SOME ALGORITHMS FOR NC MACHINING SIMULATION
AND VERIFICATION
Abstract: This paper presents an approximation method to display realistic pictures of numerical control ( NC )machining simulation very quickly. The tool movement envelope is divided into many small regions and the normal to these small reg ions is calculated. The system saves the calculated result in a file before starting animation display. When the system st arts displaying machining animation, it does not need to calculate small triangular facet s normal to the workpiece surface. It only needs to find out what part of the cutter cuts the workpiece surface and to read the normal from t he file. A highly efficient NC code verification method is also presented in this paper.The metho d first detects the error in z direction. If some points are reported to be out of the tolerance, the system divides neighborhood of these points into smaller grids and calculates the normal surface at each grid intersection and the error in the normal vector direction.
Key words:numerical control machining; simulation; verification; realistic picture
NC program validation has often been classified into two important part simulation and verification. The simulation mainly displays material removal, cutter movement and modification of a geometric model of the workpiece to keep track o f the material removal process. The verification
process requires a comparison between the final workpiece model and the geometric model of the part. This paper proposes some essential algorithms about simulation and verification. Solid geometry modeling systems offer the possibility of doing both simulation and verification [ 1j4]. Simulation is achieved by Boolean subtraction of the tool movement volume from the workpiece model. The verification is achieved by Boo lean differences between models of the workpiece and the desired part. But on a microcomputer, solid model Boolean subtraction is too slow to show animation of material removal. Some other methods are presented to increase efficiency of the simulational system. Van Hook [5] has developed a real time shaded display of a solid model being milled by a cutting tool which follows an NC path. This approach utilizes a dexel (depth element) representation of the workpiece and the cutter geometries. The data structure is a run length encoded version of a volumetric data representation. An updating rate of ten cutting operations per second is attained by using Boolean set operations on the one-dimensional dexels. The viewpoint of dependency of this approach is overcomed by an extension of the method by Huang[6], who has introduced the possibility of error assessment to Hooks method. Takafumi has also used an extension of the z-buffer method (called G-buffer ) to simulate NC milling[7]. Some people have used a surface model rather than solid model[8]. Their methods divide the surface of geometric model along u
and v directions into many grids. The normal vector is then calculated at intersections of each grid. During simulating the length of vector is reduced if it intersects the tool movement envelope. An analogy can be made with mowing a field of grass. Each vector in simulation corresponds to a blade of grass o growing p from the desired object. As the simulation progresses, the blades are i mowed down o. The final length of the vector corresponds to the amount of excess material (above the surface) or the depth of gouge (below the surface) at the point. In 1993, P- L Hsu and W-T Yang [9] presented a method for real-time 3D simulation of 3- axis milling machining . They first divided stock and toot into array of many small cubes (voxel cell). For displaying realistic picture of the process of machining, it is necessary to determine which of these small cubes would be cut and need not be displayed. Their method not only avoids the Boolean subtraction operation, but also does not need to calculate the normal vector. So this method can display the simulation picture and the cutter movement at very high speed. But because the smallest display unit is a small cube (voxel cell), it is impossible to create good realistic pictures of the simulation process. Furthermore, it cannot detect small machining errors (less than one voxel cell) .In this paper a rapid method to display the animation of material removing process of NC machining is presented. And a method is also proposed to simplify the calculation of NC verification process.
1 DISCRETIZATION OF RAW STOCK AND REALISTIC PICTURE DISPLAY
In 3-axis milling processes, only data on the z axis (parallel cutter axis ) change when the cutting tools are swept over the workpiece. So we discrete stock as an array of triangular prisms as shown in Fig. 1.
This discrete method is somewhat structure of Z-map presented by P-L Hsu and W- T Yang in 1993. Z-map structure is an array of quadrangular pillar - shaped elements. When the cutter moves and cuts this pillar, each pillar has four intersections with the cutter that are actually not in the same plane. This will bring many troubles in the display of realistic pictures. Improvement is made in this research , we use triangular prisms rather than quadrangular pillar-shaped elements done by P- L Hsu and W- T Yang. Each pillar contains three intersections and these three points construct a small facet. All these facets construct the cutting surface that is modified. For creating a high quality realistic picture, it is necessary to get the information about the normal vector of each facet. If the system calculates the normal vector to all facets with an ordinary method, it is
difficult to display a smooth animation with high quality realistic pictures of the material removing process on microcomputer.
We find that the orientation of small facet is determined by the shape of cutter movement envelope and the place where the cutter touches the facet. For example, a ball-end cutter cutting the stock is shown in Fig. 2. The newly created small triangular facets have the same orientation as the cutter surface. If the place of a small triangular facet in the local reference frame of the cutter is obtained, its normal vector can be rapidly calculated. We divide the cutter into a lot of small regions as shown in Fig. 3.
Once a cutter is chosen, we can calculate the normal vector at these discrete points before displaying animation of machining process and storing the result in a file. The cutter local reference frame is settled as shown in Fig. 3, and the cutter center coordinate is xc , yc , zc . A is a point on the cutter surface and its local coordinate is x l , y l, z l. Its coordinates x a , y a, z a can be obtained from the following equations
y a = y c + y l x a = x c + x l z a = z c + z l Because any normal vector to ball surface points to the center of the ball, the normal vector at point A is x c- x a , y c- y a , z c - z a . The cutter center coordinates x c , y c , z c can be directly read from the NC file. If the coordinate of point B on a small triangular facet is x b, y b, z b, its local coordinates are x b- x c, y b- y c , z b- z c . The normal vector to all small triangular facets can be calculated by the method at very high speed. With the normal vectors to all small triangular facets, it becomes possible and simple to create and display high quality realistic pictures at high speed on a microcomputer with Open GL. We set the mode of GL Shade Model ( Glenum mode) as GL- SOOMTH. Open GL can display realistic pictures that are nearly as good in quality as ray trace pictures. Fig. 4 shows a local zoom picture of a mold machining simulation. Gouges created by the ball- end cutter are very clearly observed. Fig. 5 shows a NURBS surface picture. NC program is created by UGII, which contains 10584 cutter location data lines. It takes 35s to complete the whole simulation display on PII300 PC
computer. For the display of realistic pictures at high speed, some other display techniques need to be used, such as the local refreshing and special face hiding algorithm [10, 11].
