发布时间 : 星期一 文章基于PLC的两工位钻孔攻丝组合机床控制系统设计更新完毕开始阅读
and place them in a I/O image area in the corresponding unit. The sampling input end, into the user program execution and outputs a refresh phase. In the two stage, even though the input state and the data changes, I/O mappings in unit area corresponding to the state and the data will not change. Therefore, if the input is a pulse signal, the pulse width must be greater than one scanning cycle, to ensure that in any case, the input can be read. Two, the user program execution stage in the user program execution phase, the programmable logic controller is always in top-down order to scan the user program (map). In the scanning each of the ladder diagram and ladder diagram, always first scan left by the contact of the control circuit, and according to the first left, after the first sequence of the control circuit by contact with the logic operation, then according to the result of the logic operation, refresh the logic coil in RAM system storage area corresponding to a state; or refresh the output coil in I/O image area corresponding to a state; or to determine whether to execute the ladder diagram of the provisions of the special function instruction. Namely, when the user during execution of the program, only the input points in I/O image area state and the data will not change, while the other output point and soft equipment in I/O image area or system RAM storage area within the state and data may have changed, but the upper ladder diagram, the procedures for the implementation of the results on the row below general use these coils or data ladder play a role; instead, the row below the trapezoidal chart, the refresh logic coil state or data can only to the next scan cycle to row in the program work. In the program execution process if the use of immediate I/O instruction can directly access point I/O. Using the I/O instruction words, input image register value is not updated, program directly from the I/O module value, output image register will be updated immediately, with the immediate input some difference. In three, the output stage when scanning the user refresh after the procedure, the programmable logic controller to output the refresh phase. During this period, CPU according to I/O image area corresponding to the state and data refresh all output latch circuit, the output circuit drives the corresponding peripheral. Then, is the real output of programmable logic controller.
Editor this paragraph features programmable logic controller has the following characteristics. A system structure, flexible, easy to expand, with volume control switch for its expertise; also can carry out the continuous process of PID loop control; and with the PC constitute a complex control system, such as DDC and DCS, the realization production process automation. Two, easy to use, simple programming, using a simple ladder diagram, logical diagram or statement list programming language, without the knowledge of computer, so the system development cycle short, easy debugging. In addition, online modification program, change the control program and does not disconnect the hardware. Three, can adapt to a variety of adverse operating environment, strong anti-interference ability, high reliability, far higher than other types of models. The application of PLC in machine tool
The application of PLC in machine tool improvement using Mitsubishi system PLC rich instruction system, so the trapezoidal chart design simple and efficient, get rid of the complex logic relations; Mitsubishi system using the built-in PLC has high integration, simplifying the external electrical control system circuit design. Using PLC ladder diagram development software editor and monitoring function, after the program，edit, modify, debug, test run, processing center for all the operating functions set accurate, normal operation, in practical work have been tested, the machining center process effective control design objective.
Electric controlling system based on PLC, which can be used to model the machine electrical control system design and development can be used for the transformation of CNC machine tools and control function in the two development, according to the different control request, modified by the program can meet, is highly flexible and functional expansibility, consistent with the open CNC system the development trend of.
