In daily study and work, when it comes to papers, everyone is certainly familiar with them. Writing papers can improve our ability to comprehensively apply what we have learned. How to write a thoughtful and literary paper? The following is the application and trend paper of PLC technology in electrical automation that I collected for you. Welcome to read the collection.
abstract:
Through the summary of practical work experience, we can find that the application and popularization of PLC technology in automatic control effectively shortens the time for technicians to troubleshoot, improves the work efficiency of workers and greatly improves the automation degree of electrical equipment. With the continuous optimization and research and development of PLC technology, its application in electrical engineering and automation control will be more extensive.
Key words:
PLC industry; Application; Automatic control;
Introduction:
The application level of automation shows a country's technological and industrial strength. PLC technology is a very important technology in automatic control of electrical engineering, which improves the level of automatic control and can effectively solve some problems and defects in equipment. Because of its good reliability and adaptability, PLC has been widely used in the field of automation control, so small that it can operate a station, a component and a device. Large enough to control a production line, multiple devices, and even the entire factory. It can be said that in today's automatic control, PLC technology is almost inseparable. This paper will summarize and discuss the application of PLC technology in the field of automatic control.
1, the concept and characteristics of PLC
1. 1, the basic meaning of PLC
The Chinese definition of PLC is programmable logic controller, which can load the control instructions of equipment into its memory to execute commands and store functions. Its microprocessor function is mainly used for digital operation of automatic control. PLC consists of power supply, input/output interface, digital-to-analog converter, instruction data memory and other components. The early PLC had a single function, only one function of logic control, long design and manufacturing cycle, complicated wiring and difficult maintenance. However, with the continuous optimization and improvement, these simple functions have been extended to multi-functional controllers integrating time sequence control, multi-computer communication, analog control and logic control. At present, PLC used in electric automatic control system is close to or equivalent to a microcomputer host, and its advantages of reliability and expansibility have been widely used in many automatic control fields.
Power supply uses rectifier module to convert our commonly used alternating current into direct current for PLC internal operation. Switching regulated power supply is widely used in PLC power supply system at present. CPU (Central Processing Unit) is the brain and core component of PLC, and its function is to run and process user data, perform mathematical and logical operations, and coordinate the whole control system. Its superior performance determines the running speed and processing capacity of PLC. The function of memory is to store information, such as user programs, system programs and logic variables. The controlled equipment connected with PLC is called input and output unit. The input unit is the hub of signal transmission to PLC and can receive signals from detection elements and command elements. The function of the output unit is to transmit the control instruction of PLC to the controlled equipment.
Communication networking is also an extremely important function of PLC, which enables data information to be exchanged between PLCs, between PLCs and intelligent devices, and between PLCs and computers to form a complete control system and achieve the purpose of centralized control. Like a computer, PLC has a network interface, which enables it to exchange data and information over a long distance through optical cable or twisted pair. Data communication can be divided into two ways: serial communication and parallel communication. Parallel communication takes words or bytes as the unit, which has a fast transmission speed, but requires a large number of transmission lines, and is suitable for short-distance data transmission. Serial is based on binary, and only one bit is transmitted at a time, so the number of transmission lines needed is small and the cost is low, which is suitable for long-distance data transmission.
1.2, the characteristics of PLC technology
Simple and efficient: simple, which we can understand as convenient installation and flexible configuration; High efficiency, which we can understand as fast running speed. Compared with the installation of computer system, the installation of PLC does not require high installation environment, and there is no need to set up special computer room or shielding measures. When in use, as long as the interface terminal is correctly connected with the executing and detecting mechanism, it can work normally. Users can make different combinations of PLC according to the needs of automatic control, and can simply and flexibly change the scale and function of the control system. Moreover, PLC programming is simple and easy to use, and technicians can program without computer professional knowledge. The execution mode of PLC program control will make it run faster and improve its reliability greatly, which is incomparable to traditional logic mode.
Strong practicability: PLC technology is suitable for various applications, and its variability and programming simplicity make it very practical. PLC has good control function and strong reliability, and can be extended according to the requirements of automatic control system. It has small volume, low power consumption and high integration, which is very suitable for automatic control in all walks of life. At present, most PLC systems are designed with highly integrated single chip microcomputer. With the strengthening of peripheral circuits for measurement and control system, PLC technology can be conveniently and flexibly applied to complex automatic control systems and equipment, such as industrial process control, industrial controller, process detection and electrical automation control system, etc., and most of them are multipolar network systems with PLC technology as the core.
Strong anti-interference ability: isolation and shielding are adopted to effectively improve the anti-interference ability of PLC technology. The control power supply of PLC is usually provided by the power grid, but the power supply of the power grid is easily disturbed, such as the start and stop of large equipment, rectifier failure, power grid short circuit and so on. , will affect the power supply of PLC, and may cause PLC operation errors or program errors, which will lead to misoperation and out-of-control of automatic control equipment. The core components of PLC should be filtered by integrated voltage regulator. Improving the grounding system of PLC, on the one hand, can improve its safety and avoid the harm of overvoltage and overcurrent in the power grid, on the other hand, it will suppress electromagnetic interference. In practical application, PLC adopts a one-point grounding method, which connects the nearby grounding point and all grounding terminals through one point to improve the anti-interference ability.
