Based on the research of PLC temperature control system of boiler

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基于总线型传感器的温控系统的设计

基于总线型传感器的温控糸统的设计陈志超(松下压缩机(大连)有限公司，辽宁大连116033)摘要:压铸产品的质量与模具的温度关系密切,通常冷却水塔与压铸设备距离比较远。

为了保证产品质量，需要实现远距离的温度采集来实时控制模具关键点的温度，该文设计了一套基于智能温度传感器的温控系统。

该系统使用Modbus协议，采用RS485总线将温度数据实时上传到上位机，通过上位机对水泵、冷却塔风扇以及电磁调节阀开度进行操作达到控制模具温度的目的值。

该装置数据传输数字化，提高了温度的测量精度，自诊断功能提高系统的可靠性，节约硬件投资，方便与企业MES系统链接。

关键词：现场总线；Modbus协议；智能传感器;PLC；人机界面中图分类号:TP271文献标识码：B文章编号#1000-0682(2021)02-0032-05 Design of temperature control system basee on bus sensorCHEN Zhichao(Panasonic Appliaaces Compressor (Dalian#Co.,Li,Liaoning Dalian116033,China# Abstract:Tha qulity of div-casting products is closWy related to tha temperature of tha div.Bui tha cooling wlar towar is usully far away from tha div casting equipment.In ordas to ensure tie product qulity good enough,it is newsay to realize tha remote temperature acquisition and upload to tiv mltw computer to control tha temperatum of tha key points of tha div in al timv.A mmpwlum control system based on inte—igeni temperature sensor is designed.Tha system uses Modbus protocol to tonsfar tha tem-pwatura data to tha mastvs computes trough RS485bus.Tha mastar computes conWols ta-div temperature by starting and stopping Wv wlar pumps and cooling Wwar fans and tha opening of solenoid vvlvv. Tha digital data transmission of tha davico improvas tha accuracy of tempwatura mexsurement,improves tha reliability of tha system,sevas hardware investwent and is convenient to link with w W ip U so MES sys-em.Keywoi'ds：field bus;Modbus protocol;intligeni temperatua;PLC;HMI0引言压铸件的成型质量受模具温度场分布影响,模具温度较高容易引起金属液粘模，铸件脱模阻力增大，增加铸件的变形量，铸件晶粒粗大，压铸效率降低;模具温度较低时,容易造成模具开裂。

