Research And Development Of Control Technology In Towed 500A Marine Controlled Source Electromagnetic Transmitting

Towed marine controlled source electromagnetic transmitter is one of the important equipment in marine electromagnetic detection equipment. After processing and inversion calculating the AC current of the transmitter and electromagnetic field data of the receiver collecting, people can understand the shallow resistivity structure below the seafloor. Marine controlled source electromagnetic method and equipment research and practical application has increasingly well-formed abroad, and this area is gradually further studied at home. However, there are some limitations in domestic research, such as low transmitting current,shallow detection depth and low operating efficiency, which hinder the further exploration of the geological structure of deep seafloor in China.This paper focuses on researching the control technology of the transmitter,which is based on natural gas hydrate resources exploration and pilot works of 127 national special subject. The research content is divided into two parts: hardware and software. The hardware mainly includes four parts: main control module, current module, power module and communication interface module. The software mainly includes three parts: high precision synchronization program, 500A current frequency conversion control and environment parameter monitoring program and current counting acquisition and storage program. The main control module combining high precision synchronization program and 500A current frequency conversion control and environment parameter monitoring program, uses ARM processor to control CPLD to synchronize the clock and generate the single frequency or the mixed frequency drive signal, which drives the IGBT inverter module to produce 500A level current waveform, to achieve a multi-frequency transmitting control technology and high-precision synchronization technology. The current module combining the current counting acquisition and storage program, converts the current signal from the Hall current sensor into analog signal, uses the sampling pulse for data acquisition and time marking and controls the U disk to real-time storage data by USB interface chip,to achieve the current acquisition, the formation of absolute time tags and USB-based chip real-time storage and other functions. The power module controls 12V and 24V lithium battery voltage conversion, which effectively isolates weak control from strong electric operation. The communication interface module integrates multiple interfaces and connects fiber optic transceivers to the myriametric cable fiber transmit between the desk computer and underwater transmitter. The application of the control technology of towed 500A marine controlled source electromagnetic transmitting is verified the applicability and technological performance by several indoor testing and marine testing. According to the experimental results, the practical application of this technology has basically reached the design requirements,which provides a new idea and method to improve the exploration accuracy of seabed hydrate and enhance the stability of the instrument. It is of great significance to the exploration of mineral resources in deep seabed.