洪灾应急个体救援设备的设计开发

摘要：随着洪水灾害的频繁发生和人口密集程度的加大，受灾区内的安全救生任务非常的艰巨。当洪水灾害突然来袭时，人们往往防不胜防。紧急情况下，得不到及时的救援，这就更为凸显了一个亟待解决的问题——如何让紧急救援工作更高效？开发出体积重量小的轻便安全，功能齐备，可操作性强和稳定耐用的个体救援设备能更好的提高救生效率。综合分析洪灾环境和救援设备的特点，提出个体救援设备的设计策略，研究内容涉及开发的可行性，色彩材料、功能动力和造型结构等方面研究。

关键词：洪灾；救援设备；个体救援设备；个体救生具

中国分类号：TB472

Design and development of a flood emergency individual rescue equipment

Abstract:With the increase of frequent flood disasters and dense degree,safety life-saving mission in the area is very difficult.When the flood disaster suddenly struck,people are impossible to guard against.In case of emergency, the lack of timely rescue,this is more to highlight a problem -- how to make the emergency rescue work more efficient?Development of small volume and weight of the portable safety, complete functions, improve the efficiency of individual life rescue equipment operation and stability and durability can be better.Comprehensive analysis of flood and rescue equipment,presents the design strategy for individual rescue equipment,the research involves the feasibility of the development, research material, color power and other structure function.

Key words:Flood;rescue equipment;Individual rescue equipment;Personal life preservers

1 引言

洪水灾害是世界上最严重的自然灾害。据联合国 1986～1995 年自然灾害统计资料：洪水灾害发生次数占全部自然灾害发生次数的 32％，造成的人员死亡数占全部自然灾害造成损失人员死亡数的1991~ 20xx年, 我国因洪涝灾害死亡39048人，平均每年死亡3550人......看到那么惊人的历史数据，我们完全有必要深入探索研究，来寻求能够降低人员伤亡数的有效途径。

面对突如其来的水灾，现有的基本上是大型的偏重的集体式船艇救援载具，它们在运输装卸或拖曳，救援辅助功能，动力技术和材料等方面存在种种不足，在第一时间会影响救援的速度，降低救援效率。因此，我觉得有必要设计一种轻便的小型的个体救援设备，紧急时刻救援人员就能人人轻松的扛着一个，使得救援工作更加快速高效，并且让更多的人参与到救援行动中去。

2 洪灾个体救援设备发展概况

2.1 洪灾个体救援设备的现状

对于水上个体救援设备,各国均制定有技术标准,其中国际标准化组织标准(ISO)、国际海事组织(IMO)海安会决议MSC.81(70) 、英国标准(BS) 、美国军用规范(MIL) 、日本标准(JIS)具有突出的先进性和代表性。

洪灾具有一定的突发性，并且灾情预报系统对突发灾害的本身限制，普通老百姓一般不太懂许多的防洪知识，也不具备洪灾自救设备，在逃生时，由于准备物资不充分、时间紧迫

等，往往出现被困、被淹情况，难以保证民众的自身安全和财产损失。

从国际大环境来看，发达国家在这一方面重视度较高，较我国发展也相对完善。目前，就中国整个应急避险行业而言，现有救生产品的设计、研发、生产、量化起步较晚，并且主要集中在工程专业应急、家庭应急、户外应急三大领域。我国对于水灾救生予以了高度关注，正在进行系统、专业的灾难应急产品设计理论探索，但是由于受到技术、成本的限制，许多产品并没有实现量产，而是停留在概念阶段。

国内外现有的洪灾救援设备有救生艇，救生筏，橡皮艇，冲锋舟和气垫船等。它们的特点是：

2.1.1救生艇

救生艇是一种具有一定浮力、强度、航速、能搭载一定人数、属具备品比较齐全的刚性小艇，它是一种非常有效的脱险工具。

按结构形式分类：①敞开式救生艇（优点：便于登乘，活动方便，操纵简单。缺点：没有支架和顶蓬，人员暴露在自然环境中）②部分封闭救生艇（这种救生艇既保留了开敞式救生艇的优点，又克服了其缺点；但是这种救生艇被风浪打翻后，艇员逃出不如开敞式救生艇那样方便。）③全封闭救生/救助艇（它设有内外能开启和关闭的通道盖，使艇员能方便的出入艇内，该通道关闭时能保证水密性，具有良好的高温隔热性能；顶盖上设有顶窗来保证艇内光线充足；有的还有自我扶正功能；因此，当今船舶越来越多地采用此类救生艇。）

按建造材料分类：①镀锌钢质艇②铝合金艇③玻璃钢艇

按功能分类：①具有自行扶正功能的救生艇②具有自供气系统的救生艇③耐火耐高温救生艇④自由降落入水救生艇

2.1.2救生筏

救生筏是在船舶遇险时船员使用的一种救援救生设备。其特点是体积少、重量轻、操作简单方便。其缺点主要表现在：无自航能力、只能在水中漂浮待救、投放后在水面易呈翻覆状态需人工扶正、浮胎易发生破损漏水等。

救生筏的种类：①刚性救生筏②气胀救生筏－－按施放方法不同分为抛投式救生筏和机械吊放式。

2.1.3橡皮艇

橡皮艇的特点：橡皮艇的优势，重量较轻、操纵性好、反应速度快，橡皮艇上附带了两个手划桨，它可以在橡皮艇失去动力或极其浅水区域或临近礁石障碍物环境中实施救助工作，操作方便简洁；橡皮艇的局限性，橡皮艇设备简单，没有齐全的导航仪器（仅一个简单的罗盘），没有灯光照明以及抗风浪能力差的弊端。

由于橡皮艇重量较轻，艇后由木质板架着一个发动机，如果橡皮艇静止不动的便轻微后倾状态。发动机马力相对较大，一旦启动（无论是向前还是向后推动）冲力便很大，艇机将下沉。它没有良好的稳性、良好的防风防浪防撞的能力以及可靠的导航仪器。

2.1.4冲锋舟

冲锋舟，是充气艇的一种,分有玻璃钢板的冲锋舟和橡皮艇式的冲锋舟。

冲锋舟具有航速快、操作简便、机动性好等特点。在水上多用操舟机驱动,也可用桨操行。

冲锋舟在完成救护、运送人员和物资等任务中起到了很大的作用,不过在使用过程中发现存在一些弊端或不足：①由于它重量轻,虽然利于运输及储存,但是乘载能力比较小,满足不了部队进行各种抗洪抢险任务的需要②舟体用玻璃钢制成的冲锋舟重量有400多公斤,体积相对比较大。而且不能被拆解,缺乏机动灵活性,不方便运输及储存。③玻璃钢冲锋舟的玻璃钢材料耐磨性差,在装运时还容易碰撞损坏。而且不能空投。

2.1.5气垫船

气垫船的原理：利用高压空气在船底和水面（或地面）间形成气垫，使船体脱离水面而实现高速航行。气垫是使用鼓风机将空气压入船底下，由船底周围的柔性围裙气封装置限制空气逸出而形成。气垫船就是利用船底与水面间的高压气垫托起船体，使其能够快速水上行进。

气垫船的功能：航行时不需要利用水的浮力支撑船体，因此除了可以在水面航行，还可以在沼泽地、湿地以及较为平坦的陆地上行驶。这些功能是其他水面船艇不具备的优势。在那些浅水急流、江河上游险滩、沼泽地带、河近岸以及冰雪地带航行，气垫船还可以跨越沟、坎，体现出其实用价值。