2 NC PROGRAM VERIFICATION
Fig. 6 shows a surface with a set of points and associated direction
vectors normal to the surface. It would be computationally expensive to calculate the intersection of all the direction vectors for each tool
movement with them. If we choose direction vectors parallel to the z axis of the cutter tool (Fig. 7), the intersection calculation is more efficient. But as R. B. Jerard and S. Z. Hussaini pointed out, choosing all vectors in z direction introduces a potential problem whenever the surface normal deviates from the z direction [8]. The problem becomes most apparent for nearly vertical surfaces as shown in Fig. 8. The uncorrectable estimate of the cutting error is the vertical distance between the surface point P and the cut point P. This effect causes overestimated errors. No errors will be missed but points will be reported to be out of tolerance. In verification of NC program, our method can be described in two steps. In the first step, the system discretes raw stock and calculates the intersection of vectors in the z direction at each discrete point with the cutter tool movement envelope. These tasks have mainly been fulfilled in the simulational phase.
We design a data structure, Small- Prism-Data ( double x , double y ,
double z , int Line-num) , to save intersection coordinates P ( βx , βy ,βz ) and the line number of NC file whose data drives the tool to cut this vector. After simulation animation display end, the system has the coordinates of all the intersections and the line number that cuts these vectors. If z - zβat all discrete points is not out of tolerance, it implies that the NC program is right . The second step of verification is not needed. Because no error will be missed in the first step, in the second step we only reprocess those points reported to be out of tolerance .If a point P ( βx , βy , βz ) at cutting surface as shown in Fig. 8 has been reported to be out of tolerance, then Δx and Δy will be created depending on the value of z - z. A vector V will be created normal to the surface of the geometrical model at the point P (x, y, z ) . The method does not calculate the intersection of V and every tool movement envelopes. We can get a list of line number from data structure Small-Prism Data{ x x , y y , z z , N um} , here x x-[ x-Δx , x +Δx ] and y y-[ y - Δy , y + Δy ] and construct several tool movement envelopes depending on the list of NC program line number. We just calculate intersections of vector V with these tool envelopes and judge if this point ( βx , βy , βz ) is out o f tolerance. Because the points are out of tolerance are much fewer than these which are not, the second step needs only to process a few points. So the method has a comparatively high process speed. Because we save line number of NC program with the
intersection cut by this line data together, it becomes possible to detect small machining errors. When some local region has very small tolerance zone, the system can divide this small region into smaller grids as show n in Fig.9. Because of knowing which lines data in NC program cut this region, we do not need to repeat the simulated calculation. We just read the data from NC program depending on the line number saved in the data structure Small Prism Data , build cutter movement envelopes and calculate normal to these small regions and the intersections.
3 DISCUSSION
Methods for simulation and verification of NC machining have been presented in this paper. We divide simulation and verification into two steps. The main task of simulation is to display realistic picture animation of NC machining process. The simulation is achieved by calculating the intersection of vectors with tool path envelopes. In order to increase computational efficiency, we use some approximation computational
methods, such as the method for calculating the normal to small triangular facets and using the z direction vector to calculate the intersection with the cutter movement envelope. They are precise enough to display the right shape of the workpiece . These methods make it possible for the system to display high quality realistic pictures very quickly on a microcomputer. Furthermore, in the simulational phase, the system saves necessary information that is needed in the next phase, i. e. verification. The verification first compares point P ( x , y , z ) on the geometric model surface with point P ( βx , y , zβ) on the cutting surface. Point P ( βx , y , zβ) is an intersection of the tool path envelope with z direction vector. If the system reports machining error at this point to be out of tolerance, the system calculates a neighborhood of point P , divides this neighborhood into small grid array and calculates the normal vector to geometric model surface at all inter section points of this grid. Then the system calculates intersection Pγof the normal vector with tool movement envelope and compares point P and point Pγalong the normal direction. Just as shown in Fig . 8, only on the nearly vertical surface, the machining errors will be overestimated and the NC machining G- Codes generated by CAM system are ordinarily impossible to contain many errors. So there are few points to be reported out of tolerance and need to be processed with the second step of the verification. So the method has high computational efficiency.
4 CONCLUSION
Now cut ting simulation as a means of testing and verifying NC cutting paths has become an important part of modern CAD/ CAM software. A three axis NC machining simulation system has already been developed based on the algorithms presented in this paper and has been successful in testing and verifying many G-Codes offered by manufacturing factories. The largest one of these G-Code files contains more than 300 000 commands to manifest that the system is practical.
