起落架為飛機起降時，負責承載衝擊、支撐機身於地面滑行、以及提供起飛姿態的重要系統，隨著飛機飛行速度的提升，可收放式的起落架已然成為必要需求。本研究針對鼻輪起落架機構設計，提出一套完整的設計流程，並以F-104 D飛機作設計實例。首先，根據既有文獻與規範，歸納出起落架配置設計的流程，依序為配置形式、配置位置與收放方向，經由配置設計的結果並依據飛機規格，選用合適的構形，收放機構採用四連桿組類型、下鎖機構採用靜對構形，並決定以10桿13接頭連桿組為收放與下鎖機構，推導其位置方程式。接著，利用Matlab中內建的最佳化fmincon函式，選擇序列二次規劃法合成出上收位置佔最小面積的桿件尺寸，並訂定七項限制條件。其後，以向量迴路法與運動係數法作運動分析，利用牛頓運動定律作力分析，評估收放致動器所需的拉力來達成上收運動。由配置設計的結果並根據航空規範，選用合適的轉向機構為多連桿類型搭配旋轉輸入源，決定以4桿4接頭連桿組為轉向機構，並以5精確點合成出桿件的尺寸。再者，如收放與下鎖機構的方法作運動分析與力分析，求出鼻輪於靜態與動態時的最小輸入扭矩，評估出轉向致動器所需的扭矩來達成轉向運動。最後，建立3D模型作動態模擬，驗證了理論推導與程式碼的正確性，並確立本研究所提出的鼻輪起落架設計流程為可行的。

This work proposes a systematic approach for the mechanism design of the nose landing gear of an aircraft. The proposed method is elucidated using a military F-104 D jet fighter for illustration purposes. The method commences by designing the general layout of the landing gear system, including the wheel arrangement, the wheel position and the retraction direction, in accordance with the available literature and aviation regulations. Based on the results of the general layout design process, appropriate configurations of the retracting and down-lock mechanism and steering mechanism are determined. For the considered F-104 D aircraft, the retracting and down-lock mechanism is found to be a four-bar linkage with a stationary configuration. Meanwhile, the configuration of the steering mechanism is a multi-link mechanism with a rotary input source. For the retracting and down-lock mechanisms, dimensional synthesis is performed using a Sequential Quadratic Programming optimization method. For the steering mechanism, the Freudenstein’s equation is derived for the dimensional synthesis with 5 design points. Kinematic and force analyses are then performed using the Vector Loop method and Newton’s classical laws of motion, respectively. The results show that the maximum actuation force and torque for the designed retracting mechanism and steering mechanism are 3042 N and 2085 N∙m, respectively. The validity of the mathematical solutions is demonstrated by means of kinetic simulations performed using a 3D model. In general, the results confirm that the method proposed in this work provides a robust and effective method for the design and analysis of the nose landing gear mechanism in commercial and military aircrafts.

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