Research Of The Aluminum Cast Rolling Former Tank’s Liquid Level Control Technology

In order to ensure the aluminum cast rolling can be carried out sustained and stable, it is necessary to control the aluminum liquid flowing into and out of the cast rolling area in the equilibrium state, that is to say to make the liquid in the former tank at a certain level. With the domestic aluminum plate industry moving in the direction of high speed casting rolling, wider and thinner, higher automation degree of aluminum cast rolling production line, therefore, higher requirement of the technology level and automation degree of aluminum cast rolling production line are put forward, higher requirement for the control accuracy of the former tank’s liquid level is also put forward.Based on aluminum cast rolling production line of Aluminum Inc in Zhengzhou, the aluminum cast rolling former tank’s level control system is studied.The aluminum liquid flow between launder and former tank, and the former tank liquid level control system are mastered by the analysis of aluminum cast rolling process. The equivalent double capacity liquid tank mathematic model of the launder and former tank is established by the analysis of former tank level control system’s characteristics and working principle, and the transfer function is obtained. According to the characteristics of large inertia and multi-disturbance, the traditional PID control and parameter self-adjusting fuzzy PID control are put forward, their control effects are compared by modeling and simulation on Matlab/Simulink, which provides a theoretical basis for the selection of the system control strategy.Based on the analysis of the design requirements and difficulties of the former tank level control system, the overall design scheme is presented which uses HMI and PLC as the control core, laser sensor measures the distance and the servo motor as the executing agency. The main function of the PLC is controlling the motion of servo motor, PLC ladder programs are written at the idea of modular programming, which include manual/automatic switch control program, cooling equipment startup program, alarm starting program and so on. HMI’s functions include collection of actual distance, displaying of the distance error, switch state and motion simulation, and delivering the result of the incremental PID control calculation to the PLC.Finally, liquid tank test platform is build to simulate the liquid flow between the launder and former tank, and the control of the adjustment valve. The real distance and distance deviation are recorded and analysis. The rationality and reliability of the designed former tank level control system are verified by experiment and data. Practice shows that the system has a good level control precision, high degree of automation, improves the quality of aluminum plate and has a good practical value.