畢業(yè)設計 食品切斷裝置的設計

畢業(yè)設計 食品切斷裝置的設計,畢業(yè)設計,食品切斷裝置的設計,食品,切斷,裝置,設計 寧波大紅鷹學院 畢業(yè)設計（論文）外文翻譯 所在學院： 機電學院 班 級： 08機自1班 姓 名： 沈鑫斌 學 號： 08141010119 指導教師： 楊光 合作導師： 2011 年 12 月 16 日 原文： 題目 Cam profile optimization for a new cam drive Abstract A complex cam shape optimization problem is studied to optimize a unique cam mechanism for a new cam drive engine. First, the optimization problem is defined through analyzing the unique cam mechanism. Multiple design specifications are included in the optimization problem by defining the output torque of the engine as the objective function and the contact stress, radius of curvature, and pressure angle as the constraints. Second, an analytical scenario is designed to find the best ever cam profiles through manipulating the different combinations of cam profile representations and optimization methods. Two types of curve representations, including general polynomial spline and B-spline, are employed in cam profile synthesis. In addition, both a classical optimization technique and a genetic algorithm (GA) based method are applied to solve the complex optimization problem. Finally, comparative studies are performed among the initial profile and the optimal profiles to demonstrate the effectiveness of these proposed design approaches on solving the cam profile optimization problem. Results show that the best profiles are obtained from a combination of the B-spline representation and the GA-based method. In addition, compared to the initial design, the engine performance is improved greatly by the proposed optimization approaches. Plate cam mechanism is a widely used machine component with the continuous contact motion of cam and follower, and can easily produce any functional motion of follower due to the rotation of cam. Cam mechanism has the diverse types by the combination of different shape of cam and motion of follower; plate or cylindrical cam, roller or flat-faced follower, and reciprocating or oscillating motion. In spite of the advantages of a few number of links, simple structure, positive motion, and compact size, cam mechanisms require the accurate shape design and precise machining procedures for satisfying the mechanical requirements. Under the low leveled design and manufacturing, cam mechanisms give the heavy effects on vibration, noise, separation, and overloading to an overall system. To avoid these effects, cam mechanism must be well designed accurately and machined precisely. Actually, a hybrid CAD/CAM approach may be the best solution that the shape data from the design process are directly combined to the machining data for the manufacturing process As an innovation of replacing the conventional crankshaft/connecting rod mechanism by cam mechanism in engine design, a new type of engine called the cam drive engine is being developed in a few places in the world. The cam drive engine has unique features over the conventional engines, among which the cam drive is the most prominent one. For cam drive, the cam profiles control the engine operation strokes by determining the timing of various intake and exhaust events. Moreover, the use of cam drive facilitates having a separate compression ratio and expansion ratio, a separation that is much more difficult to accomplish with the prevalent crankshaft/connecting rod engine design. The new type of engine is believed to have major advantages over the conventional engines, including higher power, better fuel economy, smoother operation, higher reliability, and lighter weight. The application of the cam mechanism to cam drive engine makes the design of the cam profiles essential to the overall engine performance. However,the initial cam profiles were designed using a traditional cam design approach. For the so-called trialand-error approach, the cam profiles are first generated to meet the geometry specifications such as the specified values of displacement, velocity, and acceleration at different engine events, and