鎖具作為歷史上存在已久的機構，其形態與結構會隨著時間與地點有著截然不同的形式，但其防範他人隨意打開的目的卻從未改變。隨著鎖具功能增加，其結構隨著時間推進也逐步趨於複雜，同一個操作往往會隨著當下某些部件位置的不同而有著截然不同的結果，其內部結構與運動方式會隨時間與當下整體狀態的變化有著不同形式，造就其為典型的多狀態機構。而隨著功能與對應的操作增加時，可能出現的整體狀態與可同時作動的輸入選項也隨之增加。在設計時若在功能需求未完善定義時就直接由進行實體機構生成，就有可能因為考慮不周而產生的功能間的衝突，甚至是造成最終生成的機構在功能上與原需求不一致的情況，如一開始未考慮清楚，這些問題會到實體設計後才被發現。針對此問題，本研究建立一套以功能需求為起點的多狀態鎖具機構設計方法，在具體機構形成以前先整理並檢查功能邏輯，再將確認後的結果帶入後續實體機構設計。
本研究先將設計需求整理，整理其在機構外部且可辨識的實體部件，如門把、鑰匙等，定義為Required Component（RC），從中辨識這些部件狀態會影響功能或禁止條件的情況，由此分離出其條件C與條件變換時所代表實現的作動功能T，並以Petri Net進行作動與禁止作動的形式化描述，以此建立該機構的功能模型problem Petri Net。初始模型完成後，就可以藉由Petri Net的特性來對功能描述的完備性與正確性進行分析，並利用分析結果找出缺少或表示不完整的功能關係，最終進行功能描述邏輯上的補足，以此完成機構在功能描述上的完備。接著就可以將其轉換成整體機構的整體狀態轉換圖，以此解決初步構想時人類設計者可能無法做出的完善描述，並利用其作為有向圖的連通與分離上的特性進行功能間的關係比對，以此依照功能關係有無與強弱進行功能模組的分類與建立。最後就可以依此與相關參數設定進行結合，具體化出所需之具機構結構，並對其進行模組整合與檢驗。
在設計流程完成後，本研究利用三個案例：古中國鎖具、魯班鎖與現代榫眼鎖證實本研究方法的可行性。第一個案例從初始模型的可達行為中找出尚未完整描述的必要操作，並經功能補足後完成後續設計；第二個案例以高度受部件狀態限制的操作為主，確認Petri Net能表示各部件必須依特定順序解除阻擋的行為；第三個案例則包含較多個操作上的可選性及彼此耦合的功能，用來分析多項功能放入同一個模型後的部件狀態變化、功能關係與後續整合。三大案例都證實了本研究方法的可行性，最終成功由功能定義逐步設計成實體機構。整套流程使功能需求、驗證後的功能行為、功能關係分析與最後的實體構型保有對應關係，但其中構件配置等細節仍需由設計者依照自身當下的條件來決定。

Locks have existed for a long time and have taken very different forms in different periods and places, but their purpose has always been to prevent unauthorized opening. As more functions are added, lock mechanisms become more complex. The same operation may produce different results when certain components are in different positions. As the operation proceeds and the overall state changes, the internal arrangement and motion of the mechanism may also change. This state-dependent behavior makes locks typical multi-state mechanisms. Adding more functions and corresponding operations increases the number of possible overall states and the input choices that may be available at the same time. If physical mechanism design begins before the functional requirements are fully defined, some functional relations may be overlooked, causing conflicts between functions or a final mechanism that does not behave as originally required. These problems may not become clear until the physical design has already progressed. The method developed in this study starts from the functional requirements, with the functional logic organized and checked before the physical mechanism is developed. The confirmed results are then carried into the physical design.
Design requirements are first organized around identifiable physical components outside the mechanism, such as handles and keys. These components are defined as Required Components (RCs), and their states are examined according to how they affect the required functions or prohibited operations. This identifies the distinguishable conditions C of each RC and the functional transitions T associated with changes between those conditions. The resulting operations and prohibitions are described in a Petri Net to form the problem Petri Net. Once the initial model is available, Petri Net analysis is used to find missing or incomplete functional relations and complete the functional description. The completed model is converted into an overall state transition graph. The graph lays out overall states that may be difficult for a designer to describe completely during early design. Comparing connectivity and separation in the graph shows how the functions are related. Whether these relations exist and how strong they are determines the functional module grouping. The functional modules are used together with the relevant design parameters to develop the physical mechanism and carry out module integration and checking.
After the design procedure was completed, three cases were used to verify the feasibility of the method: an ancient Chinese lock, a Burr lock, and a modern mortise lock. In the first case, the reachable behavior of the initial model revealed necessary operations that had not been fully described, and the remaining design was completed after these functions were added. The second case focused on operations that were highly constrained by component states and confirmed that the Petri Net could represent the behavior in which the components had to be released in a specific order. The third case included more operation choices and more coupled functions. When several functions were included in the same model, changes in component states, functional relations, and subsequent integration were analyzed. All three cases verified the feasibility of the method and were developed step by step from functional definition to a physical mechanism. Throughout the process, the functional requirements, verified functional behavior, functional relation analysis, and final physical configuration kept their correspondence, while details such as the component arrangement were still determined by the designer according to the actual design conditions.

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