| The ocean,as an important part of the earth,contains abundant natural resources.The exploration of natural gas hydrate,in main sea areas of China,has entered into the detailed investigation and trial mining stage.However,due to the domestic existing sea-towing seismic detection device being affected greatly by deep water,it is hard to meet the demand of the high-resolution natural gas hydrate exploration.Besides,foreign countries restrict the export of mini trace intervals and the deep-sea seismic exploration to our country.Based on that,and with the support of the national key research and development plan,the First Institute of Oceanography State Oceanic Administration and other units have conducted the research on "deep-towing,high-resolution,multi-channel seismic exploration technology and equipment".Deep-towing seismic exploration has the characteristics of large data,high cost,high risk,and so on.Streamer data transmission system,as a communication hub of towing seismic detection equipment,plays a decisive role in picking up reliable and efficient seismic information.Based on topology and function design of the existing sea-towing seismic streamer,this article designs a digital acquisition station at the front of the hydrophone channel inside the towing section,which transmits seismic information in the way of digital baseband signal,and improves the accuracy of seismic signal detection.After clearing the technical indexes of the system,it optimizes the data transmission mechanism,uses the method of uploading step by step,and design the topological structure of the data transmission system.Referring to the OSI reference model,the functional structure of the system is simplified to four layers: Application Layer,Transport Layer,Data Link Layer,Physical layer,In order to improve the stability of the data transmission system,it has compared and analyzed the error control methods commonly used,and then designs a no-waiting for the feedback retransmission error control method,which ensures the accuracy of the data transmission,and improves efficiency of the data transmission at the same time.In order to improve the efficiency of the data transmission,it uses the ring queuing data caching mechanism,which improves the instantaneous throughput of the data transmission,and effectively solves the congestion problem causing by the large capacity,multi-channel data concurrency uploading.Based on functional requirements of the system and the design of the topology,data transmission,between digital packets(streamer data transmission unit),adopts LVDS high-speed data transmission technology to realize large capacity data transmission,and synchronous clock,extracted by byte synchronous,is taken as a reference for synchronous clock of multi-channel seismic data acquisition.It takes distributed RS485 data transmission technology between digital packet and collection station(hydrophone of data acquisition unit)to realize the seismic data uploading and control commands and the synchronous clock radio downwards transmission,and uses enable-control to reduce power consumption of data transmission effectively.This article designs digital packet system framework,which takes FPGA as the core,and the function modules of digital packet are discussed from 5 parts.Referring to “the oil sea digital seismic acquisition and towing system(GB/T24261.2-2010)” standard,a system testing was carried out on the towing machine in the production plant.The results show that the design of the streamer data transmission system can realize the functional requirements of data transmission stably and efficiently.It brings greatly scientific research significance and engineering benefit for achieving independent research and development of high-resolution,multi-channel,seismic digital streamer,and it can provide indirect technology and equipment support for Marine gas hydrates high-precision detection. |
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