Pellets Expansion Performance Measurement System Design

The research status of the pellet expansion performance testing device and the understanding of the future development trend,pointed out the importance of the measurement system.According to the research of national standard and advanced device,aiming at the problem that the temperature control precision is not high,a high precision furnace temperature controlled pellet expansion performance measurement system is designed.First of all,the overall design of the measurement system,including the determination of the reduction furnace temperature,gas flow,and the determination of the quality of pellets,the experimental process of experimental device selection and control process analysis.The system is designed according to the system requirements,from the hardware and controller aspects of the design and the study.In the system hardware design,STM32F107VCT6 as data acquisition,transmission chip,and its peripheral circuit design,including memory expansion,Ethernet interface circuit design,serial communication,STM32 and the host computer to achieve Ethernet communication.Then,the temperature signal conditioning circuit is designed,including the cold junction compensation circuit and amplifier circuit,and through the least squares nonlinear fitting method,the relationship between temperature and thermoelectric power is obtained,and the precision of cold junction compensation is improved.The design of the controller is based on the structure of the reduction furnace,the heat transfer process and the temperature change characteristics,and the mathematical model of the reduction furnace is determined.On the basis of the model,the reduction furnace has the characteristics of nonlinear,time-varying and time-delay,and adopts the dynamic matrix algorithm in predictive control.The simulation results show that the dynamic matrix control reduces the overshoot and overcomes the delay phenomenon and satisfies the requirement of temperature accuracy.