关于PLC的英文文献

1. PROGRAMMABLE LOGIC CONTROLLERS1.1 INTRODUCTIONControl engineering has evolved over time. In the past humans was the main method for controlling a system. More recently electricity has been used for control and early electrical control was based on relays. These relays allow power to be switched on and off without a mechanical switch. It is common to use relays to make simple logical control decisions. The development of low cost computer has brought the most recent revolution, the Programmable Logic Controller (PLC). The advent of the PLC began in the 1970s, and has become the most common choice for manufacturing controls. PLC have been gaining popularity on the factory floor and will probably remain predominant for some time to come. Most of this is because of the advantages they offer. . Cost effective for controlling complex systems.. Flexible and can be reapplied to control other systems quickly and easily.. Computational abilities allow more sophisticated control.. Trouble shooting aids make programming easier and reduce downtime. . Reliable components make these likely to operate for years before failure.1.2 Ladder LogicLadder logic is the main programming method used for PLC. As mentioned before, ladder logic has been developed to mimic relay logic. The decision to use the relay logic diagrams was a strategic one. By selecting ladder logic as the main programming method, the amount of retraining needed for engineers and trades people was greatly reduced. Modern control systems still include relays, but these are rarely used for logic. A relay is a simple device that uses a magnetic field to control a switch, as pictured in Figure 2.1. When a voltage is applied to the input coil, the resulting current creates a magnetic field. The magnetic fieldpulls a metal switch (or reed) towards it and the contacts touch, closing the switch. The contact that closes when the coil is energized is called normally open. The normally closed contacts touch when the input coil is not energized. Relays are normally drawn in schematic form using a circle to represent the input coil. The output contacts are shown with two parallel lines. Normally open contacts are shown as two lines, and will be open (non-conducting) when the input is not energized. Normally closed contacts are shown with two lines with a diagonal line through them. When the input coil is not energized the normally closed contacts will be closed (conducting).Relays are used to let one power source close a switch for another (often high current) power source, while keeping them isolated. An example of a relay in a simple control application is shown in Figure 2.2. In this system the first relay on the left is used as normally closed, and will allow current to flow until a voltage is applied to the input A. The second relay is normally open and will not allow current to flow until avoltage is applied to the input B. If current is flowing through the first two relays then current will flow through the coil in the third relay, and close the switch for output C. This circuit would normally be drawn in the ladder logic form. This can be read logically as C will be on if A is off and B is on.1.3 ProgrammingThe first PLC were programmed with a technique that was based on relay logic wiring schematics. This eliminated the need to teach the electricians, technicians and engineers how to program a computer - but, this method has stuck and it is the most common technique for programming PLC today. An example of ladder logic can be seen in Figure 2.5. To interpret this diagram imagines that the power is on the vertical line on the left hand side, we call this the hot rail. On the right hand side is the neutral rail. In the figure there are two rungs, and on each rung there are combinations of inputs (two vertical lines) andoutputs (circles). If the inputs are opened or closed in the right combination the power can flow from the hot rail, through the inputs, to power the outputs, and finally to the neutral rail. An input can come from a sensor, switch, or any other type of sensor. An output will be some device outside the PLC that is switched on or off, such as lights or motors. In the top rung the contacts are normally open and normally closed, which means if input A is on and input B is off, then power will flow through the output and activate it. Any other combinationof input values will result in the output X being off.The second rung of Figure 2.5 is more complex, there are actually multiple combinations of inputs that will result in the output Y turning on. On the left most part of the rung, power could flow through the top if C is off and D is on. Power could also (and simultaneously) flow through the bottom if both E and F are true. This would get power half way across the rung, and then if G or H is true the power will be delivered to output Y. In later chapters we will examine how to interpret and construct these diagrams. There are other methods for programming PLC. One of the earliest techniques involved mnemonic instructions.These instructions can be derived directly from the ladder logic diagrams and entered into the PLC through a simple programming terminal. An example of mnemonics is shown in Figure 2.6. In this example the instructions are read one line at a time from top to bottom. The first line 00000 has the instruction LDN (input load and not) for input 00001. This will examine the input to the PLC and if it is off it will remember a 1 (or true), if it is on it will remember a 0 (or false). The next line uses an LD (input load) statement to look at the input. If the input is off it remembers a 0, if the input is on it remembers a 1 (note: this is the reverse of the LD). The AND statement recalls the last two numbers remembered and if they are both true the result is a 1; otherwise the result is a 0. This result now replaces the two numbers that were recalled, and there is only one number remembered. The process is repeated for lines 00003 and 00004, but when these are done there are now three numbers remembered. The oldest number is from the AND, the newer numbers are from the two LD instructions. The AND in line 00005 combines the results from the last LD instructions and now there are two numbers remembered. The OR instruction takes the two numbers now remaining and if either one is a 1 the result is a 1, otherwise the result is a 0. This result replaces the two numbers, and there is now a single number there. The last instruction is the ST (store output) that will look at the last value stored and if it is 1, the output will be turned on; if it is 0 the output will be turned off.The ladder logic program in Figure 2.6, is equivalent to the mnemonic program. Even if you have programmed a PLC with ladder logic, it will be converted to mnemonic form before being used by the PLC. In the past mnemonic programming was the most common, but now it is uncommon for users to even see mnemonic programs.Sequential Function Charts (SFC) have been developed to accommodate the programming of more advanced systems. These are similar to flowcharts, but much more powerful. The example seen in Figure 2.7 is doing two different things. To read the chart, start at the top where is says start. Below this there is the double horizontal line that says follow both paths. As a result the PLC will start to follow the branch on the left and right hand sides separately and simultaneously. On the left there are two functions the first one is the power up function. This function will run until it decides it is done, and the power down function will come after. On the right hand side is the flash function; this will run until it is done. These functions look unexplained, but each function, such as power up will be a small ladder logic program. This method is much different from flowcharts because it does not have to follow a single path through theflowchart.Structured Text programming has been developed as a more modern programming language. It is quite similar to languages such as BASIC. A simple example is shown in Figure 2.8. This example uses a PLC memory location N7:0. This memory location is for an integer, as will be explained later in the book. The first line of the program sets the value to 0. The next line begins a loop, and will be where the loop returns to. The next line recalls the value in location N7:0, adds 1 to it and returns it to the same location. The next line checks to see if the loop should quit. If N7:0 is greater than or equal to 10, then the loop will quit, otherwise the computer will go back up to the REPEAT statement continue from there. Each time the program goes through this loop N7:0 will increase by 1 until the value reaches 10.N7:0 := 0;REPEATN7:0 := N7:0 + 1;UNTIL N7:0 >= 10END_REPEAT;2. PLC ConnectionsWhen a process is controlled by a PLC it uses inputs from sensors to make decisions and update outputs to drive actuators, as shown in Figure 2.9. The process is a real process that will change over time. Actuators will drive the system to new states (or modes of operation). This means that the controller is limited by the sensors available, if an input is not available, the controller will have no way to detect a condition.The control loop is a continuous cycle of the PLC reading inputs, solving the ladder logic, and then changing the outputs. Like any computer this does not happen instantly. Figure 2.10 shows the basic operation cycle of a PLC. When power is turned on initially the PLC does a quick sanity check to ensure that the hardware is working properly. If there is a problem the PLC will halt and indicate there is an error. For example, if the PLC backup battery is low and power was lost, the memory will be corrupt and this will result in a fault. If the PLC passes the sanity checks it will then scan (read) all the inputs. After the inputs values are stored in memory the ladder logic will be scanned (solved) using the stored values - not the current values. This is done to prevent logic problems when inputs change during the ladder logic scan. When the ladder logic scan is complete the outputs will be scanned (the output values will be changed). After this the system goes back to do a sanity check, and the loop continues indefinitely. Unlike normal computers, the entire program will be run every scan. Typical times for each of the stages are in the order of milliseconds.3. SUMMARY. Normally open and closed contacts.. Relays and their relationship to ladder logic.. PLC outputs can be inputs, as shown by the seal in circuit.. Programming can be done with ladder logic, mnemonics, SFC, and structured text.. There are multiple ways to write a PLC program.。

