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Research on machine tool equipment selection based on FMS unified model framework

Abstract An Object-Oriented FMS unified model framework is proposed. Under this unified model framework, the sub problems of FMS will be solved in a way of correlation and integration The modeling and solution method of FMS machine tool equipment selection problem under the above unified model framework is studied

keyword FMS; Object oriented modeling; Machine tool selection

1. Object-oriented FMS unified model framework

in the design and operation of FMS, the following three aspects are mainly concerned, namely, physical equipment, part information and system activity information According to object-oriented domain analysis, the following three types of FMS objects can be abstracted: physical objects, information objects and control/decision objects

the above three types of objects do not exist in isolation in the FMS life cycle, and they are closely linked to form an inseparable whole. Therefore, FMS must be comprehensively and integrally described and modeled [2] In the model framework of document [2], the interrelated physical objects are mainly described On the one hand, because they are the basic resource objects of FMS, they are essential to the construction of the whole system model; On the other hand, these physical equipment objects are the main object classes involved in FMS design The machine tool selection problem in FMS design can be regarded as an operation of FMS unit object. The FMS unit object receives the machine tool equipment selection message sent from the workshop object, starts the machine tool selection model and solution algorithm encapsulated in the unit object, and transmits messages between machine tools, parts, part spectrum and other objects After selecting the machine tool, a new instance of the machine tool object is created, and the status and relevant attribute values of the FMS unit object are modified or updated

the object-oriented FMS unified model framework has the following characteristics: a. the model provides a coherent unified modeling framework for the research and solution of various sub problems in the FMS life cycle, so that these sub problems can be solved in an interrelated, integrated and dynamic way; b. Due to the great flexibility of the object-oriented method itself, the model is easy to realize the reconstruction of the object layer. At the same time, it can easily introduce new attributes and new operations into the existing objects. Using the encapsulation of objects, various advanced technologies to solve FMS specific problems can be added to the relevant objects in the form of object operations; c. The solution of FMS specific problems is only related to the specific object classes in the model, and not all object classes participate in the solution process of a certain problem, thus reducing the complexity of the model in implementation 2. Machine tool equipment selection under low pressure and large flow conditions based on the unified model framework

2 Or 5.0kn/s 1 machine tool selection problem description

the task of machine tool equipment selection in FMS design is to select the appropriate type of machine tool equipment and determine its quantity among the candidate machine tool equipment according to the requirements of part types, process procedures, production batches, cost budgets, etc. in the part spectrum In order to facilitate the construction of machine tool equipment selection model, the following symbols are introduced: P is the number of part types in the part spectrum, M is the total number of process types in the part spectrum, n is the total number of machine tool types required to complete the processing of the part spectrum, Ni is the total number of process OI in the part spectrum, MI is the number of part PI in the part spectrum, CIJ is the cost (time) required to complete the process oi on the machine tool MJ, TMJ is the available time of the machine tool MJ in a certain time domain, CMJ is the purchase cost of machine tool MJ, CB is the total budget available, Xij is the decision variable, that is, completing oi on MJ can make the graph display the number of processes with the best scale, UJ is the decision variable, that is, the number of machine tool MJ

in order to minimize the sum of the process cost of completing Part spectrum processing and the purchase cost of machine tools and equipment, the following mathematical model can be established [3]: where W0 is the weighting coefficient of process cost; WM is the weighted coefficient of machine tool purchase cost The constraints of the above model are: (1)

(2)

(3)

xij ≥ 0, integer, UJ ≥ 0, integer, (4) constraints (1) ensure that the complete aluminum body pure electric bus is provided by Shanghai Shenwo Bus Co., Ltd; Constraint (2) ensure that the processing time of the machine tool does not exceed its available time; Constraint (3) guarantee budget; Constraints (4) ensure that the decision variables are nonnegative and integer

the above model is an integer programming model, but due to many decision variables, it is difficult to solve it with standard integer programming algorithm Next, a heuristic algorithm is proposed to solve the above model, and the final solution is the near optimal solution 2.2 heuristic algorithm

2.2.1 establish the "process machine tool" cost (time) matrix [CIJ] according to the part spectrum process

"process machine tool" cost matrix [CIJ] is an m-row n-column (M × n) In the matrix, the "process" is the list of all m processes in the part spectrum, "machine tool" is the list of all n-class candidate machine tools required to complete these processes, [CIJ] reflects the processing capacity of all these machine tools and equipment. Each element AIJ in the matrix represents the processes that can be completed on each type of machine tool and the cost (hours) required to complete these processes

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