當撓性接頭在一定範圍的輸入角位移下，其輸出扭力不隨角位移而改變，使接頭之勁度幾乎為零時，我們稱此撓性接頭為定扭力接頭。此新型接頭目前尚未在任何文獻中被探討。本文之目標為發展具定扭力輸出之接頭機構，並將此機構應用於各式需扭力平衡之系統中。如裝置於人體之腳關節，可在蹲下時將位能儲存於定扭力機構中，同時平衡人體重量，起身時再藉由撓性體的彈性回復作用，達到省力的效果；或作為復健裝置，使患者的關節在活動角度範圍內，皆受到相同的阻力；透過兩個定扭力接頭互相平衡，可使接頭於旋轉區間處於一靜力平衡狀態，克服撓性機構之彈性回復行為，達到類似軸承之零勁度特性；將此機構應用於動態平衡，則能夠降低馬達在低速運轉時之轉速漣漪。本文首先提出各式定扭力機構構型，並採用形狀最佳化方法來設計定扭力接頭機構，接著分別以模擬及實驗驗證其性能，並探討不同材料對輸出定扭力特性的影響。相較於主動式扭力控制系統，使用被動式定扭力機構不需電源供應，亦不需使用感測器來做回授控制，其反應速度快，可提昇系統之可靠度，且具有結構簡單、製造容易及可微小化之優點，能廣泛的應用在各種尺寸之環境。

This research presents a type of functional joint mechanisms with constant-torque outputs. Unlike torsional springs the torque of which increase with increasing rotation, a constant-torque joint mechanism (CTM) provides a nearly constant torque during a specific rotation interval. Instead of using sensorized control, CTMs passively maintain a constant torque level. Potential applications include dynamic and static balancing of machines, human joint rehabilitative device, and human mobility assisting device. To meet practical needs, a CTM should have a large constant-torque region with sufficient flatness. We propose lumped compliance models and distributed compliance models as the two perspectives to design a CTM. For both models, design formulations are given with results discussed and compared. The prototypes of using the distributed compliance models are further verified by comparing with finite element methods. Effects of modeling, dimension, and material variations on the constant-torque properties are investigated. Guidelines are given to design CTMs of various sizes and torque magnitude. Illustrated experiments study the torque to rotation curves of using different materials. Their resistances to hysteresis and stress relaxation are compared. The proposed CTMs are further investigated in two applications: statically balancing joints and torque balancing mechanisms. Since the CTMs are compact, we expect them to fit various scales of applications that requires static or dynamic constant-torque outputs.

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