数控加工和仿真的关键算法
摘要：本设计提出了一种快速显示数控加工仿真高质量真实感图形的近似方法。刀具运动扫掠体被划分成一些小区域 ,系统计算出每个小区域的法向量并将这些向量存储在一个文件中。当显示加工动画时不必再计算毛坯表面小平面的法向量 ,仅仅需要计算是刀具的哪部分切削了该小平面 ,然后从文件中读出对应的法向量。文中还提出了一种高效率的 NC加工代码验证方法。该方法先计算 z 方向的误差,如果发现某些点超差 ,在这些点附近系统自动对毛坯进行进一步细分 ,计算出表面法向量的误差。
关键字：数控加工；仿真；验算；真实感图形；
数控加工程序的确定通常分为两个重要的部分：仿真和验算。仿真主要通过显示材料去除，切削过程以及工件几何模型的改变来记录材料去除过程。验算过程需要在最终工件模型和部件的几何模型之间比较。本文提出了一些关于仿真和验算的重要算法，实体几何模型系统提供了做仿真和验算的可能性[ 1j4]。仿真是通过刀具从工件模型的移动量的布尔减法来实现的，验算是通过工件模型和所需部分的布尔值差来实现的。但是，在微型计算机下，实体几何模型的布尔减法太慢而不能动态显示去除材料的过程。因此，提出一些其他的方法来提高仿真系统的效率。Van Hook[5]通过一个跟踪NC路径的切削刀具开发了一种实时阴影显示铣削实体模型的过程。这种方法使用一个深度元件表示工件和刀具的几何形状。该数据结构是一个体积数据表示的游程长度编码的版本。每秒十切削操作的更新率是通过使用布尔设置操作的一维dexels来获得的。这种方法所依据的观点被黄所提出的方法的延伸所克服[6]。黄将错误估计的可能性引进到Hooks的方法中。Takafumi也使用了一种z缓冲的方法（称谓G缓冲区的扩展）仿真数控铣削[ 7]。有些人使用的是表面模型而不是实体模型。他们将几何模型的表面沿着u和v 方向分为很多网格。然后计算每个网格交点的法向量。仿真过程中，如果它与刀具轨迹的包络线相交矢量的长度会减少。就好比修减一块草地的草。在仿真中每一个向量对应一棵小草，随着仿真过程刀片从i切割到o。向量的最终长度对应于这点多余材料的数量（表面以上或者挖切的深度（表面以下））。1993年， P- L Hsu and W-T Yang [9] 提出了一种三轴铣床的3D真实仿真方法。他们首先将实体划分为许多小立方体（体素细胞）的排列。为了演示机加工过程的真实图像，有必要决定切削哪些小立方体演示哪些小立方体。他们的方法不仅避免了布尔减
法运算，而且不需要计算法向量。所以这种方法能够以很高的速度演示仿真图像和切削运动。但是因为最小的显示单元是小立方体（体素细胞），不可能创建仿真过程中良好的逼真的图像。此外，它不能够检测小型加工误差（小于一个体素细胞）。本研究提出了一种快速动态显示数控机床材料移除过程的方法，并且提出了一种简化数控验算过程的方法。
1、原材料的离散化和逼真的画面显示
在三轴铣削过程中，当刀具扫过工件时只有z方向的数值发生变化。因此，如图一所示我们将原材料离散为三角棱镜阵列。
图一：原材料的离散化
1993年 P-L Hsu and W-T Yang基于z映射结构提出这种离散方法。Z映射结构是四棱柱元素的阵列。当刀具移动切削四棱柱时，每一个棱柱和刀具有不在同一表面的四个交点。这给真实图形的显示带来很多困难，这项研究对此作了提升，我们使用三棱柱而不是P-L Hsu and W- T Yang使用的四棱柱元素。每一个棱柱包括三个交点，这些交点构成一个平面。所有的这些平面构成了被修改的切削表面。为了创建高质量的真实图像，有必要获得每一个平面的法向量的信息。如果系统使用一般的方法计算所有平面的法向量，在微型计算机中就很难以高质量的真实图像流畅地显示材料去除过程动画效果。我们发现切削运动轨迹的包络和刀具接触点决定小平面的方向。例如，图二所示的是球头立铣刀切削毛坯的图形。新建的小三角形表面和切削表面方向相同，如果获得的切割器的局部参考系中的小三角形面的地方，它的法线向量可以迅速地计算出来。
图二：小三角形表面和切削表面的关系
如图三所示，我们将刀具分为好多小区域，一旦刀具被选中，我们就能够在动态显示机加工过程和存储结果之前计算在这些离散点的法向量。刀具参考系如图三所示，刀具中心的坐标为（xc , yc , zc ）。A 点为切削表面的一点相对坐标为（ x l , y l , z l ），它的绝对坐标能够有如下公式得出：
y a = y c + y l x a = x c + x l z a = z c + z l
因为球面上点的任何法向量指向球心，所以点A 的法向量为 x c - x a , y c - y a , z c - z a 。切削中心的坐标x c , y c , z c 能够直接从NC 文件中读出。假设小
三角平面上一点B 的坐标为x b , y b , z b ，它的绝对坐标为 x b - x c , y b - y c , z b - z c 。用这种方法所有小三角形平面的法向量能够迅速的计算出来。
图三：球头面铣刀上一点的法向量
利用这些小三角形平面的法向量，就有可能实现在微型计算机中使用Open GL 高速地创建并演示高质量的真实图像。我们设定的GL 阴影模型（Glenum 模式）模式为GL- SOOMTH 。Open GL 能够显示和光线跟踪图像质量的真实图像。如图
四所示为一个模具加工仿真的局部放大图。由球头铣刀造成的擦伤可以非常清楚的观察到。图五为一个非均匀有理样条曲面的图像。数控程序由UGII创建，它包含了10584条刀位数据线。在PII300个人计算机上，花费35秒完成全部的仿真演示。为了高速显示真实图像，需要用到一些其他的算法，例如局部更新和特殊表面隐藏算法[ 10, 11]。
图四：模具加工仿真的局部放大图
图五：加工仿真的非均匀有理样条曲面
图六：刀具路径包络和法向量的交点
2、数控程序的验算
图六为表面的一系列点以及相关联的垂直于表面的方向矢量。计算每一个刀具运动与它们方向向量的交点成本太过昂贵。如果我们定义方向向量平行于刀具z轴方向（图七），交点的计算就更加有效。但是 R. B. Jerard 和S. Z. Hussaini 指出选择所有向量在z方向，当表面的法向量偏离z方向时引入了一个潜在的问题[8]。
图七：刀具路径包络和z方向的交点
如图八所示，这个问题在近似垂直的表面变得更加明显。切削误差纠正的估
计是表面点P 切削点P 的垂直距离。这种效应引起错误高估。没有忽略错误但是将会提示超出公差。在数控程序的验算中我们的方法分为两步。第一步，系统分离原材料并计算刀具运动轨迹和每一个离散点在z方向的交点。这些主要在仿真阶段完成。我们设计了一种数据结构 Small- Prism-Data ( double x , double y , double z , int Line-num)，为了保存交点的坐标和NC文件的行号，它的数据驱动刀具切向量。当动态仿真演示结束后，系统就得到了所有交点的坐标以及切割向量的行号。如果所有交点的z-z没有超出公差，就表明数控程序是正确的。那么验算的第二步就不需要了。因为在第一步没有发现错误，第二步我们只是重新处理那些报告超出公差的点。如图八所示如果切削表面上一点P被报告超出公差，就会依靠z-z值创建Δx 和Δy。在垂直于模型表面上P点建立向量V，这种方法不能计算出向量V和每一个刀具轨迹的交点。我们能够从数据结构Small-Prism Data{ x x , y y , z z , N um}中得到系列行号。通过NC程序行号建立x x-[ x-Δx , x +Δx ] 和y y-[ y - Δy , y + Δy ]和许多刀具运动包络。我们仅仅计算向量V和这些刀具轨迹的交点来判断这一点是否超出公差。因为超出公差点的数量远远少于没有超出公差的点数，第二步验算只需要处理极少数的点。所以说这种方法有一种比较高的处理速度。因为我们保存了NC 程序的行号和线数据的交点，就能够侦探小型加工误差。如图九所示，当一些局部区域有非常小的公差带时，系统将这些小区域分为很多更小的网格。
