Automatic Sampling Method And Control System For Deep-water Hydrographical Sampling Studying

Analysis on sampling water is required for monitoring suspended load of the rivers and reservoirs. In recent decades, the researchers designed a variety of hydrological sampling water samplers, which have prevalence defects as follows:labor-intensive, short underwater communication distance, and imprecise depth measurement. With the impoundment of the Three Gorges Dam, to carry out hydrological sampling in more than200meters deep waters become an unavoidable problem. In order to improve the accuracy of water depth measurement, to reduce labor intensity, to solve the problems of Three Gorges Dam on deep water of hydrological sampling, this dissertation designs a automatic control system for deepwater hydrographic sampling that based on dynamic depth measurement technology, underwater acoustic communication technology, and hydraulic winch control technology.Based on national standards and hydrological sampling workflow, the control program of hydrological sampling system is identified. The control system includes underwater controller and surface controller. The underwater controller takes single-chip as the core and measure the water depth by the pressure sensor. Surface controller takes PLC as lower machine which realizes hydraulic winch control and takes PC as host computer which realizes water harvesting process control and man-machine interface. The entire system based on PC as main controller.The concrete index of pressure depth and aggregate demand is set, and the error sources of pressure sounding are analyzed. The temperature compensation experiment has been completed for pressure sensor, which can realize the temperature compensation within effective compensation range. The Kalman filter based on system model is designed to filter out outside noise. Wave model is established and the effect that the wave brings on sounding is analyzed through theory and simulation.The model that the water flow affects on the pressure is constructed by using the Bernoulli equation. And the analysis and verification is achieved through the simulation. Pressure sounding hardware platform and software are designed.According to the specific working environment of hydraulic sampling system, the requirements of the underwater acoustic communication module and the noise source of module working environment are analyzed. Water acoustic communication algorithm for multi-source noise background is studied. A threshold alternative combination of superposition method and coherent adaptive filtering of underwater acoustic signals received. This method is verified by simulation of multi-source noise suppression effect, and on this basis, the design of the hardware and software of the underwater acoustic communication module, and the algorithm embedded into the control system, greatly reducing the underwater acoustic communication error bit rate.Hydraulic winch control PLC wiring diagram and PLC program is designed, and the math model is established. Hydraulic winch speed controller and water sampler lead fish water depth positioning controller is studied and analyzed. The results show that both controllers can meet the performance requirements. The master controller software flow and human-machine interface are designed.Laboratory test and field hydrological sampling test are both accomplished, and the test results show that the depth measurement accuracy, the effect of underwater acoustic communication, dynamic response speed may meet the design requirement.On the basis of the above research, the dissertation achieved the following results:(1) A new deep-water hydraulic sampling automatic closed loop control scheme is proposed in this paper.(2) Hardware and software of underwater controller are designed to achieve a dynamic bathymetric survey; in regard to a specific water pressure sounding error, anti-jamming measures are put forward to raise dynamic water depth measurement relative error to2%or less;(3) Hardware and software of underwater acoustic communication module are designed to achieve wireless communications between surface controller and underwater controller; Method of anti-interference of multiple multi-source is proposed to make communication success rate at about60%when the underwater distance close to200m.(4) Software of surface controller is designed to realize automatic control of water harvesting process and to decline single vertical line six-point method sampling time to about450, which greatly improves the hydrological sampling efficiency.The automatic control system of deep-water hydrology sampling in this dissertation has high depth measurement accuracy, long effective underwater communication distance, high automation level. Based on dynamic measurement of water depth, this system can realize the whole closed-loop control of hydrological sampling and automatic process control of single vertical line six-point method hydrological sampling. This achievement has great significance and broad application prospects in hydrological sampling for deep water.