机械类数控外文翻译外文文献英文文献数控.docx

编号：时间：2021 年 x 月 x 日书山有路勤为径，学海无涯苦作舟书山有路勤为径，学海无涯苦作舟页码：第1页 共10页第 1 页 共 10 页Numerical ControlOne of the most fundamental concepts in the area of advanced manufacturingtechnologies is numerical control(NC).Prior to the advent of NC,all machine tools weremanual operated and controlled.Among the many limitations associated with manual controlmachine tools,perhaps none is more prominent than the limitation of operator skills.Withmanual control,the quality of the product is directly related to and limited to the skills of theoperator.Numerical control represents the first major step away from human control ofmachine tools.Numerical control means the control of machine tools and other manufacturing systemsthough the use of prerecorded,written symbolic instructions.Rather than operating a machinetool,an NC technician writes a program that issues operational instructions to the machinetool,For a machine tool to be numerically controlled,it must be interfaced with a device foraccepting and decoding the p2ogrammed instructions,known as a reader.Numerical control was developed to overcome the limitation of human operator,and ithas done so.Numerical control machines are more accurate than manually operatedmachines,they can produce parts more uniformly,they are faster,and the long-run toolingcosts are lower.Thedevelopment of NC led to the development of several otherinnovations in manufacturing technology:1.Electrical discharge machining.2.Laser cutting.3.Electron beam welding.Numerical control has also made machine tools more versatile than their manuallyoperated predecessors.An NC machine tool can automatically produce a wide variety ofpar4s,each involving an assortment of undertake the production of products that would nothave been feasible from an economic perspective using manually controlled machine toolsand processes.Like so many advanced technologies,NC was born in the laboratories of theMassachusetts Institute of Technology.The concept of NC was developed in the early 1950swith funding provided by the U.S Air Force.In its earliest stages,NC machines were able tomake straight cuts efficiently and effectively.However,curved pathswere a problem because the machine tool had to beprogrammed to undertake a series of horizontal and vertical steps to produce a curve.Theshorter is the straight lines making up the step,the smoother is 4he curve.Each line segmentin 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 partgeometry,describe the cutting tool configuration,and specify the necessary motions.Thedevelopment of the APT language was a major step forward in the further development of NCtechnology.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 theinstructions written on the tape for the machine.Together,all/f this represented giant stepforward in the control of machine tools.However,there were a number of problems with NC编号：时间：2021 年 x 月 x 日书山有路勤为径，学海无涯苦作舟书山有路勤为径，学海无涯苦作舟页码：第2页 共10页第 2 页 共 10 页at this point in its development.A major problem was the fragility of the punched paper tape medium.It was commonfor the paper containing the programmed instructions to break or tear during a machiningprocess,This problem was exacerbated by the fact that each successive time a part wasproduced on a machine tool,the paper tape carrying the programmed instructions had to rerunthought the reader.If it was necessary to produce 100 copies of a given part,it was alsonecessary to run the paper tape thought the reader 100 separate times.Fragile paper tapessimply 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 carriedthe programmed instructions as a series of holes punched in the tape,theThis most importantof 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 tointerrupt machining operations and make a new tape.It was also still necessary to run the tapethought the reader as many times as there were parts to be produced.Fortunately,computertechnology become a reality and soon solved the problems of NC,associated with punchedpaper and plastic tape.The development of a concept known as numerical control(DNC)solve the paper andplastic tape problems associated with numerical control by simply eliminating tape as themedium for carrying the programmed instructions.In direct numerical control,machine toolsare tied,via a data transmission link,to a host computer and fed to the machine tool as neededvia the data transmission linkage.Direct numerical control represented a major step forwardover punched tape and plastic tape.However,it is subject to the same limitation as alltechnologies that depend on a host computer.When the host computer goes down,themachine tools also experience down time.This problem led to the development of computernumerical control.The development of the microprocessor allowed for the development of programmablelogic controllers(PLC)and microcomputers.These two technologies allowed for thedevelopment of computer numerical control(CNC).With CNC,each machine tool has a PLCor a microcomputer that serves the same purpose.This allows programs to be input and storedat each individual machine tool.CNC solved the problems associated downtime of the hostcomputer,but it introduced another problem known as data management.The same programmight be loaded on ten different microcomputers with no communication among them.Thisproblem is in the process of being solved by local area networks that connectDigital SignalProcessorsThere are numerous situations where analog signals to be processed in many ways,likefiltering and spectral analysis,Designing analog hardware to perform these functions ispossible 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 wordsdifficult pm design analog hardware analysis of signals.The act of sampling an signal into thehat are specialised for embedded signal processingoperations,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 fora particular price/performance/usage group.Many of the largest manufacturers,like Texas编号：时间：2021 年 x 月 x 日书山有路勤为径，学海无涯苦作舟书山有路勤为径，学海无涯苦作舟页码：第3页 共10页第 3 页 共 10 页Instruments and Motorola,offer both specialised DSPsfor certain fields like motor-controlor modems,and general high-performance DSPs that can perform broad ranges of processingtasks.Development kits an software are also available,and there are companies makingsoftware development tools for DSPs that allows the programmer to implement complexprocessing algorithms using simple“drag ndrop”methodologies.DSPsmoreorlessfallintotwocategoriesdependingontheunderlyingarchitecture-fixed-point and floating-point.The fixed-point devices generally operate