图八：近似垂直表面的错误估计
图九：检测小型加工误差
3、讨论
这篇论文已经论述了数控加工仿真和验算的方法。我们将仿真和验算分为两步。仿真的主要任务是动态显示数控加工过程的真实图像，仿真是通过计算向量和刀具路径包络线的交点获得的。为了提高计算效率我们使用了一些近似计算的方法，例如计算小三角形平面的法向量，并使用z方向向量计算与刀具运动包络线的交点。它们足够精确地显示工件的正确外形。这些方法使得系统在微型计算机中高速显示高质量的真实图像成为可能。而且，在仿真阶段系统保存了下一阶段所需要的必要的信息，也就是验算。验算首先将几何模型上一点P( x , y , z )和切削表面一点P( βx , y , zβ ) 做比较。点 P( βx , y , zβ )是刀具路径包络和z方向向量的交点。如果系统报出这点的加工误差超出公差的加工错误，将会取一个临近点P，将这个临近区域分为许多小网格阵列计算出所有网格内点的几何模型表面的法向量。然后系统计算出法向量和刀具运动轨迹包络线的交点 Pγ，沿着法向上比较点P和点Pγ。像如图八所示的情况，只有近似垂直的表面，加工误差会被高估，由CAM系统生成的数控加工G代码通常是不可能含有很多错误。因此只有极少点超出加工误差，需要第二步的验算过程。这种方法有很高的计算效率。
4、结论
现在切削仿真作为一种检验数控切削途径的方法已经成为现代CAD/CAM软件
附录A Lathe fixture design and analysis Ma Feiyue (School of Mechanical Engineering, Hefei, Anhui Hefei 230022, China) Abstract: From the start the main types of lathe fixture, fixture on the flower disc and angle iron clamp lathe was introduced, and on the basis of analysis of a lathe fixture design points. Keywords: lathe fixture; design; points Lathe for machining parts on the rotating surface, such as the outer cylinder, inner cylinder and so on. Parts in the processing, the fixture can be installed in the lathe with rotary machine with main primary uranium movement. However, in order to expand the use of lathe, the work piece can also be installed in the lathe of the pallet, tool mounted on the spindle. THE MAIN TYPES OF LATHE FIXTURE Installed on the lathe spindle on the lathe fixture
On the vehicle sideslip angle estimation through neural networks: Numerical and experimental results. S. Melzi,E. Sabbioni Mechanical Systems and Signal Processing 25 (2011)：14~28 电脑估计车辆侧滑角的数值和实验结果 S.梅尔兹,E.赛博毕宁 机械系统和信号处理2011年第25期：14~28
摘要 将稳定控制系统应用于差动制动内/外轮胎是现在对客车车辆的标准（电子稳定系统ESP、直接偏航力矩控制DYC）。这些系统假设将两个偏航率(通常是衡量板)和侧滑角作为控制变量。不幸的是后者的具体数值只有通过非常昂贵却不适合用于普通车辆的设备才可以实现直接被测量,因此只能估计其数值。几个州的观察家最终将适应参数的参考车辆模型作为开发的目的。然而侧滑角的估计还是一个悬而未决的问题。为了避免有关参考模型参数识别/适应的问题,本文提出了分层神经网络方法估算侧滑角。横向加速度、偏航角速率、速度和引导角,都可以作为普通传感器的输入值。人脑中的神经网络的设计和定义的策略构成训练集通过数值模拟与七分布式光纤传感器的车辆模型都已经获得了。在各种路面上神经网络性能和稳定已经通过处理实验数据获得和相应的车辆和提到几个处理演习(一步引导、电源、双车道变化等)得以证实。结果通常显示估计和测量的侧滑角之间有良好的一致性。 1 介绍 稳定控制系统可以防止车辆的旋转和漂移。实际上，在轮胎和道路之间的物理极限的附着力下驾驶汽车是一个极其困难的任务。通常大部分司机不能处理这种情况和失去控制的车辆。最近,为了提高车辆安全，稳定控制系统(ESP[1,2]; DYC[3,4])介绍了通过将差动制动/驱动扭矩应用到内/外轮胎来试图控制偏航力矩的方法。 横摆力矩控制系统（DYC）是基于偏航角速率反馈进行控制的。在这种情况下,控制系统使车辆处于由司机转向输入和车辆速度控制的期望的偏航率[3,4]。然而为了确保稳定，防止特别是在低摩擦路面上的车辆侧滑角变得太大是必要的[1,2]。事实上由于非线性回旋力和轮胎滑移角之间的关系，转向角的变化几乎不改变偏航力矩。因此两个偏航率和侧滑角的实现需要一个有效的稳定控制系统[1,2]。不幸的是,能直接测量的侧滑角只能用特殊设备(光学传感器或GPS惯性传感器的组合)，现在这种设备非常昂贵,不适合在普通汽车上实现。因此, 必须在实时测量的基础上进行侧滑角估计，具体是测量横向/纵向加速度、角速度、引导角度和车轮角速度来估计车辆速度。 在主要是基于状态观测器/卡尔曼滤波器(5、6)的文学资料里, 提出了几个侧滑角估计策略。因为国家观察员都基于一个参考车辆模型,他们只有准确已知模型参数的情况下，才可以提供一个令人满意的估计。根据这种观点,轮胎特性尤其关键取决于附着条件、温度、磨损等特点。 轮胎转弯刚度的提出就是为了克服这些困难,适应观察员能够提供一个同步估计的侧滑角和附着条件[7,8]。这种方法的弊端是一个更复杂的布局的估计量导致需要很高的计算工作量。 另一种方法可由代表神经网络由于其承受能力模型非线性系统，这样不需要一个参
毕业论文（设计） 外文翻译 题目：机械加工介绍
