数控外文翻译说课讲解

Numerical Control

One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC).Prior to the advent of NC, all machine tools were manual operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related to and limited to the skills of the operator . Numerical control represents the first major step away from human control of machine tools.

Numerical control means the control of machine tools and other manufacturing systems though the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool, For a machine tool to be numerically controlled , it must be interfaced with a device for accepting and decoding the p2ogrammed instructions, known as a reader.

Numerical control was developed to overcome the limitation of human operator , and it has done so . Numerical control machines are more accurate than manually operated machines , they can produce parts more uniformly , they are faster, and the long-run tooling costs are lower . The development of NC led to the development of several other innovations in manufacturing technology:

1.Electrical discharge machining.

https://www.360docs.net/doc/9c6816790.html,ser cutting.

3.Electron beam welding.

Numerical control has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide variety of par4s , each involving an assortment of undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tools and processes.

Like so many advanced technologies , NC was born in the laboratories of the Massachusetts Institute of Technology . The concept of NC was developed in the early 1950s with funding provided by the U.S Air Force .In its earliest stages , NC machines were able to make straight cuts efficiently and effectively.

However ,curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve. The shorter is the straight lines making up the step ,the smoother is 4he curve . Each line segment

in the steps had to be calculated.

This problem led to the development in 1959 of the Automatically Programmed Tools (APT) language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the further development of NC technology. The original NC system were vastly different from those used punched paper , which was later to replaced by magnetic plastic tape .A tape reader was used to interpret the instructions written on the tape for the machine .Together, all /f this represented giant step forward in the control of machine tools . However ,there were a number of problems with NC at this point in its development.

A major problem was the fragility of the punched paper tape medium . It was common for the paper containing the programmed instructions to break or tear during a machining process, This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to rerun thought the reader . If it was necessary to produce 100 copies of a given part , it was also necessary to run the paper tape thought the reader 100 separate times . Fragile paper tapes simply could not withstand the rigors of shop floor environment and this kind of repeated use.

This led to the development of a special magnetic tape . Whereas the paper tape carried the programmed instructions as a series of holes punched in the tape , theThis most important of these was that it was difficult or impossible to change the instructions entered on the tape . To make even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape thought the reader as many times as there were parts to be produced . Fortunately, computer technology become a reality and soon solved the problems of NC, associated with punched paper and plastic tape.

The development of a concept known as numerical control (DNC) solve the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions . In direct numerical control, machine tools are tied, via a data transmission link, to a host computer and fed to the machine tool as needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However ,it is subject to the same limitation as all technologies that depend on a host computer. When the host computer goes down , the machine tools also experience down time . This problem led to the development of computer numerical control.

The development of the microprocessor allowed for the development of programmable

logic controllers (PLC) and microcomputers . These two technologies allowed for the development of computer numerical control (CNC).With CNC , each machine tool has a PLC or a microcomputer that serves the same purpose. This allows programs to be input and stored at each individual machine tool. CNC solved the problems associated downtime of the host computer , but it introduced another problem known as data management . The same program might be loaded on ten different microcomputers with no communication among them. This problem is in the process of being solved by local area networks that connectDigital Signal Processors

There are numerous situations where analog signals to be processed in many ways, like filtering and spectral analysis , Designing analog hardware to perform these functions is possible but has become less and practical, due to increased performance requirements, flexibility needs , and the need to cut down on development/testing time .It is in other words difficult pm design analog hardware analysis of signals.

The act of sampling an signal into thehat are specialised for embedded signal processing operations , and such a processor is called a DSP, which stands for Digital Signal Processor . Today there are hundreds of DSP families from as many manufacturers, each one designed for a particular price/performance/usage group. Many of the largest manufacturers, like Texas Instruments and Motorola, offer both specialised DSP’s for certain fields like motor-control or modems ,and general high-performance DSP’s that can perform broad ranges of processing tasks. Development kits an` software are also available , and there are companies making software development tools for DSP’s that allows the programmer to implement complex processing algorithms using simple “drag ‘n’ drop” methodologies.

