| Electroslag remelting(ESR),in the metallurgical industry,is an approach of secondary refining of steel.Since impurities such as sulfur and phosphorus are removed in the remelting process,the electroslag steel is of good quality and widely used.With the development of economy,there is an increasing demand for high-end steel.However,the control method of ESR system,currently,is still dominated by constant power or constant melting speed,and most control algorithm is still the traditional PID.Both the control method and effect are relatively old and not satisfied.With the advanced voltage swing control method,a list of contents is studied including the process modeling,the controller design,the controller optimization and the engineering realization.After that,an ESR control system based on the combined integrating system is designed.The main innovations of this paper are as follows:(1)A process model of ESR is analyzed and established.The model is mainly made up of three parts: the electrode driving model,the voltage swing model and the voltage swing detection model.The electrode driving model based on the reference characterizes by integrating feature.Besides,the voltage swing model simulates the voltage swing by multiplying the noise signal.Moreover,a voltage standard deviation calculation model is built based on the properties of the combined integrating object in order to describe the magnitude of the voltage swing.Compared with the traditional method of calculating the standard deviation by register,the model based on combined integrating helps not only analyze the system but design the controller also.(2)The combined integrating controller is applied to the ESR control system.An advanced combined integrating controller-dual combined integrating controller(CIC-DCIC)is designed to improve the control effect of the ESR process.In this paper,the cascade control structure is adopted for the established process model,which improves the stability and anti-interference ability of the control system.The dual-combined integrating controller(DCIC)is designed for the electrode driving model.The controller not only ensures fast response speed,but also solves the problem of steady-state error when there is disturbance behind the controller output.Finally,a combined integrating controller(CIC)is designed for the generalized controlled object that composed of the DCIC controller,the process model and the detection model.Compared with the traditional PID controller,the CIC-DCIC controller performs fast response and good robustness,which shows value in engineering application.(3)The CIC-DCIC controller is optimized.During the design of CIC-DCIC controller,model identification has to be applied to simplify the complex generalized controlled object model.The traditional least squares identification method needs to estimate the parameters of the pure lag link in advance,which results in inconvenience for parameter identification.In order to solve this problem,IA is used to identify the parameter and optimize the design of the CIC-DCIC controller.In the parameter identification based on the IA,the mean square error between the estimated model and the actual output is used to evaluate parameters.After multiple iterations,the optimal parameters are found.It is proved in the simulation experiments that the IA is able to accurately and effectively identify the parameters of the combined integrating object.(4)Based on the PLC,Simulink and HMI,an ESR simulation monitoring system is designed.A list of contents is studied including the basic steps of system engineering realization,the discretization of combined integrating controller,the configuration of data communication,control algorithm packaging in PLC,the construction of Simulink model and the design of HMI.The simulation system manages to configure the controller parameters,observe the response curve,and export the stored data.It helps to familiarize with the process flow of the control system and lays a foundation for the application of the control system. |
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