2.2 洪灾个体救援设备的未来发展趋势

分析救援设备的种类和结构就知道,种类日益繁多,结构形态也开始注重对细节的设计。个体救援设备的类型非常多样化，因此它的功能集成及用途的细化具有非常多的可能性,而浮力分布的多样性也是由于它具有多样化的结构。过去的设备只注重飘浮的功能以及强调浮力值，而相对忽视了浮力的分布,类型和功能比较单调。整个结构形态设计一定要具有适体性,以满足使用者其他活动的要求。配上性能优良及实用性强的营救属具,加强可营救性能。 个体救援设备的发展主要以材料、结构和属具的发展为重点和落脚点,往多功能的营救性能、舒适性和高效性方向发展。

第一，材料,包括了包覆面料和浮力材料。包覆面料应该向减轻重量和增加功能的方向发展,例如增加阻燃性、提高表面的光滑度及手感等。浮力材料则主要是气囊和高发泡倍率的泡沫塑料,存放体积的减少、使用舒适、减轻重量导致浮力的增大是它们发展的方向。 第二，结构设计,通过结构形态的设计体现完美的浮力分布,增强适体性。即从浮力分布这点出发,控制其在水中的姿势,从工效学的角度对适体性、舒适性以及在水中动作的完成进行设计控制。

第三，各种属具,保障受害者的生命安全和增加可营救性是第一目的,改良及研发新型属具, 改善现有属具的性能,集成化、小型化和功能增强是它的发展方向,例如提高示位灯的光强和使用寿命、减少其重量等。

3 现有洪灾个体救援设备的问题分析

3.1 救生艇

体积重量较大，存放运输不便，升降施放麻烦，启动需要的时间过长，不能连续启动；降落装置易锈蚀，减薄，损坏；日常的维护和保养难度比较大；环境温度低时开启前需采取暖机措施。

3.2 救生筏

无自航能力、只能在水中漂浮待救、投放后在水面易呈翻覆状态需人工扶正、浮胎易发生破损漏水；救生筏装载容器易开裂。

3.3 气垫船

体积重量庞大，运输搬运较困难，拖曳速度很慢，导致短时间内到达灾区的数量有限；成本比较高，经济性较差；使用寿命短。

3.4 橡皮艇

抗风浪能力不强，受风浪影响易颠覆；不能逆行，救援的距离较短；冷机不易启动；没齐全的导航仪器。

3.5 冲锋舟

尺寸大，比较重，运输搬运比较麻烦；装卸时间耗费较长，效率低；电力没保障。

4 洪灾的环境分析

对洪灾个体救援设备的设计，应分析洪灾突然发生时受灾环境的特殊性及普遍性，总结洪灾中发生的主要问题。包括：雨水情况的信息采集较困难会影响调度决策；缺少防汛抢险物资，降低应急抢险效率；对困在洪水中的人们救援需要大量营救人员；在洪水中容易被顺流冲走，电力、交通、通讯中断，抢险救灾及其困难；桥梁冲毁，房屋催倒，道路淹没，传染病流行，灾后出现疾病疫情；食物、水源的供给出现不足；家庭人员冲散，人员失踪。争取把产品从特殊化到一般化，以适应更多的目标受众。应用于产品设计上，洪灾个体救援设备表现的特点为：使用性方便、操作界面尽可能简单化、功能键尽量少、操作键的尺寸要尽可能大且布局合理，不可太密集，产品的整体尺寸要稍大于平均尺寸。总体上，结合洪灾发生时的环境特点，设计洪灾个体救援设备的时候，应该结合“水”这个最突出的因素，产品的耐腐蚀性、防水性、浮力等都要予以考虑。

5 洪灾个体救援设备的设计分析

5.1 洪灾个体救援设备的色彩和材料搭配

表面具有鲜明易于探测的色彩，救援设备通常采用醒目的红色或橙黄色，在必要的局部采用荧光色。通过调查发现现有的救援设备基本主体材料过重，日常保养维护较难，装置易锈蚀减薄，浮胎易破损。因此主体将由高效的聚炳烯制成，这是一种非凡的、由美国宇航局开发的树脂材料，它真正可以做到防刺穿而且不会被盐及酸腐蚀，不需要维护。它非常稳定耐用，而且相对轻便得多。

5.2 洪灾个体救援设备的功能诉求

将一些具有实用性的辅助型功能进行模块化整合，使得使用者在关键时刻比较上手和清晰。比如导航，方向把手，探照灯等。

5.3 洪灾个体救援设备的动力分析

在设备内部装用发动机，利用简单的螺旋桨推进系统解决冷机不易启动、操作性差等问题。加强了自航能力，提高了救援距离，显得很环保。

5.4 洪灾个体救援设备的造型尺寸结构分析

合理的结构设计应同时保证救生具使用时舒适合体、热负荷小,不影响呼吸、视听和正常作业, 以保证使用者乐于使用。现有的救援设备普遍体积重量大，运输装卸非常不便，拖曳升降速度慢。因此，造型尺寸和结构尽量要缩小和简单便携化，将“冲浪板”的概念引入救援设备的设计思路中，再将它与自动充气艇或筏做一结合。

6 结语

随着洪水灾害的频繁发生和人口密集程度的加大，受灾区内的安全救生任务非常的艰巨。现有的洪灾救援设备体积重量大，运输携带很不方便，装卸时间较长，因此短时间内到灾区的数量往往有限，并且在一些特殊情况下可操作性差，辅助救援的功能较少，使用起来也会带来困扰，不能在第一时间对多方位的多人进行施救，影响救援工作。通过对个体救援设备的材料、功能、动力和结构分析，开发出体积重量小的轻便安全，功能齐备，可操作性强和稳定耐用的救援设备，为突发水灾准备，让更多的人在第一时间参与到灾害救援工作中去，使得救援更快速高效，不再让更多无辜的生命消失。

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第二篇：科技论文样本

科技论文

题 目 Application of Programmable

Logic Controller

别 专 业

班 级学生姓名

学 号

指导教师 系

20xx年 11 月

Application of Programmable Logic Controller

Abstract: This paper introduces the PLC's history, structure, uses, applications, characteristics and future prospects related to PLC. This can be through a corresponding understanding of the PLC.It will be helpful to PLC applications . Key words: PLC、Application、Features

Briefly

Programmable controller is the late 60s in the United States first, and then called programmable logic controller PLC (Programmable Logic Controller), aims to replace the relay in order to implement the logic to determine, timing, counting and other sequential control functions. PLC basic design idea is the computer fully functional, flexible, universal and other advantages and relay control system, easy to understand, easy to operate, cheap and combine the advantages of the controller hardware is standard, generic. Based on the actual application objects, the software will control the content compiled into the controller user program memory. Controller and the controlled object to connect easily.

As the semiconductor technology, in particular microprocessors and micro-computer technology, to 70 after the mid, PLC has been widespread use of microprocessors as the CPU, input and output modules, and peripheral circuits are also used in large-scale Even very large scale integrated circuits, when the PLC is no longer logical to determine function, also has a data-processing, PID regulator, and data communication capabilities.

Programmable controller is a digital computing operation of an electronic system designed for industrial environment applications. It uses a programmable memory, used in its internal memory implementation of the logical, sequential control, timing, calculation and arithmetic operations such as instruction, and through digital an inputs and outputs to control various types of mechanical or the production process. PLC is a computer technology with traditional relay contact with the product of a combination of control technology, which overcomes the relay contacts control system wiring complexity of the mechanical contacts, reliability and low power consumption and 1

high, versatility and flexibility of the shortcomings of poor, full the advantages of using a microprocessor.

