Speedy calibration of low frequency vibration transducer by using linear frequency modulation signal
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摘要: 为了充分提高超低频振动校准系统的实用性,针对低频传感器校准的需要和该系统的特点,提出了利用调频正弦波作为激励信号,只需要一次测量即可实现对低频振动传感器的校准,校准时间由几十分钟缩短到几分钟甚至1min之内,校准效率大大提高.为了避免由于系统幅频特性不理想而在较高频段对传感器校准精度不高的缺点,提出了利用系统的动态频率特性和线性调频波时频域相关的特性,设计相应的数字补偿滤波器实现对信号源的瞬时补偿,从而实现振动台的线性调频振动.实验结果表明,振动台能够输出较补偿前更为理想的线性调频波,校准结果也更接近绝对校准,且重复性好,同时满足了校准效率和精度的要求.Abstract: Aiming at calibration demands of low frequency vibration transducer and characteristics of low frequency vibration calibration system, transducer was inspired by the linear frequency modulation (LFM) signal so that its frequency characteristic could be gotten through once measurement. Calibration time reduces from a score of minutes to less than one minute, therefore its calibration efficiency improves greatly. In order to avoid the imprecise calibration result at high frequency band due to imperfect frequency characteristic of the system, digital compensation filter was designed to instantaneously compensate signal source based on the dynamic frequency characteristic of the system and time-frequency domain characteristic of LFM signal. After signal source was compensated, vibration table might give rise to more ideal LFM signal, and calibration results of transducer are closer to the absolute calibration results as well as advancement in repetition rate. This method also qualifies for calibration efficacy and accuracy, and develops the practicability of calibration system.
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