模拟驾驶训练系统( 计算机仿真与液压伺服的集成系统 ),Unit 22,Computer Simulation,Computer Simulation,Computer Simulation,Computer Simulation as a powerful analytic tool widely used in scientific research and engineering design demonstrates unrivalled advantages. With computer simulation, scientists and engineers do not have to build real primary prototypes when they observe a known phenomenon, analyse a complex process, design a machine or a building, etc. Computer simulation is particularly significant when the object under study and examination is costly or even impossible to be built into a real model. For example, to study the cause of engine malfunction that has led to a series of supersonic planes crashed, or to examine the impact on passengers when an airplane crashes, researchers may have to,计算机仿真作为一种功能强大的分析工具，广泛地用于科学研究和工程设计中，且具有无与伦比的优越性。科学家们在观察已知现象、分析复杂过程、设计一台机器或一座建筑物等时，利用计算机仿真技术后，不再需要建立真实的原始模型。当研究和考察的对象价格昂贵或甚至无法实现真实模型时，计算机仿真技术显得尤为重要。例如，为了研究由于发动机故障而造成超音速飞机一系列坠毁事故的原因，或者为了检查当飞机失事时对乘客的影响，研究者需要一遍又一遍地反复,模仿飞机坠毁过程，直到找出需要达成的什么结论。显然，他们只能通过操作计算机仿真程序等进行仿真，而不是再现真实的悲剧情况。另一个例子是在工程设计中工程师必须尝试很多方案和参数，才能提出令人满意的设计。利用计算机仿真程序，工程师只须将不同的方案和参数输入到应用计算机建立的模型中，就能完成每次的重复过程，而不需构建多个不同的真实模型。,repeat simulating the calamities over and over again before they can find out what they need to reach a conclusion. Obviously, these can only be simulated by running computer simulation programs or the like, rather than replicating the tragedies. Another example is engineering design, in which engineers have to try many schemes and parameters before they can come up with a satisfactory design. Using computer simulation programs, engineers can accomplish that iterative process each time by inputting different schemes and parameters into their computer models, rather than building many different real models.,实际上，计算机仿真技术是以数学模型为基础，这些数学模型代表了被研究得或考察得物体的自然属性。数学模型包含一系列数学表达式，这些数学表达式以数学术语形式描述了对象的内在过程。计算机仿真程序包含了由这些数学表达式获得的算法。仿真的结果通常以相当抽象的形式表述，如二维曲线图表，图形。,Virtually, computer simulation is based on mathematical models representing the nature of the object under study or examination. The mathematical model comprises a series of equations that depict the inherent processes of the object in mathematical terms. A computer simulation program includes algorithms that are derived from those equations. The outcome of simulation is usually expressed in rather abstract forms, for instance, 2-D diagrams curves tables, figures.,Over the past years, computer graphics techniques have helped computer simulation by creating realistic 3-D images to depict the object to be simulated and the environment around it or the effect imposed on it. Sophisticated computer simulation package capable of providing real-time interactive moving images have emerged, although still beyond the reach of most industries. Meanwhile, many CAD systems have incorporated visual modules to enable engineers to interactively ”walk” through their 3-D pseudo models on screen to review their designs and present them to their clients. This convenience is particularly important to architects.,在过去几年里，通过创造逼真的三维图像来描述被仿真的对象和其周围所处环境及环境对其的影响效果，计算机图形学技术已促进了计算机仿真技术的发展。计算机图形技术虽然还没有广泛用于大多数行业，但能够提供实时的、交互的流动图像的计算机仿真套装软件已经出现。同时，许多结合了可视模型的计算机辅助设计系统使工程师能够交互地“走”进他们屏幕上的3D虚拟模型，检查他们的设计并将它们呈现在客户面前。这种便利对于建筑设计尤为重要。,这里还有一个例子，为了分析飞机飞行时机身的应力分布，计算机仿真软件将为这一特殊主题建立一个数学模型。该数学模型由从空气动力学、弹性力学、结构力学等理论中得出的等式组成，然后根据有限元应力分析，针对飞机的简化结构进行一系列计算，最后，由计算机仿真系统算出结果，结果将是一簇遍布飞机机身简化结构的曲线，每一条曲线指明了机身上承受同一应力的位置。仿真结果的精确性取决于数学模型的精确性，,Here is an example. To analyse the distribution of stress in a fuselage when the plane is flying, the computer simulation package will first set up a mathematical model for this specific theme which comprises equations derived from aerodynamics, elasticity, structural mechanics, then implement a series of computations on a simplified structure of the plane, based on the finite element stress analysis, finally, it gives the outcome which will be clusters of curves spread over the simplified structure of the plane, each indicating the locations in the fuselage that suffer stress of a uniform value. The accuracy of the simulation depends on the accuracy of the mathematical model,that is, how closely the model is built to represent the real plane and its environment in terms of mathematics, geometry and mechanics (as shown in Fig.22-1).,即数学模型与它代表的真实飞机以及依据数学、几何学和机械学表示的飞机所在环境的接近程度（如图22-1所示）。,Fig22-1 Computer Simulation,Computer simulation seems to be the only choice for analysing disasters, calamities and accidents. Quite a lot of impressive simulations have been made on some potentially threatening disasters and calamities, for example, the aftermaths of a global nuclear war, the disastrous effect on global climate and environment as a result of worldwide greenhouse effect, the probability of collision between an invading meteorite and the earth, etc. Other applications of computer simulation technique can be weather forecasting, simulation of combat actions in battlefield, flight programs for training future pilots, human models for testing new medici