机械加工介绍 1.车床 车床主要是为了进行车外圆、车端面和镗孔等项工作而设计的机床。车削很少在其他种类的机床上进行，而且任何一种其他机床都不能像车床那样方便地进行车削加工。由于车床还可以用来钻孔和铰孔，车床的多功能性可以使工件在一次安装中完成几种加工。因此，在生产中使用的各种车床比任何其他种类的机床都多。 车床的基本部件有：床身、主轴箱组件、尾座组件、溜板组件、丝杠和光杠。 床身是车床的基础件。它能常是由经过充分正火或时效处理的灰铸铁或者球墨铁制成。它是一个坚固的刚性框架，所有其他基本部件都安装在床身上。通常在床身上有内外两组平行的导轨。有些制造厂对全部四条导轨都采用导轨尖朝上的三角形导轨（即山形导轨），而有的制造厂则在一组中或者两组中都采用一个三角形导轨和一个矩形导轨。导轨要经过精密加工以保证其直线度精度。为了抵抗磨损和擦伤，大多数现代机床的导轨是经过表面淬硬的，但是在操作时还应该小心，以避免损伤导轨。导轨上的任何误差，常常意味着整个机床的精度遭到破坏。 主轴箱安装在内侧导轨的固定位置上，一般在床身的左端。它提供动力，并可使工件在各种速度下回转。它基本上由一个安装在精密轴承中的空心主轴和一系列变速齿轮(类似于卡车变速箱)所组成。通过变速齿轮，主轴可以在许多种转速下旋转。大多数车床有8~12种转速，一般按等比级数排列。而且在现代机床上只需扳动2~4个手柄，就能得到全部转速。一种正在不断增长的趋势是通过电气的或者机械的装置进行无级变速。 由于机床的精度在很大程度上取决于主轴，因此，主轴的结构尺寸较大，通常安装在预紧后的重型圆锥滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸，因此当工件必须通过主轴孔供料时，它确定了能够加工的棒料毛坯的最大尺寸。 尾座组件主要由三部分组成。底板与床身的内侧导轨配合，并可以在导轨上作纵向移动。底板上有一个可以使整个尾座组件夹紧在任意位置上的装置。尾座体安装在底板上，可以沿某种类型的键槽在底板上横向移动，使尾座能与主轴箱中的主轴对正。尾座的第三个组成部分是尾座套筒。它是一个直径通常大约在51~76mm之间的钢制空心圆柱体。
Lathes Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod. The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment. On most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be machined when the material must be fed through spindle. The tailsticd assembly consists, essentially, of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit aligning the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 51 to 76mm(2to 3 inches) in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw. The size of a lathe is designated by two dimensions. The first is known as the swing. This is the maximum diameter of work that can be rotated on a lathe. It is approximately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between centers. The swing thus indicates the maximum work piece diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers. Engine lathes are the type most frequently used in manufacturing. They are heavy-duty machine tools with all the components described previously and have power drive for all tool movements except on the compound rest. They commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches) center distances, but swings up to 1270 mm(50 inches) and center distances up
The development of automobile As the world energy crisis and the war and the energy consumption of oil -- and are full of energy in one day someday it will disappear without a trace. Oil is not inresources. So in oil consumption must be clean before finding a replacement. With the development of science and technology the progress of the society people invented the electric car. Electric cars will become the most ideal of transportation. In the development of world each aspect is fruitful especially with the automobile electronic technology and computer and rapid development of the information age. The electronic control technology in the car on a wide range of applications the application of the electronic device cars and electronic technology not only to improve and enhance the quality and the traditional automobile electrical performance but also improve the automobile fuel economy performance reliability and emission spurification. Widely used in automobile electronic products not only reduces the cost and reduce the complexity of the maintenance. From the fuel injection engine ignition devices air control and emission control and fault diagnosis to the body auxiliary devices are generally used in electronic control technology auto development mainly electromechanical integration. Widely used in automotive electronic control ignition system mainly electronic control fuel injection system electronic control ignition system electronic control automatic transmission electronic control ABS/ASR control