中石油职称英语考试课文详解

中石油职称英语考试课文详解中石油职称英语考试通常包含一篇阅读理解课文，考察考生对文章内容的理解和分析。

为了帮助考生更好地准备考试，本文将对中石油职称英语考试课文进行详细解析。

课文：《The Impact of Artificial Intelligence on the Oil and Gas Industry》Artificial intelligence (AI) has been widely adopted in various industries, including oil and gas. With its advanced algorithms and machine learning capabilities, AI has great potential to revolutionize the way the oil and gas industry operates.Firstly, AI can improve exploration and production processes. By analyzing vast amounts of geological and seismic data, AI algorithms can identify potential drilling locations with higher accuracy. This not only reduces exploration costs but also increases the success rate of finding new oil and gas reserves.Secondly, AI can enhance operational efficiency. In oil and gas production, AI-powered systems can monitor equipment conditions in real-time and predict failures before they occur. By implementing preventive maintenance based on these predictions, companies can minimize downtime and improve overall operational efficiency.Moreover, AI can optimize the refining process. With AI algorithms, refineries can adjust production parameters in real-time to maximize outputand minimize energy consumption. This not only increases productivity but also reduces costs and environmental impact.Additionally, AI can improve safety in the oil and gas industry. By analyzing sensor data and monitoring worker behavior, AI systems can detect potential safety hazards and provide early warnings. This helps prevent accidents and ensures the well-being of employees.Despite the numerous benefits, there are also challenges associated with the adoption of AI in the oil and gas industry. One major challenge is the data quality and availability. AI algorithms rely on high-quality and large-scale data for accurate analysis and predictions. However, acquiring and managing such data can be a complex and costly process.Furthermore, there are concerns about the impact of AI on jobs in the industry. AI-powered systems have the potential to automate various tasks that were previously done by humans. While this can increase efficiency, it may also lead to job displacement and require workers to acquire new skills to adapt to the changing landscape.To address these challenges, companies in the oil and gas industry need to invest in data infrastructure and talent development. They should prioritize collecting and managing high-quality data, as well as training their employees to work effectively with AI systems.In conclusion, artificial intelligence has a significant impact on the oil and gas industry. From exploration and production to refining and safety, AI has the potential to revolutionize various aspects of the industry. However, challenges related to data and workforce need to be addressed for successfulimplementation. Companies should embrace AI and invest in the necessary resources to fully leverage its benefits.。

