شبيه‌سازي زنجيره‌ي تامين چندسطحي تحت سيستم به‌هنگام، و بهينه‌سازي اهداف آن

SIMULATION OF JIT MULTISTAGE SUPPLY CHAIN AND OPTIMIZATION OF OBJECTIVES

تعيين سطح موجودي‌ها در طول زنجيره‌ي تامين، به‌منظور نيل به اهداف متنوع زنجيره ــ نظير رسيدن به سطح مطلوب پاسخ‌گويي و كارايي ــ كاري دشوار به نظر مي‌رسد. شبيه‌سازي ابزاري است براي حل مسايل پيچيده‌يي كه مدل‌هاي رياضي قادر به حل آن‌ها نيستند. در اين نوشتار زنجيره‌ي تامين با الگوي توليد به‌هنگام و تركيب شبيه‌سازي با بهينه‌يابي متغيرهاي زنجيره مدل‌ مي‌شود. متغيرهاي مدل شبيه‌سازي زنجيره‌ي تامين عبارت است از: مقادير دو نوع كانبان كششي و توليدي براي تعيين سطح موجودي زنجيره، و ميزان سايز دسته براي هر مرحله از زنجيره‌ي تامين. با استفاده از تكنيك فراابتكاري، مقادير اين متغيرها چنان تعيين مي‌شوند كه اهدافي مانند كاهش ديركرد در تحويل سفارشات و كاهش سطح موجودي در زنجيره‌ي تامين، به سمت بهينه‌شدن سوق داده مي‌شوند.

It is difficult to determine an inventory level all through a supply chain (SC), in such a way that the desired objectives, such as effectiveness and responsiveness, can be obtained. Simulation is a means of solving problems which cannot be solved by mathematical models, due to the complexity of the problems. Managers are, on the one hand, engaged in the strategic decision making of the chain, as well as various kinds of cooperation among members, and, on the other hand, with the quantities of inventory all through the chain. Strategies of each member of the supply chain and/or the whole supply chain can be based on meeting the needs (such as short-time delivery, producing new products, high level of availability of products, and so on) or effectiveness of the SC (low price of products, decreasing costs, and effectively using capital). Determining the level of inventory along a supply chain, in such a way that consumer satisfaction will be met to a favorable degree, taking into consideration responsiveness or effectiveness, is difficult. The present research is intended to study the inventory of a supply chain, as well as modeling the supply chain and determining multiple objectives in models for a four-stage, single-product supply chain. The use of metaheuristic techniques leads to optimization of these variables, which helps decrease delay in both product delivery and inventory levels of SC. The present paper is aimed at JIT supply chain simulation together with optimization of the objectives of the SC. Variables of the simulation model include two types of Kanbans, namely; withdrawal and production, to determine the inventory level of SC and the batch size of delivery parts for each stage of the supply chain. Using metaheuristic techniques leads to optimization of these variables towards decreasing delay in the delivery and inventory levels of SC.