Optimal Control Of Electrode Current In Electrical Smelting Furnace For Magnesia

Fused magnesia,whose other name is MgO,is an important oxide of magnesium.Normally,it is produced by using magnetite as the main raw material,and it can be obtained with the application of electric melting furnace of magnesia using three-phase alternating currents.It has the characteristics of high purity,high melting point,antioxidantion,completely structure,strongly insulation and so on.And fused magnesia is mainly used to produce refractory materials containing magnesia.In the process of smelting,the optimal tracking of smelting currents in the electric smelting furnace is usually obtained by using constant current control method.But,due to the complexity of smelting conditions,the changes of raw material in production,the serious fluctuations of three-phase current,and the time delay exists in the rotor of AC asynchronous motor and so on,so the smelting current cannot track the setting current in the production,In this thesis,the authors mainly discussed two problems influencing tracking effects of smelting currents in electric smelting furnace,the tracking optimal control problem of limited electrode current,and the tracking optimal control problem of time delay of the motor's speed.The tracking optimal problem of limited electrode current.In other words,it is the problem whether the actual current can change within a given range in the smelting process.The problem can be defined as a nonlinear dynamic optimization problem whose output has limits.In this thesis,Firstly,with the application of integral method,the above problem is transferred into a dynamic optimization problem which can be solved by sequential method;Secondly,quadratic programming method of sequential method is used to obtain the optimal value of motor 's speed for AC asynchronous motor;Finally,it is validated that the three-phase currents can be changed with a given range in the smelting process of electric smelting furnace,and the smelting grade of fused magnesia is improved effectively.The tracking optimal problem of time delay of the motor 's speed,in other words,it can be explained as follows:when the smelting current deviates from the given value,it needs to realize the changes of electrode's position.According to the position and negative rotation of AC asynchronous motor,so the actual smelting current can track the given value of current.Meanwhile,it is also an optimal tracking problem whose input has time delay.In this thesis,the optimal track problem was changed to the problem of optimal state regulator,with the application of a state transfer representation,the linear state-space representation whose input has time delay can be transferred into a linear state-space representation whose input does not has time delay,and the method without time delay can be applied to solve the problems which has time delay.Once upon a time,the relevant controller was mainly designed by using the state variable without time delay after the conversion.In this article,the controller is designed with the state variable with time delay,and an explicit expression of the controller can be calculated.In the end,a relevant simulation is used to verify the practicality of this calculation,and the smelting grade of fused magnesia has been improved.