Numerical Control Technology英文版).ppt

1、, NC Technology Email: ., Numerical Control Technology , NC Technology Email: .,Ch4 COMPUTER NUMERICAL CONTROL UNIT, NC Technology Email: .,Outline,CNC system HARDWARE ARCHITECTURE OF CNC UNIT CNC Software OPEN ARCHITECTURE SYSTEM FOR CNC UNIT, NC Technology Email: j

2、.,Introduction,Machine controls are divided into two types: numerical control (NC) computer numerical control (CNC). NC controls have to read the program each time a part is run; they have no means of editing existing programs. CNC controls can store and allow editing of loaded programs. A

3、ll machines built today are CNC machines. CNC unit is the heart of CNC machine., NC Technology Email: .,NC system,The NC machine : control unit, which processes the commands from the input media. the drive mechanisms the machine itself The most basic function of any NC machine is automati

4、c, precise, and consistent motion control., NC Technology Email: .,The makeup of a linear axis of an NC machine, NC Technology Email: .,CNC System,Definition (EIA): CNC system is a special computer system that is equipped with certain interface circuits and servo drivers, and c

5、an do part or all the works an NC system do by running the software stored in its memories. EIA(美国电子工业协会)所属的数控标准化委员会的定义: “CNC是用一个存储程序的计算机，按照存储在计算机内的读写存储器中的控制程序去执行数控装置的部分或全部功能，在计算机之外的唯一装置是接口”。 ISO(国际标准化组织)的定义: “数控系统是一种控制系统，它自动阅读输入载体上事先给定的数字，并将其译码，从而使机床移动和加工零件”。, NC Technology Email: .,CNC

6、machining System,Logical structure of CNC machine tool, NC Technology Email: .,CNC machining System, NC Technology Email: .,CNC系统的组成,从自动控制的角度来看，CNC系统是一种位置（轨迹）、速度（还包括电流）控制系统，其本质上是以多执行部件(各运动轴)的位移量、速度为控制对象并使其协调运动的自动控制系统，是一种配有专用操作系统的计算机控制系统。 从外部特征来看，CNC系统是由硬件（通用硬件和专用硬件）和软件（专用）两大部分组

7、成的。, NC Technology Email: .,CNC装置的组成和工作原理, NC Technology Email: .,CNC装置的组成和工作原理,硬件结构: CPU，存储器，总线、外设等。 软件结构：是一种用于零件加工的、实时控制的、特殊的（或称专用的）计算机操作系统。, NC Technology Email: .,CNC装置的组成和工作原理,3. 工作原理 通过各种输入方式，接受机床加工零件的各种数据信息，经过CNC装置译码，再进行计算机的处理、运算，然后将各个坐标轴的分量送到各控制轴的驱动电路，经过转换、放大

8、去驱动伺服电动机，带动各轴运动。并进行实时位置反馈控制，使各个坐标轴能精确地走到所要求的位置。 简要工作过程： 1）输入： 输入内容零件程序、控制参数和补偿数据。 输入方式穿孔纸带阅读输入、磁盘输入、光盘输入、手健盘输 入，通讯接口输入及连接上级计算机的DNC接口输入., NC Technology Email: .,CNC装置的组成和工作原理,2）译码：以一个程序段为单位，根据一定的语法规则解释、翻译成计算机能够识别的数据形式，并以一定的数据格式存放在指定的内存专用区内。 3）数据处理：包括刀具补偿，速度计算以及辅助功能的处理等。 4）插补：插补的任务是通过插补计算程序

9、在一条曲线的已知起点和终点之间进行“数据点的密化工作”。 5）位置控制：在每个采样周期内，将插补计算出的理论位置与实际反馈位置相比较，用其差值去控制进给伺服电机。 6）I/O处理：处理CNC装置与机床之间的强电信号输入、输出和控制。 7）显示：零件程序、参数、刀具位置、机床状态等。 8）诊断：检查一切不正常的程序、操作和其他错误状态。, NC Technology Email: .,CNC unit,CNC unit is the core of the whole CNC system. It is composed of hardware and software.

10、The hardware : microprocessors, electronic memory modules, I/O interfaces, and position control modules, etc. CNC software controls all functions of the machine and its efficiency of operation, and manages all local programming at the machine tool and graphic simulation of the cutting process if ava

11、ilable. The hardware and the software work together to do all functions of CNC unit, which an ordinary NC system can never do., NC Technology Email: .,The main functions and features of CNC unit,Controlling function (the number of control axes and synchronously control axes) Preparatory f

12、unction Interpolation function Feed function Feed Rate Override Rapid motion Spindle function, NC Technology Email: .,The main functions and features of CNC unit,6. Miscellaneous function 7. Compensation function Tool length compensation, cutter radius compensation , and tool nose radius

13、compensation. Technical parameters compensation 8. Enhanced graphic display function 9. Self-diagnosis function 10. Communication function 11. Programming function, NC Technology Email: .,Functional interface between hardware and software in CNC unit, NC Technology Email: .,HAR