Programmable Logic Controller for users, is a non-contact device, to change the program can change the production process, so you can use in the preliminary design stage programmable controller, in the implementation phase to determine whether or process. On the other hand, from the programmable controller manufacturers manufacturing point of view, in the manufacturing phase of the user's order request does not require specially designed controllers, suitable for mass production. Because of these characteristics, programmable controllers came soon after the welcome by the industrial control sector, and rapid development. At present, the programmable controller, factory automation has become a powerful tool, has been widely used. PLC part of the structure and the role of each part

Programmable controller structure varied, but its composition is basically the same general principles are based on the microprocessor as the core structure. Usually by the central processing unit (CPU), memory (RAM, ROM), input and output unit (I / O), power supply and programmer, and several other components.

Central processing unit (CPU)

PLC-core CPU as a whole, plays the role of commander in chief. CPU generally by the control circuit, an arithmetic logic unit and register form. These circuits are often encapsulated in an integrated circuit chip. CPU through the address bus, data bus, control bus and storage units, input-output interface circuit to connect. CPU features are the following: from memory to read instructions, implementation of the instruction, remove an instruction to deal with interrupts.

Memory (RAM, ROM)

Memory is mainly used for storage of system programs, user procedures and data. Memory storage system software, known as the system program memory; application memory store known as the user program memory; repositories of data storage is called data memory. Commonly used memory are RAM, EPROM, and EEPROM. RAM is a read-write operation can be random access memory storage of user program to generate user data area, stored in the RAM in the user program can be easily 2

modified. RAM memory is a high-density, low power, inexpensive semiconductor memory that can be used to do backup power lithium batteries. Power-down, it can effectively maintain the stored information. EPROM, EEPROM are read-only memory. Curing with these types of storage systems management processes and applications.

Input-output unit (I / O unit)

I / O unit is actually passed between the PLC and the controlled object interface to input and output signal components. I / O module has a good electrical isolation and filtering effect. PLC input interface receives the input devices are a variety of switches, buttons and sensors. PLC, the output control device is often the solenoid valves, contactors, relays, but relays are AC and DC type, high voltage type and low-voltage type, voltage-and current-mode.

Power

PLC power supply unit includes power supply and battery backup systems, power supply unit's role is to convert the inner workings of an external power supply voltage. PLC has a regulated power supply is used to PLC's CPU unit and I / O module power supply.

Programmer

PLC Programmer is the most important peripherals. Programmer using the user program into the PLC memory, you can also check with the programmer program, modify the program to monitor PLC's working condition. In addition, a personal computer to add the appropriate hardware interface and software packages, you can use a personal computer to the PLC program. The use of computers as a programmer, you can direct the preparation and display the ladder.

Over the years, programmable controller (hereinafter referred to as PLC) from its birth, is now to realize the logical connection to the storage logical leap; its function from weak to strong, and achieved a logic control to digital control progress; its applications from small to large, simple control device to achieve a monomer to a qualified motion control, process control and distributed control across a variety of tasks. PLC in dealing with today's analog and digital computing, human-computer 3

interfaces, and networks in all aspects of power have been greatly improved, to become the mainstream of industrial control field control equipment, in all walks of life playing an increasingly important role.

PLC applications

At present, PLC at home and abroad have been widely used in iron and steel, petroleum, chemical, electric power, building materials, machinery manufacturing, automobile, textile, transportation, environmental protection and culture and entertainment in various industries, the use of mainly divided into the following categories.

Switch the amount of logic control

To replace the traditional relay circuit, logic control, sequential control, both for the control of a single piece of equipment can also be used for multi-cluster control and automation lines. Such as injection molding machines, presses, stapler machine, combination machine tool, grinding, packaging and production lines, plating lines and so on.

Industrial Process Control

In the industrial production process, there are some such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), PLC, with the corresponding A / D and D / A converter module and a variety of control algorithm program to deal with analog to complete the closed-loop control. PID regulation is a general closed-loop control system using a lot about the kind of adjustment. Process control in metallurgy, chemical industry, heat treatment, boiler control situations have a very wide range of applications.

Motion Control

PLC can be used in a circular motion or linear motion control. Generally use a dedicated motion control modules such as may drive a stepper motor or servo motor single-axis or multi-axis position control module, are widely used in all kinds of machinery, machine tools, robots, elevators and other occasions.

Data Processing

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PLC with mathematics (including matrix operations, functions, operation, logic operation), data transmission, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing. Data processing is generally used, such as paper making, metallurgy, food industry, some of the large-scale control system.

Communication and networking

PLC communication with the communication between PLC and the PLC and other communication between intelligent devices. With the development of factory automation network, now have a PLC communication interface, communication is very convenient.

PLC Application Characteristics

High reliability, strong anti-interference ability

High reliability is the key to performance of electrical control equipment. PLC due to the use of modern large scale integrated circuit technology and strict manufacturing process, the internal circuitry to take the advanced anti-jamming technology, with high reliability. Constitute the use of PLC control systems, and on the same scale as compared relay contactor systems, electrical wiring and switch contacts have been reduced to a few hundred or even a few thousandths of the failure thus greatly reduced. In addition, PLC hardware failures with a self-testing features, failure to issue timely warning information. In the application software, application of those peripheral devices can also be incorporated into the fault self-diagnosis procedure,

The system, in addition to PLC circuits and equipment other than access to the protection Fault self-diagnosis. In this way, the entire system will be extremely high reliability.

Supporting complete, fully functional applicability

PLC development today, has formed a series of all sizes, product can be used for occasions of all sizes to industrial control. In addition to the logical processing functions other than, PLC most computing power has improved the data can be used for a variety of digital control areas. A wide variety of functional units in large 5

numbers, so that PLC penetrated into the position control, temperature control, CNC and other industrial control. Enhanced communication capabilities coupled with PLC and human-machine interface technology, the use of the composition of a variety of PLC control systems very easily.

To learn to use, well received by engineers and technicians Welcome

PLC-oriented industrial control equipment, industrial and mining enterprises. It is easy to interface, the programming language easily acceptable for the engineering and technical personnel. Ladder language, graphic symbols and expressions and the relay circuit is very close to, in order not familiar with electronic circuits, computer principles and do not understand assembly language to engage in industrial control to open the door.

System design, the workload is small, easy to maintain, easy to transform

PLC logic with memory logic, instead of wiring, greatly reducing the control equipment external wiring, so that control system design and construction of the cycle is much shorter, while routine maintenance is also easier up and, more importantly, is to make the same equipment have been changes in procedures to change the the production process possible. This is particularly suitable for multi-variety and small batch production of occasions.

● power lines, control lines, as well as PLC power lines and I / O lines should be split wiring, isolation transformers and PLC and I / O should be used between Shuangjiao cable. The PLC's IO lines and power lines separate the alignment, such as to be in the same groove, the separation of bundled communication lines, DC lines, if conditions allow, the best sub-slot alignment, which will not only enable them the greatest possible spatial distance, and can interfere to a minimum.

● PLC should stay away from strong interference sources such as welding, high power silicon rectifier devices and large-scale power equipment, high-voltage electrical installation can not be a switch in the same cabinet. PLC in the cabinet should stay away from power lines (the distance between the two should be more than 200mm). With the PLC installed in the same cabinet within the inductive load, such as the power of the larger relays, contactor coil should be parallel RC circuit arc. 6

● PLC input and output separately from the best alignment, quantity and analog switches must be laid separately. The transmission of analog signals should be shielded wire, one end or both ends of the shield should be grounded, grounding resistance should be less than shield resistance 1 / 10.

