類別:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/36
2024-03-29T13:35:37Z齒輪機構之運動特徵分析與合成
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/24895
標題: 齒輪機構之運動特徵分析與合成; Kinematic Characteristics and Synthesis of Geared Mechanisms Using the Concept of Kinematic Fractionation
作者: Yu-Ching Yeh; 葉又菁
摘要: 本論文主要利用運動分解的概念進行齒輪機構運動的特徵分析與合成,以及經由運動特徵進行齒輪機構的分類。齒輪機構可被分解為數個單自由度的運動單元,每個運動單元則被視為齒輪機構內的運動傳輸模組。運動單元間的拓樸構造連接可分為雙鏈結型與同軸三角型,內文將分析內含四個運動單元,單自由度至六桿,以及兩個自由度至七桿的齒輪機構,並且說明及表列其對應的拓樸構造;藉由選擇輸入與輸出端的位置,可得到齒輪機構內所有可能的運動傳輸路徑並將路徑以控制區塊圖表示。利用控制區塊的增益計算公式,將輸入端與輸出端的運動關係公式化為增益矩陣。
接著進一步討論運動單元內部條件對整體運動增益的影響;運動單元內輸出入桿件的不同及運動單元間的共同連接部分的接頭條件會共同影響整體增益的表現形式,利用增益表現形式的差異可將內含四個運動單元,單自由度至六桿,以及兩個自由度至七桿的齒輪機構做完整分類,根據增益型式分類及運動特徵可得到功能導向之齒輪設計方法。; A methodology based on the concept of kinematic fractionation for the revelation of kinematic characteristics and classification of geared mechanisms is presented. It is shown that structurally non-fractionated geared mechanisms can be considered as the combination of kinematic units (KUs). Each KU is considered as the basic motion transmission module inside a geared mechanism. Admissible connections of KUs are identified according to the structural characteristics of one- and two-DOF geared mechanisms of up to four KUs. Such configurations are then used to construct possible propagation paths of motion via the assignments of input and output links. Since the propagation paths can be modeled by the control block diagram problems, the kinematic relations between input and output links are formulated to gain matrices. According to the types of entities in a gain matrix, various kinematic behaviors are disclosed. The complete kinematic behavior of single KU is revealed and three gain forms of KU is basic of global gain since the geared mechanism is combination of KUs. The global gain of the mechanism is determined by three factors: the configuration decides the transmission flow at KU level, the common linkage between KUs of the mechanism limit the thin edge type of local input and output in the connection of KUs, the assignment of input, ground and output decides the thin edge type of global input and output. From the factor of global gain, there are three gain type are identified and characteristics of geared mechanism are more clear. It is believed that such kinematic characteristics can be readily transformed into the functional requirements and synthesis of geared mechanisms of up to four KUs can be accomplished much easier.2007-01-01T00:00:00Z黃銅線及鍍鋅線應用於線切割之性能研究
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/46934
標題: 黃銅線及鍍鋅線應用於線切割之性能研究; A Study on the Performance of Brass and Zinc-Coated Wire Electrodes in WEDM
作者: Yu-Ju Lee; 李育儒
摘要: 線切割加工能使用的線電極種類繁多,但線電極對加工性能的影響過去未見討論。本研究欲探討線電極對加工特性之影響,以提供未來線電極設計之參考。文中使用鍍鋅線與黃銅線,進行不同加工道次切割數種厚度的SKD-11材料。結果顯示鍍鋅線不僅在面切割速度上優於黃銅線,在工件上也呈現更好的形狀精度以及更優異的表面粗糙度。導致此差異的原因可歸納為三大基本因素,分別為熱、電與汽化的性質。研究中針對鍍鋅線與黃銅線在熱、電與汽化相關等特性設計實驗,整合實驗結果可發現使用鍍鋅線做為線電極材料,其表面的多孔結構可增加線電極與加工液接觸的面積,協助熱量的排除,並因為鍍鋅線有較低的熔點與沸點,因此較容易發生汽化帶走熱量,而具有較佳的熱量排除機制;另外由於鍍鋅線有較低的電子親合能,在放電加工過程中會產生較大的放電間隙,配合上鍍鋅線的低沸點與高飽和蒸氣壓,於加工中產生大量氣體,使放電渣較容易排除,而達到較佳的清洗性。最後本研究歸納了各種在放電加工上影響線電極效果之因素,建議如欲改善黃銅線之加工效能,可將黃銅線的表面改成多孔結構,以協助熱量排除;如欲發展新線種,可設計多層不同材質的線電極,例如最內層選用鉬或鎢等高剛性、高熔點材料,中間層則選用導電性良好的黃銅或純銅,最外層則鍍上一層鋅,此種新型電極應可滿足線電極的所有需求。預期有極佳的剛性、優異的導電率、優良的熱量排除機制以及良好的清洗性。