Research On Steelmaking-Continuous Casting Production Scheduling Problem With Uncertain Processing Time Based On Lagrangian Framework

The uncertainty of processing time directly affects the rhythm of steelmaking-continuous casting production,disturbs the dynamic balance between logistics and time,and reduces the flexible matching of product structure and production capacity,which makes it difficult to ensure the enforceability of steelmaking-continuous casting production scheduling.How to formulate efficient steelmaking-continuous casting production scheduling optimization plan with uncertain processing time,which is the key to improve the large steel plant equipment production efficiency,shorten the waiting time of the process,reduce the material consumption and energy consumption.The traditional probability description method describes the uncertainty of processing time in steelmaking-continuous casting production scheduling based on the statistical distribution obeyed by known uncertain factors.However,for the relationship existing between unknown two adjacent processes,the traditional probability description method is difficult to describe accurately.On the basis of the deterministic solution space with fixed processing time,the uncertainty of the processing time parameter increases the different solution spaces corresponding to different processing times,which will make the scheduling solution space become larger.The existing methods are difficult to guarantee the quality of the solution for the steelmaking-continuous casting production scheduling problem with uncertain processing time and it is difficult to obtain an approximate optimization feasible solution that meets the actual production requirements in a short time.In view of the above difficulties,this paper takes the National Natural Science Foundation project "Research on the optimization method of steelmaking-continuous casting batch planning and production scheduling in uncertain environment"(61873174),"Research on scheduling method of steelmaking-continuous casting main and auxiliary equipment based on efficient Lagrangian relaxation iterative algorithm"(61503259),the steelmaking-continuous casting production scheduling problem with uncertain processing time under the Lagrangian framework is studied.The main work is as follows:Firstly,aiming at the analysis and description of the processing time uncertainty in the steelmaking-continuous casting production scheduling,the steelmaking-continuous casting production scheduling model suitable for the optimized uncertain processing time is developed,and the description method based on Markov chain is studied.It is used to accurately describe the randomness of uncertain processing time.Analyze the actual processing time data of actual steel mills and establish a Markov chain transfer matrix to accurately simulate the probability of uncertain processing time.Secondly,aiming at the inefficiency of traditional Lagrange relaxation algorithm in solving steelmaking-continuous casting production scheduling due to the exact solution of each iteration,an improved surrogate subgradient algorithm based on gradient direction controllable iterative optimization strategy without predicting the optimal value was designed.The improved improved surrogate subgradient algorithm overcomes the problem of sawtooth oscillation when the traditional surrogate subgradient algorithm searches within the feasible domain and improves the convergence speed of the algorithm under the premise of ensuring the quality of the algorithm,which is used to improve the efficiency of solving the steelmaking-continuous casting production scheduling problem.Finally,based on a large steel company in China the c#language compiler algorithm program was used for experimental simulation test.The experimental results show that the proposed method guarantees the solution quality and solution speed of the steelmaking-continuous casting production scheduling optimization problem with uncertain processing time,and has good feasibility and effectiveness.