Modeling And Sliding Mode Control Of Cement Raw Material Vertical Mill

As an important building material in China,cement has been used in construction,water conservancy,road engineering and other fields.After decades development,China’s cement industry has experienced several stages of technology introduction,digestion and absorption,and independent innovation,and its production technology,equipment,automation and information technology have been greatly improved.As a new type equipment for cement raw meal grinding,vertical mill has gradually replaced the previous ball mill and been successfully used at home and abroad with its advantages of high production efficiency,clean operating environment and low noise.There are many uncertain factors in the grinding process,and the lag is obvious due to the long production process,which will affect the stable operation of the grinding process,and then will lead to a large fluctuation in the output and quality of raw cement.Therefore,with the goal of green development and intelligent manufacturing,this paper breaks through the key technology of "neck sticking" in the automation of cement raw meal grinding industry,and focuses on the research of modeling and sliding mode control method of cement raw meal vertical mill,providing theoretical support for its intelligent production.The main contents of this paper are as follows:In order to accurately describe the dynamic process of cement raw meal grinding,this paper analyzes the vertical grinding process of cement raw meal firstly,and determines the key process parameters and control variables in the grinding process.Secondly,based on the field historical data,the moving average filter is used to filter the data,and then the least square method and neural network algorithm are used to fit the data,the rationality of data fitting is verified by simulation.Then,considering the heteroscedasticity of the least square method,the weighted least square method is given to establish the dynamic model of cement raw meal vertical mill.The simulation results show that the fitting effect of the method is better than the least square method,and the standard deviation of the fitting data is reduced to 0.2176.In view of the control problem of the cement raw material vertical mill,based on the theory of sliding mode control,the main process parameters of cement raw material vertical mill can be tracked accurately.Firstly,according to the fitted dynamic relationship of cement vertical mill grinding,the linear sliding mode controller is designed and its stability is proved,the simulation results show the effectiveness of the controller design.In order to improve the dynamic tracking performance of the sliding mode controller further,a nonsingular terminal sliding mode controller for cement raw meal grinding is designed.Due to the introduction of the nonlinear term,the tracking time to the desired command is greatly reduced,but at the same time,due to the acceleration of the convergence speed,the chattering during the convergence is more obvious.In order to reduce the chattering problem of the nonsingular terminal sliding mode controller caused by the too fast convergence speed,the integral term is introduced into the nonsingular terminal sliding mode controller to eliminate the steady-state chattering.It is proved by arrival conditions of inequality type that the nonsingular terminal sliding mode controller of cement raw meal grinding with the integral term can track the desired command in a finite time,and the convergence time to the stable state is given.Considering the uncertain factors in the process of cement raw meal grinding,the nonlinear disturbance observer is used to estimate the unknown compound disturbance.Then,a linear sliding mode controller with integral term is designed to track the desired instruction.The corresponding stability proof is given.Finally,the simulation results show that the sliding mode controller with disturbance observer can track the expected instruction accurately.