超声波测振信号的Hilbert变换解调方法研究

Study on Hilbert Transformdemodulation Method for the Ultrasonic Vibrationmeasurement Signal

以纵向压力波形式定向传播的超声波遇到振动物体时,反射超声波信号的相位会因多普勒效应而被振动所调制.对该反射超声波信号求导得到含有时变相位及时变幅值的调幅调频信号,采用Hilbert变换解调方法求取该调幅调频信号的瞬时幅值和瞬时频率.由于超声波信号存在幅值衰减,而超声波频率不易受外界干扰,故从瞬时频率中提取被测物体的振动速度,并由振动速度求导得到振动加速度.仿真及实验结果表明:Hilbert变换解调方法能够有效地从反射超声波信号中提取瞬时频率信息,而且与实际振动速度及振动加速度相比较,从瞬时频率中提取的振动速度及振动加速度具有较高的准确性.

When the ultrasound that directionally propagate at the method of the longitudinal pressure waves meet vibrate object.The reflected ultrasound signal phase ismodulated by vibration signal for the Doppler effect.The AM-FM signal which have time varying phase and time varying amplitude was achieved from the derivative of the reflected ultrasound signal.The instantaneous frequency and instantaneous amplitude of the AM-FM signal were obtained through the Hilbert transform demodulation method.The amplitude attenuation of the ultrasound signal was inevitable,but its frequency was not susceptible to external disturbances.So the vibration speed of the object was obtained from the instantaneous frequency of the AM-FM signal.The vibration acceleration was achieved from the derivative of the vibration speed.Simulation and experiment result show that the instantaneous frequency can be achieved effectively from AM-FM signal through Hilbert transform demodulation method.Also,compared with the actually vibration velocity and vibration acceleration the actually vibration velocity and vibration acceleration extracted achieved from instantaneous frequency have high accuracy.