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基于
PLC
三层
电梯
控制
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基于PLC的三层电梯控制,基于,PLC,三层,电梯,控制
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Programmable logic controllerA programmable logic controller (PLC) or programmable controller is used for electrical and mechanical process automation of the digital computer, such as control of machinery on factory assembly lines, amusement facilities, or lighting. Programmable controller is used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is a real time system since output results must be produced in response to input conditions within a bounded time; otherwise it will lead to wrong operation1. DevelopmentEarly PLCs were designed to replace relay logic systems. These ladder logic of the programmable controller is a very similar with the relay logic diagrams. Select representation for the purpose of this procedure is to reduce the existing technical personnels training needs. Other early programmable controller using instruction list programming, programming logic solver is based on a stack. Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Logic, a very high-level programming language designed to program PLCs based on state transition diagrams. Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, for the aforementioned reasons. Update format such as logic and function block (this is a similar logic description using digital logic integrated circuit), but they are still not popular ladder logic language. A major reason is that the programmable controller to solve the problem in a predictable and repeating sequence logic, and ladder logic language can use other formats for programmers (write logic), people see the logic of time, all the problems more easily programmed.2. Functionality The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually about 4 wide, 3 high, and 3 deep. Most of these devices have a LCD screen to watch the size of a small stamp simplified the ladder logic input/output point (only a small part of the program being visible at a given time) and status, and the screen by an electromagnetic four-way rocker button control combined with four different used to view and edit the logic of the button, similar to video remote control button. Most controllers has a small socket to connect through the RS - 232 or RS - 485 and personal computers, so that programmers can use for programming simple Windows application rather than forced to use a small LCD and button. Unlike ordinary PLC, is usually a modular, greatly expanded, controller does not usually take modular and extensible, not but they provide robust design of certainty and perform logic value less than PLC. 3. PLC Topics3.1System scaleA small PLC is a fixed number of input and output generated connection. If the base model has enough I/O usually can be extended. Modular programmable controller has a chassis (also called a rack) in which place has a different function module. The choice of processor and I/O module is customized for a particular application. Several racks can have a single processor; there may be thousands of input and output. A kind of special high speed serial I/O link is the frame to reduce multiple lines using distributed discrete processors. 3.2User interface PLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control. A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface.3.3Communications PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BCAnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols. Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser. PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.3.4Programming PLC programs are typically written in a special application on a personal computer, and then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays. Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.IEC 61131-3 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST (structured text, similar to the PASCAL programming language), IL (teaching list, similar to the assembly language) and the SFC (sequential function chart). These techniques emphasize the logical operation of the organization. Although the basic concept of PLC programming is common all producers, I/O, memory organization and instruction set different Settings PLC program means not completely interchangeable. Even within a single manufacturer product line may not be directly compatible with different models. 4. Digital and analog signalsDigital or discrete signal like a binary switch, create a simple on or off the signal (1 or 0, respectively, true or false). Button, limit switches and photoelectric sensor is to provide discrete signal equipment. Discrete signals are sent using either voltage or current , where a specific range is designated as On and another as Off. For example, a PLC might use 24 V DC I/O, with values above 22 V DC representing On, values below 2VDC representing Off, and intermediate values undefined. Initially, PLCs had only discrete I/O.Analog signal like the volume control range from 0. This is often interpreted as an integer value (count), PLC and range of accuracy depends on the equipment and the number of bits used to store the data. Programmable controller usually use 16-bit processor binary symbols, range - an integer value between 32768 and 32767. Pressure, temperature, flow, and weight are often represented by analog signals. Analog signals can use voltage or current with a magnitude proportional to the value of the process signal. For example, a simulation of 0-10 v or 4-20 mA input will be converted to an integer value 0-32767.可编程逻辑控制器 可编程逻辑控制器（PLC）或可编程序控制器是用于机电过程自动化的数字计算机，例如控制机械厂生产线、游乐设施或照明装置。可编程控制器在许多工业和机器中使用。与通用的计算机不同的是，PLC是专为多个输入和输出管理，扩展温度范围、不受电磁噪音影响、抗震动和冲击所设计。控制器的操作程序通常存储在电池供电或非易失性的内存中。PLC是实时的系统，因为系统产生的输出结果必须在有限的时间内回馈到输入，否则会导致错误操作。1.发展早期的可编程控制器是设计来取代继电器逻辑系统。这些可编程控制器的“阶梯逻辑”是与继电器逻辑示意图非常类似的。选择此程序表示法的目的是为了减少对现有技术人员的培训需求。其他早期的可编程控制器使用指令列表编程，基于一个堆栈编程逻辑求解器进行求解。 现代可编程控制器在各种各样的方式可以被编程，从梯形逻辑语言到更加传统的编程语言例如BASIC和C语言。另一个方法是状态逻辑，被设计的一种非常高级编程语言根据状态转换图的可编程控制器编程。很多早期可编程控制器没有可编程终端的逻辑图形表示法，逻辑反而是被描绘成一系列在一些版本的布尔格式的逻辑表达式，类似于布尔代数。随着编程码发展，由于上述原因它变成更常见的梯形逻辑语言。更新的格式如国家逻辑和功能块（这是类似的逻辑描述使用数字逻辑集成电路时的方式）的存在，但它们仍没有梯形逻辑语言流行。一个主要原因是可编程控制器解决问题用一个可预测和重复的序列的逻辑，并且梯形逻辑语言可以用其他格式让程序员（写逻辑）的人看到逻辑的时间，所有问题更加容易地程序化。2.功能PLC的功能经过多年的发展，包括连续的继电器控制，运动控制，过程控制，分布式控制系统和网络。一些现代PLC的数据处理，存储，处理能力和通信能力相当于台式电脑。PLC编程结合远程I/O硬件，一台通用台式计算机允许在某些应用中重叠使用某一可编程控制器。在重工业中PLC被认为没有这些桌面计算机为主的逻辑控制器的实际性强，因为PLC在台式计算机系统中运行不是很稳定，并且，因为台式计算机硬件没有被设计成耐温度、湿气、振动和耐用作为可编程控制器的处理器。除桌面基于逻辑的硬件局限之外，例如Windows操作系统不适合自己的确定性逻辑的执行，结果是PLC逻辑不可能总是对规定逻辑变化的输入状态与极端性预计的时间一致。尽管如此，这样桌面逻辑被应用在较不重要情况，像实验室自动化和小型设施中使用该应用程序的要求不高，因为他们的价格一般都远远低于昂贵的PLC。 在最近数年，小产品称为PLR（可编程逻辑继电器），并且因为名字相似，变得更常见并被接受。这些很像PLC已经应用于轻工业，它只有少部分的输入/输出（例如一些真实的输入输出信号）参与，低成本，很理想。这些小设备尺寸和形状比较普通地几位制造商制作，并且由更大的PLC制作商来填满他们低端产品规格。俗名包括PICO控制器、纳米PLC和其他的小控制器。多数这些控制器有在8到12数字输入、4到8数字输出，多达2个模拟输入。尺寸通常是4英寸宽、3英寸高、3英寸深。大多数这样的设备有一个小邮票大小的液晶屏幕来观看简化梯子逻辑的输入/输出点（只有一小部分程序被可见于给定的时间）和状况，并且这些屏幕由一个电磁四通摇臂按钮操纵加上四个不同的用于浏览和编辑的逻辑电钮，类似于录像机遥控按钮。控制器大多数有一个小插座为通过连接RS-232或RS-485到个人计算机，以便程序员可能为编程使用简单的窗口应用而不是被迫使用微小的LCD和电钮。不像普通PLC，通常是模块化，大大扩展,控制器通常不会取模块化并且不是可扩展的，但是他们提供稳健设计的确定性和执行逻辑的价值比PLC少。3.可编程序控制器PLC3.1系统规模 一个小的PLC是固定数量的输入和输出生成的连接。如果基础模型具有足够的I/O通常可扩展。 模块化可编程控制器有一个机箱（也称为机架）在其中放置具有不同的功能模块。处理器和I/O模块的选择被定制为特定的应用
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