● AC output line and DC output lines do not use with a cable, the output lines should be away from the high-voltage lines and power lines, to avoid parallel.

(3) I / O side of the wiring

Input wiring

● Input Connection general rule, not too long. However, if the environment interfere with smaller, less voltage drop when the input wiring can be properly longer.

● Input / output lines can not be used with a cable, input / output lines should be separated.

● normally open contact form as far as possible connected to the input side, so that the establishment of the ladder in line with the relay schematic, easy to read.

Output Connection

● output wiring is divided into separate output and the public output. In different groups, using different types and voltage levels of output voltage. However, the output in the same group can only use the same type, the same voltage level of power.

● As the PLC's output components are encapsulated in the printed circuit board, and connected to the terminal board that if the load short-circuit by connecting the output components, printed circuit boards will be burned.

● When using relay outputs, the inductive load to bear the size will affect the life of the relays, therefore, the use of inductive load should be a reasonable choice, or add isolation relays.

● PLC may interfere with the output load, so to take measures to control, such as the DC output of the continued flow of control protection, the exchange of the output RC snubber circuit, transistors and resistors Triac output bypass the protection. PLC applications that need attention

PLC is an industrial automation control equipment, general do not need to take what measures can be used directly in industrial environments. However, despite the 7

higher reliability described above, a strong anti-interference ability, but when the production environment is too bad, especially strong electromagnetic interference, or improper installation on the procedure may cause error or operator error, resulting in incorrect input and cause false output, which will result in loss of control and misuse of equipment, movement, and thus can not guarantee the normal operation of PLC, PLC control system to improve reliability, on the one hand require PLC equipment manufacturers to improve anti-jamming capability; the other hand.

To design, install and use of maintenance caused a high degree of attention, multi-party cooperation in order to improve problem-solving, effectively enhance the anti-jamming performance of the system. Therefore, in use should be aware of the following issues:

1. The work environment

Temperature

PLC require environmental temperature is 0 ~ 55oC, installation can not be placed in a large heat components below the space around the ventilation cooling should be enough.

Humidity

To ensure the PLC, insulation, air relative humidity should be less than 85% vibration

PLC should be made from a strong vibration source, to prevent the vibration frequency of 10 ~ 55Hz frequent or continuous vibration. When the inevitable use of environmental vibration, the damping must be taken measures, such as use of damping glue and so on.

Air

To avoid corrosion and flammable gases such as hydrogen chloride, hydrogen sulfide and so on. For more dust in the air or corrosive gases in the environment, can be installed in a closed PLC good control room or control cabinet.

Power Supply

PLC for the power line disturbance caused by a certain ability to resist. Demanding in terms of reliability or power supply interference is particularly serious 8

circumstances, you can install a isolation transformer with a shield in order to reduce interference between equipment and ground. General PLC has a 24V DC output provided to the input, when using an external DC power input, we should use DC power supply. Because an ordinary rectifier filter power supply, because of ripple effects, easy to make PLC received an error message.

2. Control System Interference and its source

On-site PLC control system for electromagnetic interference is the most common and most likely one of the factors affecting system reliability, the so-called root of the problem symptoms first, identify the problems in order to propose solutions to the problem. Must therefore be aware of on-site sources of interference. The source of interference and the general classification.

PLC control system affect the sources of interference, most produce dramatic changes in the current or voltage of the area, the reason is the current changes in magnetic field, the equipment produces electromagnetic radiation; the magnetic field change generated currents, electromagnetic waves generated high-speed. Is usually different modes of electromagnetic interference by jamming is divided into common-mode interference and differential mode interference. Common mode interference is the signal-to-ground potential difference, mainly by the string into the power grid, ground potential difference, and spatial electromagnetic radiation in the signal lines were induced state (in the same direction) voltage superimposed formed. Common-mode voltage by using asymmetric circuit can be converted to differential mode voltage, a direct impact on measurement and control signals,

Components caused by damage (which is some of the system I / O module of the main reasons for the higher failure rate), which can interfere with common-mode DC, also for the exchange. Differential mode interference refers to the act on the signal interference between bipolar voltage, mainly by the spatial coupling between the electromagnetic field in the signal sensing and conversion by the imbalance in the circuit formed by the common-mode interference voltage, such interference superimposed on the signal directly affects the measurement and control accuracy. PLC system, the main source of interference and avenues for

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strong electrical interference

PLC system, the normal power supply by the grid. As the grid covering a wide range, it will be all the space the electromagnetic interference induced voltage line on the road. In particular, the changes in the internal network, knives switching surges, large-scale power equipment starts and stops, caused by AC and DC drives harmonics, grid short-circuit transient shocks are transmitted through the transmission lines the power of the original edge.

Cabinet interference

High-voltage electrical control cabinet, large inductive load, confusing layout are easy on the PLC to a certain degree of interference.

The introduction of interference from the signal line

With the PLC control system connected to various types of signal transmission lines, apart from various kinds of information transmission and effective addition, there is always an external interference signal intrusion. This interference There are two main ways: First, through the signal transmitter power supply or shared string instrument power supply into the power grid disturbance, which are often neglected; second signal line is subject to space interference of electromagnetic radiation sensors, that is the signal Online external sensor interference, and this is very serious. Introduced by signal interference can cause I / O signal abnormalities and accuracy of work greatly reduces the component will cause serious damage.

From the grounding system disorder interference

Ground is to improve the electronic equipment Electromagnetic Compatibility (EMC) is one effective means. Proper grounding, can inhibit the effects of electromagnetic interference, but also the outgoing interference suppression devices; while the wrong ground, but will introduce a serious interference signals, so that PLC system will not work properly.

The interference within the system from the PLC

Mainly by the system of internal components and circuit interaction between the electromagnetic radiation, such as the logic of mutual radiation and its effects on 10

analog circuits, analog interaction with the logical implications and the inter-component does not match and so on.

Inverter Interference

First, start-up and run the inverter harmonics generated in the process conducted interference generated on the power grid, causing power grid voltage distortion, affecting the quality of electricity supply grid; second inverter output will produce a strong electromagnetic radiation interference, affecting the normal peripheral equipment work.

3. The main anti-interference measures

a reasonable processing power and suppress the interference power introduced

For the power grid disturbance can be installed into a shield with a variable ratio of 1:1 isolation transformers, in order to reduce interference between equipment and ground, you can also power input tandem LC filter circuit.

The correct choice of access sites, improve the grounding system

Good grounding is to ensure that the work of an important condition for reliable PLC can prevent accidental voltage shock hazard. The purpose of grounding usually have two, one for security, and the second is to suppress interference. Sound grounding system is PLC control system of anti-electromagnetic interference of the important measures.

PLC control system including the system ground, the shield, the exchange of land and protect the land. Grounding system chaotic disruption of the PLC system is primarily a place of potential uneven distribution of access, different access to potential difference exists between locations, causing ground loop currents, affecting the system work properly. For example, cable shield must be grounded point, if the cable shield at both ends of A, B are grounded, there is ground potential difference, there is current flowing through the shield, when an exception condition occurs, such as lightning strikes, the ground current would be greater.

In addition, the shield, grounding wire and the earth might constitute a closed loop, under the effect of changing magnetic field, shielding layer would give rise to induced currents, through the shielding layer and the coupling between the cores 11

interfere with the signal circuit. If the system with other ground handling chaos, the resulting circulation in the ground line may generate potential distribution ranges, impact within the PLC logic and analog circuits work properly. PLC logic voltage interfere with the work of a lower tolerance, logic ground potential interference likely to influence the distribution of PLC logic and data storage operations, resulting in confusion of data, programs run fly or crash.

