發(fā)布時間：2018-04-18 01:27

  本文選題：T樣條曲面 + 計算機輔助制造��； 參考：《浙江大學(xué)》2014年博士論文

【摘要】：為了在計算機輔助制造過程中更方便地表達形狀復(fù)雜的零件,尤其是便于對自由曲面生成多軸加工刀路,學(xué)術(shù)界和工業(yè)界一直在尋求合適的數(shù)學(xué)表達方法。多面體模型和多片張量積曲面復(fù)合模型是當(dāng)前最流行的兩種數(shù)學(xué)模型,但是它們在表達復(fù)雜工件和刀具路徑生成方面各自有不足之處。而在另一方面,T樣條曲面突破了張量積結(jié)構(gòu)的桎梏,發(fā)展了局部控制域的概念,減少了曲面控制頂點數(shù)量并使其自由地排列。由于其出色的曲面表達能力,T樣條已經(jīng)在計算機輔助設(shè)計、造型、有限元分析等領(lǐng)域得到了廣泛應(yīng)用。針對上述CAM業(yè)界由來已久的問題,本文提出了一整套解決方案。將T樣條引入CAM過程中,用于表達自由曲面。利用T樣條曲面參數(shù)域原像特殊的拓撲結(jié)構(gòu),直接對其完成刀具路徑規(guī)劃。該項工作為解決自由曲面的計算機輔助制造提供了新思路,同時也拓展了新型曲面的應(yīng)用,增強了CAD/CAM領(lǐng)域的交叉發(fā)展。本文完成了以下幾項工作： 一、經(jīng)過比較和總結(jié)CAM系統(tǒng)自由曲面的常見數(shù)學(xué)表達方法,提出使用T樣條曲面作為計算機輔助制造的數(shù)學(xué)模型。建立了T樣條節(jié)點／控制頂點一體化數(shù)據(jù)結(jié)構(gòu),發(fā)展了局部控制域的概念,完善了T樣條曲面點求值與局部幾何性質(zhì)的計算方法。在此基礎(chǔ)上,結(jié)合刀具路徑參數(shù)與誤差標(biāo)準(zhǔn),直接在T樣條曲面上生成加工刀路。連通了復(fù)雜形狀零件的CAD造型設(shè)計與CAM加工規(guī)劃之間的鴻溝。 二、針對傳統(tǒng)等高度分層加工的加工余量不均勻、引發(fā)刀具顫振、損害成形表面等缺點,提出一種漸進型分層加工方法(Morphing machining strategy, MMS)。利用了T樣條曲面自由的參數(shù)域拓撲結(jié)構(gòu),將復(fù)雜的工件和毛坯形狀表達于單一曲面。以切削深度和工序余量等加工參數(shù)作為約束條件,基于能量最小化方法調(diào)整控制頂點,使T樣條曲面從設(shè)計形狀向毛坯形狀整體變形,生成一系列變形曲面。然后,將按逆序把這些曲面作為加工層,從毛坯開始逐層加工,最終得到工件的設(shè)計形狀。 三、提出了一種基于改進型空間填充曲線(Improved space-filling curve, ISFC)的精加工刀路生成方法。為了克服傳統(tǒng)空間填充曲線無法在非矩形域上生成刀具路徑的缺點,針對T樣條曲面不規(guī)則的參數(shù)原像以及帶孔洞的拓撲結(jié)構(gòu),調(diào)整網(wǎng)格點安排策略,保證形成合法胞腔,防止邊界附近區(qū)域出現(xiàn)欠切削材料。另外,針對刀具路徑拐角容易引起切削不足的問題,添加Hermite補償曲線,使刀具在拐角平滑過渡并且清除多余材料。 四、整合上述T樣條曲面點及幾何性質(zhì)計算方法,漸進型分層加工方法,ISFC精加工刀路生成算法,開發(fā)了一套針對T樣條曲面的CAM原型系統(tǒng)。該系統(tǒng)能夠讀取和查看T樣條曲面,結(jié)合用戶輸入的加工參數(shù),生成加工分層,并在各曲面層內(nèi)規(guī)劃單連通刀具路徑。對于生成的刀路,系統(tǒng)可以進行線框走刀仿真。然后根據(jù)五軸機床配置,進行刀路后處理,輸出用于實際切削加工的數(shù)控NC代碼。 為了驗證刀路算法和軟件性能,在實驗章節(jié)選用了包括鼠標(biāo)凸模、變速箱端蓋、人造指骨模型等傳統(tǒng)機械零件以及生物醫(yī)療器件,進行了刀路生成、軟件仿真以及實際機床加工。實驗成果表明了本文算法的可行性,高效性,以及軟件系統(tǒng)的可靠性。進一步說明了T樣條曲面在表達復(fù)雜零件和刀路規(guī)劃方面具有優(yōu)秀的性質(zhì),適合應(yīng)用于自由曲面的計算機輔助制造。
[Abstract]:In order to facilitate the expression of complex shape parts in computer aided manufacturing process, especially for the generation of multi axis machining tool path on the free surface, academia and industry have been expressed in seeking appropriate mathematical methods. Polyhedral model and multi chip tensor product surface two kinds of mathematical models of composite model is the most popular, but they the expression of complex workpiece and tool path generation of their own shortcomings. On the other hand, T spline surface breaks the shackles of the tensor product structure, the development concept of local control domain, reduce the number of control points and the amount of surface free arrangement. Because of its excellent surface expression ability, T spline have been in the computer aided design, modeling, finite element analysis has been widely used. In the CAM industry long-standing problems, this paper puts forward a set of solutions. The T spline The introduction of the CAM process, for the expression of the free-form surface. Using topological structure of T spline surface parameter domain preimage special, complete tool path planning on it. This work provides a new way to solve the computer aided manufacturing of freeform surface, but also opens a new surface should be used, enhance the cross development in the field of CAD/CAM in this paper. The following work has been finished:
