Study Of The Emitting Ultrasonic Wave And Control Technology Of Underwater Target Detector For Fuze

In allusion to the characters of naval local battle in the future,the target detectors of fuze for underwater ordnance munitions require higher level of target delectability and intelligentalization,especially as the maneuverability,concealment and degree of automation for submarine being improved.The traditional fuze target detective technique cannot be fitted for the demand of modern high-tech war,so the new fuze detecting underwater target technique should be researched to make the fuze underwater target detecting systems have quick-exact target discovering,identifying and tracking capacities,which is very important to improve the underwater ordnance munitions' integrated fighting abilities.This paper mainly investigate key issues of ultrasonic emitting technology for the fuze of depth charge,and studied both theoretically and experimentally on the topics of wave forming,emitting and controlling mechanism.Firstly,on the basis of massive relative papers,status and trend of the research of ultrasonic detecting technology have been outlined systematically in detail.An emitting controlling model consist of single frequency pulse signal and symmetrical triangular linear frequency modulated pulse signal for the underwater detector has been proposed.In the searching phase,long lasting single frequency signal is emitted,while in the chasing phase,modulated signal is emitted.Based on the narrow/wide band ambiguity function theory,detecting performance of linear modulated signal is analyzed,with the conclusion that wideband ambiguity function is more suitable for the detection of high speed target.The wideband ambiguity function of 4 kinds of signals,namely,single frequency pulse,linear modulated pulse,symmetrical triangular frequency modulation pulse and multi carrier pulse are modelled and calculated.Simulation shows that single frequency pulse have better distance measuring performance for high speed and long distance target.But for low speed and close distance,symmetrical triangular frequency modulation pulse has better anti-interference ability.With numerical method,wideband ambiguity function of single frequency pulse and symmetrical triangular frequency modulation pulse signals are solved.Detecting capability,such as distance resolution,velocity resolution and anti-interference ability,versus parameters of the two signals has been analyzed.The result shows that,in the searching phase,the long lasting signal frequency pulse could obtain rough information of the target,while in the chasing phase,symmetrical triangular frequency modulation pulse leads to more precise target information.Then,parameters of both signal are chosen.The case of interference from neighboring munitions to an ultrasonic target detector with depth bomb fuze system is analyzed.On the basis of Doppler frequency control method and dual-window control method,auto emission control strategy of ultrasonic multi-window CW/FM wave based on fuze power voltage and the echo signal.The voltage signal from the fuze initiates the ultrasonic target detector,which then emits single frequency pulse signal.In the effective detecting range,if it receives two echo signals in a row,sends out symmetrical triangular linear frequency modulation pulse signal immediately;otherwise,keeps sending out single-frequency pulse;if the interval time of receiving the echo signal twice is less than the minimum detecting period,sends out a detonator signal immediately.This paper also designed a multi-window control signal which can distinguish and track target through altering the transmitting period,and only the control windows are allowed to receive signal.If two windows in a row both received echo signal,we can judge that the signal is the echo signal of its transmitting signal;the designed period of the two transmitting signals in a row are different,if there is echo signal in one control window,but there isn't in the second one,we can judge that it is the interference signal rather than its own echo signal.And through this kind of method that adjusting the value of transmitting period,we can get rid of the interference from neighboring munitions.DSP Builder,hardware description language and finite state machine are used to design single frequency/symmetrical triangular linear frequency modulation pulse signal generator and a controller circuit.Modelsim is used to conduct a computer simulation in single frequency/symmetrical triangular linear frequency modulation pulse signal generator and the function,timing of controller circuit.The results showed that the design of "found door " can delay the open time,control the door width,and repetition frequency,which satisfies the requirements of discovery complete,target recognition,decision at the single way detection period.Using SR-500 piezoelectric transducers,the designed signal generator and emitting control circuit has been tested and verified experimentally.The result indicates that the multi-window control method could effectively avoid the interferes of neighboring munitions,and achieve the ranging and emission control function.