The distribution of simulated ground potential measurement accuracy will lead to decline, causing a serious distortion of the signal and control, and malfunction.

● safe or Power Ground

● System Grounding

PLC controller in order to control various devices with the same potential and the ground, called the system ground. Grounding resistance value is no larger than 4Ω, generally takes the PLC equipment systems to switching power supply and control cabinet with a negative termination, as a control system to.

● Signal and Shield Grounding

General requirements for signal line must have a unique reference, the shielded cable conducted interference encountered may arise occasions, but also in situ, or control room, the only ground to prevent the formation of "ground loop." The signal source ground, the shield should be grounded in the signal side; no grounding should be grounded in the PLC side; signal line the middle connector, the shielding layer of insulation should be firmly connected and be dealt with multi-point ground must be avoided; multiple test point signal and multi-core shielded twisted-pair shielded twisted pair cables to connect the total, the shield should be connected with each other, and by the insulation treatment, select the appropriate ground at a single point of contact.

Inverter Interference Suppression

Inverter interference processing generally have the following ways:

The use of filters, the filter has a strong anti-jamming capability, but also with the device itself to prevent the interference of conduction to the power supply, in some cases, both the peak voltage of absorption.

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The use of the output reactor in the inverter to the motor to increase AC reactor between the main is to reduce the inverter output in the energy transfer process lines produce electromagnetic radiation, affecting other devices work properly.

Programmable controller in the country's development and future development

In the industrial production process, large amount of sequence control switch, which in accordance with the terms of the logical sequence of actions, and follow the logic of the relationship between the protection of controlling the motion of chain, and the large number of discrete volume data acquisition. Traditionally, these functions through a pneumatic or electrical control systems to achieve. In 1968 the United States GM (General Motors) companies to replace the electrical control devices, following the requirements of the second year, the U.S. Digital Equipment Corporation (DEC) has developed technology based on integrated circuits and electronic control devices, the first time a means of application of procedural in electrical control, and this is the first generation of programmable logic controller, said the Programmable,

Recognized as the world's first PLC.

Limited to the conditions and computer components at the time the level of development, the early PLC mainly by discrete components and the composition of small and medium-scale integrated circuits, you can complete the simple logic control and timing, counting function. The 20th century, emerged in the early 70s microprocessor. It will soon be introducing programmable logic controller, so that PLC increased the computing, data transmission and processing functions, complete with computer features a real industrial control device. In order to facilitate familiar with relays, contactors systems engineering and technical personnel to use, programmable controllers and relays using a similar ladder circuit as the main programming language.

And will participate in computing and processing are all computer storage devices in order to relay name. PLC at this time for the computer technology and the concept of conventional control relay product of the combination. Personal computer (abbreviated as PC) developed later, for convenience, but also to reflect the features 13

programmable controllers, programmable logic controller to be known as Programmable Logic Controller (PLC).

The 20th century, the mid to late 70s, programmable controller, into the practical stage of development, the introduction of computer technology has fully programmable controller, to function has been a leap. A higher computing speed, ultra-small size, more reliable design of industrial interference, analog computing, PID function and highly cost-effective to lay it in modern industry position. The 20th century, early 80s, a programmable controller in the advanced industrial countries has been widely used. This period is characterized by the development of programmable controller, large-scale, high-speed, high-performance, the product series.

Another feature of this stage is the world's production of an increasing number of countries programmable controller, the output on the rise. This marks the programmable logic controller has entered a mature stage.

The last century, the mid-80s to 90, is PLC's fastest-growing period, annual growth rate has been maintained at 30 ~ 40%. During this period, PLC capability in dealing with analog and digital computing power, man-machine interface capabilities and network capabilities have been greatly upgraded, PLC gradually entering the field of process control, in some applications to replace the field of process control in the dominant DCS system.

The late 20th century, characterized by the development of programmable controller is more adapted to the needs of modern industry. From the control of scale, this time developed a mainframe and super-minicomputer; from control point of view, the birth of a wide range of special function units for pressure, temperature, speed, displacement and other kinds of control occasions; from supporting the ability of products, the production of a variety of man-machine interface unit, communication unit, so that application of programmable controllers for industrial control equipment, matching easier. At present, the Programmable controller in machinery manufacturing, petrochemical, metallurgy iron and steel, automobile, light industry and other areas of applications have undergone a considerable development.

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China's introduction of programmable controllers, application, development, production is accompanied by reform and opening up began. Initially in the introduction of a large number of devices used in programmable controllers. Next, in a variety of business equipment and products in the expanding application of the PLC. At present, China has been able to produce their own small programmable logic controller. House Electric Co., Ltd. Shanghai East production of CF series, Hangzhou Machine Tool Electrical Apparatus Factory production DKK and D series, Dalian Institute of modular machine tool production of S-series, Suzhou computer factory YZ series produced by a variety of products already have a certain scale obtained in the application of industrial products.

In addition, Wuxi Huaguang Corporation, Shanghai Rural Island companies, joint ventures are also a relatively well-known PLC manufacturers. It can be expected that with the deepening of China's modernization process, PLC in China will have a wider application of heaven and earth.

Future PLC

In the 21st century, PLC will have greater development. From a technical point of view, the new achievements in computer technology will be more used in the design and manufacture of programmable controllers, there will be exponentially faster, bigger storage capacity, more intelligent species occurring; from the product scale view, further to the ultra-small and ultra-large direction; from the complementary product in terms of product variety will be richer, more complete specifications, the perfect man-machine interface, a comprehensive communications equipment will be better adapted to a variety of industrial control the occasion demands; from the market point of view, all countries produce more varieties of products, each situation will be as international competition intensifies and the broken.

Monopoly of a few brands will appear in the international market situation, there will be an international common programming language; judging from the development of networks, programmable controllers and other industrial control computer networking constitutes a large-scale control system is programmable 15

controller technology development. The current Distributed Control System DCS (Distributed Control System) in the already large number of programmable controller applications. Along with the development of computer networks, programmable controllers, as automation and control network and the network of internationally important component in the industry and industry in many areas outside the play an increasing role.

Conclusion

PLC control system interference is a very complex issue, so in the anti-jamming design should be comprehensive consideration of various factors, rational and effective anti-interference suppression to be able to make PLC control system work properly. With the PLC application areas are continuously expanding, how efficient and reliable use of PLC has also become an important factor in their development. In the 21st century, PLC will have greater development, product variety will be richer, more complete specifications, through the perfect man-machine interface, a comprehensive communications equipment will be better adapted to the needs of a variety of occasions, industrial control, PLC as an automatic control network and the network of internationally important component of.

In the field of industrial control to play an increasingly greater role.