2. How is 2.PLC technology applied in electrical automation?
2. 1, switch control
Switch control is the most basic application in PLC technology. The purpose of switch control is to make PLC produce corresponding switch outputs according to the historical input combination and current input sequence of switches, so as to realize the system working in a given logical order. PLC is commonly used in electrical control circuits, and the switching elements that can provide switching signals include temperature switches, travel switches, buttons and so on. The function of the travel switch can be used to feed back the running position. Install a travel switch at the designated position of electrical equipment, and the contact of the travel switch is connected to the input point of PLC, so that the PLC program can make corresponding output through the on-off state of the input point. If we want electrical equipment to complete an action or a series of actions, we must transmit signals to PLC through buttons to complete the instruction operation. The signal given by the temperature switch is also a switch value. In order to simplify the control system, the temperature signal that is not the switching value is processed into the switching value. When the set temperature is reached, the relay in the temperature switch will be turned on, which will send a signal to PLC, and PLC will decide whether to execute the command according to the received signal.
2.2, sequence control
Application of sequential control in electrical engineering. If a control system is decomposed into several independent control actions, and in order to ensure the normal operation of production, each independent control action can perform tasks in a given order without any mistakes. The three basic elements to realize PLC logic control are work task, transmission target and transmission condition. Both of them are indispensable, and the sequence control function cannot be realized. By improving and optimizing these three conditions, the stability and efficiency of the automatic control system can be effectively improved. Implementing execution in a given order is the most basic feature of sequence control system, and sequential control can be subdivided into logical order, conditional order and time order. Logical order is to execute commands in sequence according to given conditions. Conditional sequence refers to whether the execution conditions can meet the requirements of logical control. Timing is the execution time, when to start executing the command and when to stop executing the command. Sequential control improves the level of automation control in industrial field. Sequential control is a typical control mode in industrial automatic control system, which is widely used, such as the control of traffic lights and the control of commodity packaging production lines.
2.3, closed-loop control
In the traditional field of electrical engineering, the popularization and application of automation is not high, and more manual methods are used to start and stop electrical equipment, which will not guarantee the safety and reliability of the equipment, but also reduce the work efficiency. The application of PLC in analog closed-loop control effectively solves this kind of problem. In the application of industrial production and daily life, closed-loop control is widely used in automatic control systems, such as the automatic control of running motors and the control systems of motor speed, flow, liquid level, temperature and pressure. , all adopt closed-loop control system. Closed-loop control can be divided into single closed-loop control and multiple closed-loop control systems. For systems where controlling the ratio of two process variables is more important than controlling the absolute value between them, such as controlling the speed of two devices that need to be synchronized, a single closed-loop control system can be adopted. Multi-closed-loop control system keeps the ratio of two process data variables constant, such as the control of automatic temperature regulation system of electrical equipment. When selecting the closed-loop control system, the best scheme should be selected according to the needs.
3. The application and development direction of 3.PLC technology in electrical automatic control system.
At present, with the development of microelectronic technology such as large-scale integrated circuits, PLC technology has become very mature. Not only the reliability is improved, the cost is reduced, the control function is enhanced, and the power consumption and volume are reduced, but also with the development of image display, communication network and data processing, PLC develops in the direction of continuous production process control. On the one hand, in order to meet the needs of miniaturization of automatic control system, we should vigorously develop PLC with higher cost performance, faster speed and smaller volume. On the other hand, it is also developing in the direction of large-scale PLC with faster speed, larger capacity and better technology. With the development of electrical automation to more complex control system, people put forward higher requirements for the transmission and processing ability of PLC data information, and the capacity of its memory is also increasing.
In order to meet all kinds of automatic control requirements in the field of automation control, in recent years, many new modules and devices have been developed and applied in PLC technology, such as intelligent input and output module, intelligent detection module for PLC troubleshooting, temperature control module and so on. The application and development of these new modules have enhanced the use function of PLC, expanded the application scope of PLC and improved the stability of automation system. In the future, the development trend of PLC software technology will be towards the coexistence and complementarity of multiple programming languages. The programming language of PLC will be enriched and expanded on the basis of time series function language, instruction language and ladder diagram language, and will develop to a higher level.
With the development of related software and hardware technology, business model and social value, PLC will develop towards virtualization. PLC virtualization is to simulate or simulate a specific PLC hardware system by using general standard hardware modules and software. The development of PLC virtualization will make any individual or organization avoid repeated manufacturing, improve the efficiency of service and software construction, and accelerate the construction and landing of various applications. Moreover, the application of PLC virtualization will fundamentally change the security governance mode and security architecture in the existing automatic control system.
4. Concluding remarks
Because of its own characteristics and advantages, PLC technology plays an important role in the field of electrical automation, which ensures the safety and reliability of electrical automation system and improves the degree of automation and work efficiency. With the continuous development and innovation of PLC technology, the application of electrical automation will also get a very broad development space. This paper briefly summarizes the basic meaning, characteristics and development prospect of PLC, and expounds the application of PLC technology in the field of electrical automation for mutual learning.
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