Research On Integrated Scheduling Of Process Tree Cycle Decomposition

Different from the flow shop and job shop scheduling problems in traditional industry,integrated scheduling is a scheduling that processes the product processing and assembly synchronously in multi variety and small batch products with complex tree structure.In the existing "process" as the optimization object of research,the path to study the main line,such as the long path,critical path,the path of tailgating,timing,etc.,but with long path or quasi series algorithm of critical path as the main line,if the same leaf node equipment appear short path began early processes,the scheduling policy will be invalid if it is applied for the first time.In a series of algorithms with closely linked paths as the main line,if the two processes on the non-closely linked paths are leaf node operations,the "short time" scheduling strategy will be invalid.In a series of algorithms based on the time selection path of subsequent procedures,only when a certain procedure group is scheduled,the subsequent procedure group can start processing,so the processes in the processes group will form an unusable machining gap in the already scheduled processes sequence.Therefore,the compactness of continuous processing between processes can be further improved in the existing algorithms which take the process path as the research angle.At the same time,in the related research with "equipment" as the optimization object,whether the key equipment is taken as the main line of the research or the equipment driver is taken as the main line of the research,the equipment with more processing processes will form many processing gaps between the process sequence,so the strength of integrated scheduling parallel processing can also be further improved.In view of the problems that can further improve the compactness of process continuous processing and parallel processing in the current integrated scheduling,this paper proposes an optimization algorithm and establishes an algorithm model from the perspective of structural characteristics,scheduling units and special equipment of general complex product integrated scheduling.Then the research results are extended and applied to resource-symmetric two-shop distributed integrated scheduling.The specific research content is divided into the following four parts:1.In the general complex product scheduling problem,an algorithm considering hierarchical scheduling order was proposed to solve the complex product scheduling problem with a large number of processes in the same layer in tree process.Based on the priority and short time scheduling strategies,a leaf node scheduling strategy is proposed.The idle time of equipment can be effectively reduced by priority scheduling of leaf node processes that are not constrained by previous processes,which not only improves the tightness of longitudinal processing between processes,but also realizes the parallel optimization of horizontal processes.Experimental results show that the proposed algorithm is better than the latest algorithms in the same research field.At the same time,the petri net is used to simulate the actual scheduling process of the factory,and the feasibility and effectiveness of the algorithm are verified by practical simulation.2.In the general complex product scheduling problem,an algorithm of process tree subtree cyclic decomposition was proposed from the perspective of scheduling unit in product processing.Firstly,a subtree cyclic decomposition strategy is proposed and a subtree scheduling unit is established.Secondly,the process adjustment strategy is proposed to effectively solve the conflict problem of the process sequence.Finally,a processes constraint relationship audit strategy is proposed to ensure the processes constraint relationship strictly in the scheduling process.Compared with the latest research results of scheduling unit based on "process group" and "process string",the optimization effect of the proposed algorithm is better.3.In order to expand the diversity of special equipment in the general complex product scheduling problem,a scheduling algorithm considering the weight of multiprocess equipment is proposed.The algorithm defines a new special equipment in the integrated scheduling: multi-process equipment.On the basis of this,the definition of equipment priority and process constraint degree was proposed.Taking multiprocess equipment as the research object,the total processing time of complex products was reduced by making full use of machining gap between processes on multi-process equipment.Compared with the latest algorithm for "critical equipment",the optimization effect of the proposed algorithm is better.4.Based on the above optimization algorithm model,a two-shop scheduling algorithm based on process tree cyclic decomposition is proposed for resourcesymmetric distributed integrated scheduling problem.The related influencing factors in the integrated scheduling were considered comprehensively,such as the overall structure of the process tree,the attributes of the processes themselves,the constraint relations between the processes and the transport conditions of special equipment,etc.,and the workshop scheduling scheme based on subtree cyclic decomposition and the process allocation scheme based on the principle of workshop process balance were proposed.The proposed algorithm achieves the optimization effect of shorter production time,fewer process migration times and higher average utilization rate of workshop equipment for resource-symmetric two-shop integrated scheduling.Compared with other existing resource-symmetric two-shop scheduling algorithms,the proposed algorithm has better scheduling performance.