数字机床控制系统中英文对照外文翻译文献.docx

1、数字机床控制系统中英文对照外文翻译文献中英文资料翻译文献翻译原文：Numerical ControlOne 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 cont

2、rol 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.Nume

3、rical 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 nu

4、merically 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

5、 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.2.Laser cutting.3.Electron beam welding.Numerical con

6、trol has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide variety of par 4s , each involving an assortment of undertake the production of products that would not have been feasible from an economic perspective using

7、 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 wer

8、e 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 the curve . Eac

9、h 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 mo

10、tions. 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 wri

11、tten on the tape for the machine .Together, all of 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

12、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 p

13、roduce 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 t

14、he paper tape carried the programmed instructions as a series of holes punched in the tape , theThis most mportant 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

15、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 tap

16、e.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

17、 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

18、host computer goes down , the machine tools also experience down time . This problem led to the development of computer numerical control.The evelopment of the microprocessor allowed for the development of programmable logic controllers (PLC) and microcomputers . These two technologies allowed for t

19、he 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

20、 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 ignal Processors.There are numerous situations where analog signals

21、 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 othe

22、r 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 man

23、y manufacturers, each one designed for a particular price/performance/usage group. Many of the largest manufacturers, like Texas Instruments and Motorola, offer both specialised DSPs for certain fields like motor-control or modems ,and general high-performance SPs that can erform broad ranges of pro

24、cessing tasks. Development kits an software are also available , and there are companies making software development tools for DSPs that allows the programmer to implement complex processing algorithms using simple “drag n drop” methodologies.DSPs more or less fall into two categories depending on t

25、he 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 differe

26、nce 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 DSPs behave more like common general-purpose CPUs ,with register

27、-files.There are thousands of different DSPs 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

28、DSPs: Texas Instruments, Motorola, AT&T and Analog Devices.Digital-to-analog conversionIn 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 f

29、ed an amplifier or similar audio equipment . This digital to analog conversion (DCA) is performed by a circuit with the same name & Different DCAs provide different performance and quality , as measured by THD (Total harmonic distortion ), number of bits, linearity , speed, filter characteristics an

30、d other things.The TMS320 family DQP of Texas InstrumentsThe TLS320family consists of fixed-point, floating-point, multiprocessor digital signal processors (DSPs) , and foxed-point DSP controllers. TMS320 DSP have an architecture designed specifically for real-time signal processing . The F/C240 is

31、a number of theC2000DSP 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

32、 the right choice for a wide range of processing applications:- Very flexible instruction set- Inherent operational flexibility -High-speed performance-Innovative parallel architecture-Cost effectivenessDevices within a generation of the TMS320 family have the same CPU structure but different on-chi

33、p 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.T