K-L分解在可控震源锁相控制中的应用

Application of Karhunen-Loève Expansion for the Phase-locked Control System in Seismic Vibrator

可控震源相位畸变使地震子波旁瓣能量增强,主瓣分辨率降低,从而降低地震勘探的分辨率。由于可控震源-大地耦合条件多变,导致可控震源激发力信号中含有较强随机噪声,在锁相环中采用常规过零检测方法难以对该反馈信号进行准确的相位检测,这严重影响了可控震源锁相控制系统的应用效果。为了提高可控震源锁相控制中反馈信号的相位检测精度,提出一种基于K-L分解的可控震源激发力信号相位提取方法。理论分析和实验表明,对于通带内含有强高斯噪声的可控震源激发信号,K-L分解方法利用其去除信号与噪声相关性的能力,不但能够显著提高可控震源反馈信号的信噪比,而且不损害原有信号的相位特性。将其应用于轻便电磁式可控震源的锁相控制中,结果表明该方法不但解决了锁相环的噪声敏感问题,而且显著提高了可控震源的相位控制质量和地震子波质量。

The phase distortion in seismic vibrator can result in increase in seismic wavelet side lobes and decrease in main lobe resolution ratio,there by causing resolution reduction in seismic survery.Variable coupling conditions between vibrators and the earth,which bring about plenty of noises,distort the force signals radiated by vibrators.Consequently,the phase of feedback signal can be hardly detected accurately with zero-cross detection method in phase-locked loop,which affects the effectiveness of phase-locked control system applied to vibrator seriously.In order to improve the measurement accuracy of the phase of vibrators ＇ feedback signal.A phase detection method based on Karhunen-Loève expansion is proposed.And theoretical analysis and experiments show that the method,benifiting from its capability of removing correlation between available signal and random noise,peforms well in increasing signal to noise ratio of the feedback signal output by vibrators without ruining the original signal＇phase characteristic when strong noise exists within the pass band Experiments based the method were implemented in portable vibrator driven by electromagnetic force.The results show that the method not only solved the noise susceptibility of phase-locked loop,but also improved the quality of phase control and the seismic wavelets notably.