机床改造
机床改造概述
机床改装就是利用原先闲置的旧设备，对其进行必要的技术改造，以满足新的生产需要而进行的一项技术革新手段。据报道，在一些工业发达的国
家，设备的平均役龄期限控制在 15-20 年之间，设备的“技术老化”期已短于 10 年。上述国家旧机床改装率超过 80%以上。目前我国的大部分生产企业所使用的都是旧设备，明显存在着工艺不足、技术老化的问题，而且对旧机床或设备的改装起步较晚，改装数量较少。
随着计算机技术的快速发展，上世纪七十年代开发使用的可编程序控制器PLC 自动控制系统，具有不受工作环境条件限制、可靠性高、功能强、灵活通用等特点，受到各行业的青睐。PLC 技术得到了空前的发展，与数控技术、工业机器人并称为工业自动控制的三大支柱。
经改装的机床提高了零件的加工精度和自动化程度，使生产效率有了很大的改观，具有投资小、见效快、改装工作量少、制作和调试周期短、旧设备利用率高、且将来不加工此类零件时可较容易恢复机床原有的工作性能等特点，对中小型生产企业的加工具有一定的实际意义。 可编程控制器
可编程逻辑控制器实质是一种专用于工业控制的计算机，其硬件结构与微型机相似，基本构成为： 1. 电源
可编程逻辑控制器的电源在整个系统中起着十分重要的作用。如果没有一个良好的、可靠的电源系统是无法正常工作的，因此，可编程逻辑控制器的制造商对电源的设计和制造也十分重视。一般交流电压波动在+10%(+15%)范围内，可以不采取其它措施而将PLC直接连接到交流电网上去 2. 中央处理单元(CPU)
中央处理单元(CPU)是可编程逻辑控制器的控制中枢。它按照可编程逻辑控制器系统程序赋予的功能接收并存储从编程器键入的用户程序和数据；检查电源、存储器、I/O以及警戒定时器的状态，并能诊断用户程序中的语法错误。当可编程逻辑控制器投入运行时，首先它以扫描的方式接收现场各输入装置的状态和数据，并分别存入I/O映像区，然后从用户程序存储器中逐条读取用户程序，经过命令解释后按指令的规定执行逻辑或算数运算的结果送入I/O映像区或数据寄存器内。等所有的用户程序执行完毕之后，最后将I/O映像区的各输出状态或输出寄存器内的数据传送到相应的输出装置，如此循环运行，直到停止运行。为了进一步提高可编程逻辑控制器的可靠性，近年来对大型可编程逻辑控制器还采用双CPU构成冗余系统，或采用三CPU
的表决式系统。这样，即使某个CPU出现故障，整个系统仍能正常运行。 3. 存储器
存放系统软件的存储器称为系统程序存储器。存放应用软件的存储器称为用户程序存储器。 4. 输入输出接口电路
（1） 现场输入接口电路由光耦合电路和微机的输入接口电路，作用是可编程逻辑控制器与现场控制的接口界面的输入通道。
（2） 现场输出接口电路由输出数据寄存器、选通电路和中断请求电路集成，作用可编程逻辑控制器通过现场输出接口电路向现场的执行部件输出相应的控制信号。 5. 功能模块
PLC的内部有很多功能模块，它为PLC的控制功能提供了便利。如计数、定位功能模块，通信模块等。
可编程逻辑控制器投入运行后，其工作过程一般分为三个阶段，即输入采样、用户程序执行和输出刷新三个阶段。完成上述三个阶段称作一个扫描周期。在整个运行期间，可编程逻辑控制器的CPU以一定的扫描速度重复执行上述三个阶段。 1. 输入采样阶段
在输入采样阶段，可编程逻辑控制器以扫描方式依次地读入所有输入状态和数据，并将它们存入I/O映像区中的相应的单元 中，即使输入状态和数据发生变化，I/O映像区中的相应单元的状态和数据也不会改变。因此，如果输入是脉冲信号，则该脉冲信号的宽度必须大于一个扫描周期，才能保证在任何情况下，该输入均能被读入。 2. 用户程序执行阶段
在用户程序执行阶段，可编程逻辑控制器总是按由上而下的顺序依次地扫描用户程序(梯形图)。在扫描每一条梯形图时，又总是先扫描梯形图左边的由各触点构成的控制线路，并按先左后右、先上后下的顺序对由触点构成的控制线路进行逻辑运算，然后根据逻辑运算的结果，刷新该逻辑线圈在系统RAM存储区中对应位的状态；或者刷新该输出线圈在I/O映像区中对应位置的状态；或者确定是否要执行该梯形图所规定的特殊功能指令。即，在用户程序执行过程中，只有输入点在I/O映像区内的状态和数据不会发生变化，