可编程控制器英文文献及其翻译

Programmable Logic ControllerA programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are 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 an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.1．HistoryThe PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay.In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of thePLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner.One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance.The automotive industry is still one of the largest users of PLCs.2．DevelopmentEarly PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver.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. Newer formats such as State Logic and Function Block (which is similar to the way logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic.A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats.3．ProgrammingEarly PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs.Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory.More recently, PLCs are usually programmed using special application software written for use on desktop computers, and connecting between the desktop computer and the PLC such as via Ethernet or RS-232 cabling. Such software allows entry and editing of the ladder style logic, and then may provide additional functionality to assist debugging and troubleshooting the software, for example by highlights portions of the logic to show current status during operation or via simulation. Finally, the software may allow uploading and downloading of the program between the computer and the PLC, for backup and restoration purposes. Alternately, specific devices known as programming boards are used to hard wire the logic into the controller by the use of a removable chip, such as an EEPROM, where the program is transferred to the programming board from the workstation via serial or other bus logic.4．FunctionalityThe 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 verymuch 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 such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.5．FeaturesThe main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.6．System styleA small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants.7．PLC compared with other control systemsPLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands or millions of units.For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit busses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic.Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls.Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.PLCs may include logic for single-variable feedback analog control loop, a "proportional, integral, derivative" or "PID controller." A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has become less distinct.PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.可编程控制器可编程逻辑控制器（PLC）或可编程控制器是一种数字化的计算机，机电流程自动化应用，如机械控制的工厂流水线，机动游戏，或照明装置。

基于S7_1500PLC的小功率加热炉温度控制系统_赵帅

《工业控制计算机》2015年第28卷第4期本文以小功率加热炉为被控对象，以西门子S7－1500PLC 为控制器，实现了小功率加热炉温度控制系统的闭环控制。

该控制系统采用PID算法［2］，并通过HMI实现了手动和自动模式［3］的选择和PID控制器的各项参数进行设定，控制系统操作简单、运行可靠、控制精度高。

1控制系统原理及硬件设计1．1控制系统原理温度控制系统的原理图如图1所示。

基于S7－1500PLC 的温度控制系统以小功率加热炉为被控对象，温度控制范围为0～100℃，采用AD590集成温度传感器对小功率加热炉温度进行采集，将采集到的0～10V模拟量电压信号通过A／D转换后，变为数字量信号，然后经过PID控制，再通过D／A转换成0～10V的模拟量电压信号控制加热器对小功率加热体进行加热。

HMI与PLC通过PROFINET通讯，可对PID控制器的各项参数进行调节或者进行手动或自动模式间的切换。

图1基于S7－1500PLC的温度控制系统原理框图1．2控制系统硬件设计S7－1500PLC的网络拓扑结构如图2所示。

各个模块之间采用PROFINET协议进行通讯。

S7－1500系列PLC采用CPU1511－1PN。

它具有一个带有两个端口的PROFINET接口；支持追踪功能；集成了运动控制，高速计数器，PID控制等工艺功能；具有强大的系统诊断功能；此外，还有程序防拷贝和访问保护等功能，安全性很高。