14、DWARE ARCHITECTURE OF CNC UNIT,CNC unit is the core of CNC system. The hardware comprising a CNC unit is made up of microprocessors, electronic memory modules, I/O interfaces, and position control modules, etc. , which is just like an ordinary computer system., NC Technology Email: .,Type

15、s of CNC Unit,by the architecture of printed circuit boards All-in-one board architecture multi-functional modules architecture by the number of microprocessors single microprocessor multi- microprocessors by the manufacturing fashions ordinary personal computer architecture special purpose architec

16、ture according to their opening degree Close architecture PC-plug-in-NC architecture NC-plug-in-PC architecture software based open architecture of CNC unit, NC Technology Email: .,All-in-one board architecture,All-in-one architecture CNC unit comprises main board, position control card,

17、PLC card, displayer card, and power supply. Main board is a big printed circuit board; other functional cards are small size, each is installed in a card rack on the main board., NC Technology Email: .,Sketch map of All-in-one board architecture, NC Technology Email: ., NC Tech

18、nology Email: .,Multi-functional modules architecture,In this architecture, CNC unit is divided into several function modules. Its hardware and software are designed with modularization method, that is to say, each function module is made of printed circuit of same size, and the control s

19、oftware of function modules are also designed in modularization. Hence, customers can establish their own CNC units by combining their selected function modules into the card racks of a motherboard. CNC control module, position control card, PLC card, graph display card and communication card are fa

20、miliar function modules., NC Technology Email: .,a holonomic CNC lath system, NC Technology Email: .,Single microprocessor architecture,There is only one microprocessor, which processes various NC tasks by time-sharing in a centralized control way. in this architecture. Some CN

21、C system, though having more than two processors ,can only be called single microprocessor systems, because there is only one microprocessor on duty of controlling and occupying the system bus, while the others cannot occupy the system bus and cannot access main memory. This architecture is simple a

22、nd can be implemented easily, whereas, for reason of centralized controlling, its performances and abilities are limited by the byte length, data width, address ability, and calculating speed of microprocessor., NC Technology Email: .,Multi-microprocessors architecture,distributed system

23、master-and-servant system bus based multi host microprocessor system., NC Technology Email: .,Distributed system,there is a communication network route between each two microprocessors. Interactions within microprocessors and shared resources are achieved via network communication technol

24、ogy, NC Technology Email: .,Master-and-servant system,A processor is called master microprocessor, others are servant microprocessors, and they are all independent systems. Only master microprocessor can control the bus, access the resources attached with the bus, control and monitor serv

25、ant microprocessors, and coordinate the operations of servant microprocessors., NC Technology Email: .,Bus based multi CPU system, NC Technology Email: .,Special purpose architecture,CNC units of this architecture are designed and manufactured by different enterprises respectiv

26、ely. They have convenient layouts, compact structures, and high performances for special purpose, but have no general characters; hence, one CNC unit cannot be changed or substituted by another CNC unit, which is manufactured by a different enterprise. FANUC CNC system, SIEMENS CNC system, and A-B s

27、ystem (American) are of this architecture, NC Technology Email: .,Personal computer architecture,CNC unit of this architecture base on industry computer (IPC) platform, and is built by plugging in certain control cards and NC software. IPC platform has made CNC unit cheaper and cheaper in

28、 price, and easily to be substituted when fault occurs,IPC,CNC unit,CNC system, NC Technology Email: .,Typical CNC Units,SIEMENS (German) FANUC (Japan) ALLEN-BRANDLEY (American A-B) HNC (HuaZhong Numerical Control system Blue-Sky (ShenYang Institute of Computing Technology), NC Technology

29、 Email: .,CNC SOFTWARE,In CNC system, there are various kinds of software codes, which fall into two groups: user software and system software., NC Technology Email: .,User software,User software is also called part program, which is programmed and inputted by using numerical c

30、ontrol language (such as APT) to indicate the machining procedure of the part. It is compiled into a program with various G-codes and M-codes arranged according to the process sequence., NC Technology Email: .,System software,CNC system software can be sorted into two packages: managing s

31、oftware and control software., NC Technology Email: .,The function of control software,(1) Compiling the part codes inputted by users After receiving the part codes, compiler will translate, trim and store them into a specified format; decode the machining instructions in part codes and d

32、o decimal-binary transitions to coordinate data; calculate tools center path considering the offset of tool radius; pre-calculate some constants that will be used in interpolation calculation and speed control process, etc., NC Technology Email: .,The function of control software,(2) Inte

33、rpolation calculations Interpolation calculation subroutine has the same functions with hardware interpolator in NC system,!, e. ,to assign electrical pulses for axes. It is a strict real time program, and demands as less as possible number of instruction codes, that is to say, to shorten the time f

