Research And Design On The Measuring And Controlling System Of Bypass On-line Rheometer

Rheometer is an important test instrument for measuring fluid properties.It's widely used in many areas,for example,plastic processing,oil production and food processing.It plays aspecial role in polymer processing.The engineers can use it to measure melt viscosity and melt index in order to get knowledge of molecular structure changes.It is useful for determining the production process,optimizing structure parameters and improving product quality.However,in most domestic status quo of actual production,the offline rheometers is often used to finish testing.But the data that offline rheometers provide are delayed,which can not accurately describe the actual situation.There are commercialization on-line rheometer in foreign countries,but the price is too high.So it is of big significance to develop the rheometer with online testing function.This paper will research the measurement and control system and finish the software design for the designed bypass rheometer.The ultimate goal is to make the system have the on-line measurement function of melt viscosity and melt index.The specific contents are as follows:Firstly,the measuring principles of viscosity and melt index on bypass rheometer are introduced,and different measurement control flows are designed for them.Then finish the viscosity measurement and control system based on distributed control system structure.In the lower machine,PLC is treated as the center,and directly connect to the sensors,thermocouples,etc.In the middle part,Modbus protocol based on TCP / IP is adopted to assign a function code and register address to each variable.The host computer use the LabVIEW as the platform to complete the overall software design.It includes communication,data processing,storage,HMI.The result shows that the system can realize the on-line measurement of melt viscosity successfully.In the study of melt index measurement and control system,the fuzzy self-tuning PID is utilized to keep the pressure drop before and after capillary stable.Firstly,design the system identification experiment to get the input and output data.And the MATLAB system identification toolbox is used to deal with the data in order to understand the dynamic performance of the system.Then a fuzzy self-tuning PID controller is designed for the system.Using the Simulink modules to discuss the stability and anti-interference ability by simulation.Finally,completing the melt index measurement and control system designing by making use of fuzzy toolbox in LabVIEW.In this paper,research work based on LabVIEW for implementation of the melt viscosity and melt index online measurement has important theoretical and practical significance.It is very useful for further research about developing the control system of bypass on-line rheometer with independent intellectual property rights.