on16-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 importantarchitectural 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 moreimportantly,making C-compilers inherently inefficient.Floating-point DSPs behave morelike common general-purpose CPUs,with register-files.There are thousands of different DSPs on the market,and it is difficult task finding themost 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 AnalogDevices.Digital-to-analog conversionIn the case of MPEG-Audio decoding,digital compressed data is fed into the DSP whichperforms the decoding,then the decoded samples have to be converted back into the analogdomain,and the resulting signal fed an amplifier or similar audio equipment.This digital toanalog conversion(DCA)is performed by a circuit with the same name&Different DCAsprovide 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 InstrumentsThe TLS320family consists of fixed-point,floating-point,multiprocessor digital signalprocessors(DPs),and foxed-point DSP controllers.TMS320 DSP have an architecturedesigned specifically for real-time signal processing.The F/C240 is a number oftheC2000DSP platform,and is optimized for control applications.TheC24x series of DSPcontrollers combines this real-time processing capability with controller peripherals to createan ideal solution for control system applications.The following characteristics make theTMS320 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 effectivenessDevices within a generation ofthe TMS320 family have the same CPU structure butdifferenton-chipmemoryandperipheralconfigurations.Spin-off devicesusenewcombinations of On-chip memory and peripherals to satisfy a wide range of needs in theworldwide electronics market.By integrating memory and peripherals onto a single chip,TMS320 devices reduce system costs and save circuit board space.编号：时间：2021 年 x 月 x 日书山有路勤为径，学海无涯苦作舟书山有路勤为径，学海无涯苦作舟页码：第4页 共10页第 4 页 共 10 页The 16-bit,fixed-point DSP core of the C24x devices provides analog designers adigital solution that does not sacrifice the precision and performance of their systemperformance can be enhanced through the use of advanced control algorithms for techniquessuch as adaptive control,Kalman filtering,and state control.The C24x DSP controller offerreliability and programmability.Analog control systems,on the other hand,are hardwiredsolutions and can experience performance degradation due to aging,component tolerance,and drift.The high-speed central processing unit(CPU)allows the digital designer to processalgorithms in real time rather than approximate results with look-up tables.The instruction setof these DSP controllers,which incorporates both signal processing instructions andgeneral-purpose control functions,coupled with the extensive development time and providesthe same ease of use as traditional 8-and 16-bit microcontrollers.The instruction set alsoallows you to retain your software investment when moving from other general-purposeC2xxgeneration,source code compatible with theC2x generation,and upwardly source codecompatible with the C5x generation of DSPs from Texas Instruments.The C24x architecture is also well-suited for processing control signals.It uses a 16-bitword length along with 32-bit registers for storing intermediate results,and has two hardwareshifters available to scale numbers independently of the CPU.This combination minimizesquantization and truncation errors,and increases p2ocessing power for additional functions.Such functions might include a notch filter that could cancel mechanical resonances in asystem or an estimation technique that could eliminate state sensors in a system.The C24xDSP controllers take advantage of an set of peripheral functions that allowTexas 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 timerThe DSP controller peripheral library is continually growing and changing to suit the oftomorrows embedded control marketplace.The TMS320F/C240 is the first standard device introduced in the 24x series of DSPcontrollers.It sets the standard for a single-chip digital motor controller.The 240 can execute20 MIPS.Almost all instructions are executed in a simple cycle of 50 ns.This highperformance allows real-time execution of very comple8 control algorithms,such as adaptivecontrol and Kalman filters.Very high sampling rates can also be used to minimize loopdelays.The 240 has the architectural features necessary for high-speed signal processing anddigital control functions,and it has the peripherals needed to provide a single-chip solutionfor motor control applications.The 240 ismanufactured using submicron CMOStechnology,achieving a log power dissipation rating.Also included are several power-downmodes for further power savings.Some applications that benefit from the advanced编号：时间：2021 年 x 月 x 日书山有路勤为径，学海无涯苦作舟书山有路勤为径，学海无涯苦作舟页码：第5页 共10页第 5 页 共 10 页processing power of the 240 include:-Industrial motor drives-Power inverters and controllers-Automotive systems,such as electronic power steering,antilock brakes,and climatecontrol-Appliance and HVAC blower/compressor motor controls-Printers,copiers,and other office products-Tape drives,magnetic optical drives,and other mass storage products-Robotic and CNC milling machinesTo function as a system manager,a DSP must have robust on-chip I/O and otherperipherals.The event manager of the 240 is unlike any other available on a DSP.Thisapplication-optimized peripheral unit,coupled with the high performance DSP core,enablesthe use of advanced control techniques for high-precision and high-efficiency fullvariable-speed control of all motor types.Include in the event manager are specialpulse-width modulation(PWM)generation functions,such as a programmable dead-bandfunction and a space vector PWM state machine for 3-phase motors that providesstate-of-the-art maximum efficiency in the switching of power transistors.There independent up down timers,each with its own compare register,support thegeneration of asymmetric(noncentered)as well as symmetric(centered)PWM waveforms.Open-Loop and Closed-Loop ControlOpen-loop Control SystemsThe word automatic implies that there is a certain amount of sophistication in thecontrol system.By automatic,it generally means That the system is usually capable ofadapting to a variety of operating conditions and is able to respond to a class of inputssatisfactorily.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 andmost economical type of control system.inaccuracy lies in the fact that one may not know theexact characteristics of the further,which has a definite bearing on the indoor temperature.This alco points to an importa