Research On The Draft Detecting System Of The Floating Side-scanning

As the key factors of Three Gorges ship lift ship safe and efficient navigation,draft detection depends on the real-time and efficient ship draft detection system.The existing ship draft inspection system has two kinds:one is water swept ship draft detection system based on ultrasonic wave;the other is side-swept ship draft surveying system based on the ultrasonic.The above two kinds of draft detection system detection devices are fixed installation.As the water level of the ship lift channel changes up and down a larger,the installation of maintenance not only is inconvenient,but also affects the system draft detection range.In order to overcome the shortcomings of existing draft detection methods,this paper designed a floating side-swept ship draft inspection system.The main research works are as follows:First,the paper analysis the acoustic wave propagation characteristics by constructing a mathematical model of spherical wave sound field radiation.Then,the principle of ultrasonic transducer is analyzed,and the optimal matching impedance of the transducer under resonant condition is analyzed according to the relevant parameters of the ultrasonic transmitting transducer.The method of measuring the transducer bandwidth by three-voltage method is also analyzed in detail.Second,The design of the floating side-swept ship draft inspection system installs the multiple ultrasonic emission array at each angle on the floating body to accommodate a wide range of ship draft.The paper mainly introduces system working principle and the design combination realization function of each module.The module design specifically includes:The transmitting modulation module adopts the method of amplifying the continuous complementary pulse signal to drive the transducer to emit sound wave;The enable module uses the short time-division multiplexing to enable the transmitting modulation circuit to eliminate the single frequency transmission and the multi-channel effect on the receiving end signal demodulation;The receiving module amplifies the weak ultrasonic signal into a direct current signal;The data acquisition module adopts the mean filtering method to eliminate the secondary noise introduced in the data acquisition process.;the data fusion module is responsible for integrating the multi-channel acoustic wave data and the water level information into one frame data;the data transmission module transmits the data of each frame to data processing software module via RS485 and the data processing software module finally uses the related algorithm of filtering,labeling and amplitude subdivision based on the ultrasonic amplitude intensity to realize the ship draft.Third,in order to eliminate the multi-channel interference between the ultrasonic array channels,the paper proposed the use of frequency domain feature recognition to demodulate of ultrasonic signals.From the hardware,it uses low noise and wide band operational amplifier on the millivolt-level ultrasound signal amplification and the amplified signal is acquired by the acquisition card and the amplitude spectrum obtained by FFT is used to identify and extract the ultrasonic signals.After a lot of experiments in different laboratory and on-site experiments,the system is proved that the technical approach is feasible and the measurement accuracy of draft is satisfied.