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可编程控制器的应用

摘要：本文介绍了PLC的历史、结构、用途、应用领域、特点及对未来PLC的相关展望。通过本文可以对PLC有相应的了解。能对PLC的应用有一定的帮助。 关键词：PLC、应用、特点

一、简述 可编程控制器是60年代末在美国首先出现，当时叫可编程逻辑控制器PLC（Programmable Logic Controller），目的是用来取代继电器，以执行逻辑判断、计时、计数等顺序控制功能。PLC的基本设计思想是把计算机功能完善、灵活、通用等优点和继电器控制系统的简单易懂、操作方便、价格便宜等优点结合起来，控制器的硬件是标准的、通用的。根据实际应用对象，将控制内容编成软件写入控制器的用户程序存储器内。控制器和被控对象连接方便。

随着半导体技术，尤其是微处理器和微型计算机技术的发展，到70年代中期以后，PLC已广泛地使用微处理器作为中央处理器，输入输出模块和外围电路也都采用了中、大规模甚至超大规模的集成电路，这时的PLC已不再是逻辑判断功能，还同时具有数据处理、PID调节和数据通信功能。

可编程控制器是一种数字运算操作的电子系统，专为在工业环境下应用而设计。它采用了可编程序的存储器，用来在其内部存储执行逻辑运算，顺序控制、定时、计算和算术运算等操作的指令，并通过数字式和模拟式的输入输出，控制各种类型的机械或生产过程。PLC是微机技术与传统的继电接触控制技术相结合的产物，它克服了继电接触控制系统中机械触点的接线复杂、可靠性低、功耗高、通用性和灵活性差的缺点，充分利用微处理器的优点。

可编程控制器对用户来说，是一种无触点设备，改变程序即可改变生产工艺，因此可在初步设计阶段选用可编程控制器，在实施阶段再确定工艺过程。另一方面，从制造生产可编程控制器的厂商角度看，在制造阶段不需要根据用户的订货要求专门设计控制器，适合批量生产。由于这些特点，可编程控制器问世以后很快受到工业控制界的欢迎，并得到迅速的发展。目前，可编程控制器已成为工厂自动化的强有力工具，得到了广泛的应用。

二、PLC的结构及各部分的作用

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可编程控制器的结构多种多样，但其组成的一般原理基本相同，都是以微处理器为核心的结构。通常由中央处理单元（CPU）、存储器（RAM、ROM）、输入输出单元（I/O）、电源和编程器等几个部分组成。

1．中央处理单元（CPU）

CPU作为整个PLC的核心，起着总指挥的作用。CPU一般由控制电路、运算器和寄存器组成。这些电路通常都被封装在一个集成电路的芯片上。CPU通过地址总线、数据总线、控制总线与存储单元、输入输出接口电路连接。CPU的功能有以下一些：从存储器中读取指令，执行指令，取下一条指令，处理中断。

2．存储器（RAM、ROM）

存储器主要用于存放系统程序、用户程序及工作数据。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；存放工作数据的存储器称为数据存储器。常用的存储器有RAM、EPROM和EEPROM。RAM是一种可进行读写操作的随机存储器存放用户程序，生成用户数据区，存放在RAM中的用户程序可方便地修改。RAM存储器是一种高密度、低功耗、价格便宜的半导体存储器，可用锂电池做备用电源。掉电时，可有效地保持存储的信息。EPROM、EEPROM都是只读存储器。用这些类型存储器固化系统管理程序和应用程序。

3．输入输出单元（I/O单元

I/O单元实际上是PLC与被控对象间传递输入输出信号的接口部件。I/O单元有良好的电隔离和滤波作用。接到PLC输入接口的输入器件是各种开关、按钮、传感器等。PLC的各输出控制器件往往是电磁阀、接触器、继电器，而继电器有交流和直流型，高电压型和低电压型，电压型和电流型。

4．电源

PLC电源单元包括系统的电源及备用电池，电源单元的作用是把外部电源转换成内部工作电压。PLC内有一个稳压电源用于对PLC的CPU单元和I/O单元供电。

5．编程器

编程器是PLC的最重要外围设备。利用编程器将用户程序送入PLC的存储器，还可以用编程器检查程序，修改程序，监视PLC的工作状态。除此以外，在个人 18

计算机上添加适当的硬件接口和软件包，即可用个人计算机对PLC编程。利用微机作为编程器，可以直接编制并显示梯形图。

多年来，可编程控制器（以下简称PLC）从其产生到现在，实现了接线逻辑到存储逻辑的飞跃；其功能从弱到强，实现了逻辑控制到数字控制的进步；其应用领域从小到大，实现了单体设备简单控制到胜任运动控制、过程控制及集散控制等各种任务的跨越。今天的PLC在处理模拟量、数字运算、人机接口和网络的各方面能力都已大幅提高，成为工业控制领域的主流控制设备，在各行各业发挥着越来越大的作用。

三、PLC的应用领域

目前，PLC在国内外已广泛应用于钢铁、石油、化工、电力、建材、机械制造、汽车、轻纺、交通运输、环保及文化娱乐等各个行业，使用情况主要分为如下几类：

1.开关量逻辑控制

取代传统的继电器电路，实现逻辑控制、顺序控制，既可用于单台设备的控制，也可用于多机群控及自动化流水线。如注塑机、印刷机、订书机械、组合机床、磨床、包装生产线、电镀流水线等。

2.工业过程控制

在工业生产过程当中，存在一些如温度、压力、流量、液位和速度等连续变化的量（即模拟量），PLC采用相应的A/D和D/A转换模块及各种各样的控制算法程序来处理模拟量，完成闭环控制。PID调节是一般闭环控制系统中用得较多的一种调节方法。过程控制在冶金、化工、热处理、锅炉控制等场合有非常广泛的应用。

3.运动控制

PLC可以用于圆周运动或直线运动的控制。一般使用专用的运动控制模块，如可驱动步进电机或伺服电机的单轴或多轴位置控制模块，广泛用于各种机械、机床、机器人、电梯等场合。

4.数据处理

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PLC具有数学运算（含矩阵运算、函数运算、逻辑运算）、数据传送、数据转换、排序、查表、位操作等功能，可以完成数据的采集、分析及处理。数据处理一般用于如造纸、冶金、食品工业中的一些大型控制系统。

5.通信及联网

PLC通信含PLC间的通信及PLC与其它智能设备间的通信。随着工厂自动化网络的发展，现在的PLC都具有通信接口，通信非常方便。

四、PLC的应用特点

1.可靠性高，抗干扰能力强

高可靠性是电气控制设备的关键性能。PLC由于采用现代大规模集成电路技术，采用严格的生产工艺制造，内部电路采取了先进的抗干扰技术，具有很高的可靠性。使用PLC构成控制系统，和同等规模的继电接触器系统相比，电气接线及开关接点已减少到数百甚至数千分之一，故障也就大大降低。此外，PLC带有硬件故障自我检测功能，出现故障时可及时发出警报信息。在应用软件中，应用者还可以编入外围器件的故障自诊断程序，使系统中除PLC以外的电路及设备也获得故障自诊断保护。这样，整个系统将极高的可靠性。

2.配套齐全，功能完善，适用性强

PLC发展到今天，已经形成了各种规模的系列化产品，可以用于各种规模的工业控制场合。除了逻辑处理功能以外，PLC大多具有完善的数据运算能力，可用于各种数字控制领域。多种多样的功能单元大量涌现，使PLC渗透到了位置控制、温度控制、CNC等各种工业控制中。加上PLC通信能力的增强及人机界面技术的发展，使用PLC组成各种控制系统变得非常容易。

3.易学易用，深受工程技术人员欢迎

PLC是面向工矿企业的工控设备。它接口容易，编程语言易于为工程技术人员接受。梯形图语言的图形符号与表达方式和继电器电路图相当接近，为不熟悉电子电路、不懂计算机原理和汇编语言的人从事工业控制打开了方便之门。

4.系统的设计，工作量小，维护方便，容易改造

PLC用存储逻辑代替接线逻辑，大大减少了控制设备外部的接线，使控制系统设计及建造的周期大为缩短，同时日常维护也变得容易起来，更重要的是使同 20

一设备经过改变程序而改变生产过程成为可能。这特别适合多品种、小批量的生产场合。

（2）安装与布线

● 动力线、控制线以及PLC的电源线和I/O线应分别配线，隔离变压器与PLC和I/O之间应采用双胶线连接。将PLC的IO线和大功率线分开走线，如必须在同一线槽内，分开捆扎交流线、直流线，若条件允许，分槽走线最好，这不仅能使其有尽可能大的空间距离，并能将干扰降到最低限度。

● PLC应远离强干扰源如电焊机、大功率硅整流装置和大型动力设备，不能与高压电器安装在同一个开关柜内。在柜内PLC应远离动力线（二者之间距离应大于200mm）。与PLC装在同一个柜子内的电感性负载，如功率较大的继电器、接触器的线圈，应并联RC消弧电路。

● PLC的输入与输出最好分开走线，开关量与模拟量也要分开敷设。模拟量信号的传送应采用屏蔽线，屏蔽层应一端或两端接地，接地电阻应小于屏蔽层电阻的1/10.