S7－1500控制系统最多可包含32个模块，CPU运算速度快，系统性能有了较大提高。

采用ET200SP组成分布式I／O系统，它包含模拟量输入模块AI4×U／I2－wire ST和模拟量输出模块AQ4×U／I ST。

模拟量输入模块AI4×U／I2－wire ST带有4个模拟量输入通道，电压测量的输入范围有±10V（精度16位）、±5V（精度16位）、1～5V（精度15位）、0～10V（精度15位）4种选择，电流测量的输入范围有4～20mA（精度15位）和0～20mA（精度15位）两种选择；模拟量输出模块AQ4×U／I ST带有4个模拟量输出通道，电压的输出范围有±10V（精度16位）、±5V（精度15位）、1～5V（精度13位）、0～10V（精度15位）4种选择，电流的输出范围有±20mA（精度16位）、4～20mA（精度14位）和0～20mA（精度15位）三种选择。

机电一体化英语Unit 3 Lesson 4

Unit 2 Lesson 4 Basics of PLC
COUNTERS-These again do not physically exist. They are simulated counters and they can be programmed to count pulses. Typically these counters can count up, down or both up and down. Since they are simulated they are limited in their counting speed. Some manufactures also include high-speed counters that are hardware based. We can think of these as physically existing. Most times these counters can count up, down or up and down.
Unit 2 Lesson 4 Basics of PLC
DATA STORAGE-Typically there are registers assigned to simply store data. They are usually used as temporary storage for math or data manipulation (操作；操纵；控制). They can also typically be used to store data when power is removed from the PLC. Upon power-up they will still have the same contents as before power was removed. Very convenient and necessary?

关于PLC英文文献(1)

