复杂地表条件下的电磁式可控震源广义预测控制方法

作为一种浅层高分辨率可控震源,电磁式可控震源在浅层地震勘探中受到了广泛的重视。电磁式可控震源激发信号质量总是受到地表条件影响,在地形平坦,并且震源基板与大地耦合条件良好的情况下,电磁式可控震源能够取得良好的勘探效果。而在地形起伏,基板与大地耦合较差的复杂地表条件下,当前可控震源控制系统激发信号存在比较严重的畸变,控制精度严重下降,地震勘探误差变大。为此研究适于复杂地表条件的可控震源高精度控制系统具有重要意义。将可控震源与大地看成一个系统,耦合条件不同意味着系统模型是变化的,因此控制系统应采用与模型无关的控制算法才能适应变化的地表条件。针对上述问题,在分析电磁式可控震源输出信号畸变特性,以及产生畸变原因的基础上,探讨电磁式可控震源激发信号估计的方法,研究利用广义预测控制方法与相位预补偿、零相位滤波方法相结合实现对可控震源激发信号相位、幅度畸变的控制。经仿真实验,广义预测控制后电磁式可控震源激发信号相位最大偏差由125°减小到3°,最大幅度畸变由133%减小到4%,在3 000 m/s速度模型下,由震源激发信号畸变导致的定位误差从1.5 m减小到小于0.2 m,提高了复杂地表条件下电磁式可控震源地震勘探精度,实现了复杂地表条件下可控震源激发信号高精度控制。

The electromagnetic seismic vibrator generalized predictive control system under varying ground conditions

As a kind of high resolution seismic exploration equipment, electromagnetic vibrator received widespread attention. The electromagnetic seismic vibrator output signal is always influenced by the surface conditions. In flat terrain, when the baseplate and groud was in good coupling,the electromagnetic vibrator can obtain good exploration result. But under complex surface condition, conventional seismic vibrator control method is difficult to achieve a good effect. Electromagnetic vibrator excitation signal often exist serious distortion, affect the precision of seismic exploration. According to the above problem, this paper analyzes the electromagnetic seismic vibrator output signal distortion characteristics, the reasons of the distortion, and discusses the electromagnetic seismic vibrator output force estimation method, explores the generalized predictive control method to realize the effective control of the vibrator output signal phase. As the simulation experiment shows, the generalized predictive control reduced the largest phase deviation of electromagnetic seismic vibrator output signal ,from 75 ° reduce to 3 °.And the largest amplitude error reduced to 4% from 133%.In the speed model of 3000 m/s , the positioning error caused by the source excitation signal distortion, reduced from 1.5m to less than 0.2m. The prospecting precision of electromagnetic seismic vibrator was improved.