Research On Integrated Scheduling Algorithm Of Two Workshops With Flexible Processing Machines

In the traditional manufacturing process,we always put the product processing and assembling as two sparate stages,and the focus of the problem is mainly for batch processing of parts.With the increase of the demand for social diversification,the order of multi-variety and small batch increases gradually.In this demand environment,a new production scheduling mode is needed to meet the needs of people's customized products.In this way,the integrated scheduling problem came into being,it regards the product processing and assembly process as the processing process,and it maps the complex product to virtual processing tree.Since the sequential constraints and assembly constraints between processes are considered at the same time,the integrated scheduling has important research significance and practical application value in shortening the product manufacturing cycle time and improving the efficiency of the production system.After years of development,the research on the problem of integrated scheduling has been developed from the production environment of the single plant to the distributed production environment.The focus of the research at this stage is mainly to solve the problem of integrated scheduling between the two workshops and has achieved good research results.However,the previous two workshops integrated scheduling research literatures only consider the complex products being processed in the general machines.And with the development of the processing technology and the automation technology,the production system which more flexible like the flexible manufacturing systems and CNC machining center plays an increasingly importment role in the actual production,the flexible job shop scheduling problem is more consistent with the actual production problem.So in this paper,we mainly study the problem of integrated scheduling with flexible machines.Aiming at the problem of complex product scheduling in flexible processingmachines of the two workshops,firstly,this paper proposes the integrated flexible scheduling algorithm of two workshops based on the earliest start time.In this algorithm,the earliest start time strategy,the fastest processing speed strategy and the long path strategy are proposed.In each iteration process,it determines the scheduling process,the processing workshop and processing machine,as well as the start time of the process in the same time.The example shows the algorithm can solve the problem of complex procuct scheduling int the two workshops with flexible machines.secondly due to the greedy algorithm does not necessarily always produce good solution of the problem,then,the integrated flexible scheduling algorithm of two workshops based on the beam search is proposed in this paper.It adopts the beam search algorithm framework,and uses the above strategies as the local selection strategy.In order to limit the number of the children nodes,the filtering rules is proposed.Also the global evaluation strategy is proposed to keep the single child node for each parent node.Therefore,it can be regarded as an extension of the integrated flexible scheduling algorithm of two workshops based on the earliest start time.The algorithm complexity analysis and example show that the proposed algorithm can optimize the scheduling results under the condition of increasing complexity.Finally,the integrated flexible scheduling algorithm of two workshops based on buffer-process early migration is proposed.It uses the parent long-path priority strategy,the long-time strategy and the available machine less strategy to determine the scheduling sequence.In order to determine the processing workshop and the processing machine,the leaf-node process selection strategy,the buffer-process early migration strategy and the common processing strategy are proposed.In the end,it uses the forward greedy strategy,combined with the product process constraints,migration time constraints and machine occupied constraints to determine the start time of each process.The result shows that the algorithm can realize the integrated scheduling of products in the two workshops with flexible processing machines in a lower complexity.