关于PLC英文文献(1)A PLC programming environment based on a virtual plantSang C. Park & Chang Mok Park & Gi-Nam WangAbstract This paper proposes the architecture of a PLC programming environment that enables a visual verification of PLC programs that integrates a PLC program with a corresponding plant model, so that users can intuitively verify the PLC program in a 3D graphic environment. The plant model includes all manufacturing devices of a production system as well as corresponding device programs to perform their tasks in the production system, and a PLC program contains the control logic for the plant model. For the implementation of the proposed PLC programming environment, it is essential to develop an efficient methodology to construct a virtual device model as well as a virtual plant model. The proposed PLC programming environment provides an efficient construction method for a plant model based on the DEVS (Discrete Event Systems Specifications) formalism, which supports the specification of discrete event models in a hierarchical, modular manner.Keywords PLC verification . Plant model . Virtual device model . Virtual factory simulation1 IntroductionGenerally, industrial production lines are dynamic systems whose states change according to the occurrence of variousevents, and thus exhibit the characteristics of a discrete event system. If manufacturers are to remain competitive in a continuously changing marketplace, they must not only continue to improve their products but also strive to improve production systems continuously [10]. Thus, an efficient prototyping environment for production systems is crucial. A modern production line is a highly integrated system composed of automated workstations such as robots with tool-changing capabilities, a hardware handling system and storage system, and a computer control system that controls the operations of the entire system. The implementation of a production line requires much investment, and decisions at the design stage have to be made very carefully in order to ensure that a highly automated manufacturing system willsuccessfully achieve the intended benefits. Simulation is an essential tool in the design and analysis of complex systems that cannot be easily described by analytical or mathematical models [5, 6]. It is useful for calculating utilization statistics, finding bottlenecks, pointing out scheduling errors and even for creating manufacturing schedules. Traditionally, various simulation languages, including ARENA® and Auto- Mod®, are used for the simulation of manufacturing systems [14]. Those simulation languages have been widely accepted both in industry and in academia; however, they remain as analysis tools for the rough design stage of a production line, because their simulation models are not realistic enough to be utilized for a detailed design or for implementation purposes. For example, real production lines are usually controlled by PLC (ProgrammableLogic Controller) programs [3], as shown in Fig. 1, but conventional simulation languages roughly describe the control logic with independent entity flows (job flows) between processes.Fig. 1 Production system controlled by a PLC programFor a detailed design (virtual prototyping) of a production line, it is necessary to create a much more detailed simulation model that can forecast not only the production capability of the system but also the physical validity and efficiency of co-working machines and control programs. As shown in Fig. 1, various machines that operate simultaneously in an industrial manufacturing system are usually controlled by PLCs, currently the most suitable and widely employed industrial control technology [1–4]. A PLC (Programmable Logic Controller) emulates the behavior of an electric ladder diagram. As they are sequential machines, to emulate the workings of parallel circuits that respond instantaneously, PLCs use an input/ output image table and a scanning cycle. When a program is being run in a PLC, it is continuously executing a scanning cycle. The program scan solves the Boolean logic related to the information in theinput table with that in output and internal relay tables. In addition, the information in the output and internal relay tables is updated during the program scan. In a PLC, this Boolean logic is typically represented using a graphical language known as a ladder diagram [3]. Previous approaches on PLC programs can be categorized into two groups; (1) Verification of a given PLC program [18, 19], and (2) Generation of a dependable PLC program [15–17]. In the first group, various software tools have been developed for the verification of PLCbased systems via the use of timed automata, such asUPPAAL2k, KRONOS, Supremica and HyTech, mainly for programs written in a statement list language also termed Boolean [2]. These software tools verify PLC programs to a certain extent; however, they remain limited. Since they are mainly focusing on the checking of theoretical attributes (safety, liveness, and reachability), it is not easy for users to determine whether the PLC programs actually achieve the intended control objectives. In the second group, many researchers have focused on the automatic generation of PLC programs from various formalisms including state diagrams, Petri nets and IDEF0. These formalisms can help the design process of control logics, however, it is still difficult to find hidden errors, which are the most difficult part of the verification of a control program. To cope with the problem, we need a more transparent PLC programming environment helping users to recognize hidden errors. The objective of this paper is to propose the architecture of a PLC programming environment that enables the visual validation of a PLC program. The proposed PLC programming environment employs a virtual plant model consisting of virtual devices, so that users can easily verify the PLC program. The overall structure of the paper is as follows. Section 2 illustrates the architecture of the proposed PLC programming environment, while Section 3 describes an efficient construction methodology for a plant model, which can be synchronized with a PLC program. Section 4 shows an example and illustrations. Finally, concluding remarks are given in Section 5.2 Visual validation of PLC programsTo design the architecture of the PLC programming environment, it is importantto understand the basic procedure used to construct a PLC program (ladder diagram). Chuang et al. [1] proposed a procedure for the development of an industrial automated production system that consists of nine steps. They are: (1) Define the process to be controlled; (2) Make a sketch of the process operation;(3) Create a written sequence listing of the process step by step; (4) On the sketch, add the sensors needed to carry out the control sequence; (5) Add the manual controls needed for the process-setup or for operational checks; (6) Consider the safety of the operating personnel and make additions and adjustments as needed;(7) Add the master stop switches required for a safe shutdown; (8) Create a ladder logic diagram that will be used as a basis for the PLC program; and (9) Consider the possible points where the process-sequence may go astray. The most time-consuming task for the control logic designers is the 8-th step, which is usually done by the repetitive method of ‘Code writing, testing and debugging’until the control objectives are achieved [2]. The bottleneck of the 8-th step is that the conventional PLC programming environments are not especially intuitive, particularly for the testing and debugging of a PLC program, as they showonly the status of a PLC without providing any links to the target system (production line). For the validation of a PLC program, engineers need to imagine the state changes of a production line from the input and output ports of a PLC. That is the reason conventional PLC programming environments are often inefficient and prone to human error. As the configurations of production lines and their control programs become more complicated, there is a strong need for a more intuitive PLC programming environment. It is hoped that this paper will take positive steps in this direction. Figure 2 shows the architecture of the proposed PLC programming environment. It consists of two layers, a model layer and an application layer. The model layer has three models, a plant model (virtual factory model), a PLC program (control model) and an I/O mapping model. The plant model includes all manufacturing devices of the production system as well as the corresponding device programs to perform their tasks inthe production system, and the PLC program contains the control logic for the plant model. For the integration of the plant model and the PLC program, it is necessary to define the mapping between the plant model and the PLC program, which is described by the I/O mapping model. The application layer simultaneously provides two interfaces to users. The ‘PLCsimulator’ performs the simulation of the control program, and the ‘plant model visualizer’ shows the corresponding plant model (3D graphic models) reflecting the changing states of the production system during the PLC simulation. Thus, it becomes much easier for users to verify the PLC program through the plant model visualizer.。

