樹狀供應鏈網路下之二層級存貨整合機制

Abstract

在這個競爭激烈與快速變動的環境中，許多企業之間的競爭，不只是個別廠商之間的競爭，而是整體供應鏈之間的競爭，然而當供應鏈中各成員追求的目標不一致，形成供應鏈管理上之困難。在配銷系統中，供應鏈是由許多成員所組成，因此為滿足顧客準時交貨與相關服務水準要求，供應鏈中各成員必須透過適當的資訊分享達成協同合作，使所有成員朝共同目標努力，以提高整體供應鏈的績效。 本研究主要運用供應鏈系統層級存貨 (Echelon inventory)的概念於配銷體系之供應鏈中，以建構樹狀之供應鏈監控機制。本研究首先依據服務水準目標與層級存貨(Echelon inventory)之間的關係，在給定服務水準目標的情形之下建構最小化供應鏈二層級存貨模型；接著再利用各限制式之特性，發展求解一對二之二層級模式之演算法，並有效擴展為一對多之二層級模式的演算法。接著建立數值範例，以提出之演算法求解模式，並利用所得到之層級存貨上界作為監控指標，此外經由模擬驗證本研究所設定的層級存貨監督上界之有效性，最後透過實驗設計的方式，提出當環境改變時對整體存貨上界監控指標之影響。 經由模擬驗證以實驗設計的結果主要有下列結論： (1)本研究以層級存貨取代階段存貨作為監督上界，使整體供應鏈系統能夠在較低存貨量的情況下，得到較佳的服務水準。主要原因為系統中存貨配置之不同，以及利用整體的資訊來進行規劃所致。 (2)當系統中因時間差造成不同階段之成員之間的需求相關性不同時，存貨監控上界亦會改變，然而正相關越強時，整體存貨監控上界越高。 (3)當下游兩成員面對之外界需求函數有所差異時，會對整體存貨監控上界有顯著的影響。

Under drastic rivalry and rapid environmental changes, the competition is not only existed between individual enterprises, but extends further to their supply chain. However, if the members in a supply chain do not have the same goal and heads in different directions, the supply chain itself will be difficult to manage and results in poor performance. Under the distribution system, supply chain is composed of many members. In order to fulfill customer orders on time and meet customer service requirements, it is essential for all members to share their information and synchronize their operations. This research attempts to develop a monitoring scheme of a divergent distribution supply chain based on the concepts of echelon inventory. Initially, a two-echelon model is constructed with the goal of minimizing the entire echelon inventory up-to-level in a supply chain under the different service level requirements. Next, an algorithm for one wholesaler with two retailers’ model is developed to search the minimal echelon inventory up-to-level at each echelon by utilizing the character of constraints, and can be further extended to one wholesaler with multiple retailers’ model. With the findings of minimal echelon inventory up-to-level, our proposed monitoring scheme is validated through simulation study. Finally, the experimental design is utilized to analyze how the environmental changes affect the echelon inventory up-to-level. Based on the simulation validation and experimental design result, the conclusions are drawn as follows: (1) Compared to the traditional stage-based inventory monitoring scheme, our proposed echelon-based monitoring scheme can obtain a higher service level with the lower inventory up-to-level. The main reason is that our approach will effectively reallocate inventory up-to-level by utilizing overall information obtained from the entire supply chain. (2) The echelon inventory up-to-level would be changed whenever the correlation between demands faced by the members of the different stages changes. The echelon inventory up-to-level increases as the correlation becomes more positive. (3) The difference of demand nature faced by members in downstream has significant effect on the echelon inventory up-to-level.