DSP’s more or less fall into two categories depending on the underlying architecture-fixed-point and floating-point. The fixed-point devices generally operate on 16-bit words, while the floating-point devices operate on 32-40 bits floating-point words. Needless to say , the fixed-point devices are generally cheaper . Another important architectural difference is that fixed-point processors tend to have an accumulator architecture, with only one “general purpose” register , making them quite tricky to program and more importantly ,making C-compilers inherently inefficient. Floating-point DSP’s behave more like common general-purpose CPU’s ,with register-files.

There are thousands of different DSP’s on the market, and it is difficult task finding the most suitable DSP for a project. The best way is probably to set up a constraint and wishlist, and try to compare the processors from the biggest manufacturers against it.

The “big four” manufacturers of DSPs: Texas Instruments, Motorola, AT&T and Analog Devices.

Digital-to-analog conversion

In the case of MPEG-Audio decoding , digital compressed data is fed into the DSP which performs the decoding , then the decoded samples have to be converted back into the analog domain , and the resulting signal fed an amplifier or similar audio equipment . This digital to analog conversion (DCA) is performed by a circuit with the same name & Different DCA’s provide different performance and quality , as measured by THD (Total harmonic distortion ), number of bits, linearity , speed, filter characteristics and other things.

The TMS320 family DQP of Texas Instruments

The TLS320family consists of fixed-point, floating-point, multiprocessor digital signal processors (D[Ps) , and foxed-point DSP controllers. TMS320 DSP have an architecture designed specifically for real-time signal processing . The’ F/C240 is a number of the’C2000DSP platform , and is optimized for control applications. The’C24x series of DSP controllers combines this real-time processing capability with controller peripherals to create an ideal solution for control system applications. The following characteristics make the TMS320 family the right choice for a wide range of processing applications:

--- Very flexible instruction set

--- Inherent operational flexibility

---High-speed performance

---Innovative parallel architecture

---Cost effectiveness

Devices within a generation of the TMS320 family have the same CPU structure but different on-chip memory and peripheral configurations. Spin-off devices use new combinations of On-chip memory and peripherals to satisfy a wide range of needs in the worldwide electronics market. By integrating memory and peripherals onto a single chip , TMS320 devices reduce system costs and save circuit board space.

The 16-bit ,fixed-point DSP core of the ‘C24x device s provides analog designers a digital solution that does not sacrifice the precision and performance of their system performance can be enhanced through the use of advanced control algorithms for techniques such as adaptive control , Kalman filtering , and state control. The ‘C24x DSP controller offer reliability and programmability . Analog control systems, on the other hand ,are hardwired solutions and can experience performance degradation due to aging , component tolerance, and drift.

The high-speed central processing unit (CPU) allows the digital designer to process algorithms in real time rather than approximate results with look-up tables. The instruction set of these DSP controllers, which incorporates both signal processing instructions and

general-purpose control functions, coupled with the extensive development time and provides the same ease of use as traditional 8-and 16-bit microcontrollers. The instruction set also allows you to retain your software investment when moving from other general-pur pose‘C2xx generation ,source code compatible with the’C2x generation , and upwardly source code compatible with the ‘C5x generation of DSPs from Texas Instruments.

The ‘C24x architecture is also well-suited for processing control signals. It uses a 16-bit word length along with 32-bit registers for storing intermediate results, and has two hardware shifters available to scale numbers independently of the CPU . This combination minimizes quantization and truncation errors, and increases p2ocessing power for additional functions. Such functions might include a notch filter that could cancel mechanical resonances in a system or an estimation technique that could eliminate state sensors in a system.

The ‘C24xDSP controllers take advantage of an set of peripheral functions that allow Texas Instruments to quickly configure various series members for different price/ performance points or for application optimization.

This library of both digital and mixed-signal peripherals includes:

---Timers

---Serial communications ports (SCI,SPI)

---Analog-to-digital converters(ADC)

---Event manager

---System protection, such as low-voltage and watchdog timer

The DSP controller peripheral library is continually growing and changing to suit the of tomorrow’s embedded control mark etplace.

