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毕业设计
食品切断装置的设计
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毕业设计 食品切断装置的设计,毕业设计,食品切断装置的设计,食品,切断,装置,设计
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宁波大红鹰学院 毕业设计（论文）外文翻译 所在学院： 机电学院 班 级： 08机自1班 姓 名： 沈鑫斌 学 号： 08141010119 指导教师： 杨光 合作导师： 2011 年 12 月 16 日原文： 题目 Cam profile optimization for a new cam driveAbstract 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 processAs 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.译文：题目 新型凸轮轮廓优化 摘 要： 凸轮轮廓优化问题是对一个独特的新型凸轮驱动引擎的优化研究。第一，优化问题的定义通过独特的凸轮结构的分析。优化问题中的多个设计规范包括通过定义引擎输出扭矩为目标的功能与接触应力，曲率半径，和压力角的约束。第二，分析方案旨在通过操纵凸轮轮廓线凸轮轮廓交涉找到最好的和优化方法的不同组合。两种类型的代表曲线，包括一般多项式的样条曲线和B样条，用于凸轮轮廓的合成。另外，传统优化技术和遗传基础学(GA)的一种方法都将应用于解决复杂的优化问题。最后，比较研究执行初始配置文件和最优的配置文件，以证明这些凸轮轮廓优化问题的建议的设计方法的有效性。结果显示，代表曲线B样条的和和遗传基础学相组合可获得最佳的配置文件。此外，相对于最初的设计，优化后发动机性能大幅提高。凸轮机构是凸轮与从动件的持续接触的运动是一种广泛使用的机器组件。从动件凸轮机构由于旋转能容易产生任何功能运动。凸轮机构具有多样的组合，不同形状和运动从动件凸轮：板或圆柱凸轮、滚筒或平底从动件、往复式或振荡运动。尽管有一些数量优势,结构简单、运动积极,以及体积小,需要准确的形成凸轮机构设计和精密的加工程序以满足机械的要求。在设计与制造凸轮机构给重对一个整体的系统振动、噪声、分离和超载影响。为了避免这些效应,必须精心设计凸轮机构的准确、高加工精度。事实上,混合制造(CAD/CAM)方法可能是一个最好的解决办法,即形成数据设计过程的数据直接结合生产过程的加工。作为取代传统曲轴/连接杆用凸轮发动机设计中的创新，在世界中的少数几个地方正在制定一种新型的发动机凸轮驱动引擎的调用。相对传统的发动机，凸轮驱动引擎具有独特的功能，其中凸轮驱动器是最突出的一个。对于凸轮的驱动器，凸轮配置文件通过确定各种进、排气事件的时间来控制发动机运动行程。此外，凸轮驱动器使用方便有一个单独的压缩比和膨胀率，就更难实现完成与曲轴/连接杆引擎设计的分离。这种新型发动机被认为已经超过传统的发动机，包括更高的功率、 燃油经济性更好、 运作畅顺，更高的可靠性和重量更轻的主要优势。凸轮机构凸轮驱动发动机中的应用使得凸轮发动机设计的整体性能显得至关重要。但是，初始凸轮配置文件旨在运用传统凸轮的设计方法。所谓的反复试验的方法，首先生成凸轮，以满足如位移，速度和加速度在不同的引擎事件中指定的值的几何规格，然后生成凸轮的可行性进行检查，以满足设计规范，包括输出扭矩发动机，曲率半径和压力角等。虽然这种方法原理简单，但它的缺点是显而易见的。第一，这种方法不是有效的。它已多次应用以实现令人满意的发动机性能。因此，它会导致一个艰
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