First, through the common mathematical comparison and summary of CAM system for free surface expression method is proposed using the T spline surface as a mathematical model for computer aided manufacturing. Established T spline node / control points of the unified data structure, the development of the concept of local control domain, improve the calculation method of T spline surface and local geometric point evaluation nature. On this basis, combined with the tool path parameter and standard error, direct generation of tool path in T spline surface. The gap between the connected parts with complex shape CAD design and CAM machining programming.
Two, the traditional machining allowance highly stratified processing is not uniform, causing damage to the surface forming tool chatter, and other shortcomings, put forward a kind of incremental hierarchical processing method (Morphing machining strategy, MMS). By using the parameter domain topology T spline surface free, the workpiece and the blank shape complex expressed on a single surface with the cutting depth and the process allowance and other processing parameters as constraint conditions, energy minimization method to adjust the control points based on T spline surface deformation from the design to the overall shape of the blank shape, generating a series of deformation surface. Then, according to the reverse surface as the processing layer, from the rough start step by step processing, final design the shape of the workpiece.
Three, the paper proposes an improved based on space filling curves (Improved space-filling curve, ISFC) of the precision machining tool path generation method. In order to overcome the traditional space filling curve cannot generate the tool path in the non rectangular domain shortcomings, for the parameter preimage of T spline surface and irregular topology with holes, adjust the grid arrange strategy, ensure the formation of legal cell, prevent the emergence of less cutting material area near the boundary. In addition, the tool path is easy to cause the problem of insufficient corner cutting, adding Hermite compensation curve, so that the tool in the corner smooth transition and remove excess material.
Four, the integration of the T spline method to calculate the surface point and geometric properties, incremental hierarchical processing method, ISFC machining tool path generation algorithm developed for T spline surface CAM prototype system. The system can read and view the T spline surface, combined with the processing of user input parameters, generate hierarchical processing, and in the surface layer planning single connected tool path. For the generation of the tool path, the system can take the knife frame simulation. Then according to the five axis machine tool configuration, road postprocessing, output for the actual machining NC NC code.
In order to verify the tool path algorithm and software performance, in the experiment section were selected including the mouse punch, gearbox cover, artificial phalangeal model of the traditional mechanical parts and biomedical devices, the tool path generation, software simulation and actual machining. The experimental results show the feasibility of this algorithm, the efficiency and reliability of the software. The system is further illustrated. T spline surface has excellent properties in the expression of complex parts and tool path planning, suitable for computer aided manufacturing of freeform surface.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TH164

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本文編號：1766199