34、or performing interpolation calculations ,because the time is determinative to the feed speed of interpolation. In some CNC system ,it is adopted to combine rough interpolation and fine interpolation, NC Technology Email: .,The function of control software,(3) Tool compensation All types

35、of CNC machine tools require some form(s) of compensation, such as tool length compensation, cutter radius compensation, and tool nose radius compensation. Though applied for different reasons on different machine types ,all forms of compensation allow the CNC user to allow for unpredictable conditi

36、ons related to tooling. Generally speaking, if the CNC user is faced with any unpredictable situations during programming, it is likely that the CNC control manufacturer has come up with a form of compensation to deal with the problem., NC Technology Email: .,The function of control softw

37、are,(4) Speed control Speed control subroutine aims at controlling the speed of pulses assigning, i.e. controlling the frequency of interpolation calculation according to the setting speed code (or corresponding speed instruction) to guarantee the preset feed velocity. While there is an unexpected a

38、brupt changing in velocity during machining, the speed control subroutine should automatically speed up or slow down the velocity to avoid pace loss in drive system. Speed control can be implemented totally by software method (software timer method), and can also be implemented by hardware means., N

39、C Technology Email: .,The function of control software,(5) Position control Position control is in the position loop of servo system. This work can be done by either software or hardware. Position control software compares interpolation calculated position with real measured position in e

40、ach sampling cycle, and control the motor using the difference. position control software can usually adjust the magnification of the position loop circuit, compensate the error of pitch of screws in each direction of axes, and compensate the non-return-to-zero when reverse the motion, so that the l

41、ocation precision would be improved., NC Technology Email: .,Position control, NC Technology Email: .,Managing Software,managing software connects each function subroutine to hardware. Managing software is composed of part program I/O; display of part program, tool position, sy

42、stem parameters, running status and alarm information, static and dynamic tool path; and diagnosis codes ,by which CNC unit can carry out self-diagnosis and spot the faults. It is also on duty of synchronizing various procedures., NC Technology Email: .,Managing Software,Managing software

43、 can be divided into two groups: one comprises the subroutines that tie to hardware, and another is independent of hardware. Software, which depends on hardware, manages and drives peripheral equipment, such as CRT displayer, keyboard, and communication equipments, etc. ,and performs real time proce

44、sses ,i. e. ,interruption management and various processors management, which are all real time tasks. Independent software manages time, tasks, memory, and internal communications, and synchronizes various procedures., NC Technology Email: .,Parallel processing, NC Technology Email: jtbg

45、.,Real time processing, NC Technology Email: .,Parallel processing,Parallel process means that computer implements two or more tasks at the same time or within the same time interval. It can improve the processing speed greatly. methods to realize parallel process Time overlap meth

46、od (时间重叠) resource-sharing technology （资源共享） resource-apposition （资源重复）, NC Technology Email: .,Time overlap method,Time overlap method, based on flow line technique, staggers the processing time of procedures, and makes many procedures use parts of the equipment respectively at the same

47、time., NC Technology Email: .,Resource-sharing technology,resource-sharing technology is based on time-sharing principle, and makes many procedures use the same resource in turn., NC Technology Email: .,Application domain,Nowadays, resource-apposition parallel process technolog

48、y is widely and successfully adopted in the hardware design of CNC system, for example, adopting Multi-microprocessors architecture to improve process speed. On the other hand, resource time-sharing technology and time overlap flow line technique are mainly used in software designing., NC Technology

49、 Email: .,Real time process,Real time process means that CNC system can react in time to the requests and events of system equipment(s). Interruption technology is the main feature of real time process. There are many types of interruption： external interruption internal timer interruptio

50、n hardware fault interruption, software interruption, NC Technology Email: .,Architecture of CNC System Software,CNC system software architecture is the organizing and managing mode of CNC system software, i.e., tasks dividing scenario, tasks scheduling mechanism, method of information ex

51、changing between tasks, and method of system integration. It manages and coordinates each executing of tasks in proper time order and logical relationship to meet the control needs of CNC system. There are two different architectures: tandem architecture interruption architecture., NC Technology Ema

52、il: .,Tandem architecture,CNC system software: foreground application and background application. Foreground application is a real time interruption service program, which realizes the real tine functions background application is a loop running program, which realizes the input of part p

53、rogram, do some preparatory processes and manages tasks of procedures. Foreground and background applications work cooperatively to implement all functions and controls of CNC system., NC Technology Email: .,Tandem architecture,The system program can be generally carried out in the follow

54、ing courses: first, system startup second, initializing process entering the loop executing of background application. During the executing of background application, real time interruption procedures intervene every now and then to implement every real time controls., NC Technology Email: jtbguet.e

55、du.,Tandem architecture, NC Technology Email: .,Interruption architecture,There is no distinction of background and foreground applications in this architecture. Except for initializing procedure, this architecture divides all control programs into interruption service procedures with different priorities, so that becomes a large multilevel interruption system. The system managing functions are mainly implemented by the communications between interruption service procedures in