; Many kinds of wire electrodes were used on wire electric discharge machining (WEDM), but the research of the wire electrode has few been discussed. In this study, the impact of wire electrode will be discussed, in order to be the reference of design the wire electrode in the future. In the article, brass wire and zinc-coated brass wire were used as electrodes in WEDM. Experiments were conducted with different workpiece thicknesses and different cutting processes. And material SKD-11 was used as the workpiece. According to the experimental result, zinc-coated brass wire is not only good at machining speed but also can form good shape accuracy and good surface roughness. It could be concluded that the three basic elements like heat, electric and evaporation were the main factors. This study focused on these three basic physical properties of zinc-coated brass wire and brass wire, and also designed and conducted the experiments with the characteristics of heat, electric and evaporation. It is discovered that there are some micro holes on the surface of zinc-coated brass wire while it is used as an electrode. Hence, the contact area between the fluid and the wire electrode will increase and that will lead to a better heat removal, being easy to evaporate and a better cooling mechanism because of the lower melting point and boiling point of zinc-coated brass wire. Moreover, the lower electron affinity of zinc-coated brass wire would lead to the larger gap distance during WEDM process. And with the characteristics of lower boiling point and induced higher saturated vapor pressure, zinc-coated brass wire can produce much more vapor resulting that the discharge debris could be easily eliminated to achieve the better flush-ability. At last, this study has figured out all the factors which can influence the efficiency of wire electrode and machine efficiency. A design with multi layers of electrode composed of different materials like the most inner layer with molybdenum or tungsten material with high boiling point and stiffness, the median layer with brass or copper which is good at conductivity and the outer layer with zinc-coated was proposed as an innovative electrode design. Multi-layer wire electrode would be the optimum choice to obtain a good stiffness, conductivity, heat removal rate and debris eliminating.2010-01-01T00:00:00Z麥克風陣列結合波束成型理論進行聲源定位及應用聲學攝影機於加工系統之振噪分析
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68849
標題: 麥克風陣列結合波束成型理論進行聲源定位及應用聲學攝影機於加工系統之振噪分析
; Using Microphone Arrays with Beamforming in Sound Source Localization and Application of Sound Camera for Noise and Vibration Analysis of Machining Systems
作者: Tzu-Yin Su; 蘇紫茵
摘要: 就像人有兩個耳朵一樣,多個感測器組成陣列後可以進行聲源定位。此技術應用廣泛,從早期用於軍事科技,到現代智慧聲控裝置或輔助工業噪音檢測,皆能見到其蹤影,亦是一項發展已久的技術,研究者也努力從陣列排列方式或演算法優化追求提升定位精準度及運算速度。
本研究首先將聲音感測器以直線的方式排列建立一維等間距線性陣列系統,並使用波束成型演算法進行聲源定位,進而建構完整的自動聲源追蹤系統;接著為了追蹤空間中的聲源位置,以一維陣列系統為基礎建立二維的聲源定位陣列,利用不同的排列形式設計各種陣列幾何的配置,並探討對應的聲源辨識能力與解析度,進而找出最佳的陣列排序方式;接著將二維陣列系統與工業相機結合,建立出可視化的聲場量測系統,並設計靜止、二維移動和三維空間移動的聲源實驗,測試此系統的靈敏度與定位能力;最後將本系統與三維數位影像相關法(digital image correlation,DIC)結合可精準定位聲源的三維空間位置,並將分析結果與市售的聲學攝影機相互比對以驗證本系統之可行性。另一部份則是將聲源定位應用於振噪分析的實例研究,與傳統量測工具相互搭配,針對內藏式主軸、馬達加工系統與機械手臂三種不同加工系統進行量測,將運轉訊號分離出環境背景噪音、電子元件噪音與運轉機械噪音並分項討論,也從異常訊號特徵推論結構有零件鬆動、基座不穩等問題,並成功使用聲學攝影機找到發出異音的缺陷軸承;最後則將聲學攝影機拍攝結果相互比較,討論聲源定位技術於實例應用的可行性。; Similar to human’s two ears, the sound can be “heard” and localized by the sensor array. This technology is widely used in many fields from military technology at early stages to smart voice control devices or assisting industrial noise detection. This technique has been developed for a long time. Researchers usually focus on the topics for the location of those sensors that were placed or developing the algorithm in order to improve locating accuracy, precision, and speed.