● 交流输出线和直流输出线不要用同一根电缆，输出线应尽量远离高压线和动力线，避免并行。

（3）I/O端的接线

输入接线

● 输入接线一般不要太长。但如果环境干扰较小，电压降不大时，输入接线可适当长些。

● 输入/输出线不能用同一根电缆，输入/输出线要分开。

● 尽可能采用常开触点形式连接到输入端，使编制的梯形图与继电器原理图一致，便于阅读。

输出连接

● 输出端接线分为独立输出和公共输出。在不同组中，可采用不同类型和电压等级的输出电压。但在同一组中的输出只能用同一类型、同一电压等级的电源。

● 由于PLC的输出元件被封装在印制电路板上，并且连接至端子板，若将连接输出元件的负载短路，将烧毁印制电路板。

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● 采用继电器输出时，所承受的电感性负载的大小，会影响到继电器的使用寿命，因此，使用电感性负载时应合理选择，或加隔离继电器。

● PLC的输出负载可能产生干扰，因此要采取措施加以控制，如直流输出的续流管保护，交流输出的阻容吸收电路，晶体管及双向晶闸管输出的旁路电阻保护。

五、PLC应用中需要注意的问题

PLC是一种用于工业生产自动化控制的设备，一般不需要采取什么措施，就可以直接在工业环境中使用。然而，尽管有如上所述的可靠性较高，抗干扰能力较强，但当生产环境过于恶劣，电磁干扰特别强烈，或安装使用不当，就可能造成程序错误或运算错误，从而产生误输入并引起误输出，这将会造成设备的失控和误动作，从而不能保证PLC的正常运行，要提高PLC控制系统可靠性，一方面要求PLC生产厂家提高设备的抗干扰能力；另一方面，要求设计、安装和使用维护中引起高度重视，多方配合才能完善解决问题，有效地增强系统的抗干扰性能。因此在使用中应注意以下问题：

1.工作环境

（1）温度

PLC要求环境温度在0~55oC，安装时不能放在发热量大的元件下面，四周通风散热的空间应足够大。

（2）湿度

为了保证PLC的绝缘性能，空气的相对湿度应小于85%（无凝露）。

（3）震动

应使PLC远离强烈的震动源，防止振动频率为10~55Hz的频繁或连续振动。当使用环境不可避免震动时，必须采取减震措施，如采用减震胶等。

（4）空气

避免有腐蚀和易燃的气体，例如氯化氢、硫化氢等。对于空气中有较多粉尘或腐蚀性气体的环境，可将PLC安装在封闭性较好的控制室或控制柜中。

（5）电源

PLC对于电源线带来的干扰具有一定的抵制能力。在可靠性要求很高或电源干扰特别严重的环境中，可以安装一台带屏蔽层的隔离变压器，以减少设备与地 22

之间的干扰。一般PLC都有直流24V输出提供给输入端，当输入端使用外接直流电源时，应选用直流稳压电源。因为普通的整流滤波电源，由于纹波的影响，容易使PLC接收到错误信息。

2.控制系统中干扰及其来源

现场电磁干扰是PLC控制系统中最常见也是最易影响系统可靠性的因素之一，所谓治标先治本，找出问题所在，才能提出解决问题的办法。因此必须知道现场干扰的源头。

（1）干扰源及一般分类

影响PLC控制系统的干扰源，大都产生在电流或电压剧烈变化的部位，其原因是电流改变产生磁场，对设备产生电磁辐射；磁场改变产生电流，电磁高速产生电磁波。通常电磁干扰按干扰模式不同，分为共模干扰和差模干扰。共模干扰是信号对地的电位差，主要由电网串入、地电位差及空间电磁辐射在信号线上感应的共态（同方向）电压叠加所形成。共模电压通过不对称电路可转换成差模电压，直接影响测控信号，造成元器件损坏（这就是一些系统I/O模件损坏率较高的主要原因），这种共模干扰可为直流，亦可为交流。差模干扰是指作用于信号两极间的干扰电压，主要由空间电磁场在信号间耦合感应及由不平衡电路转换共模干扰所形成的电压，这种干扰叠加在信号上，直接影响测量与控制精度。

（2）PLC系统中干扰的主要来源及途径

强电干扰

PLC系统的正常供电电源均由电网供电。由于电网覆盖范围广，它将受到所有空间电磁干扰而在线路上感应电压。尤其是电网内部的变化，刀开关操作浪涌、大型电力设备起停、交直流传动装置引起的谐波、电网短路暂态冲击等，都通过输电线路传到电源原边。

柜内干扰

控制柜内的高压电器，大的电感性负载，混乱的布线都容易对PLC造成一定程度的干扰。

来自信号线引入的干扰

与PLC控制系统连接的各类信号传输线，除了传输有效的各类信息之外，总会有外部干扰信号侵入。此干扰主要有两种途径：一是通过变送器供电电源或共 23

用信号仪表的供电电源串入的电网干扰，这往往被忽视；二是信号线受空间电磁辐射感应的干扰，即信号线上的外部感应干扰，这是很严重的。由信号引入干扰会引起I/O信号工作异常和测量精度大大降低，严重时将引起元器件损伤。 来自接地系统混乱时的干扰

接地是提高电子设备电磁兼容性（EMC）的有效手段之一。正确的接地，既能抑制电磁干扰的影响，又能抑制设备向外发出干扰；而错误的接地，反而会引入严重的干扰信号，使PLC系统将无法正常工作。

来自PLC系统内部的干扰

主要由系统内部元器件及电路间的相互电磁辐射产生，如逻辑电路相互辐射及其对模拟电路的影响，模拟地与逻辑地的相互影响及元器件间的相互不匹配使用等。

变频器干扰

一是变频器启动及运行过程中产生谐波对电网产生传导干扰，引起电网电压畸变，影响电网的供电质量；二是变频器的输出会产生较强的电磁辐射干扰，影响周边设备的正常工作。

3.主要抗干扰措施

（1）电源的合理处理，抑制电网引入的干扰

对于电源引入的电网干扰可以安装一台带屏蔽层的变比为1：1的隔离变压器，以减少设备与地之间的干扰，还可以在电源输入端串接LC滤波电路。

（2）正确选择接地点，完善接地系统

良好的接地是保证PLC可靠工作的重要条件，可以避免偶然发生的电压冲击危害。接地的目的通常有两个，其一为了安全，其二是为了抑制干扰。完善的接地系统是PLC控制系统抗电磁干扰的重要措施之一。