system electronic control suspension system electronic control power steering system vehicle dynamic control system the airbag systems active belt system electronic control system and the automatic air-conditioning and GPS navigation system etc. With the system response the use function of quick car high reliability guarantees of engine power and reduce fuel consumption and emission regulations meet standards. The car is essential to modern traffic tools. And electric cars bring us infinite joy will give us the physical and mental relaxation. Take for example automatic transmission in road can not on the clutch can achieve automatic shift and engine flameout not so effective improve the driving convenience lighten the fatigue strength. Automatic transmission consists mainly of hydraulic torque converter gear transmission pump hydraulic control system electronic control system and oil cooling system etc. The electronic control of suspension is mainly used to cushion the impact of the body and the road to reduce vibration that car getting smooth-going and stability. When the vehicle in the car when the road uneven road can according to automatically adjust the height. When the car ratio of height low set to gas or oil cylinder filling or oil. If is opposite gas or diarrhea. To ensure and improve the level of driving cars driving stability. Variable force power steering system can significantly change the driver for the work efficiency and the state so widely used in electric cars. VDC to vehicle performance has important function it can according to the need of active braking to change the wheels of the car car motions of state and optimum control performance and increased automobile adhesion controlling and stability. Besides these appear beyond 4WS 4WD electric cars can greatly improve the performance of the value and ascending simultaneously. ABS braking distance is reduced and can keep turning skills effectively improve the stability of the directions simultaneously reduce tyre wear. The airbag appear in large programs protected the driver and passengers safety and greatly reduce automobile in collision of drivers and passengers in the buffer to protect the safety of life. Intelligent electronic technology in the bus to promote safe driving and that the other functions. The realization of automatic driving through various sensors. Except some smart cars equipped with multiple outside sensors can fully perception of information and traffic facilities
外文翻译 通常，应变计应用在两个方面：在机械和结构的实验力分析中和应用力，扭矩，压力,流量以及加速度传感器结构中。非粘贴丝式应变计通常是当作专门的转换器来使用，其结构是使用一些有预载荷的电阻丝连接成惠斯登电桥，如图4.11： 在最初的预载荷中，四根金属丝的应变和电阻在理论上是相等的，它们组成一个平衡电桥，并且e0 = 0 （参考第10章电桥电路特性）。输入端一个小的位移（满量程≈0.04 mm）将会使两根金属丝的拉力增大而使另外两根的拉力减小（假设金属丝不会变松弛），引起电阻阻值的变化，电桥失衡，输出电压与输入位移成比例。金属丝可以由砷镍、镍铬和铁镍等多种合金制造，直径约为0.03 mm，可以承受的最大应力仅为0.002 N，灵敏系数为2到4，每个桥臂的电阻为120Ω到1000Ω, 最大激励电压5到10V，满量程输出典型值为20到50mV。 粘结丝式应变计（现在主要被粘贴箔式结构的应变计取代）应用于应力分析和作为转换器。具有很细丝式敏感栅粘贴在待测试件表面，来感受应变。金属丝被埋入矩形的粘合剂中，不能弯曲从而如实地反映待测试件的压缩和拉伸应力。因为金属丝的材料和尺寸与那些非粘贴应变计相似，所以灵敏度和电阻具有了可比性。 粘贴箔式应变计采用与丝式应变计相同或类似的材料，现在主要用于多用途力分析任务及多种传感器中。 其感应元件是利用光腐蚀工艺加工成厚度小于0.0002的薄片，当其形状改变时，它具有很大的灵活性。如图4.12： 例如，这三个线形敏感栅应变计被设计成端部宽大的形状。这种局部的增大将会减小横向灵敏度，以及在测量应变沿敏感栅单元的长度方向的分量时产生的干扰输入信号。在丝式应变计中，这种端部形状也应用在纵向单元的连接处，以便增加横向抗干扰能力。并且在制造过程中也非常方便在图4.12上的全部四个应变计上焊接焊盘。