The TMS320F/C240 is the first standard device introduced in the ‘24x series of DSP controllers. It sets the standard for a single-chip digital motor controller. The ‘240 can execute 20 MIPS. Almost all instructions are executed in a simple cycle of 50 ns . This high performance allows real-time execution of very comple8 control algorithms, such as adaptive control and Kalman filters. Very high sampling rates can also be used to minimize loop delays.

The ‘ 240 has the architectural features necessar y for high-speed signal processing and digital control functions, and it has the peripherals needed to provide a single-chip solution for motor control applications. The ‘240 is manufactured using submicron CMOS technology, achieving a log power dissipation rating . Also included are several power-down modes for further power savings. Some applications that benefit from the advanced processing power of the ‘240 include:

---Industrial motor drives

---Power inverters and controllers

---Automotive systems, such as electronic power steering , antilock brakes, and climate control

---Appliance and HV AC blower/ compressor motor controls

---Printers, copiers, and other office products

---Tape drives, magnetic optical drives, and other mass storage products

---Robotic and CNC milling machines

To function as a system manager, a DSP must have robust on-chip I/O and other peripherals. The event manager of the ‘240 is unlike any other available on a DSP . This application-optimized peripheral unit , coupled with the high performance DSP core, enables the use of advanced control techniques for high-precision and high-efficiency full variable-speed control of all motor types. Include in the event manager are special pulse-width modulation (PWM) generation functions, such as a programmable dead-band function and a space vector PWM state machine for 3-phase motors that provides state-of-the-art maximum efficiency in the switching of power transistors.

There independent up down timers, each with it’s own compare register, supp ort the generation of asymmetric (noncentered) as well as symmetric (centered) PWM waveforms.

Open-Loop and Closed-Loop Control

Open-loop Control Systems

The word automatic implies that there is a certain amount of sophistication in the control system. By automatic, it generally means That the system is usually capable of adapting to a variety of operating conditions and is able to respond to a class of inputs satisfactorily . However , not any type of control system has the automatic feature. Usually , the automatic feature is achieved by feed.

g the feedback structure, it is called an open-loop system , which is the simplest and most economical type of control system.inaccuracy lies in the fact that one may not know the exact characteristics of the further ,which has a definite bearing on the indoor temperature. This alco points to an important disadvantage of the performance of an open -loop control system, in that the system is not capable of adapting to variations in environmental conitions or to external disturbances. In the case of the furnace control, perhaps an experienced person can provide control for a certain desired temperature in the house; but id the doors or windows are opened or closed intermittently during the operating period, the final temperature inside the house will not be accurately regulated by the open-loop control.

An electric washing machine is another typical example of an open-loop system , because the amount of wash time is entirely determined by the judgment and estimation of the

human operator . A true automatic electric washing machine should have the means of checking the cleanliness of the clothes continuously and turn itsedt off when the desired degised of cleanliness is reached.

Closed-Loop Control Systems

What is missing in the open-loop control system for more accurate and more adaptable control is a link or feedback from the output to the input of the system . In order to obtain more accurate bontrol, the controlled signal c(t) must be fed back and compared with the reference input , and an actuating signal proportional to the difference of the output and the input must be sent through the system to correct the error. A system with one or more feedback pat(s like that just described is called a closed-loop system. human being are probably the most complex and sophisticated feedback control system in existence. A human being may be considered to be a control system with many inputs and outputs, capable of carrying out highly complex operations.

To illustrate the human being as a feedback control system , let us consider that the objective is to reach for an object on aperform the task. The eyes serve as a sensing device which feeds back continuously the position of the hand . The distance between the hand and the object is the error , which is eventually brought to zero as the hand reacher the object. This is a typical example of closed-loop control. However , if one is told to reach for the object and then is blindolded, one can only reach toward the object by estimating its exact position. It isAs anther illustrative example of a closed-loop control system, shows the block diagram of the rudder control system ofThe basic alements and the bloca diagram of a closed-loop control system are shown in fig. In general , the configuration of a feedback control system may not be constrained to that of fig & . In complex systems there may be multitude of feedback loops and element blocks.

