Basic Research Of High-Accuracy Vibrator Based On GMM For Geological Prediction

Seismic exploration is an important way for oil and gas detection. The traditionally used explosive sources would harm the environment with dangers. And the normally used vibrators, which are also called the non-explosive sources, could adjust parameters such as the size of frequency, sweep time and so on. Besides the features such as "Safety" and "environment protection", the vibrators can achieve higher resolution results. The electrodynamic vibrator is a kind of high precision excitation equipment used for seismic exploration in the shallow subsurface, but the excitated signal’s energy is relatively weak, which causes the decrease of the signal to noise ratio. In order to solve this problem, this paper discussed on developing a new electrodynamic vibrator based on the Giant Magnetostrictive Actuator (GMA). The Giant Magnetostrictive Material has a higher magnet-mechanical energy conversion rate, related to normal ferromagnetic materials, thus the vibrator based on GMA should generate more mechanical energy and achieve better exploration results.In order to meet the demand that the GMA vibrator should excite the chirp signal, the paper researched on several aspects:(1) Considering the hysteresis model and the variable frequency situation, this paper treated the magnetic hysteresis as a phase lag between the input and output signal. And the mathematical model was built as a second order system with time delay process with a validation conducted.(2) The Lysmer equation was used to describe the vibration model of the plane-telluric system, and the equation was solved with the Runge-Kutta method. The influence of the damping ratio and system natural frequency on the dynamic responses under the chirp signal was discussed.(3) To satisfy the precise phase control of the excitated signal, phase compensation and PID were introduced as a control strategy for the actuator. The phase lag was obtained by FFT, and the input signal was in the same phase with the output signal after the phase compensation. PID was used for error reduction and improving the response characteristics. Verification experiments were conducted and the experimental results proved that the control strategy discussed in this paper was effective.