毕业设计(论文)外文资料翻译 系部： 专业： 姓名： 学号： 外文出处：English For Electromechanical (用外文写) Engineering 附件：1.外文资料翻译译文；2.外文原文。 指导教师评语： 此翻译文章简单介绍了各机床的加工原理，并详细介绍了各机床的构造，并对方各机床的加工方法法进行了详细的描述， 翻译用词比较准确，文笔也较为通顺，为在以后工作中接触英 文资料打下了基础。 签名： 年月日注：请将该封面与附件装订成册。
附件1：外文资料翻译译文 机床 机床是用于切削金属的机器。工业上使用的机床要数车床、钻床和铣床最为重要。其它类型的金属切削机床在金属切削加工方面不及这三种机床应用广泛。 车床通常被称为所有类型机床的始祖。为了进行车削，当工件旋转经过刀具时，车床用一把单刃刀具切除金属。用车削可以加工各种圆柱型的工件，如：轴、齿轮坯、皮带轮和丝杠轴。镗削加工可以用来扩大和精加工定位精度很高的孔。 钻削是由旋转的钻头完成的。大多数金属的钻削由麻花钻来完成。用来进行钻削加工的机床称为钻床。铰孔和攻螺纹也归类为钻削过程。铰孔是从已经钻好的孔上再切除少量的金属。 攻螺纹是在内孔上加工出螺纹，以使螺钉或螺栓旋进孔内。 铣削由旋转的、多切削刃的铣刀来完成。铣刀有多种类型和尺寸。有些铣刀只有两个切削刃，而有些则有多达三十或更多的切削刃。铣刀根据使用的刀具不同能加工平面、斜面、沟槽、齿轮轮齿和其它外形轮廓。 牛头刨床和龙门刨床用单刃刀具来加工平面。用牛头刨床进行加工时，刀具在机床上往复运动，而工件朝向刀具自动进给。在用龙门刨床进行加工时，工件安装在工作台上，工作台往复经过刀具而切除金属。工作台每完成一个行程刀具自动向工件进给一个小的进给量。 磨削利用磨粒来完成切削工作。根据加工要求，磨削可分为精密磨削和非精密磨削。精密磨削用于公差小和非常光洁的表面，非精密磨削用于在精度要求不高的地方切除多余的金属。 车床 车床是用来从圆形工件表面切除金属的机床，工件安装在车床的两个顶尖之间，并绕顶尖轴线旋转。车削工件时，车刀沿着工件的旋转轴线平行移动或与工件的旋转轴线成一斜角移动，将工件表面的金属切除。车刀的这种位移称为进给。车
汽车保险中英文对照外文翻译文献(文档含英文原文和中文翻译)
汽车保险 汽车保险是在事故后保证自己的财产安全合同。尽管联邦法律没有强制要求，但是在大多数州（新罕布什和威斯康星州除外）都要求必须购买汽车保险；在各个州都有最低的保险要求。在鼻腔只购买汽车保险的两个州，如果没有足够的证据表明车主财力满足财务责任法的要求，那么他就必须买一份汽车保险。就算没有法律规定，买一份合适的汽车保险对司机避免惹上官和承担过多维修费用来说都是非常实用的。 依据美国保险咨询中心的资料显示，一份基本的保险单应由6个险种组成。这其中有些是有州法律规定，有些是可以选择的，具体如下： 1.身体伤害责任险 2.财产损失责任险 3.医疗险或个人伤害保护险 4.车辆碰撞险 5.综合损失险 6.无保险驾驶人或保额不足驾驶人险 责任保险 责任险的投保险额一般用三个数字表示。不如，你的保险经纪人说你的保险单责任限额是20/40/10，这就代表每个人的人身伤害责任险赔偿限额是2万美元，每起事故的热身上海责任险赔偿限额是4万美元，每起事故的财产损失责任险的赔偿限额是1万美元。 人身伤害和财产损失责任险是大多数汽车保险单的基础。要求汽车保险的每个州都强令必须投保财产损失责任险，佛罗里达是唯一要求汽车保险但不要求投保人身伤害责任险的州。如果由于你的过错造成了事故，你的责任险会承担人身伤害、财产损失和法律规定的其他费用。人身伤害责任险将赔偿医疗费和误工工资；财产损失责任险将支付车辆的维修及零件更换费用。财产损失责任险通常承担对其他车辆的维修费用，但是也可以对你的车撞坏的灯杆、护栏、建筑物等其他物品的损坏进行赔偿。另一方当事人也可以决定起诉你赔偿精神损失。
高精度稳压直流电源 文摘:目前对于可调式直流电源的设计和应用现在有很多微妙的,多种多样的,有趣的问题。探讨这些问题(特别是和中发电机组有关),重点是在电路的经济适用性上,而不是要达到最好的性能。当然，对那些精密程度要求很高的除外。讨论的问题包括温度系数，短期漂移，热漂移，瞬态响应变性遥感和开关preregualtor型机组及和它的性能特点有关的的一些科目。 介绍 从商业的角度来看供电领域可以得到这样一个事实，在相对较低的成本下就可以可以获得标准类型的0.01%供电调节。大部分的供电用户并不需要这么高的规格，但是供应商不会为了减少客户这么一点的费用而把0.1%改成0.01%。并且电力供应的性能还包括其他一些因素，比如说线路和负载调解率。本文将讨论关于温度系数、短期漂移、热漂移,和瞬态的一些内容。 目前中等功率直流电源通常采用预稳压来提高功率/体积比和成本，但是只有某些电力供应采用这样的做法。这种技术的优缺点还有待观察。 温度系数 十年以前，大多数的商业电力供应为规定的0.25%到1%。这里将气体二极管的温度系数定位百分之0.01[1]。因此，人们往往会忽视TC（温度系数）是比规定的要小的。现在参考的TC往往比规定的要大的多。为了费用的减少，后者会有很大的提高，但是这并不是真正的TC。因此，如果成本要保持在一个低的水平，可以采用TC非常低的齐纳二极管，安装上差动放大电路，还要仔细的分析低TC绕线电阻器。 如图1所示，一个典型的放大器的第一阶段，其中CR1是参考齐纳二极管，R是输出电位调节器。
图1 电源输入级 图2 等效的齐纳参考电路 假设该阶段的输出是e3，提供额外的差分放大器，在稳定状态下e3为零，任何参数的变化都会引起输出的漂移；对于其他阶段来说也是一样的，其影响是减少了以前所有阶段的增益。因此，其他阶段的影响将被忽略。以下讨论的内容涵盖了对于TC整体的无论是主要的还是次要的影响。 R3的影响 CR1-R3分支的等效的电路如图2所示，将齐纳替换成了它的等效电压源E'和内部阻抗R2。对于高增益调节器，其中R3的变化对差分放大器的输入来说可以忽略不计，所以前后的变化由R3决定。 如果进一步假定IB << Iz;从（1）可以得到 同时，
机床加工外文翻译参考文献(文档含中英文对照即英文原文和中文翻译) 基本加工工序和切削技术 基本加工的操作 机床是从早期的埃及人的脚踏动力车和约翰·威尔金森的镗床发展而来的。它们为工件和刀具提供刚性支撑并可以精确控制它们的相对位置和相对速度。基本上讲，金属切削是指一个磨尖的锲形工具从有韧性的工件表面上去除一条很窄的金属。切屑是被废弃的产品，与其它工件相比切屑较短，但对于未切削部分的厚度有一定的增加。工件表面的几何形状取决于刀具的形状以及加工操作过程中刀具的路径。 大多数加工工序产生不同几何形状的零件。如果一个粗糙的工件在中心轴上转动并且刀具平行于旋转中心切入工件表面，一个旋转表面就产生了，这种操作称为车削。如果一个空心的管子以同样的方式在内表面加工，这种操作称为镗孔。当均匀地改变直径时便产生了一个圆锥形的外表面，这称为锥度车削。如果刀具接触点以改变半径的方式运动，那么一个外轮廓像球的工件便产生了；或者如果工件足够的短并且支撑是十分刚硬的，那么成型刀具相对于旋转轴正常进给的一个外表面便可产生，短锥形或圆柱形的表面也可形成。