数控

在先进制造技术领域最根本的观念之一是数控（NC）。数控来临之前，所有机床是手工操作和控制。手动控制机床有许多限制，或许没有比操作者的技能更突出。用手动控制，产品质量直接相关，并仅限于操作者的技能。数控具有重要的意义在于它摆脱手动控制机床。

数控机床意味着，机器操作和其他手写机器操作系统的到来。操作机床，数控技术员只要写出机床的指示程序，机床就会自动控制，它必须与一个接口接受和解码程序指示，作为一个读者已知的设备。

数控开发，克服了人工操作的局限性，并且已经完成。数控机床比手动操作机器更为准确，他们可以使得生产部分更得体，他们更快，从长远来说他的时间花费成本较低。数控的开发推动了制造业的技术创新发展：

1。电火花加工。2。激光切割。3。电子束焊接。

数控机床也比他们更早的机器更为的灵活。一种数控机床能自动产生的种类繁多，每个涉及的零件，从经济的角度，将不会被可行的手动控制机床和工艺产品的生产品种所替代。

像许多先进技术一样，数控出生于美国麻省理工学院的实验室。该数控概念是在50年代初由美国空军提出。在最初阶段，数控机床能够使直接有效地削减人力。

然而，制作弯曲的零件是一个问题，因为机床要进行编程，进行横向和纵向的一系列步骤，以产生一个曲线。较短的可以用直线组成，是平滑曲线。它的的每一步骤都必须进行计算。

这个问题导致了1959年自动编程工具（APT）语言的发展，使用类似数控英文语句来定义几何零件，描述刀具配置，并制定所需的方案。新的APT语言的发展是重大的一步，推动数控技术的进一步发展。原来的数控系统广泛使用穿孔纸，后来由磁性塑料带代替。一个使用穿孔纸的人解释了该机器的磁带使用说明。总之，所有一切都代表数控控制的大步发展。然而，有一些问题，就是数控在这点上的发展。

一个主要的问题是该打孔纸带中的脆弱性。就是在输入程序指令时纸带的撕裂，比这个问题更加严重的是，在机床制造过程中的连续性，携带的纸带编程指示必须重新运行。如果生产预先制定的100份，还需要运行100个纸带独立运行的时间。脆弱的纸带根本无法承受这样的环境，这样的无法重复使用。

这导致了一个特殊磁带的发展。而通过在磁带打孔系列的编程指令中的纸带，其中最重要的是，很难或者不可能改变磁带上输入的指令。即使是在一个最微小的调整方案，也需要中断才能加工，并制作出新的磁带。它仍然需要尽可能多的时间运行磁带来实现要产生部分。幸运的是，计算机技术成为了现实，并很快解决了数控问题，这与打孔纸

和胶带密切相关。

作为知名的数控概念发展（DNC）解决了纸张和塑料带与数控相关作为执行指令的编程语言磁带的问题。在直接数字控制下，精密机床的束缚，通过数据传输链路，连接在主机和机器工具，通过数据传输连接需要。直接数字控制穿孔纸带和塑料带的应用上是一个重大的进步。但是，它受所有技术，在主机上却有相同的限制。当主机出现故障，机器工具也会出现故障。这个问题引导了计算机数控的发展。

关于可编程逻辑控制器（PLC）和微型计算机的发展使微处理器的发展。这两项技术的发展，计算机数字控制（CNC）允许的数控系统。每台机器工具，PLC或微型计算机，它为同样的目的。这允许程序自动输入和存储在每个机床上。数控解决相关的主机停机的问题，但它推出了著名的数据管理的另一个问题。同样的程序可能会被装上10种不同的微型电脑，它们之间没有沟通。此问题处理是在当地区域网络的过程中解决的connectDigital信号处理器的。

在许多情况下的模拟信号会用各种方法处理问题，在很多方面像滤波和频谱分析，设计模拟硬件来执行这些职能是可能的，但已变得越来越少，由于更高的性能需求，灵活性的需求，以及需要削减减少开发/测试的时间的需求。正是在困难时，换句话说，是模拟信号的硬件设计分析改变了现状。