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Based on the research of PLC temperature control system of boilerAbstract: from the development condition of boiler, PLC type selection, system software and hardware design, communication up and down a machine, the configuration program design is presented in several aspects, such as. By the temperature control system of PLC debugging the advantages of the simple, low cost, easy to maintenance, and easy to expand to the corresponding field of industrial control, good portability is of great importance to the industrial developmentKey words: PLC; The sensor; Temperature; The automatic controWith the continuous development of economy, the environment problem increasingly prominent. Boiler as the heating system is one of the most important energy conversion device energy consumption is huge, every year the national boiler combustion of more than one third of total energy consumption. At present, the domestic most of the urban heating system in the operation of the boiler equipment aging basic rely on manual operation, automation level is low, safety performance is poor, the combustion efficiency is not high, the air pollution is very serious. Therefore, the configuration of automatic temperature control system for boiler in today's increasingly serious environmental pollution situation is extremely important.1 boiler temperature control based on PLC is introducedThis system is based on PLC boiler temperature control, through the boiler internal sensor for temperature and flow rate feedback to system parameters such as temperature control, the automatic control of boiler temperature is realized.PLC programmable controller is a kind of combined relay controller and computer, through the installer, central processing unit CPU as the core and I/O devices connected to its use in the field of industrial control computer is slightly different with ordinary computer, mainly by the CPU, memory cell, basic components such as the I/O interface circuit, power supply, plus extension, programmer, external equipment, etc. PLC programmable controller can not only replace the ordinary relay, but also has A variety of extensions, such as A/D module, etc. Therefore, the use of PLC for automatic control of boiler provides a new solution, some advanced control method to the application.Using PLC programmable controller for boiler system, realize the automatic control of the temperature, on the one hand can improve combustion efficiency, reduce fuel use and emissions of harmful gas in flue gas, reducing the air pollution; PLC control system, on the other hand, through a variety of sensors inside the boiler temperature, pressure, flow and other related parameters, realized the automatic control of the parameters such as temperature. Reduces the manual labor, basically just in the engine room control room can fully understand the operation of the boiler, reduce the manpower cost, improve the level of the automation management system.2 the temperature control system design2.1 the temperature control system designThis design by Siemens S7-300 programmable controller for the next bit machine, two industrial control machine for PC. PC through industrial control software to realize early warning functions such as alarm, under a machine adopts Siemens S7-300 programmable controller, realize automatic control, such as temperature, flow rate in the boiler control level and safety guaranteed.System for the temperature of the object, and using PT100 type thermal resistance sensors inside the boiler water temperature, and then passed to EM235 module temperature transmitter, convert the signal through the PID arithmetic, adjusted to get a stable PID parameter values, then the input signal to the silicon controlled voltage regulator to control the voltage of the heater, achieve the purpose of regulating temperature.2.2 the temperature control system hardware design1) the host system. Using two sets of industrial control computer host, one of them as the main control machine, another one is complementary host, make double insurance. Configuration software WINCCSP26.0 using Siemens industrial control configuration software.2) PLC programmable controller. Systems use Siemens SP - 300 - PLC programmable controller. Its modular structure, easy to implement distributed configuration and high cost performance, strong electromagnetic compatibility, resistance to shock impact performance is good, in a wide range of industrial control field, become a kind of economical and practical solution. Variety of increasing performance of CPU and rich with many convenient features I/O extension module (including SM signal module, communication processor CP, IM interface module, etc.). The user can choose according to actual application module.3) the instrument equipment. In order to improve the anti-interference ability, type selection of instrument meter DDZ -IH 45 ma current output for 0123, to ensure the reliability of the system. Instrument include: flow transmitting, pressure transmitter, temperature transmitter, liquid level transmitter, micro oxygen transmitter, pressure transmitter, etc.4) the frequency conversion control room. Mainly includes: power supply control cabinet, frequency conversion control cabinet, boiler circulating pump frequency conversioncontrol cabinet, control cabinet is equipped with various types of relay contactor, relay, etc., low voltage electrical equipment to complete the motor start and stop.2.3 the temperature control system software design2.3.1 PID instruction algorithmPID controller according to the error of the system parameter values, calculated by proportional integral and differential control quantity to control, so called, PID