Study On An Underwater Acoustic Real-time Surveillance System For Bred Fish In Net Cages Of Deep Water

Fish culturing in net cages of deep water is a kind of new high-tech,which is cultivation of marine fishes in deep water with net cages. For the global marine fishery resorcese are going downhill nowdays, it is being popularized in the whole country as a high-tech to keep developing in sea aquaculture. In order to achieve real time monitoring nets and fish and give an alarm in time when the fish escape, it is important to research and develop the safety establishment to match the net cages.It is indicated by a great deal of investigation that the underwater monitor equipment matched to the net cages of deep water has great pratical value and market demand and it is necessary to develop a set of flexible and advanced underwater monitor equipment.In order to display the active state of fish in net cages of deep water, we developed the real time fish-monitoring equipment for net cages of deep water. It takes advantages of underwater acoustic propagation and reflection characristics to monitor net and fish in long term. This article foucoses on the anlysis of the techniques of monitoring fish in net cages of deep water home and abroad, the research and discuss on the methods for distilling the fish echo waves among noises and reverberations. The paper proposes a monitor method aiming at net safty, and based on the research, prototype instruments of both acoustic monitor system and industrialized system are designed preliminarily.The paper expatiates on the details of the design and research achivements in aspects of general scheme, circuit design, software design and etc. The system applies CPLD to design transmitting signal so that the transmitting signal frequency and pulse width accuracy are ensured. In order to resist noises and improve the echo signal's SNR, the new ISP is used to pre-amplify the two-channel underwater acoustic echo signal and MAX274 is applied to realize a narrowband filter with central frequency at 50kHz/200kHz. Signal processing based on Labview platform is adopted to resist disturbance and distrill echo signal and ensure the signal detection effect. Based on the above research, the prototype instruments of acoustic monitor system is designed. The experiments in a pool and in sea area have been performed many times. Based on the success in the sea area test, 51 series single chip computer is adopted as central processor and controller to controll the rotation of transducers, signal transmitting, signal receiving and echo signal processing. The detailed implementation is performed and the preliminary design of prototype instruments of industrialized system is completed.