then the feasibility of the generated cam profiles is checked to meet the other design specifications, including the output torque of the engine, radius of curvature, and pressure angle, etc.. Although this approach is simple in principle,its disadvantages are obvious. First, this ap-proach is not efficient. It has to be applied many times in order to achieve a satisfactory engine performance.Therefore, it results in a laborious and timeconsuming design process. Moreover, since the cam design problem involves the determination of the profiles of both intake cam and exhaust cam, the interplays of the two profiles add more complexity to the trial-and-error approach. Finally, although the result found by this approach is feasible, it is very unlikely to be optimal. Therefore, it is necessary to use an optimal design approach, in conjunction with an appropriate cam profile representation, to determine the most suitable cam profiles of both intake cam and exhaust cam in order to meet the multiple design specifications. This is the motivation of the proposed research. To this end, we first review the previous research on cam design and optimization as follows. The cam design has changed dramatically over the past decades by taking advantage of the tremendous advance in computing devices and mathematics tools,especially the splines. The impetus for the change is the demand for cams with higher speeds, smoother operation, and better performance. The research activities on cam design can be classified into two categories according to the curve representation of cam profile: polynomial-based methods and spline-based methods. In the review of the past studies on cam design and optimization, we address the following three aspects in this research. First, the multiple design specifications for the cam drive engine are considered in the optimization problem. We select the output torque at a specified engine speed as the objective function. In addition, the other important design specifications,including contact stress, radius of curvature, and pressure angle, are considered as the constraints in the optimization problem. The major difference of the proposed research from typical cam profile optimization is that the output torque is selected as the objective function instead of the residual vibrations. The reason is that the presence of residual vibrations is not prominent because the follower (See Fig. 1) is designed to have enough rigidity in the cam-follower mechanism. In contrast, the output torque at a specified engine speed is one of the major concerns from the engine design aspect. The choice of the output torque as the objective function provides multidisciplinary aspects to the proposed research, in which both cam design and engine design are included. Second,instead of studying only one cam in the past studies, the proposed research aims to optimize intake cam and exhaust cam simultaneously to make the cam-follower mechanism fulfill appropriately the different engine events during the whole engine cycle.The complexity of the optimization problem increases accordingly since both cams are designed in the optimization problem. Finally, to study comprehensively the optimization problem, an analytical scenario is designed to investigate how the optimization results are affected by different combinations of cam profile representations and optimization methods. A complex cam profile optimization problem hasbeen investigated for a unique cam mechanism in a new cam drive engine. First, the optimization problem has been defined by taking into account multiple design specifications. The output torque of the engineis considered as the objective function. In addition,the other design specifications, including the contact stress, the pressure angle, and the radius of curvature,are selected as the constraints. Second, an analytical scenario has been designed to investigate how the optimization results are affected by