This study starts with 1-D array system with uniform arrangement, using beamforming algorithm in sound source localization and constructs an automatic source tracking system. For tracking the sound source in space, it carries on 2-D array system and discussed different geometric forms of the array with their locating ability and resolution, therefore finding out the best arrangement. Next combines this 2-D system with industrial camera to practicing an acoustic source visualizing system and then tests its sensitivity and locating ability by tracking a steady sound source, moving in a plane and in space. Lastly, combines this 2-D sound source tracking system with 3-D digital image correlation can locate the sound source in a 3-D space and compare the experimental results with those from a commercially available product, sound camera, to evaluate the system.
The other part of this thesis is noise and vibration analysis, which cooperates this sound source localization technology with traditional measurement tools such as microphone and accelerometer. In these 3 cases, which include built-in high-speed spindle, machining system, and robotic arm, this study separates the operation signal for background noise, electronic components noise and mechanical noise from the machines. Finally, the capability of the practical application of sound source localization technology is discussed by the measuring results of the sound camera in these cases.2020-01-01T00:00:00Z鹽析法高分子毛細結構於迴路式熱管之應用研究
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/37720
標題: 鹽析法高分子毛細結構於迴路式熱管之應用研究; Investigation of the Salt-leaching Polymer Wick Structure Applied to Loop Heat Pipe
作者: Yun-Ming Chang; 張云銘
摘要: 迴路型熱管(Loop Heat Pipe, LHP)為一種高傳熱量、長傳輸距離的被動二相熱傳裝置,具有相當大的潛力應用在航太科技及電子元件散熱。目前迴路式熱管中的毛細結構大多以燒結金屬粉末的方式來製作,應用於迴路式熱管系統時,因金屬材料熱導係數高易有熱洩漏問題而降低性能;再者,對於經燒結所製得之毛細結構,其毛細結構參數(有效孔徑、孔隙度、滲透度)會受到燒結粉末的粒徑、形狀以及燒結時的溫度、時間等因素所影響,因此不易控制其參數來進行探討。有鑑於此,本文以低熱導係數的聚苯乙烯為材料,利用鹽析法來製作可應用於迴路式熱管之高分子毛細結構,藉由改變氯化鈉粒徑大小及其在高分子材料中的比例來調控有效孔徑與孔隙度。經實際製作並量測毛細結構參數結果顯示,其有效孔徑量測值可落於所欲控制孔徑範圍內,孔隙度可精確控制在平均絕對百分比誤差1.65 %內。綜整所量值之參數值,並以曲面擬合的方式求出高分子毛細結構參數關係式:lnκ=-20.47+lnrc+4.31ε2.5,此式將有助於迴路式熱管的設計以及熱傳性能的預測。
將所製作出不同有效半徑、孔隙度、壁厚參數的高分子毛細結構,置入於迴路式熱管中進行熱傳性能測試。測試結果顯示,在結構強度與製程條件允許下,毛細結構壁厚愈薄、有效半徑愈小以及孔隙度愈高,均有助提升迴路式熱管熱傳性能。在蒸發器表面溫度85 ℃的條件下,高分子毛細結構最佳參數組合(壁厚為1.5 mm、有效半徑為5.9 μm、孔隙度為80 %)之迴路式熱管其熱傳量可達320 W,熱阻0.234 ℃/W。實驗所量測補償室溫度與理論預測之值,其平均絕對百分比誤差為5.65 %。再者,將參數相接近的高分子以及金屬毛細結構,先後置入迴路式熱管中進行熱傳性能測試比較,結果顯示具高分子毛細結構迴路式熱管其熱傳性能與具金屬毛細結構迴路式熱管相接近。熱傳導係數為造成性能差異的主因,低熱導係數之高分子毛細結構雖可降低熱洩漏量,使迴路式熱管在較低之操作溫度下運作,但亦會降低毛細結構外部之蒸發表面熱傳係數,使蒸發表面散熱效率變差。
將低熱導係數的高分子毛細結構應用於熱洩漏較為嚴重的平板型迴路式熱管,製作出主要毛細結構為金屬以及次要毛細結構為高分子的複合式雙層毛細結構。在主要毛細結構厚度同為2 mm的條件下,測試結果顯示平板型迴路式熱管性能的熱傳量可達140 W、熱阻為0.38 ℃/W,相較於金屬毛細結構的熱傳量40 W、熱阻0.69 ℃/W,具低熱導係數高分子的複合式雙層毛細結構可有效降低熱洩漏對系統熱傳性能的影響。
利用鹽析法除了可製作出高孔隙度與高滲透度之高分子毛細結構,使具高分子毛細結構迴路式熱管之熱傳性能與具金屬毛細結構迴路式熱管相同,其在製作特性上還具有成本較低、可調控毛細結構參數、可加工性等優點,因此可將鹽析法高分子毛細結構應用於迴路式熱管,有助於提升迴路式熱管之應用性。; Loop heat pipe (LHP), which is a passive two-phase thermal transport device with high heat transfer capacity and long transport distance, has a great potential for applications of spacecrafts and electronic cooling. At present, the wick structures of the LHP are almost manufactured by sintering of metal powder. However, the use of sintered metal wick with high thermal conductivity may cause heat transmit into the evaporator core easily, which is called the problem of “heat leakage”. Besides, the wick parameters of sintered metal are difficult to control in the sintering process. Therefore, the main purpose of this study are