control and PID control. In the field of industrial control, PID is still in wide use. Three kinds of control volume have different characteristics, separately to exist advantages and disadvantages are clearly, when used with various restrictions would have problems, how to adjust the PID parameter of the stability, becomes the current control of the most important step.2.3.2 characteristics of PID control algorithm1) the proportion (P) control. Proportional (P) control is one of the most simple control method, the controller output to the input error signal is proportional to the relationship. Controller will happen if skewed, adjust the control output, the accused to reduce the amount of deviation in the direction of change. Deviation reduce speed determined by proportional coefficient Kp, Kp the faster, the greater the deviation decrease. But this will cause oscillation, especially in the hysteresis link is larger, the proportional coefficient Kp reduce the possibility of oscillation will be reduced, but at the same time can also lead to slow adjustment. Proportional control weakness is can't eliminate the steady-state error, integral control must be available to assist.2) the integral (I) control. The output of the controller in the integral control is proportional to the input of the error signal integral relationship. After entering the steady state, if exist steady-state error control system, in order to eliminate the steady-state error of the system, the integral item must be added. As time increases, the integral term will also increase, so even the relatively small error integral item will also be increased with the increase of time, it will further reduce the steady state, the existence of error to zero. So the proportional integral (PI) controller can make the system enter the steady-state no steady-state error.3) differential (D) control. Under differential control, the controller output differential increases, the input error signal differential will also increase. The automatic control system for error control, there will be other unnecessary problems such as movements will more serious instability. That is to say, in the controller only introduced "ratio" is often not enough. Proportional action is only magnified error amplitude, but join differential item to avoid large errors. Because it can predict the direction of the error change, but the differential control can enlarge the high frequency noise, lower signal-to-noise ratio in the system, resulting in a decline in the ability of the system suppress interference. That is to say, differential control can't eliminate the residual.2.3.3 PID parameter settingPID parameters setting is mainly to adjust P, Pi, Pt. To change the system characteristic and causing the system to achieve satisfaction index.2.3.4 PID algorithm program implementationIn the SP -300 -PID function is accomplished by PID instruction function block, by regularly perform PID function block. According to the PID operation rule, according to a given at the time, proportional integral differential data, calculate the control quantity.3 the PID program designSiemens PLC control program is to use the programming software S7V5. 3.First input analog signals, the boiler's current voltage by numerical display. Second watch boiler the current temperature is normal, alarm indicator lamp whether can normal use. Initiator, observation after the start position, initialize the PID parameters, close the program, zero analog, continue to stop boiler heating but still shows the temperature. Set temperature, the interrupt program, adjust PID parameter, output PID arithmetic as a result, the output analog signals.4 the configuration module design1) Configuration software design. Select the configuration design of this system software is Siemens WINCC configuration software, WINCC is a powerful, has the very good open software. All kinds of complex task, WINCC can handle. WINCC belongs to man-machine interface configuration tool, its biggest characteristic is to system integration on the basis of the configuration. As long as the preset of various software modules for simple configuration, you can easily implement each function of monitoring layer, shortens the time of system integration to improve the working efficiency.WINCC configuration software with Microsoft system as a platform, provide powerful editing functions, and itself contains rich graphics resources, convenient design all kinds of industrial used figure, and easy to edit, at the same time with the computer's versatility, reducing the workload. Users can design and editing function, make full use of the open sexual function. Because belong to Siemens, when using WINCC configuration software can easily to create S7-300 PLC in the system variables, edit and modify, greatly convenient for the user.2) please communication up and down. Connect the PLC and the computer connection, after the completion of the set up communication in software.3) the system debugging. Again and again, after the completion of up and down a machine connection adjust PID temperature control parameters, in order to get the optimal PID parameter values. Oscillation phenomenon occurring in a system, by adding differential adjustment, multiple optimal PID parameters resulting from the debug.5 conclusionThis system adopts the single loop PID control, through many times to adjust PID parameter, get a quick response and high precision control of the boiler temperature control system, complete the intended target. Due to the use of configuration design of the interface, make the system more concise and practical, the temperature control is more flexible and convenient, and can be expanded to the related industrial control field.。