抽样一个信号是专门为嵌入式信号处理的操作，这种处理器被称为数字信号处理器，是数字信号处理器的代表。今天有数百个家庭的DSP从尽可能多的制造商，每一个特定的价格/性能/使用组来设计的。大的厂家很多，像德州仪器，摩托罗拉，都提供专门的DSP像马达控制或调制解调器这些领域的，和一般的高性能DSP处理，可以执行广泛的任务范围。软件开发工具包也可以，也有公司做好DSP的，允许程序员可以实现复杂的处理算法，利用简单的“拖放'和'下降”的方法的软件开发工具。

DSP的或多或少取决于两类下降的基础架构的定点和浮点。定点设备操作一般在16位，而浮点器件上32-40位浮点操作。不用说，定点设备一般比较便宜。另一个重要的结构不同的地方是，定点处理器往往只有一个“通用的蓄电池架构”，这使得他们的方案很棘手，更重要的是，制造的C-编译器固有的低效率。浮点DSP的表现更像是共同的通用CPU的寄存器文件。

在市场上有成千上万不同的数字信号处理器，找到项目最合适的数字信号处理器是一个艰巨的任务。最好的办法可能是成立一个约束和心愿，并试图针对它的最大制造商的处理器来进行比较。

“四大”的数字信号处理器制造商：德州仪器，摩托罗拉，AT＆T和模拟设备。

数字至模拟转换

MPEG音频解码，数字压缩的数据反馈到执行的DSP解码，解码后的样本，将转换成模拟域回来，与由此产生的信号放大器或类似的音频设备。这个数字到模拟转换（DCA）的工作由一个具有相同名称和不同音频媒体的电路提供不同的性能和质量，如THD（总

谐波失真），对位，线性度，速度，过滤特征和其他一些。

TMS320系列DQP的德州仪器

该TLS320family仪器由定点，浮点组成，数字信号处理器的多处理器（DSP）及foxed 点DSP控制器。 TMS320系列数字信号处理器设计了实时信号处理具体的架构。F/C240是C2000DSP平台，并控制应用而优化。C24x的DSP控制器系列，结合这个控制器外设的实时处理能力，以创造一个控制系统应用的理想解决方案。以下特点使TMS320系列正确选择应用广泛的加工范围：

---非常灵活的指令集

---固有业务灵活性

---高速性能

---创新的并行结构

---成本效益

一代的TMS320系列器件具有相同的CPU结构，但不同的片上存储器和外设配置不同。附带了设备使用的片上存储器和外设新组合，以满足全球电子市场的需求范围。通过整合到一个单一芯片内存和外设，TMS320系列设备降低了系统成本和节省电路板空间。

16位定点DSP的C24x核心器件模拟设计提供了数字解决方案，不牺牲精度和系统性能，可通过为技术先进的控制算法，如适应控制使用增强，卡尔曼滤波，和国家控制。C24x DSP控制器提供的可靠性和可编程性。模拟控制系统，一方面，是硬连线解决方案和经验，可能因老化性能降低，元件容差和漂移。

高速中央处理单元（CPU）可处理的数字化设计，事实上，并不是与查表结果近似的算法。这些指令集的DSP控制器，它集成了信号处理指令和通用控制功能，具有广泛的开发时间，并提供了结合传统的8位和16位微控制器使用相同的环节。指令集还允许您保留您的软件投资在其他普通C2x上，源代码C2x代兼容，源代码与德州仪器的数字信号处理器C5x代兼容。

在C24x架构也非常适用于控制信号的处理。它用于存储中间结果的32位寄存器的16位字，并有两个硬件可用号码提供给独立的CPU。这种组合减少量化误差和截断，以及附加功能增加进化的能力。这些职能可能包括取消陷波器，可以在一个系统或一个机械共振技术，可消除系统状态的传感器。