using polystyrene with low thermal conductivity as the material and manufacturing the polymer wick structures by the method of salt-leaching in biotechnology area. By the method of salt leaching, the porosity can be controlled by adjusting the volume ratio between polymer material and sodium chloride, and the pore radius also can be controlled by adjusting the particle size of sodium chloride. Hence, polymer wick structures with different porosity and pore radius are manufactured, and the wick parameters that included pore size, pore radius and permeability are also measured. The results show that the pore size parameter lies in the desired range, and the porosity is able to be controlled within 1.65 % MAPE. Summarizing the permeability of the polymer wicks with different porosity and pore radius, the formulas of polystyrene wick structure between permeability, pore radius and porosity expressed specific as lnκ=-20.47+lnrc+4.31ε2.5 is established. The formulas would help the design of LHP and the prediction of the heat transfer performance of LHP.
The polymer wick structures with various wick parameters are installed into a LHP, and the heat transfer performance of LHP system is conducted and compared with sintered metal wick structures. The results of the test reveal when the smaller the thickness and pore radius are, and the larger the porosity is, the performance of the heat transfer would be much better. Hence, a wick structure with the thickness of 1.5 mm, the pore radius of 5.9 micron, the porosity of 80 % is installed into a LHP system to carry out the performance. The capacity of heat transfer in LHP with polymer wick structure approaches 320 W, the thermal resistant is 0.234 ℃/W under the evaporator temperature of 85 ℃. The comparison of the compensation chamber temperature between the predicted results and experimental data shows a good agreement (within 5.65 %). Furthermore, in compare with metal wick structure at the similar porosity and pore radius, the performance of the LHP with metal wick structures is little better than the LHP with polymer wick structure. The thermal conductivity of wick material is major cause of different performance. Polymer wick structure with low thermal conductivity can reduce the compensation chamber temperature, but also decrease the evaporative heat transfer coefficient at the outside surface of wick structure.
According to the literature, the heat leak problem is more serious in the flat LHP than the cylindrical LHP. This problem also makes the thermal resistance of flat LHP higher. Hence this study tries to solve the difficulties by the use of low thermal conductivity polymer wick structure. Then, a composite double layer wick structure, which is composed of the primary wick structure sintered with metal powder and the secondary wick structure made of the low thermal conductivity polymer is applied to the flat loop heat pipe. The results show that when primary wick thickness of composited double-decked wick structure is 2 mm and the temperature of the evaporators is less than 100 ℃. The maximum heat transfer capacity increases from 40 W to 180 W. In addition, the thermal resistance decreases from 0.69 ℃/W to 0.38 ℃/W.
In short, polymer wick structure, comparing with metal wick structure, has some advantages in the characteristics in its production, such as low manufacturing cost, easily controllable, perfect processing, and so forth. Moreover, these merits would promote its application in the LHP.2008-01-01T00:00:00Z