Research On Autonomous Diagnosis Method And Key Technology In The Detection Process Of Small Water Quality Monitoring Station

With the increasing attention of the state to water resources protection,local environmental protection departments and water resources protection departments have gradually taken various effective measures to supervise and remediate the surface water and groundwater.The online water quality automatic monitoring system,which can monitor the water quality in real time,quickly,and reliably,is an important foundation for the supervision and protection of water resources.At present,the online water quality automatic monitoring system is developing rapidly,but there are still problems such as high cost of monitoring equipment,insufficient monitoring parameters,and long detection period.Most of the monitoring equipment does not have fault alarm information,and so cannot quickly locate the fault source when the equipment is failing,which increases the maintenance time and cost,resulting in the loss of water quality monitoring data.Aiming at the existing problems of the current online water quality automatic monitoring system,a nine-parameter small water quality monitoring system was designed based on sequential injection analysis technology.Based on the fault diagnosis method which combining Fault Tree Analysis method(FTA)and expert system method,a fault diagnosis expert system for the water quality detection process of the small water quality monitoring station was designed to realize the autonomous diagnosis function,reduce the workload of system maintenance personnel and reduce equipment operation and maintenance costs.First of all,aiming at the existing problems of the current water quality monitoring system,a small water quality monitoring system was designed,which mainly includes the overall scheme design of the system,the analysis of the water quality testing method,the design of the water quality monitoring process,the hardware design of the system,and the software design of the system.The overall framework of the system was determined through the overall scheme design of the system.Based on the national environmental protection water quality testing nine-parameter industry standard,the water quality testing methods were analyzed The hardware design of the system mainly includes the design of the conventional five-parameter integrated sensor,the design of the micro-reagent water quality monitoring platform based on sequential injection analysis technology,and the hardware design of the embedded system which was based on STM32 MCU.The software design of the system mainly includes the software design of the lower computer and the software design of the upper computer.Keil V5 programming software was used as the lower computer software.The software design based onC/OS-Ⅲ real-time operating system platform was used to control the detection process of micro-reagent water quality monitoring platform and signal acquisition,processing and transmission.Lab VIEW software was used as the upper computer software to control the operation of the entire monitoring process.It has functions such as system monitoring,system parameter setting,water quality monitoring process view,historical data curve and so on.Secondly,common failures of the small water quality monitoring system were analyzed.A small water quality monitoring system fault tree was established based on the logical relationship between the fault facts.The established fault tree was analyzed qualitatively and quantitatively.FTA and expert system were integrated to establish a fault diagnosis expert system for the small water quality monitoring stations.Expert system design mainly includes the establishment of knowledge base,the design of diagnostic reasoning unit and the design of man-machine interface.The information of each node of the fault tree was transformed into production rule knowledge using the downward method.And the knowledge base was established using a knowledge representation method that combines the production rule method and the frame representation.The principle of the realization of the diagnostic reasoning function was analyzed.The reasoning strategy and control strategy of the reasoning engine were designed.Finally,the water quality detection performance was tested.The standard deviation coefficient(RSD)and accuracy(RE)of each water quality parameter were obtained by comparing the measured value of the water quality monitoring system with the measured value using the national standard method.The repeatability,reliability and accuracy of water quality testing performance were proved by experiments to meet the industry standards for the testing of various water quality parameters The reliability of the fault diagnosis expert system was proved by the fault diagnosis experiment.The small-scale water quality monitoring system and fault diagnosis expert system designed in this paper realize the online automatic monitoring of nine parameters of water quality.The fault source can be quickly and accurately located when the equipment is failing.The system design saves construction costs and operation and maintenance costs,ensures the smooth operation of the system,lays a good foundation for water environment governance,and provides a scientific basis for water resources research.