5X00070G01 EMERSON 数字量控制

5X00070G01 EMERSON 数字量控制数字量控制实际的物理量，除了开关量、模拟量，还有数字量。如机床部件的位移，常以数字量表示。
数字量的控制，有效的办法是NC，即数字控制技术。这是50年代诞生于美国的基于计算机的控制技术。当今已很普及，并也很完善。目前，先进国家的金属切削机床，数控化的比率已超过40％～80％，有的甚至更高。 PLC也是基于计算机的技术，并日益完善。故它也完全可以用于数字量控制。PLC可接收计数脉冲，频率可高达几k到几十k赫兹。可用多种方式接收这脉冲，还可多路接收。有的PLC还有脉冲输出功能，脉冲频率也可达几十k。有了这两种功能，加上PLC有数据处理及运算能力，若再配备相应的传感器（如旋转编码器）或脉冲伺服装置（如环形分配器、功放、步进电机），则完全可以依NC的原理实现种种控制。高、中档的PLC，还开发有NC单元，或运动单元，可实现点位控制。运动单元还可实现曲线插补，可控制曲线运动。所以，若PLC配置了这种单元，则完全可以用NC的办法，进行数字量的控制。新开发的运动单元，甚至还发行了NC技术的编程语言，为更好地用PLC进行数字控制提供了方便。用于数据采集随着PLC技术的发展，其数据存储区越来越大。如OMRON公司的PLC，前期产品C60P的DM区仅64个字，而后来的C60H达到1000个字；到了CQMI可多达6000个字。这样庞大的数据存储区，可以存储大量数据

5X00070G01 EMERSON 数字量控制可以用计数器，累计记录采集到脉冲数，并定时地转存到DM区中去。 数据采集也可用A/D单元，当模拟量转换成数字量后，再定时地转存到DM区中去。PLC还可配置上小型打印机，定期把DM区的数据打出来。PLC也可与计算机通讯，由计算机把DM区的数据读出，并由计算机再对这些数据作处理。这时，PLC即成为计算机的数据终端。电业部门曾这么使用PLC，用以实时记录用户用电情况，以实现不同用电时间、不同计价收费办法，鼓励用户在用电低谷时多用电，达到合理用电与节约用电的目的。5用于进行监控PLC自检信号很多，内部器件也很多，多数使用者未充分发挥其作用。
5X00070G01 EMERSON 数字量控制其实，完全可利用它进行PLC自身工作的监控，或对控制对象进行监控。这里介绍一种用PLC定时器作看门狗，对控制对象工作情况进行监控的思路。如用PLC控制某运动部件动作，看施加控制后动作进行了没有，可用看门狗办法实现监控。具体作法是在施加控制的同时，令看门狗定时器计时。如在规定的时间内动作完成，即定时器未超过警戒值的情况下，已收到动作完成信号，则说明控制对象工作正常，无需报警。若超时，说明不正常，可作相应处理。如果控制对象的各重要控制环节，都用这样一些看门狗”看”着，那系统的工作将了如指掌，出现了问题，卡在什么环节上也很好查找。还有其它一些监控工作可做。对一个复杂的控制系统，特别是自动控制系统，监控以至进一步能自诊断是非常必要的。它可减少系统的故障，出了故障也好查找，可提高累计平均无故障运行时间，降低故障修复时间，提高系统的可靠性。

5X00070G01 EMERSON Digital quantity control Digital quantity control of actual physical quantities, in addition to switching quantities, analog quantities, and digital quantities. For example, the displacement of machine tool components is often expressed in digital quantities.
The effective way to control digital quantity is NC, that is, digital control technology. This is a computer-based control technology that was born in the United States in the 1950s. Today it is very popular and very well developed. At present, the ratio of metal cutting machine tools in advanced countries has exceeded 40% to 80%, and some even higher. PLC is also based on computer technology, and increasingly perfect. Therefore, it can also be used for digital quantity control. The PLC can receive counting pulses at frequencies as high as a few k to tens of k Hertz. The pulse can be received in a variety of ways, and can be received in multiple ways. Some PLC also has pulse output function, pulse frequency can also reach tens of k. With these two functions, coupled with PLC data processing and computing capabilities, if equipped with the corresponding sensor (such as rotary encoder) or pulse servo device (such as ring distributor, power amplifier, stepper motor), you can completely achieve various controls according to the principle of NC. High and mid-range PLC, also developed NC unit, or motion unit, can achieve point control. The motion unit can also realize curve interpolation and control curve motion. Therefore, if the PLC is configured with this unit, it can completely use the NC method to control the digital quantity. The newly developed motion unit, and even the NC technology programming language has been issued, which provides convenience for better digital control with PLC. With the development of PLC technology, its data storage area is getting larger and larger. For example, the PLC of OMRON company, the DM area of the early product C60P is only 64 words, and the later C60H reaches 1000 words; To CQMI can be up to 6000 words. Such a large data storage area can store a large amount of data.
5X00070G01 EMERSON Digital quantity control can use a counter to accumulate the number of pulses collected and periodically transferred to the DM area. Data acquisition can also be used as A/D unit, when the analog amount is converted to digital amount, and then periodically transferred to the DM area. The PLC can also be configured with a small printer to regularly type out the data in the DM area. PLC can also communicate with the computer, the data in the DM area is read out by the computer, and the data is processed by the computer. At this time, the PLC becomes the data terminal of the computer. The electricity industry has used PLC to record the user’s electricity consumption in real time, so as to achieve different electricity consumption time, different pricing and charging methods, and encourage users to use more electricity when the electricity is low, so as to achieve the purpose of reasonable electricity consumption and saving electricity. There are many PLC self-test signals for monitoring, and many internal devices, and most users do not give full play to their role.
5X00070G01 EMERSON Digital quantity control In fact, it can be fully used to monitor the PLC’s own work, or to monitor the control object. This paper introduces the idea of using PLC timer as a watchdog to monitor the work of the control object. If the PLC is used to control the action of a moving part, see whether the action is carried out after the control is applied, the watchdog method can be used to achieve monitoring. This is done by using a watchdog timer while exerting control. If the action is completed within the specified time, that is, the timer does not exceed the alarm value, and the action completion signal has been received, it indicates that the control object works normally and there is no need to alarm. If the timeout occurs, it indicates that the fault is abnormal and you can handle it accordingly. If each important control link of the control object uses such a watchdog to “see”, the work of the system will be well understood, and if there is a problem, it is also very good to find what link is stuck in. There are other monitoring tasks that can be done. For a complex control system, especially an automatic control system, it is necessary to monitor and further self-diagnose. It can reduce the system failure, fault can be found, can improve the cumulative average trouble-free running time, reduce the fault repair time, improve the reliability of the system.