PLC控制系统的地线包括系统地、屏蔽地、交流地和保护地等。接地系统混乱对PLC系统的干扰主要是各个接地点电位分布不均，不同接地点间存在地电位差，引起地环路电流，影响系统正常工作。例如电缆屏蔽层必须一点接地，如果电缆屏蔽层两端A、B都接地，就存在地电位差，有电流流过屏蔽层，当发生异常状态如雷击时，地线电流将更大。

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此外，屏蔽层、接地线和大地有可能构成闭合环路，在变化磁场的作用下，屏蔽层内又会出现感应电流，通过屏蔽层与芯线之间的耦合，干扰信号回路。若系统地与其它接地处理混乱，所产生的地环流就可能在地线上产生不等电位分布，影响PLC内逻辑电路和模拟电路的正常工作。PLC工作的逻辑电压干扰容限较低，逻辑地电位的分布干扰容易影响PLC的逻辑运算和数据存贮，造成数据混乱、程序跑飞或死机。模拟地电位的分布将导致测量精度下降，引起对信号测控的严重失真和误动作。

● 安全地或电源接地

将电源线接地端和柜体连线接地为安全接地。如电源漏电或柜体带电，可从安全接地导入地下，不会对人造成伤害。

● 系统接地

PLC控制器为了与所控的各个设备同电位而接地，叫系统接地。接地电阻值不得大于4Ω，一般需将PLC设备系统地和控制柜内开关电源负端接在一起，作为控制系统地。

● 信号与屏蔽接地

一般要求信号线必须要有唯一的参考地，屏蔽电缆遇到有可能产生传导干扰的场合，也要在就地或者控制室唯一接地，防止形成“地环路”。信号源接地时，屏蔽层应在信号侧接地；不接地时，应在PLC侧接地；信号线中间有接头时，屏蔽层应牢固连接并进行绝缘处理，一定要避免多点接地；多个测点信号的屏蔽双绞线与多芯对绞总屏蔽电缆连接时，各屏蔽层应相互连接好，并经绝缘处理，选择适当的接地处单点接点。

(3）对变频器干扰的抑制

变频器的干扰处理一般有下面几种方式：

加隔离变压器，主要是针对来自电源的传导干扰，可以将绝大部分的传导干扰阻隔在隔离变压器之前。

使用滤波器，滤波器具有较强的抗干扰能力，还具有防止将设备本身的干扰传导给电源，有些还兼有尖峰电压吸收功能。

使用输出电抗器，在变频器到电动机之间增加交流电抗器主要是减少变频器输出在能量传输过程中线路产生电磁辐射，影响其它设备正常工作。

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六、PLC的国内外状况及未来展望

在工业生产过程中，大量的开关量顺序控制，它按照逻辑条件进行顺序动作，并按照逻辑关系进行连锁保护动作的控制，及大量离散量的数据采集。传统上，这些功能是通过气动或电气控制系统来实现的。19xx年美国GM（通用汽车）公司提出取代继电气控制装置的要求，第二年，美国数字设备公司（DEC）研制出了基于集成电路和电子技术的控制装置，首次采用程序化的手段应用于电气控制，这就是第一代可编程序控制器，称Programmable ,是世界上公认的第一台PLC。

限于当时的元器件条件及计算机发展水平，早期的PLC主要由分立元件和中小规模集成电路组成，可以完成简单的逻辑控制及定时、计数功能。20世纪70年代初出现了微处理器。人们很快将其引入可编程控制器，使PLC增加了运算、数据传送及处理等功能，完成了真正具有计算机特征的工业控制装置。为了方便熟悉继电器、接触器系统的工程技术人员使用，可编程控制器采用和继电器电路图类似的梯形图作为主要编程语言，并将参加运算及处理的计算机存储元件都以继电器命名。此时的PLC为微机技术和继电器常规控制概念相结合的产物。个人计算机（简称PC）发展起来后，为了方便，也为了反映可编程控制器的功能特点，可编程序控制器定名为Programmable Logic Controller（PLC）。

20世纪70年代中末期，可编程控制器进入实用化发展阶段，计算机技术已全面引入可编程控制器中，使其功能发生了飞跃。更高的运算速度、超小型体积、更可靠的工业抗干扰设计、模拟量运算、PID功能及极高的性价比奠定了它在现代工业中的地位。20世纪80年代初，可编程控制器在先进工业国家中已获得广泛应用。这个时期可编程控制器发展的特点是大规模、高速度、高性能、产品系列化。这个阶段的另一个特点是世界上生产可编程控制器的国家日益增多，产量日益上升。这标志着可编程控制器已步入成熟阶段。

上世纪80年代至90年代中期，是PLC发展最快的时期，年增长率一直保持为30~40%。在这时期，PLC在处理模拟量能力、数字运算能力、人机接口能力和网络能力得到大幅度提高，PLC逐渐进入过程控制领域，在某些应用上取代了在过程控制领域处于统治地位的DCS系统。

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20世纪末期，可编程控制器的发展特点是更加适应于现代工业的需要。从控制规模上来说，这个时期发展了大型机和超小型机；从控制能力上来说，诞生了各种各样的特殊功能单元，用于压力、温度、转速、位移等各式各样的控制场合；从产品的配套能力来说，生产了各种人机界面单元、通信单元，使应用可编程控制器的工业控制设备的配套更加容易。目前，可编程控制器在机械制造、石油化工、冶金钢铁、汽车、轻工业等领域的应用都得到了长足的发展。

我国可编程控制器的引进、应用、研制、生产是伴随着改革开放开始的。最初是在引进设备中大量使用了可编程控制器。接下来在各种企业的生产设备及产品中不断扩大了PLC的应用。目前，我国自己已可以生产中小型可编程控制器。上海东屋电气有限公司生产的CF系列、杭州机床电器厂生产的DKK及D系列、大连组合机床研究所生产的S系列、苏州电子计算机厂生产的YZ系列等多种产品已具备了一定的规模并在工业产品中获得了应用。此外，无锡华光公司、上海乡岛公司等中外合资企业也是我国比较著名的PLC生产厂家。可以预期，随着我国现代化进程的深入，PLC在我国将有更广阔的应用天地。

21世纪，PLC会有更大的发展。从技术上看，计算机技术的新成果会更多地应用于可编程控制器的设计和制造上，会有运算速度更快、存储容量更大、智能更强的品种出现；从产品规模上看，会进一步向超小型及超大型方向发展；从产品的配套性上看，产品的品种会更丰富、规格更齐全，完美的人机界面、完备的通信设备会更好地适应各种工业控制场合的需求；从市场上看，各国各自生产多品种产品的情况会随着国际竞争的加剧而打破，会出现少数几个品牌垄断国际市场的局面，会出现国际通用的编程语言；从网络的发展情况来看，可编程控制器和其它工业控制计算机组网构成大型的控制系统是可编程控制器技术的发展方向。目前的计算机集散控制系统DCS（Distributed Control System）中已有大量的可编程控制器应用。伴随着计算机网络的发展，可编程控制器作为自动化控制网络和国际通用网络的重要组成部分，将在工业及工业以外的众多领域发挥越来越大的作用。

七、结束语

PLC控制系统中的干扰是一个十分复杂的问题，因此在抗干扰设计中应综合考虑各方面的因素，合理有效地抑制抗干扰，才能够使PLC控制系统正常工作。 27

随着PLC应用领域的不断拓宽，如何高效可靠的使用PLC也成为其发展的重要因素。21世纪，PLC会有更大的发展，产品的品种会更丰富、规格更齐全，通过完美的人机界面、完备的通信设备会更好地适应各种工业控制场合的需求，PLC作为自动化控制网络和国际通用网络的重要组成部分，将在工业控制领域发挥越来越大的作用。

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