Research Of Waveform Reproduction Technology On Calibration Shaking Table

Low-frequency electromagnetic shaking table is widely used for thecalibration of speed and acceleration sensor in earthquake engineering. Up tonow, the study of calibration techniques and the regulations of ground motionvisualizer is still frontier and hot topic to China. Ground motion visualizer isdesigned for seismic data acquisition equipment. The way using the seismicwaves to detect the Ground motion visualizer examination could better reflectthe true performance of the instrument. And this method is still quite new bothin China and abroad. To realize the method needs to reproduce the earthquakewave in a high precision firstly.Because of the non-flat feature of electromagnetic shaking table itself, itappears to be nonlinearity in some frequency band. When input the seismicwaves, the output waves will get a poor result which makes the output wavesdifferent from the original waves. It is necessary to find ways to improve theprecision of waveform reproduction in the electromagnetic shaking table.This paper is based on the data in "The uncorrected acceleration recordsby Wenchuan earthquake8.0". We select the seismic wave signal bycomparing the seismic signal frequency width, frequency characteristic,amplitude, the epicenter distance and other factors from the seismic data ofSichuan Wolong, Guangyuan Shijing, Shawan and Maoxian Diban to carry outthe test and research.In order to compensate non-flat region in the system and improve theprecision of waveform reappearance, the paper obtains the transfer function,and also analyses the frequency response characteristic of the electromagneticvibration table. In order to get the transfer function smoother, the paperchooses the analysis method of harmonic signal, using the inverse transferfunction to reconstruct the driving signal.In order to compensate the deviation in nonlinear region, the paper usesthe iterative learning control (ILC) to improve the precision of waveformreproduction. Meanwhile, combined with the new driving signal, it couldreduce the number of iteration. In view of the above methods, the paper writesa set of ILC system software, which realized the signal acquisition, analysisand automatic control. After testing the shaking table, it gets a good resultwhich proved the feasibility of this method.