Design Of Helmet - Type Color Image Sonar Digital Circuit

As a maritime country, China put a new premium on the underwater sonar imaging technology because of the special needs of dam safety detection, the development of marine resources and the war of the oceans. The sonar system is needed to complete the underwater target detection especially when the detection water area is turbid; the visibility is very low, even the target in a few meters away cannot be seen by using underwater video camera.At present, most of the sonar system is installed in untethered underwater robots, large ships, dam and the underwater mooring anchor. The most common features of these sonar, there are bulky, inflexible, complex operation and so on, determines there are not suitable for underwater frogmen use alone. Therefore, the authors’ research group is commissioned by Chinese Navy Command sailing security to research man-portable sonar. The author of this paper is responsible for the design and implementation of the sonar system digital circuit.The man-portable sonar has advantages of small size, light weight, carry-home, multi-function, high-resolution and so on. These advantages made it suitable for underwater frogman use alone. This sonar system mainly consists of four parts:waist control box, head sonar, underwater video glasses and onshore IPC. It is mainly mounted on the helmet, diving wetsuit and it carried by frogmen alone. The frogmen can be observed the results of sonar targets directly through underwater video glasses, and they can independent operations or operations according to the command sent by the land-based industrial displays. Finally, this sonar is shaped as the helmet type color image sonar (TKIS-I).Considering the specific requirements of sonar systems and performance indication, eventually, the embedded system design is adopted.Digital circuit adopt the design that base on a dual-processor:a processor is responsible for the completion of video signals of the display control functions; another processor is responsible for the transducer signal transmission, reception of control, stepper motor control, position switch control, underwater video glasses image gain control, communications control of the RS-485, the control process and algorithm realization of the entire signal process. Digital circuit design includes hardware and software design of each module, both of which are equally important, the software design is base on the hardware-based platform. Hardware design include: minimum system of embedded processors, power modules, underwater video glasses display module, stepper motor drive modules, memory modules, and RS-485communication module. The design and implementation of the routine of soft is adopting C language modular programming idea in KEIL ARM-MDK development platform. In the digital circuit part of the sonar system, only two switching control entities are designed:one can control the system power on and off and complete image adjustment underwater video glasses gain in real-time; the other is the position switch, which is consist of six gears and different ranges can be selected according to the actual situation detection range. In this way, the target resolution in short-range and the target detection in long-range can be balance. Both on-off operations are simple, easy and do not require a long time to learn, which is beneficial for underwater frogmen.The TKIS-I sonar system has been used by the Navy, and numerous applications test in lakes and marine did over and over again. The results of test are perfectly, which is clear imaging, low background noise, using convenience. Sonar system performance is stable, reliable and digital circuit design had completed the desired objectives.