Control System Design And Research On Control Method For Directly Heating Annealing Of Steel Bars

In recent years, the material production heat treatment technology of line, bars develops very fast. The applications up to industry, energy, electric power, aerospace, etc, down to household modeling is more and more wide. So the requirement is also more and more high. It needs further processing to improve line, bar performance by heat treatment. Moreover, along with the enhancement of people’s consciousness in environment protection. It puts forward higher requirements to save energy and reduce pollution as well. Heat treatment furnace for indirectly heating furnace, usually have the features of large lag, and waste of energy. So this thesis uses the direct heating of bars by electric. In this thesis, it develops a computer control system and studies on temperature control method taking an alloy factory actual project as the background.The control system adopts a two-level control system with PC upper computer at the management level and PLC at the process-control level. PC utilizes industrial control computer that it uses WinCC to configure the software programming and PLC to implement the main control function. PLC chooses Siemens S7-300 series production with the core unit of S7 314C PN/DP CPU.This thesis’s theoretical deduction is studied from perspective of the physical laws of each link when researching on the control method for direct heating annealing of bars. It is concluded that controlled object possesses the characteristics of nonlinear, time-varying and moreover because of the steel bar is out of the physical properties of uniform, such as resistivity. It’s unable to establish accurate mathematical model. So the qualitative analysis is used to simplify and to get the transfer function of the object. Because of the characteristics like time-varying, inaccurate model and process requirement, the control system of annealing temperature controlling uses hybrid fuzzy PI controller. The controller combines the advantages of fuzzy control and PI control. Thinking heating speed and accuracy, it can realize uniform heating in heating period, no static error in heat preservation period to improve the performance of steel bar. This thesis provides guidance for the future design of similar system.