| The flow gauge verification system is used to verify the performance index of the water flow meter.Especially for the manufacturing enterprise of flow meter,there are a lot of instrument verification and experimental work in the process of new product development,which requires the flow rate verification system to participate in the completion.Therefore,it is of great significance for production and scientific research to design an efficient and accurate verification system for water flow meter.The traditional flowmeter verification relies on manual operation or semi automatic,and the verification operation is complex and the efficiency is low.Based on the standard meter method,the flow and pressure decoupling control based on feedforward compensation is carried out to obtain the flow and pressure decoupling control based on feedforward compensation.The scheme of the verification system is determined.The stability and controllability of flow and pressure in the verification process are completed,and the water flowmeter is under constant pressure condition.The uncertainty of the system expansion is reduced and the measurement error caused by the difference between the actual working pressure and the verification work pressure is eliminated,and the reliability of the system verification results is improved.The system selects the standard table method to verify the flow meter.Taking the Kingview as the monitoring software of the upper computer,the monitoring data is recorded,analyzed,the verification results and the verification process are monitored through the upper computer.Realize the automatic verification of the verification system,improve the verification efficiency of the verification system;use the PLC as the lower computer to complete the collection of data such as flow,pressure and temperature,as well as the control of the executive agency such as frequency converter and regulating valves,and improve the system's Automatic control function.In order to provide a standard and stable verification environment,based on the automatic calibration system of flow gauges,the flow meter calibration system is analyzed,and a two input and two output coupling model(TITO)with the opening of control valve and the frequency of frequency converter as input,and the output of flow and pressure as output are established.The mathematical model of the system is established by using the experimental modeling and combining with the MATLAB system identification toolbox.Through the calculation of relative gain matrix,the coupling degree between pressure and flow is analyzed in detail.The system adopts feed-forward decoupling control algorithm based on PID control system decoupling control scheme is designed,and the simulation model is established on the Simulink platform,respectively on the system without decoupling model,feedforward compensation decoupling control model,feedforward compensation decoupling-PID control model of three cases were analyzed,And through the OPC technology,complete the realization of control algorithm in MATLAB.The design of the automatic calibration system for the water flowmeter can accomplish the verification test of the water flowmeter,automatically give the verification report,and add decoupling control on this basis.Through the analysis of experimental data,the coupling effect between flow and pressure is basically eliminated,which can provide full range verification within 0.15 to 0.25MPa pressure range.According to the research on the expanded uncertainty of the system,it is shown that by adding flow and pressure decoupling control to eliminate the uncertainty caused by the pressure factors in the undecoupled state,the expanded uncertainty of the system is reduced from 0.71%to 0.41%(k=2).The system has a high degree of automation,and can reliably and reliably calibrate flowmeters under constant pressure.The research results have certain reference value and practical application value for further improving the accuracy and reliability of flowmeter calibration. |
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