different combinations of cam profile representations and optimization methods. To this end, two types of curve representations, i.e., general polynomial spline and Bspline,have been used in cam profile synthesis.Moreover, both a classical optimization technique and a genetic algorithm (GA)-based method have been applied to solve the optimization problem. Finally, a series of comparative studies have been performed among the initial design and the optimal design of the cam profiles. Three sets of the optimal profiles have been generated through manipulating different combinations of the cam profile representations and the optimization methods. Results show that the best profiles are obtained from the combination of the Bspline representation and the GA-based method. The best profiles provide better results in terms of the output torque and the smoothness value, compared to the other two sets of optimal profiles. Moreover, the output torque generated by the best profiles increases by 28% compared to that generated by the initial profiles. 譯文： 題目 新型凸輪輪廓優(yōu)化 摘 要： 凸輪輪廓優(yōu)化問題是對一個獨特的新型凸輪驅(qū)動引擎的優(yōu)化研究。第一，優(yōu)化問題的定義通過獨特的凸輪結(jié)構(gòu)的分析。優(yōu)化問題中的多個設計規(guī)范包括通過定義引擎輸出扭矩為目標的功能與接觸應力，曲率半徑，和壓力角的約束。第二，分析方案旨在通過操縱凸輪輪廓線凸輪輪廓交涉找到最好的和優(yōu)化方法的不同組合。兩種類型的代表曲線，包括一般多項式的樣條曲線和B樣條，用于凸輪輪廓的合成。另外，傳統(tǒng)優(yōu)化技術(shù)和遺傳基礎(chǔ)學(GA)的一種方法都將應用于解決復雜的優(yōu)化問題。最后，比較研究執(zhí)行初始配置文件和最優(yōu)的配置文件，以證明這些凸輪輪廓優(yōu)化問題的建議的設計方法的有效性。結(jié)果顯示，代表曲線B樣條的和和遺傳基礎(chǔ)學相組合可獲得最佳的配置文件。此外，相對于最初的設計，優(yōu)化后發(fā)動機性能大幅提高。 凸輪機構(gòu)是凸輪與從動件的持續(xù)接觸的運動是一種廣泛使用的機器組件。從動件凸輪機構(gòu)由于旋轉(zhuǎn)能容易產(chǎn)生任何功能運動。凸輪機構(gòu)具有多樣的組合，不同形狀和運動從動件凸輪：板或圓柱凸輪、滾筒或平底從動件、往復式或振蕩運動。 盡管有一些數(shù)量優(yōu)勢,結(jié)構(gòu)簡單、運動積極,以及體積小,需要準確的形成凸輪機構(gòu)設計和精密的加工程序以滿足機械的要求。在設計與制造凸輪機構(gòu)給重對一個整體的系統(tǒng)振動、噪聲、分離和超載影響。為了避免這些效應,必須精心設計凸輪機構(gòu)的準確、高加工精度。事實上,混合制造(CAD/CAM)方法可能是一個最好的解決辦法,即形成數(shù)據(jù)設計過程的數(shù)據(jù)直接結(jié)合生產(chǎn)過程的加工。 作為取代傳統(tǒng)曲軸/連接桿用凸輪發(fā)動機設計中的創(chuàng)新，在世界中的少數(shù)幾個地方正在制定一種新型的發(fā)動機凸輪驅(qū)動引擎的調(diào)用。相對傳統(tǒng)的發(fā)動機，凸輪驅(qū)動引擎具有獨特的功能，其中凸輪驅(qū)動器是最突出的一個。對于凸輪的驅(qū)動器，凸輪配置文件通過確定各種進、排氣事件的時間來控制發(fā)動機運動行程。此外，凸輪驅(qū)動器使用方便有一個單獨的壓縮比和膨脹率，就更難實現(xiàn)完成與曲軸/連接桿引擎設計的分離。這種新型發(fā)動機被認為已經(jīng)超過傳統(tǒng)的發(fā)動機，包括更高的功率、 燃油經(jīng)濟性更好、 運作暢順，更高的可靠性和重量更輕的主要優(yōu)勢。 凸輪機構(gòu)凸輪驅(qū)動發(fā)動機中的應用使得凸輪發(fā)動機設計的整體性能顯得至關(guān)重要。但是，初始凸輪配置文件旨在運用傳統(tǒng)凸輪的設計方法。所謂的反復試驗的方法，首先生成凸輪，以滿足如位移，速度和加速度在不同的引擎事件中指定的值的幾何規(guī)格，然后生成凸輪的可行性進行檢查，以滿足設計規(guī)范，包括輸出扭矩發(fā)動機，曲率半徑和壓力角等。雖然這種方法原理簡單，但它的缺點是顯而易見的。第一，這種方法不是有效的。它已多次應用以實現(xiàn)令人滿意的發(fā)動機性能。因此，它會導致一個艱苦和耗時的設計過程。此外，由于凸輪設計上的問題涉及的進氣凸輪和排氣凸輪圖譜測定，兩個相互影響的配置文件添加了反復試驗法的復雜性。最后，雖然結(jié)果發(fā)現(xiàn)這種方法是可行的，它是不太可能是最佳的。因此，它是使用優(yōu)化設計方法，配合適當?shù)耐馆嗇喞硎?，以確定最合適的進氣凸輪和排氣凸輪的凸輪，以滿足多個設計規(guī)范。這是擬議的研究目的。為此，我們首先回顧以往研究的凸輪設計和優(yōu)化如下。 凸輪設計在過去的幾十年中利用巨大的計算機設備的進步和數(shù)學工具有了急劇的改變,尤其是插值。推動這一變化主要是因為如今的需求高速度、光滑的操作和更好的性能。凸輪設計研究活動可以分為兩類,根據(jù)凸輪升程曲線表示:根據(jù)多項式方法和依據(jù)單一方法。 在回顧過去凸輪設計和優(yōu)化研究,我們的著重在這三個方面的研究。第一,多規(guī)范設計凸輪驅(qū)動引擎中考慮了優(yōu)化問題。我們選擇的輸出扭矩在一個特定目標函數(shù)為發(fā)動機轉(zhuǎn)速。此外,另一個重要設計規(guī)范,包括接觸應力、曲率半徑的,壓力角,視為優(yōu)化問題的約束。最大的不同是提出了研究典型的凸輪輪廓優(yōu)化選擇的目標函數(shù)代為輸出轉(zhuǎn)矩替剩余的振動。原因是,殘余振動的存在并不突出,因為從動件(見圖1),是專為在凸輪機制擁有足夠的剛度。相反,從引擎設計方面主要的問題是在一個特定的輸出轉(zhuǎn)矩轉(zhuǎn)速。目標函數(shù)提供多學科方面所提出的研究為輸出轉(zhuǎn)矩的選擇,其中包括有cam設計和發(fā)動機設計。第二, 在過去的研究中不是只有一個凸輪的研究,該研究旨在優(yōu)化凸輪和排氣凸輪攝入，同時使凸輪機構(gòu)履行適當不同的發(fā)動機在整個事件的發(fā)動循環(huán)。該優(yōu)化問題的復雜性相應增加，自從兩個凸輪的優(yōu)化設計問題。最后,綜合研究該優(yōu)化問題,設計了一種分析方案是對優(yōu)化結(jié)果進行不同的組合,影響凸輪輪廓陳述和優(yōu)化方法。 一個復雜的凸輪輪廓優(yōu)化問題一直追究一個獨特的凸輪機構(gòu)在一個新的凸輪驅(qū)動引擎。首先,該優(yōu)化問題的定義考慮多個設計規(guī)范的標準。發(fā)動機的輸出轉(zhuǎn)矩作為目標函數(shù)。此外,該另設計規(guī)范,包括接觸應力、壓力角和曲率半徑的,選為約束條件。其次,設計了分析場景對優(yōu)化結(jié)果進行不同的組合,影響凸輪輪廓陳述和優(yōu)化方法。為此,兩種類型的曲線表現(xiàn),那就是, 一般多項式樣條函數(shù)和樣條，已用于凸輪廓線的合成。此外,無論是古典的優(yōu)化技術(shù)和基于遺傳算法(GA)的方法已經(jīng)被應用于解決優(yōu)化問題。最后,一系列的比較研究已進行初步設計中優(yōu)化設計的凸輪輪廓。三組最優(yōu)型材產(chǎn)生不同的組合，通過操縱凸輪廓線的陳述和優(yōu)化方法。結(jié)果表明，得到了最好的剖面相結(jié)合的方法樣條描述和基于遺傳算法。最好的結(jié)果,以型材提供更好的輸出力矩和光滑的價值,比其他兩組最優(yōu)配置文件。此外,所產(chǎn)生的輸出轉(zhuǎn)矩的最佳型材增加28%相比,所產(chǎn)生的初始配置文件。