行模态实验，用简支梁两点的驱动点及跨点频响函数（共四组数据）辨识力传感器附加质量大小。该方法辨识精度取决于频响函数测量精度，而实验中因噪声影响常使测量的频响函数在某些频段质量较低。因该方法计算不依赖全频段数据，故实践中可针对性选取四组频响函数中均具有较高质量的公共频段数据参与计算，以提高辨识精度。%The measured frequency response functions (FRFs)are usually inaccurate due to the force transducer mass loading effects in shaker modal testing.And the amount of the extra mass (of the transducer)contributing to the test is generally unknown to us at all.A method for the identification and correction of extra mass of the transducer based on the measured FRFs was investigated.The changes of the structure’s FRFs due to the additional mass were analyzed and a general formula for expressing the additional mass using the measured FRFs was derived.Then,the method was verified with case studies using simulated experimental data.Finally,the modal testing of a simple supported beam was conducted using shaker and laser doppler vibrometer.And the additional mass of force transducer was identified by using two point FRFs and two transfer FRFs of the beam.It should be noted that the exactness of identification depends greatly on the accuracy of the measured FRFs while the FRFs in some frequency bands are often heavily contaminated by the noise in practical testing.However,a significant advantage of the method is that the calculation does not rely on the full-band data.Therefore,in practice,certain frequency bands in which all the four FRFs are of high quality can be selected for calculation and the accuracy of identification will be improved.