近幾年來，許多工廠都使用U型生產線取代傳統直線型生產線。在此型態下，系統中加入了多能工和及時(Just In Time)生產的概念，讓管理者可藉由靈活調度生產線上作業員的方式，迅速回應市場需求。因此，相較於傳統直線型生產線，U型生產線不但可以縮減人力也使得生產線更具有彈性。此外，由於過去學者們較少探討多個目標下之生產線平衡問題，以及為適應需求變動的環境和少量多樣的生產方式，本研究將考慮在多個目標下， 於一條U型生產線上生產多種產品的生產線平衡問題。
再者，由於過去學者曾經指出針對生產線平衡問題，若同時考量多個決策目標來衡量生產線平衡之績效，將更能符合實際生產情況。所以本研究將同時考量最小化工作站數目和生產週期時間之誤差值，利用目標規劃演算法可同時處理多個決策目標之特性，先針對每一個決策目標建立一個目標值，再利用數學規劃軟體求解，令每一個決策目標與目標值之誤差(deviation)總和最小。以期當生產線上發生一些決策目標互相衝突時，能提供管理者參考以適時做出最理想的決策。

In recent years, a lot of factories use U-shape assembly line instead of traditional straight assembly line for their manufacturing processes. In this situation, operators are multi-skilled to perform most of the operations. The managers can use this kind of U-line layout to respond the market’s demand quickly, dispatch operators flexibly. Thus, the number of workstations required on a U-line is less than a traditional line did. In the past, researchers didn’t discuss the multi-objective line balancing problems. To adapt the enterprises to a variety of production environment, in this thesis, we study the multi-objective model for U-line balancing problems.
Minimizing the deviation value of the cycle time and the number of workstations are studied in this research. Also a goal programming model is implemented to solve this problem. In fact, we judge a target value for each different goal first and the satisfactory solution is found by using the mathematic software subsequently. In goal programming, minimizing the deviational variables and reaching goals as close as possible are achieved simultaneously.

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