在C24xDSP控制器考虑让德州仪器具备快速配置不同价格/性能点或各种系列的成员进行应用优化的外设功能设置的优势。这两个数字和混合信号外设库包括：

---定时器

---串行通信接口（SCI的，SPI）

---模拟到数字转换器（ADC）

---事件管理器

---系统保护，如低电压和看门狗定时器

该DSP控制器外设库是不断增长和变化的，以适应未来的嵌入式控制市场。

该TMS320F/C240于的介绍是第一个标准装置中的DSP控制器24x系列。它决定一个单芯片的数字电机控制器的标准。该C240可以执行20 MIPS。几乎所有的指令执行时间为50 ns。这一高性能允许实时非常完整的控制算法，如自适应控制，卡尔曼滤波的执行。非常高的采样率也可用于尽量减少循环延迟。

在240C具有高速信号处理和数字控制功能所必需的建筑特色，以及它需要提供一个电机控制应用的单芯片解决方案的外设。该240C使用亚微米CMOS制造技术，实现了日志的功耗等级。还包括一些掉电模式，进一步节省功耗。有些应用程序从240C具有先进的处理能力的好处：

---工业马达驱动器

---电源逆变器和控制器

---汽车系统，如电子动力转向，防抱死制动系统和气候控制

---家电和空调风机/压缩机电机控制

---打印机，复印机和其他办公用品

---磁带机，磁光盘驱动器和其他大容量存储产品

---机器人和数控铣床

要作为一个系统管理员，必须有强大的DSP芯片上的I / O和其他外围设备。该240事物管理器是不同于其他任何可以用一个数字信号处理器的处理器。此应用程序优化的周边装置，与高性能的DSP核心，可提供了高精确度和高效率的全变速控制的所有汽车类型的先进控制技术。事物管理器包括特殊的脉冲宽度调制（PWM）生成功能，如可编程死区的功能和空间矢量PWM状态机，3相马达，提供了完善的设施，最先进的最高效率开关电源晶体管。

有独立的定时器，每个与它自己比较的寄存器，支持非对称代（noncentered）以及对称（中心）的PWM波形。

开环和闭环控制系统

开环控制系统

这个词意味着有一个复杂的控制系统自动控制一定的数额。它通常意味着该系统通常是能够适应不同的作业条件，并能有令人满意的回应。然而，并非任何类型的控制系统都具有自动功能。通常情况下，自动控制功能是通过feed来完成的。

g的反馈结构，它被称为开环系统，该系统是精确控制的一个事实，就是可能不知道确切的控制，特点在于最简单，最经济，它有一个明确的轴承温度。这也指出了一个开环控制系统的性能重要的缺馅，该系统不能够适应变化的环境或外部干扰。在此控制情况下，或许是有经验的人提供了一个理想中的外室温控制，门或窗被打开或在营运期间，关闭间歇性，在房子里的最后温度不会精确的受开环控制。

电动洗衣机是另一种开环系统的典型例子，因为洗的时间是完全由人类的判断和估

计确定的。一个真正的全自动电动洗衣机应具有的检查不断清洁的衣服的功能，关闭时所需达到清洁的目的。

闭环控制系统

闭环控制缺少更准确和更适应由输出反馈提高系统的输入。为了获得更准确的控制信号必须反馈，并参考输入，以及一个驱动信号成比例的输出和输入的差异，必须通过系统发送而修正错误。与一个或更多反馈，就像是刚才所说的是被称为闭环系统。人类系统是可能是最复杂和精密的反馈控制系统的存在。一个人可以被认为是一个控制系统有许多输入和输出，开展高度复杂的操作能力。

为了说明人类作为一个正反馈控制系统，让我们考虑该计划的目的是达成一个任务对象。眼睛作为传感装置，不断地反馈手的位置。之间的距离和对象的错误，最终到零。这是一个闭环控制的典型例子。然而，如果被告知要达到目标，然后是看不到的，只能达到对对象估计其确切位置。据国际检索单位一个闭环控制系统的算例，表明了该控制系统基本的一个闭环控制系的图框。如图所示。一般来说，一个反馈控制系统配置不得限制该feedback。在复杂的系统有可能反馈回路和元素块过多。