平坦的表面是经常需要的，它们可以由刀具接触点相对于旋转轴的径向车削产生。在刨削时对于较大的工件更容易将刀具固定并将工件置于刀具下面。刀具可以往复地进给。成形面可以通过成型刀具加工产生。 多刃刀具也能使用。使用双刃槽钻钻深度是钻孔直径5-10倍的孔。不管是钻头旋转还是工件旋转，切削刃与工件之间的相对运动是一个重要因数。在铣削时一个带有许多切削刃的旋转刀具与工件接触，工件相对刀具慢慢运动。平的或成形面根据刀具的几何形状和进给方式可能产生。可以产生横向或纵向轴旋转并且可以在任何三个坐标方向上进给。 基本机床 机床通过从塑性材料上去除屑片来产生出具有特别几何形状和精确尺寸的零件。后者是废弃物，是由塑性材料如钢的长而不断的带状物变化而来，从处理的角度来看，那是没有用处的。很容易处理不好由铸铁产生的破裂的屑片。机床执行五种基本的去除金属的过程：车削，刨削，钻孔，铣削。所有其他的去除金属的过程都是由这五个基本程序修改而来的，举例来说，镗孔是内部车削；铰孔，攻丝和扩孔是进一步加工钻过的孔；齿轮加工是基于铣削操作的。抛光和打磨是磨削和去除磨料工序的变形。因此，只有四种基本类型的机床，使用特别可控制几何形状的切削工具1.车床，2.钻床，3.铣床，4.磨床。磨削过程形成了屑片，但磨粒的几何形状是不可控制的。 通过各种加工工序去除材料的数量和速度是巨大的，正如在大型车削加工，或者是极小的如研磨和超精密加工中只有面的高点被除掉。一台机床履行三大职能：1.它支撑工件或夹具和刀具2.它为工件和刀具提供相对运动3.在每一种情况下提供一系列的进给量和一般可达4-32种的速度选择。 加工速度和进给 速度，进给量和切削深度是经济加工的三大变量。其他的量数是攻丝和刀具材料，冷却剂和刀具的几何形状，去除金属的速度和所需要的功率依赖于这些变量。 切削深度，进给量和切削速度是任何一个金属加工工序中必须建立的机械参量。它们都影响去除金属的力，功率和速度。切削速度可以定义为在旋转一周时
汽车变速器设计 ----------外文翻译 我们知道，汽车发动机在一定的转速下能够达到最好的状态，此时发出的功率比较大，燃油经济性也比较好。因此，我们希望发动机总是在最好的状态下工作。但是，汽车在使用的时候需要有不同的速度，这样就产生了矛盾。这个矛盾要通过变速器来解决。 汽车变速器的作用用一句话概括，就叫做变速变扭，即增速减扭或减速增扭。为什么减速可以增扭，而增速又要减扭呢？设发动机输出的功率不变，功率可以表示为 N = w T，其中w是转动的角速度，T是扭距。当N固定的时候，w与T是成反比的。所以增速必减扭，减速必增扭。汽车变速器齿轮传动就根据变速变扭的原理，分成各个档位对应不同的传动比，以适应不同的运行状况。 一般的手动变速器内设置输入轴、中间轴和输出轴，又称三轴式，另外还有倒档轴。三轴式是变速器的主体结构，输入轴的转速也就是发动机的转速，输出轴转速则是中间轴与输出轴之间不同齿轮啮合所产生的转速。不同的齿轮啮合就有不同的传动比，也就有了不同的转速。例如郑州日产ZN6481W2G型SUV车手动变速器，它的传动比分别是：1档3.704:１；2档2.202:1；3档1.414:1；4档1:1；5档（超速档）0.802:1。 当汽车启动司机选择1档时，拨叉将1/2档同步器向后接合1档齿轮并将它锁定输出轴上，动力经输入轴、中间轴和输出轴上的1档齿轮，1档齿轮带动输出轴，输出轴将动力传递到传动轴上（红色箭头）。典型1档变速齿轮传动比是3:1,也就是说输入轴转3圈，输出轴转1圈。 当汽车增速司机选择2档时，拨叉将1/2档同步器与1档分离后接合2档齿轮并锁定输出轴上，动力传递路线相似，所不同的是输出轴上的1档齿轮换成2档齿轮带动输出轴。典型2档变速齿轮传动比是2.2:1，输入轴转2.2圈，输出轴转1圈，比1档转速增加，扭矩降低。
中文4285字 附录1 LATHES & MILLING A shop that is equipped with a milling machine and an engine lathe can machine almost any type of product of suitable size. The basic machines that are designed primarily to do turning，facing and boring are called lathes. Very little turning is done on other types of machine tools，and none can do it with equal facility. Because lathe can do boring，facing，drilling，and reaming in addition to turning，their versatility permits several operations to be performed with a single setup of the workpiece. This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool. Lathes in various forms have existed for more than two thousand years. Modern lathes date from about 1797，when Henry Maudsley developed one with a leads crew. It provided controlled，mechanical feed of the tool. This ingenious Englishman also developed a change gear system that could connect the motions of the spindle and leadscrew and thus enable threads to be cut. Lathe Construction.The essential components of a lathe are depicted in the block diagram of picture. These are the bed，headstock assembly，tailstock assembly，carriage assembly，quick-change gearbox，and the leadscrew and feed rod. The bed is the back bone of a lathe. It usually is made of well-normalized or aged gray or nodular cast iron and provides a heavy，rigid frame on which all the other basic components are mounted. Two sets of parallel，longitudinal ways，inner and outer，are contained on the bed，usually on the upper side. Some makers use an inverted V-shape for all four ways，whereas others utilize one inverted V and one flat way in one or both sets. Because several other components are mounted and/or move on the ways they must be made with precision to assure accuracy of alignment. Similarly，proper precaution should betaken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The ways on most modern lathes are surface hardened to