Study And Design Of Control System Of Phased Array Vibroseis

Vibroseis is one of important parts of seism exploration technology. Also it is the headwaters of producing seismic signal. Controllable vibroseis is an effective instrument in cities with a dense population where use of impact vibroseis is not allowed, Which aimed for lossless exploration. But, the seismic wave generated by single controllable vibroseis spreads hale-global underground. Energy is dispersive and resolution is low. So multi-vibroseis combination seism is put forward for increasing energy and improving SNR of seismic data, yet the wave is mainly vertical and the energy can't be fully used. Introduced technology of phased array radars, seismic wave direction can be realized, thus given an effective method for high resolutions exploration underground. Aboard, in the seventies, American Oil company has been done the experiment for beam-forming in Tulsa, Oklahoma, mainly aimed deep-ground plumb. Effect of seismic wave is proved. However, no such research results have been issued in our country. Design and research of phased array vibroseis is a new try for shallow stratum exploration. For reference phased array radar technology, this paper put forward design plan of phased array vibroseis based on the research of portable high frequency vibroseis system. And finished designing prototype of instrument, further more, field experiment have been carried on. In theory, start with analysis of phased array vibroseis, put forward theory of seismic phased array beam-forming, set up the model of phased array vibroseis system, and given the distributed structure of vibroseis system. It makes up of master management unit and slave vibroseis units. The master management unit is responsible for setting, transmission sweeping parameters, and controlling the whole system. while the slave unit takes charge of producing and driving sweeping signal. Mainly, the paper discussed the hardware and software design of phased array vibroseis system. The modules of signal producing and power amplifier are kernel parts of slave vibroseis unit. Signal producing module adopted Direct Digital Synthesis (DDS) technology. It has wide bandwidth, short frequency transform time, high frequency resolution, continuous phase and simple circuit etc, fully satisfy signal requirement for phased array vibroseis. Furthermore, AD9852 can realize linear frequency modulation sweep, and programmable of Δf makes the last output vibration signal continuous. The circuit consists of sweep module, amplifier and filter module, and realization of all kinds of sweep signals. Power amplifier module amplifiers the sweep signal, driving the vibroseis push-and-pull the ground and forming elastic waves. This circuit applied mutual symmetrical push-pull structure, namely class-AB mode. To ensure working stably, the circuit introduced several feedbacks. Furthermore the heat dissipation and protected circuit are fully considered. Initial phase controllable and synchronization of seismic wave are the key technologies for realization phase control. Actually, it translated for controlling of signal generated by sweep module. Direct phase control and time delay are adopted to solve the first problem, about the latter, the communication like broadcast way of Ethernet is ok. The control software is composed of main management unit and vibroseis control unit, some key flow charts are provided. The function of software list as follow: for multi-vibroseis, realization wave beam-forming, provided with several sweep modes, selection and setting of all kinds of parameters, and real time error report. Moreover, the paper deals with the experiments of phased array vibroseis system. It is composed of consistency test and time delay test. In order to validate the feasibility of phased array vibroseis and the correctness of phased array method, seism experiments of single-vibroseis, multi-vibroseis and phased array vibroseis have been done in village qin---suburb of Changchun. The result is: phased array vibroseis system can advance resolution and SNR of reflection signal of object stratum. It's feasible for shallow stratum seismic exploration. Finally, the conclusions of the thesis are summarized, and suggestions are...